R. Horisberger

A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current $$e^{\pm }p$$ scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb $$^{-1}$$ and span six orders of magnitude in negative four-momentum-transfer squared, $$Q^2$$ , and Bjorken x. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in $$\alpha _s(M_Z^2)=0.1183 \pm 0.0009 \mathrm{(exp)} \pm 0.0005\mathrm{(model/parameterisation)} \pm 0.0012\mathrm{(hadronisation)} ^{+0.0037}_{-0.0030}\mathrm{(scale)}$$ . An extraction of $$xF_3^{\gamma Z}$$ and results on electroweak unification and scaling violations are also presented.

The PILATUS 1M detector is a hybrid pixel array detector with over one million pixels that operate in single photon counting mode. The detector, designed for macromolecular crystallography, is the largest pixel array detector currently in use at a synchrotron. It is a modular system consisting of 18 multichip modules covering an area of 21 cm x 24 cm. The design of the components as well as the manufacturing of the detector including the bump-bonding was performed at the Paul Scherrer Institute (PSI). The use of a single photon counting detector for protein crystallography requires detailed studies of the charge collection properties of the silicon sensor. The 18 modules are read out in parallel, leading to a full frame readout-time of 6.7 ms. This allows crystallographic data to be acquired in fine-varphi-slicing mode with continuous rotation of the sample. The detector was tested in several experiments at the protein crystallography beamline X06SA at the Swiss Light Source at PSI. Data were collected both in conventional oscillation mode using the shutter, as well as in a fine-varphi-slicing mode. After applying all the necessary corrections to data from a thaumatin crystal, the processing of the conventional data led to satisfactory merging R-factors of the order of 8.5%. This allows, for the first time, determination of a refined electron density map of a macromolecular biological crystal using a silicon pixel detector.

The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors, capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2×1017 O/cm3 in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5×1014 cm−2 (1 MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the “Hamburg model”: its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed, including differences due to charged and neutral hadron irradiation.

Time-resolved experiments in powder diffraction are limited by the long time required to record spectra with current detectors. A major improvement can be made by using a massively parallel X-ray detection system together with a fast read out. The Mythen detector (Microstrip system for time-resolved experiments) has been built for the Powder Diffraction Station of the Material Science beamline at the Swiss Light Source to meet these requirements. The specifically developed read out chip (Mythen chip), the detector system and first measurements are shown.

EIGER is an advanced family of single photon counting hybrid pixel detectors, primarily aimed at diffraction experiments at synchrotrons. Optimization of maximal functionality and minimal pixel size (using a 0.25μm process and conserving the radiation tolerant design) has resulted in 75×75μm2 pixels. Every pixel comprises a preamplifier, shaper, discriminator (with a 6 bit DAC for threshold trimming), a configurable 4/8/12 bit counter with double buffering, as well as readout, control and test circuitry. A novel feature of this chip is its double buffered counter, meaning a next frame can be acquired while the previous one is being readout. An array of 256×256 pixels fits on a ∼2×2cm2 chip and a sensor of ∼8×4cm2 will be equipped with eight readout chips to form a module containing 0.5 Mpixel. Several modules can then be tiled to form larger area detectors. Detectors up to 4×8 modules (16 Mpixel) are planned. To achieve frame rates of up to 24 kHz the readout architecture is highly parallel, and the chip readout happens in parallel on 32 readout lines with a 100 MHz Double Data Rate clock. Several chips and singles (i.e. a single chip bump-bonded to a single chip silicon sensor) were tested both with a lab X-ray source and at Swiss Light Source (SLS) beamlines. These tests demonstrate the full functionality of the chip and provide a first assessment of its performance. High resolution X-ray images and “high speed movies” were produced, even without threshold trimming, at the target system frame rates (up to ∼24kHz in 4 bit mode). In parallel, dedicated hardware, firmware and software had to be developed to comply with the enormous data rate the chip is capable of delivering. Details of the chip design and tests will be given, as well as highlights of both test and final readout systems.

Evidence for a new resonance $\ensuremath{\theta}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\eta}$ in the process $\frac{J}{\ensuremath{\psi}}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\eta}\ensuremath{\eta}$ is presented. The resonance parameters of the $\ensuremath{\theta}$ are $M=1640\ifmmode\pm\else\textpm\fi{}50$ MeV and $\ensuremath{\Gamma}={220}_{\ensuremath{-}70}^{+100}$ MeV. ${J}^{\mathrm{PC}}={2}^{++}$ is preferred over ${0}^{++}$.

A measurement is presented of the inclusive neutral current e ± p scattering cross section using data collected by the H1 experiment at HERA during the years 2003 to 2007 with proton beam energies E p of 920, 575, and 460 GeV. The kinematic range of the measurement covers low absolute four-momentum transfers squared, 1.5 GeV2<Q 2<120 GeV2, small values of Bjorken x, 2.9⋅10−5<x<0.01, and extends to high inelasticity up to y=0.85. The structure function F L is measured by combining the new results with previously published H1 data at E p =920 GeV and E p =820 GeV. The new measurements are used to test several phenomenological and QCD models applicable in this low Q 2 and low x kinematic domain.

The first measurement of lepton-jet momentum imbalance and azimuthal correlation in lepton-proton scattering at high momentum transfer is presented. These data, taken with the H1 detector at HERA, are corrected for detector effects using an unbinned machine learning algorithm (multifold), which considers eight observables simultaneously in this first application. The unfolded cross sections are compared with calculations performed within the context of collinear or transverse-momentum-dependent factorization in quantum chromodynamics as well as Monte Carlo event generators.

Cross sections for elastic photoproduction of J/ψ and ϒ mesons are presented. For J/ψ mesons the dependence on the photon-proton centre-of-mass energy Wγp is analysed in an extended range with respect to previous measurements of 26≤Wγp≤285GeV. The measured energy dependence is parameterized as σγp∝Wγpδ with δ=0.83±0.07. The differential cross section dσ/dt for J/ψ mesons is derived, its dependence on Wγp and on t is analysed and the effective trajectory (in terms of Regge theory) is determined to be α(t)=(1.27±0.05)+(0.08±0.17)·t/GeV2. Models based on perturbative QCD and on pomeron exchange are compared to the data.

Results from a detailed study using the Crystal Ball detector at the SLAC e+e storage ring SPEAR of the inclusive photon spectra from 1.8 X 106 i(t' and 2.2&& 106 J/P decays are presented.Radiative transitions from the P to the 1'2 ~o states are observed with photon energies of 126.0+0.2+4,169.6+0.3 +4, and 258.4+0.4+4Mev and branching ratios 8(i('~y X2, &, p) =(8.0%0.5+0.7)%,(9.0+0.5+0.7)%, and (9.9+0.5+0.8)%,respectively.Values for the natural linew'idths of the p states are obtained: I (p2 l 0)=0.8 -4.9, &3.8, and 13 -21 MeV, respectively (90% C.L.).Improved values are found for the branchmg ratios 8(g'~yg, ) =(0.28+0.06)%and B(J//~yes, ) =(1.27+0.36)%,and for the natural width I (g, ) =11.524.5 MeV.I.

From a partial-wave analysis of the $K\overline{K}\ensuremath{\pi}$ system in the decay $\frac{J}{\ensuremath{\psi}}\ensuremath{\rightarrow}\ensuremath{\gamma}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$, it is determined that the quantum numbers of the $K\overline{K}\ensuremath{\pi}$ resonance at 1440 MeV, previously identified as the $E(1420)$, are ${J}^{\mathrm{PC}}={0}^{\ensuremath{-}+}$. This new particle has been named the $\ensuremath{\iota}$.

Diffractive electroproduction of rho and phi mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb^-1. About 10500 rho and 2000 phi events are analysed in the kinematic range of squared photon virtuality 2.5 < Q^2 < 60 GeV^2, photon-proton centre of mass energy 35 < W < 180 GeV and squared four-momentum transfer to the proton |t| < 3 GeV^2. The total, longitudinal and transverse cross sections are measured as a function of Q^2, W and |t|. The measurements show a transition to a dominantly "hard" behaviour, typical of high gluon densities and small q\bar{q} dipoles, for Q^2 larger than 10 to 20 GeV^2. They support flavour independence of the diffractive exchange, expressed in terms of the scaling variable (Q^2 + M_V^2)/4, and proton vertex factorisation. The spin density matrix elements are measured as a function of kinematic variables. The ratio of the longitudinal to transverse cross sections, the ratio of the helicity amplitudes and their relative phases are extracted. Several of these measurements have not been performed before and bring new information on the dynamics of diffraction in a QCD framework. The measurements are discussed in the context of models using generalised parton distributions or universal dipole cross sections.

The readout chip for the CMS pixel detector has to deal with an enormous data rate. On-chip zero suppression is inevitable and hit data must be buffered locally during the latency of the first level trigger. Dead-time must be kept at a minimum. It is dominated by contributions coming from the readout. To keep it low an analog readout scheme has been adopted where pixel addresses are analog coded. We present the architecture of the final CMS pixel detector readout chip with special emphasis on the analog readout chain. Measurements of its performance are discussed.

Inclusive charm and beauty cross sections are measured in e-p and e+p neutral current collisions at HERA in the kinematic region of photon virtuality 5<Q^2<2000 GeV^2 and Bjorken scaling variable 0.0002<x<0.05. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb^-1. The numbers of charm and beauty events are determined using variables reconstructed by the H1 vertex detector including the impact parameter of tracks to the primary vertex and the position of the secondary vertex. The measurements are combined with previous data and compared to QCD predictions.

A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV2 ≤Q 2≤12 GeV2, and low Bjorken x, 5⋅10−6≤x≤0.02. The result is based on two data sets collected in dedicated runs by the H1 Collaboration at HERA at beam energies of 27.6 GeV and 920 GeV for positrons and protons, respectively. A combination with data previously published by H1 leads to a cross section measurement of a few percent accuracy. A kinematic reconstruction method exploiting radiative ep events extends the measurement to lower Q 2 and larger x. The data are compared with theoretical models which apply to the transition region from photoproduction to deep inelastic scattering.

A first measurement is reported of the longitudinal proton structure function F_L(x,Q^2) at the ep collider HERA. It is based on inclusive deep inelastic e^+p scattering cross section measurements with a positron beam energy of 27.5 GeV and proton beam energies of 920, 575 and 460 GeV. Employing the energy dependence of the cross section, F_L is measured in a range of squared four-momentum transfers 12 < Q^2 < 90 GeV^2 and low Bjorken x 0.00024 < x < 0.0036. The F_L values agree with higher order QCD calculations based on parton densities obtained using cross section data previously measured at HERA.

A search has been made with the Crystal Ball Detector for axionlike particles in radiative $\frac{J}{\ensuremath{\Psi}}$ decays. An upper limit on the branching ratio $B(\frac{J}{\ensuremath{\Psi}}\ensuremath{\rightarrow}\ensuremath{\gamma}+a)&lt;1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ (90% C.L.) is obtained. This result holds for long-lived, noninteracting pseudoscalar or vector particles of mass less than 1 GeV. Thus, this experiment also places stringent limits on the existence of other possible light bosons such as those arising in supersymmetric theories.

A measurement of the inclusive deep-inelastic neutral current e+p scattering cross section is reported in the region of four-momentum transfer squared, 12<=Q^2<=150 GeV^2, and Bjorken x, 2x10^-4<=x<=0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E_e=27.6 GeV and E_p=920 GeV, respectively. The data are combined with previously published data, taken at E_p=820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data.

The production of leading neutrons, where the neutron carries a large fraction x L of the incoming proton's longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb−1. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6<Q 2<100 GeV2, Bjorken scaling variable 1.5⋅10−4<x<3⋅10−2, longitudinal momentum fraction 0.32<x L <0.95 and neutron transverse momentum p T <0.2 GeV. The leading neutron structure function, $F_{2}^{LN(3)}(Q^{2},x,x_{L})$ , and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of Q 2, x and x L . Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function.

Inclusive $$ep$$ double differential cross sections for neutral current deep inelastic scattering are measured with the H1 detector at HERA. The data were taken with a lepton beam energy of $$27.6$$ GeV and two proton beam energies of $$E_p=460$$ and 575 GeV corresponding to centre-of-mass energies of 225 and 252 GeV, respectively. The measurements cover the region of $$6.5\times 10^{-4} \le x \le 0.65$$ for $$35\le Q^2 \le 800$$ GeV $$^2$$ up to $$y=0.85$$ . The measurements are used together with previously published H1 data at $$E_p=920$$ GeV and lower $$Q^2$$ data at $$E_p=460$$ , $$575$$ and $$920$$ GeV to extract the longitudinal proton structure function $$F_L$$ in the region $$1.5\le Q^2 \le 800$$ GeV $$^2$$ .

A BSTRACT Inclusive e ± p single and double differential cross sections for neutral and charged current deep inelastic scattering processes are measured with the H1 detector at HERA. The data were taken at a centre-of-mass energy of $ \sqrt {s} = {319} $ GeV with a total integrated luminosity of 333.7 pb −1 shared between two lepton beam charges and two longitudinal lepton polarisation modes. The differential cross sections are measured in the range of negative four-momentum transfer squared, Q 2 , between 60 and 50 000 GeV 2 , and Bjorken x between 0 . 0008 and 0 . 65. The measurements are combined with earlier published unpolarised H1 data to improve statistical precision and used to determine the structure function $ xF_{3}^{{\gamma Z}} $ . Ameasurementoftheneutralcurrentparityviolating structure function $ F_{2}^{{\gamma Z}} $ is presented for the first time. The polarisation dependence of the charged current total cross section is also measured. The new measurements are well described by a next-to-leading order QCD fit based on all published H1 inclusive cross section data which are used to extract the parton distribution functions of the proton.

Measurements of open charm and beauty production cross sections in deep inelastic ep scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon $$2.5~\hbox {GeV}^2\le Q^2 \le 2000\, \hbox {GeV}^2$$ and Bjorken scaling variable $$3 \cdot 10^{-5} \le x_\mathrm{Bj} \le 5 \cdot 10^{-2}$$ . The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as $$m_c(m_c) = 1.290^{+0.046}_{-0.041} \mathrm{(exp/fit)}$$ $${}^{+0.062}_{-0.014} \mathrm{(model)}$$ $${}^{+0.003}_{-0.031} \mathrm{(parameterisation)}$$ GeV and $$m_b(m_b) = 4.049^{+0.104}_{-0.109} \mathrm{(exp/fit)}$$ $${}^{+0.090}_{-0.032} \mathrm{(model)}$$ $${}^{+0.001}_{-0.031} \mathrm{(parameterisation)}~\mathrm{GeV}$$ .

The design, construction and performance of the H1 silicon vertex detector is described. It consists of two cylindrical layers of double-sided, double-metal silicon sensors read out by a custom designed analog pipeline chip. The analog signals are transmitted by optical fibres to a custom-designed ADC board and are reduced on PowerPC processors. Details of the design and construction are given and performance figures from the first data-taking periods are presented.

A large quantum-limited area X-ray detector for protein crystallography is under development at the Swiss Light Source. The final detector will be 2k � 2k pixels covering 40 � 40 cm 2 : A three-module prototype with 1120 � 157 pixels covering an active area of 24:3 � 3: 4c m 2 has been tested. X-rays above 6 keV with peak count rates exceeding 5 � 10 5 X-ray/pixel/s could be detected in single photon counting mode. Statistics of module production and results of threshold trimming are presented. To demonstrate the potential of this new detector, protein crystal data were collected at beamline 6S of the SLS. r 2002 Elsevier Science B.V. All rights reserved. PACS: 87.64.Bx

We have determined the momentum ${p}_{{\ensuremath{\mu}}^{+}}$ of muons from the decay ${\ensuremath{\pi}}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ at rest, by analyzing a surface muon beam in a magnetic spectrometer equipped with a silicon microstrip detector. The result ${p}_{{\ensuremath{\mu}}^{+}}=(29.79200\ifmmode\pm\else\textpm\fi{}0.00011)$ MeV/c leads to a squared muon-neutrino mass of ${m}_{{\ensuremath{\nu}}_{\ensuremath{\mu}}}^{2}=(\ensuremath{-}0.016\ifmmode\pm\else\textpm\fi{}0.023)$ Me${\mathrm{V}}^{2}$, which corresponds to a "laboratory" upper limit of 0.17 MeV (C.L.=0.9) for the muon-neutrino mass. The cosmological upper limit of the neutrino mass (65 eV), the muon mass, and the new value of ${p}_{{\ensuremath{\mu}}^{+}}$ yield the pion mass ${m}_{{\ensuremath{\pi}}^{+}}=(139.57022\ifmmode\pm\else\textpm\fi{}0.00014)$ MeV. Alternatively, if one does not use the cosmological upper limit of ${m}_{{\ensuremath{\nu}}_{\ensuremath{\mu}}}$, then a combined fit including the new ${p}_{{\ensuremath{\mu}}^{+}}$ value, and the ${m}_{{\ensuremath{\mu}}^{+}}$ and ${m}_{{\ensuremath{\pi}}^{\ensuremath{-}}}$ values from other experiments and the $\mathrm{CPT}$ theorem (${m}_{{\ensuremath{\pi}}^{+}}={m}_{{\ensuremath{\pi}}^{\ensuremath{-}}}$) leads to ${m}_{{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}}=(139.57037\ifmmode\pm\else\textpm\fi{}0.00021)$ MeV. As a side result, the mean kinetic energy of the pions stopped in the production target, made of isotropic graphite, immediately before their decay is found to be $\stackrel{-}{{T}_{{\ensuremath{\pi}}^{+}}}=(0.425\ifmmode\pm\else\textpm\fi{}0.016)$ eV. This is consistent with the hypothesis that the pions are trapped in the potential well of a spherical harmonic oscillator, $V(r)={V}_{0}+\frac{1}{2}{k}_{s}{r}^{2}$, with ${k}_{s}=(1.144\ifmmode\pm\else\textpm\fi{}0.088)\ifmmode\times\else\texttimes\fi{}{10}^{17}$ eV/${\mathrm{cm}}^{2}$.

This report summarises the final results obtained by the RD48 collaboration. The emphasis is on the more practical aspects directly relevant for LHC applications. The report is based on the comprehensive survey given in the 1999 status report (RD48 3rd Status Report, CERN/LHCC 2000-009, December 1999), a recent conference report (Lindström et al. (RD48), and some latest experimental results. Additional data have been reported in the last ROSE workshop (5th ROSE workshop, CERN, CERN/LEB 2000-005). A compilation of all RD48 internal reports and a full publication list can be found on the RD48 homepage (http://cern.ch/RD48/). The success of the oxygen enrichment of FZ-silicon as a highly powerful defect engineering technique and its optimisation with various commercial manufacturers are reported. The focus is on the changes of the effective doping concentration (depletion voltage). The RD48 model for the dependence of radiation effects on fluence, temperature and operational time is verified; projections to operational scenarios for main LHC experiments demonstrate vital benefits. Progress in the microscopic understanding of damage effects as well as the application of defect kinetics models and device modelling for the prediction of the macroscopic behaviour has also been achieved but will not be covered in detail.

An ${{\ensuremath{\eta}}_{c}}^{\ensuremath{'}}$ candidate state is observed at a mass $M=3592\ifmmode\pm\else\textpm\fi{}5$ MeV and with a natural linewidth $\ensuremath{\Gamma}&lt;8$ MeV (95% confidence level), by using the "crystal ball" NaI(Tl) detector at the Stanford Linear Accelerator Center (SPEAR). The evidence is found in the inclusive photon spectrum in decays of the ${\ensuremath{\psi}}^{\ensuremath{'}}(3684)$, where a signal is observed corresponding to a radiative transition to this state with branching ratio between 0.2% and 1.3% (95% confidence interval, including an uncertainty due to correlation with width).

A measurement of elastic deeply virtual Compton scattering gamma* p -> gamma p using e^+ p and e^- p collision data recorded with the H1 detector at HERA is presented. The analysed data sample corresponds to an integrated luminosity of 306 pb^-1, almost equally shared between both beam charges. The cross section is measured as a function of the virtuality Q^2 of the exchanged photon and the centre-of-mass energy W of the gamma* p system in the kinematic domain 6.5 < Q^2 < 80 GeV^2, 30 < W < 140 GeV and |t| < 1 GeV^2, where t denotes the squared momentum transfer at the proton vertex. The cross section is determined differentially in t for different Q^2 and W values and exponential t-slope parameters are derived. Using e^+ p and e^- p data samples, a beam charge asymmetry is extracted for the first time in the low Bjorken x kinematic domain. The observed asymmetry is attributed to the interference between Bethe-Heitler and deeply virtual Compton scattering processes. Experimental results are discussed in the context of two different models, one based on generalised parton distributions and one based on the dipole approach.

The production of jets is studied in deep-inelastic ep scattering at large negative four momentum transfer squared 150<Q^2<15000 GeV^2 using HERA data taken in 1999-2007, corresponding to an integrated luminosity of 395 pb^-1. Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q^2, jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurements is alpha_s(M_Z) = 0.1168 +/-0.0007 (exp.) +0.0046/-0.0030 (th.) +/-0.0016(pdf).

We have measured the differential cross section $\frac{{d}^{2}\ensuremath{\sigma}}{d\ensuremath{\Omega}d{T}_{\ensuremath{\pi}}}$ and the polarization parameter $P$ for the production of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ in various target nuclei ($^{1}\mathrm{H}$, $^{2}\mathrm{H}$, Be, C, O, Al, Ni, Cu, Mo, and Pb) by protons with a kinetic energy of 585 MeV, for production angles ${\ensuremath{\theta}}_{\ensuremath{\pi}}=22.5\ifmmode^\circ\else\textdegree\fi{}, 45\ifmmode^\circ\else\textdegree\fi{}, 60\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, \mathrm{and} 135\ifmmode^\circ\else\textdegree\fi{}$, and for pion kinetic energies ${T}_{\ensuremath{\pi}}$ of 24, 35, 46, 88, 151, 192, and 254 MeV (all quantities in the laboratory system). Our data disagree strongly with recent data for 580-MeV protons. On the other hand, for pion energies up to 150 MeV, our cross sections differ little from those measured for a proton energy of 730 MeV. For nuclei with $A>20$, the total production cross sections $\ensuremath{\sigma}({\ensuremath{\pi}}^{+})$ and $\ensuremath{\sigma}({\ensuremath{\pi}}^{\ensuremath{-}})$ show the ${Z}^{\frac{1}{3}}$ and ${N}^{\frac{2}{3}}$ proportionality expected from theoretical arguments. There is evidence in our data of a shift of the ${\ensuremath{\pi}}^{+}$ energy distributions compared to the ${\ensuremath{\pi}}^{\ensuremath{-}}$ distributions due to the effects of the Coulomb field of the nuclear protons on the emitted pions.NUCLEAR REACTIONS $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, Be, C, O, Al, Ni, Cu, Mo, Pb $p$, ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${T}_{p}=585$ MeV; measured $\ensuremath{\sigma}({T}_{\ensuremath{\pi}}, {\ensuremath{\theta}}_{\ensuremath{\pi}})$ and asymmetry parameter $P({T}_{\ensuremath{\pi}}, {\ensuremath{\theta}}_{\ensuremath{\pi}})$.

Abstract Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy $$\sqrt{s}=319$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>319</mml:mn> </mml:mrow> </mml:math> GeV are measured. The data are collected with the H1 detector at HERA corresponding to an integrated luminosity of 136 pb $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> . Charged particle multiplicities are measured as a function of photon virtuality $$Q^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Q</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> , inelasticity y and pseudorapidity $$\eta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>η</mml:mi> </mml:math> in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of $$Q^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Q</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> and the Bjorken variable $$x_{\mathrm{bj}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>x</mml:mi> <mml:mi>bj</mml:mi> </mml:msub> </mml:math> are converted to the hadron entropy $$S_{\mathrm{hadron}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>S</mml:mi> <mml:mi>hadron</mml:mi> </mml:msub> </mml:math> , and predictions from a quantum entanglement model are tested.

The DELPHI Microvertex detector, which has been in operation since the start of the 1990 LEP run, consists of three layers of silicon microstrip detectors at average radii of 6.3, 9.0 and 11.0 cm. The 73728 readout strips, oriented along the beam, have a total active area of 0.42 m2. The strip pitch is 25 μm and every other strip is read out by low power charge amplifiers, giving a signal to noise ratio of 15:1 for minimum ionizing particles. On-line zero suppression results in an average data size of 4 kbyte for Z0 events. After a mechanical survey and an alignment with tracks, the impact parameter uncertainty as determined from hadronic Z0 decays is well described by (69pt)2 + 242 μm, with pt in GeV/c. For the 45 GeV/c tracks from Z0 → μ− decays we find an uncertainty of 21 μm for the impact parameter, which corresponds to a precision of 8 μm per point. The stability during the run is monitored using light spots and capacitive probes. An analysis of tracks through sector overlaps provides an additional check of the stability. The same analysis also results in a value of 6 μm for the intrinsic precision of the detector.

A silicon microstrip detector with capacitive coupling of the diode strips to the metallization and with individual polysilicon resistors to each diode has been developed. The detector was tested in a minimum ionizing particle beam showing a performance similar to conventional strip detectors and a spatial resolution of 3.5 μm. Capacitive coupling allows the decoupling of the leakage current from the input to the charge sensitive preamplifier especially in the case of LSI electronics.

The hybrid pixel detectors used in the high-energy physics experiments currently under construction use a vertical connection technique, the so-called bump bonding. As the pitch below 100μm, required in these applications, cannot be fulfilled with standard industrial processes (e.g. the IBM C4 process), an in-house bump bond process using reflowed indium bumps was developed at PSI as part of the R&D for the CMS-pixel detector. The bump deposition on the sensor is performed in two subsequent lift-off steps. As the first photolithographic step a thin under bump metalization (UBM) is sputtered onto bump pads. It is wettable by indium and defines the diameter of the bump. The indium is evaporated via a second photolithographic step with larger openings and is reflowed afterwards. The height of the balls is defined by the volume of the indium. On the readout chip only one photolithographic step is carried out to deposit the UBM and a thin indium layer for better adhesion. After mating both parts a second reflow is performed for self-alignment and obtaining high mechanical strength. For the placement of the chips a manual and an automatic machine were constructed. The former is very flexible in handling different chip and module geometries but has a limited throughput while the latter features a much higher grade of automatization and is therefore much more suited for producing hundreds of modules with a well-defined geometry. The reliability of this process was proven by the successful construction of the PILATUS detector. The construction of PILATUS 6M (60 modules) and the CMS pixel barrel (roughly 800 modules) has started in early 2006.

The production of jets is studied in deep-inelastic e + p scattering at low negative four momentum transfer squared 5<Q 2<100 GeV2 and at inelasticity 0.2<y<0.7 using data recorded by the H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb−1. Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q 2 and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction ξ. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling α s .

A measurement is presented of inelastic photo- and electroproduction of J/ψ mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J/ψ mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a k T factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.

Inclusive production of D* mesons in deep-inelastic ep scattering at HERA is studied in the range 5 < Q^2 <100 GeV^2 of the photon virtuality and 0.02 < y < 0.7 of the inelasticity of the scattering process. The observed phase space for the D* meson is p_T(D*) > 1.25 GeV and |eta(D*)| < 1.8. The data sample corresponds to an integrated luminosity of 348 pb^{-1} collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F_2^{ccbar} to the proton structure function F_2 is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers.

Characterization and performance measurements have been done on several EIGER detector systems, produced with chips coming from two different lots, both with a lab X-ray source and at the Swiss Light Source (SLS). Results on the detector calibration, electronic noise, threshold dispersion, minimum achievable energy threshold, maximum detectable incoming photon flux and maximum frame rate are presented. An EIGER module is constructed from a ∼4×8cm2 monolithic silicon sensor bump-bonded to 2 ×4 readout chips and contains 0.5 Mpixel. The first EIGER 500 K systems have been produced and images taken with these detectors are shown. Modules can be tiled together to form large area detectors; both a 9 Mpixel and a 16 Mpixel systems are at present under development for the coherent small angle X-ray scattering and protein crystallography beamlines of the SLS.

Abstract A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities $$5.5&lt;Q^2 &lt;80\,\mathrm {GeV}^2 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>5.5</mml:mn><mml:mo>&lt;</mml:mo><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo>&lt;</mml:mo><mml:mn>80</mml:mn><mml:mspace /><mml:msup><mml:mrow><mml:mi>GeV</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math> and inelasticities $$0.2&lt;y&lt;0.6$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>0.2</mml:mn><mml:mo>&lt;</mml:mo><mml:mi>y</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.6</mml:mn></mml:mrow></mml:math> is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of $$290\,\mathrm {pb}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>290</mml:mn><mml:mspace /><mml:msup><mml:mrow><mml:mi>pb</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> . Double-differential inclusive jet, dijet and trijet cross sections are measured simultaneously and are presented as a function of jet transverse momentum observables and as a function of $$Q^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> . Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective $$Q^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> -interval are also determined. Previous results of inclusive jet cross sections in the range $$150&lt;Q^2 &lt;15{,}000\,\mathrm {GeV}^2 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>150</mml:mn><mml:mo>&lt;</mml:mo><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo>&lt;</mml:mo><mml:mn>15</mml:mn><mml:mo>,</mml:mo><mml:mn>000</mml:mn><mml:mspace /><mml:msup><mml:mrow><mml:mi>GeV</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math> are extended to low transverse jet momenta $$5&lt;P_\mathrm{T}^\mathrm{jet} &lt;7\,\mathrm {GeV} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>5</mml:mn><mml:mo>&lt;</mml:mo><mml:msubsup><mml:mi>P</mml:mi><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mi>jet</mml:mi></mml:msubsup><mml:mo>&lt;</mml:mo><mml:mn>7</mml:mn><mml:mspace /><mml:mi>GeV</mml:mi></mml:mrow></mml:math> . The data are compared to predictions from perturbative QCD in next-to-leading order in the strong coupling, in approximate next-to-next-to-leading order and in full next-to-next-to-leading order. Using also the recently published H1 jet data at high values of $$Q^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> , the strong coupling constant $$\alpha _s(M_Z)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>α</mml:mi><mml:mi>s</mml:mi></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>M</mml:mi><mml:mi>Z</mml:mi></mml:msub><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> is determined in next-to-leading order.

A readout chip for silicon strip detectors with analog event pipeline has been fabricated (SACMOS 2 μm technology) and tested. The chip has been designed to operate at the HERA ep collider at a bunch crossing rate of 10.4 MHz. Each channel has a layout width of 44 μm and consists of a fast, low noise, low power preamplifier followed by a switched capacitor analog event pipeline. The preamplifier consists of a single CMOS push-pull gain cell and offers minimal power consumption. A novel feature of our chip is a self-reading architecture that allows the preamplifier to re-read its own pipeline buffers and thus permits a extensive parallel analog signal processing that is digitally controlled. The results from radiation damage tests with 60Co are given for doses up to 240 krad.

Abstract To optimally use the high flux delivered by current, third-generation synchrotron radiation sources like the Swiss Light Source at the Paul Scherrer Institute two detector systems are currently being developed. The Mythen detector system is a one-dimensional 15k channel microstrip detector for powder diffraction. It allows major improvement in time-resolved powder diffraction due to its massively parallel detection of X-rays and fast readout. The Pilatus detector is a 2k × 2k pixel detector for protein crystallography. Its advantages compared to current state-of-the-art CCDs are a much better signal-to-noise ratio, a point spread function of 1 pixel and a very short readout time of 6.7 ms. This allows data to be taken in fine φ -slicing mode which will improve the data quality.

The pixel detector is the innermost tracking device of the CMS experiment at the LHC. It is built from two independent subdevices, the pixel barrel and the end disks. The barrel consists of three concentric layers around the beam pipe with mean radii of 4.4, 7.3 and 10.2 cm. There are two end disks on each side of the interaction point at ±34.5 and ±46.5cm. This article gives an overview of the pixel barrel detector, its mechanical support structure, electronics components, services and its expected performance.

We investigate the four-photon final state produced in γγ colissions. In the π0π0 channel we observe f(1270) production with predominantly helicity 2 and measure a partial width Γγγ 2.9+0.6−0.4 ± keV (independent of assumptions on the helicity). We observe A2(1310) production in the π0η channel and find a partial width Γγγ = 0.77 ± 0.18 ± 0.27 KeV (assuming helicity 2). We give an upper limit for f ≈ ηη.

The CMS experiment at the (LHC) includes a hybrid silicon pixel detector for the reconstruction of charged tracks and of the interaction vertices. The barrel region consists of n-in-n sensors with 100×150μm2 cell size processed on diffusion oxygenated float zone silicon. A biasing grid is implemented and pixel isolation is achieved with the moderated p-spray technique. An extensive test program was carried out on the H2 beam line of the CERN-SPS. In this paper we describe the sensor layout, the beam test setup and the results obtained with both irradiated and non-irradiated prototype devices. Measurements of charge collection, hit detection efficiency, Lorentz angle and spatial resolution are presented.

The cross section for the diffractive deep-inelastic scattering process ep -> e X p is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data sample covers the range x_pom<0.1 in fractional proton longitudinal momentum loss, 0.1 < |t| < 0.7 GeV^2 in squared four-momentum transfer at the proton vertex and 4 < Q^2 < 700 GeV^2 in photon virtuality. The cross section is measured four-fold differentially in t, x_pom, Q^2 and beta=x/x_pom, where x is the Bjorken scaling variable. The t and x_pom dependences are interpreted in terms of an effective pomeron trajectory and a sub-leading exchange. The data are compared to perturbative QCD predictions at next-to-leading order based on diffractive parton distribution functions previously extracted from complementary measurements of inclusive diffractive deep-inelastic scattering. The ratio of the diffractive to the inclusive ep cross section is studied as a function of Q^2, beta and x_pom.

We are developing a new family of hybrid, single photon counting X-ray detectors for very high frame rate applications. A dedicated readout chip was designed, to be used as building block for detectors up to 9 Mpixel and about 550cm2 area. It has an area of 19.3×20.0mm2 and contains 256×256 pixels of 75×75μm2, resulting in an active region of 19.2×19.2mm2. Each pixel contains a 12 bit counter with double buffering for continuous image acquisition. Moreover, it allows a partial readout (4, 8 or 12 bits) with corresponding frame rates up to 24, 12 and 8 kHz. The chip is designed with Hardening By Design techniques [1], to obtain high radiation tolerance from a standard commercial 0.25μm CMOS technology. The chip was recently received from fabrication and it is at present under test.

A search for first generation scalar and vector leptoquarks produced in ep collisions is performed by the H1 experiment at HERA. The full H1 data sample is used in the analysis, corresponding to an integrated luminosity of 446 pb^-1. No evidence for the production of leptoquarks is observed in final states with a large transverse momentum electron or with large missing transverse momentum, and constraints on leptoquark models are derived. For leptoquark couplings of electromagnetic strength lambda=0.3, first generation leptoquarks with masses up to 800 GeV are excluded at 95% confidence level.

The cross section of the diffractive process e + p → e + Xp is measured at a centre-of-mass energy of 318 GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction with photon virtualities Q 2 < 2 GeV2 and in deep-inelastic scattering with 4 GeV2 < Q 2 < 80 GeV2. The results are compared to next- to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering.

The strong coupling constant αs is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of αs(mZ) at the Z-boson mass mZ are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be αs(mZ)=0.1157(20)exp(29)th . Complementary, αs(mZ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value αs(mZ)=0.1142(28)tot obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.

For the protein crystallography beamlime of the Swiss Light Source (SLS), which will be operational in summer 2001, the PILATUS detector (PIxeL ApparaTUs for the SLS) is currently being built. The goal of the PILATUS project is a hybrid pixel system with a size of 40×40 cm2 having 2000×2000 pixels. The detector will be operated in single photon counting mode for 12 keV X-rays. The prototype pixel read-out chip has a noise of 75e− with sensor, a low threshold dispersion and a maximum count rate of 1 MHz/pixel. Due to the expected radiation dose in operation at the beamline, the chip is designed in radiation hard DMILL technology.

A model--independent search for deviations from the Standard Model prediction is performed using the full $e^\pm p$ data sample collected by the H1 experiment at HERA. All event topologies involving isolated electrons, photons, muons, neutrinos and jets with transverse momenta above 20 GeV are investigated in a single analysis. Events are assigned to exclusive classes according to their final state. A dedicated algorithm is used to search for deviations from the Standard Model in the distributions of the scalar sum of transverse momenta or the invariant mass of final state particles and to quantify their significance. Variables related to angular distributions and energy sharing between final state particles are also introduced to study the final state topologies. No significant deviation from the Standard Model expectation is observed in the phase space covered by this analysis.

A search for single top quark production is performed in the full e±p data sample collected by the H1 experiment at HERA, corresponding to an integrated luminosity of 474 pb−1. Decays of top quarks into a b quark and a W boson with subsequent leptonic or hadronic decay of the W are investigated. A multivariate analysis is performed to discriminate top quark production from Standard Model background processes. An upper limit on the top quark production cross section via flavour changing neutral current processes σ(ep→etX)<0.25pb is established at 95% CL. Limits on the anomalous coupling κtuγ are derived.

Measurements are presented of single and double-differential dijet cross sections in diffractive photoproduction based on a data sample with an integrated luminosity of 47 pb^-1. The events are of the type ep -> eXY, where the hadronic system X contains at least two jets and is separated by a large rapidity gap from the system Y, which consists of a leading proton or low-mass proton excitation. The dijet cross sections are compared with QCD calculations at next-to-leading order and with a Monte Carlo model based on leading order matrix elements with parton showers. The measured cross sections are smaller than those obtained from the next-to-leading order calculations by a factor of about 0.6. This suppression factor has no significant dependence on the fraction x_gamma of the photon four-momentum entering the hard subprocess. Ratios of the diffractive to the inclusive dijet cross sections are measured for the first time and are compared with Monte Carlo models.

The inclusive production of D∗±(2010) mesons in deep-inelastic e±p scattering is measured in the kinematic region of photon virtuality 100<Q2<1000GeV2 and inelasticity 0.02<y<0.7. Single and double differential cross sections for inclusive D∗ meson production are measured in the visible range defined by |η(D∗)|<1.5 and pT(D∗)>1.5GeV. The data were collected by the H1 experiment during the period from 2004 to 2007 and correspond to an integrated luminosity of 351pb−1. The charm contribution, F2cc¯, to the proton structure function F2 is determined. The measurements are compared with QCD predictions.

The diffractive process ep \rightarrow eXY, where Y denotes a proton or its low mass excitation with MY < 1.6 GeV, is studied with the H1 experiment at HERA. The analysis is restricted to the phase space region of the photon virtuality 3 \leq Q2 \leq 1600 GeV2, the square of the four-momentum transfer at the proton vertex |t| < 1.0 GeV2 and the longitudinal momentum fraction of the incident proton carried by the colourless exchange xIP < 0.05. Triple differential cross sections are measured as a function of xIP, Q2 and beta = x/xIP where x is the Bjorken scaling variable. These measurements are made after selecting diffractive events by demanding a large empty rapidity interval separating the final state hadronic systems X and Y . High statistics measurements covering the data taking periods 1999-2000 and 2004-2007 are combined with previously published results in order to provide a single set of diffractive cross sections from the H1 experiment using the large rapidity gap selection method. The combined data represent a factor between three and thirty increase in statistics with respect to the previously published results. The measurements are compared with predictions from NLO QCD calculations based on diffractive parton densities and from a dipole model. The proton vertex factorisation hypothesis is tested.

The cross section of diffractive deep-inelastic scattering ep \rightarrow eXp is measured, where the system X contains at least two jets and the leading final state proton is detected in the H1 Forward Proton Spectrometer. The measurement is performed for fractional proton longitudinal momentum loss xIP < 0.1 and covers the range 0.1 < |t| < 0.7 GeV2 in squared four-momentum transfer at the proton vertex and 4 < Q2 < 110 GeV2 in photon virtuality. The differential cross sections extrapolated to |t| < 1 GeV2 are in agreement with next-toleading order QCD predictions based on diffractive parton distribution functions extracted from measurements of inclusive and dijet cross sections in diffractive deep-inelastic scattering. The data are also compared with leading order Monte Carlo models.

We have measured the momentum of muons from the decay π+ → μ+νμ at rest to be pμ+ = 29.79207±0.00012 MeV/c. This result leads to a laboratory upper limit of 0.16 MeV (CL = 0.9) for the muon-neutrino mass. The cosmological upper limit of the neutrino mass, the muon mass and the new pμ+-value yield the pion mass mπ+ = 139.57031 ± 0.00016 MeV. The mean kinetic energy of the pions stopped in the isotropic-graphite production target immediately before their decay is found to be Tπ+ = 0.415 ± 0.027 eV.

We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, π+→π0e+νe, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering ∼3πsr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure, which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two 3-month beam periods in 1999/2000 with π+ stopping rates between 1.3·103π+/s and 1.3·106π+/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5–150MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds.

A 256-strip silicon detector with 25 μm strip pitch, connected to two 128-channel NMOS VLSI chips (Microplex), has been tested using straight-through tracks from a ruthenium beta source. The readout channels have a pitch of 47.5 μm. A single multiplexed output provides voltages proportional to the integrated charge from each strip. The most probable signal height from the beta traversals is approximately 14 times the rms noise in any single channel.

The process of charm quark fragmentation is studied using D * ± meson production in deep-inelastic scattering as measured by the H1 detector at HERA. The parameters of fragmentation functions are extracted for QCD models based on leading order matrix elements and DGLAP or CCFM evolution of partons together with string fragmentation and particle decays. Additionally, they are determined for a next-to-leading order QCD calculation in the fixed flavour number scheme using the independent fragmentation of charm quarks to D * ± mesons. Two different regions of phase space are investigated defined by the presence or absence of a jet containing the D * ± meson in the event. The fragmentation parameters extracted for the two phase space regions are found to be different.

Abstract The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive deep inelastic ep scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of $$\alpha _s(M_Z^2)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:msubsup> <mml:mi>M</mml:mi> <mml:mi>Z</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> and the PDFs, was performed with the result $$\alpha _s(M_Z^2)= 0.1156 \pm 0.0011~\mathrm{(exp)}~ ^{+0.0001}_{-0.0002}~ \mathrm{(model}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:msubsup> <mml:mi>M</mml:mi> <mml:mi>Z</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>0.1156</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.0011</mml:mn> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>exp</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> <mml:msubsup> <mml:mspace /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>0.0002</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.0001</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>model</mml:mi> </mml:mrow> </mml:mrow> </mml:math> $$\mathrm{+ parameterisation)}~ \pm 0.0029~\mathrm{(scale)}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mi>parameterisation</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> <mml:mspace /> <mml:mo>±</mml:mo> <mml:mn>0.0029</mml:mn> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>scale</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> . The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of $$\alpha _s(M_Z^2)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:msubsup> <mml:mi>M</mml:mi> <mml:mi>Z</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> , $$\alpha _s(M_Z^2)=0.1155$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:msubsup> <mml:mi>M</mml:mi> <mml:mi>Z</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>0.1155</mml:mn> </mml:mrow> </mml:math> and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input.

The envisaged upgrade of the Large Hadron Collider (LHC) at CERN towards the Super-LHC (SLHC) with a 10 times increased luminosity of 1035 cm−2 s−1 will present severe challenges for the tracking detectors of the SLHC experiments. Unprecedented high radiation levels and track densities and a reduced bunch crossing time in the order of 10 ns as well as the need for cost effective detectors have called for an intensive R&D program. The CERN RD50 collaboration "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" is working on the development of semiconductor sensors matching the requirements of the SLHC. Sensors based on defect engineered silicon like Czochralski, epitaxial and oxygen enriched silicon have been developed. With 3D, Semi-3D and thin detectors new detector concepts have been evaluated and a study on the use of standard and oxygen enriched p-type silicon detectors revealed a promising approach for radiation tolerant cost effective devices. These and other most recent advancements of the RD50 collaboration are presented.

The readout chip for the CMS pixel detector must handle an enormous flux of data, while keeping the data loss at a minimum. Full size prototype readout chips bump-bonded to sensors have been tested in a pion beam simulating an LHC-like environment, and the data loss as a function of particle fluence has been measured.

The PILATUS detector (pixel apparatus for the SLS) is a large all silicon quantum-limited area X-ray detector for protein crystallography. A three-module array with 1120×157 pixels covering an active area of 24.3×3.6 cm2 is in operation. Its main features are an excellent point-spread function, a very high dynamic range and a readout time of <7 ms. X-rays with energy above 6 keV can be detected in single photon counting mode. To demonstrate the potential of the detector, fine φ-sliced protein crystal data were collected in continuous sample rotation mode at beamline X06SA of the SLS.

The proposed luminosity upgrade of the Large Hadron Collider (S-LHC) at CERN will demand the innermost layers of the vertex detectors to sustain fluences of about 1016 hadrons/cm2. Due to the high multiplicity of tracks, the required spatial resolution and the extremely harsh radiation field new detector concepts and semiconductor materials have to be explored for a possible solution of this challenge. The CERN RD50 collaboration “Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders” has started in 2002 an R&D program for the development of detector technologies that will fulfill the requirements of the S-LHC. Different strategies are followed by RD50 to improve the radiation tolerance. These include the development of defect engineered silicon like Czochralski, epitaxial and oxygen-enriched silicon and of other semiconductor materials like SiC and GaN as well as extensive studies of the microscopic defects responsible for the degradation of irradiated sensors. Further, with 3D, Semi-3D and thin devices new detector concepts have been evaluated. These and other recent advancements of the RD50 collaboration are presented and discussed.

Using 2674 nb−1 of data taken at √s from 5.00 to 7.25 GeV with a trigger sensitive to decays of lower-mass particles produced in two-photon collisions, we have observed 56±12 events consistent with the reaction e+e−→e+e−η, η→γγ. Background has been subtracted using separated-beam data. We obtain Γγγ(η)=0.56±0.16 keV and the pseudoscalar-nonet mixing angle θP=−17.6°±3.6°.Received 13 September 1983DOI:https://doi.org/10.1103/PhysRevD.28.2896©1983 American Physical Society

In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages.

Measurements of cross sections for events with charm and beauty jets in deep inelastic scattering at HERA are presented. Events with jets of transverse energy $E_{T}^{\mathrm{jet}}>6$ GeV and pseudorapidity −1.0<η jet<1.5 in the laboratory frame are selected in the kinematic region of photon virtuality Q 2>6 GeV2 and inelasticity variable 0.07<y<0.625. Measurements are also made requiring a jet in the Breit frame with $E_{T}^{*{\mathrm{jet}}}>6$ GeV. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb−1. The numbers of charm and beauty jets are determined using variables reconstructed using the H1 vertex detector with which the impact parameters of the tracks to the primary vertex and the position of secondary vertices are measured. The measurements are compared with QCD predictions and with previous measurements where heavy flavours are identified using muons.

A search for physics beyond the Standard Model in neutral current deep inelastic scattering at high negative four-momentum transfer squared Q2 is performed in e±p collisions at HERA. The differential cross section dσ/dQ2, measured using the full H1 data sample corresponding to an integrated luminosity of 446pb−1, is compared to the Standard Model prediction. No significant deviation is observed. Limits on various models predicting new phenomena at high Q2 are derived. For general four-fermion eeqq contact interaction models, lower limits on the compositeness scale Λ are set in the range 3.6 TeV to 7.2 TeV. Leptoquarks with masses MLQ and couplings λ are constrained to MLQ/λ>0.41–1.86TeV and limits on squarks in R-parity violating supersymmetric models are derived. A lower limit on the gravitational scale in 4+n dimensions of MS>0.9TeV is established for low-scale quantum gravity effects in models with large extra dimensions. For the light quark radius an upper bound of Rq<0.65⋅10−18m is determined.

A measurement of the integrated luminosity at the ep collider HERA is presented, exploiting the elastic QED Compton process ep \rightarrow ep. The electron and the photon are detected in the backward calorimeter of the H1 experiment. The integrated luminosity of the data recorded in 2003 to 2007 is determined with a precision of 2.3%. The measurement is found to be compatible with the corresponding result obtained using the Bethe-Heitler process.

A measurement is presented of single- and double-differential dijet cross sections in diffractive deep-inelastic ep scattering at HERA using data collected by the H1 experiment corresponding to an integrated luminosity of 290 pb−1. The investigated phase space is spanned by the photon virtuality in the range of 4 < Q 2 < 100 GeV2 and by the fractional proton longitudinal momentum loss x ℙ < 0.03. The resulting cross sections are compared with next-to-leading order QCD predictions based on diffractive parton distribution functions and the value of the strong coupling constant is extracted.

A first measurement is presented of exclusive photoproduction of $$\rho ^0$$ mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years 2006 and 2007 at a centre-of-mass energy of $$\sqrt{s}=319$$ GeV and correspond to an integrated luminosity of 1.16 pb $$^{-1}$$ . The $$\rho ^0$$ mesons with transverse momenta $$p_T<1$$ GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum, $$x_L>0.35$$ , are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality $$Q^2 < 2$$ GeV $$^2$$ , the total energy of the photon–proton system $$20 < W_{\gamma p}< 100$$ GeV and the polar angle of the leading neutron $$\theta _n < 0.75$$ mrad. The cross section of the reaction $$\gamma p \rightarrow \rho ^0 n \pi ^+$$ is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a $$\rho ^0$$ meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering, $$\sigma ^\mathrm{el}(\gamma \pi ^+ \rightarrow \rho ^0\pi ^+)$$ , is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction $$\gamma p \rightarrow \rho ^0 n \pi ^+$$ .

The H1 Collaboration reports the first measurement of the 1-jettiness event shape observable $\tau_1^b$ in neutral-current deep-inelastic electron-proton scattering (DIS). The observable $\tau_1^b$ is equivalent to a thrust observable defined in the Breit frame. The data sample was collected at the HERA $ep$ collider in the years 2003-2007 with center-of-mass energy of $\sqrt{s}=319\,\text{GeV}$, corresponding to an integrated luminosity of $351.1\,\text{pb}^{-1}$. Triple differential cross sections are provided as a function of $\tau_1^b$, event virtuality $Q^2$, and inelasticity $y$, in the kinematic region $Q^2>150\,\text{GeV}^{2}$. Single differential cross section are provided as a function of $\tau_1^b$ in a limited kinematic range. Double differential cross sections are measured, in contrast, integrated over $\tau_1^b$ and represent the inclusive neutral-current DIS cross section measured as a function of $Q^2$ and $y$. The data are compared to a variety of predictions and include classical and modern Monte Carlo event generators, predictions in fixed-order perturbative QCD where calculations up to $\mathcal{O}(\alpha_s^3)$ are available for $\tau_1^b$ or inclusive DIS, and resummed predictions at next-to-leading logarithmic accuracy matched to fixed order predictions at $\mathcal{O}(\alpha_s^2)$. These comparisons reveal sensitivity of the 1-jettiness observable to QCD parton shower and resummation effects, as well as the modeling of hadronization and fragmentation. Within their range of validity, the fixed-order predictions provide a good description of the data. Monte Carlo event generators are predictive over the full measured range and hence their underlying models and parameters can be constrained by comparing to the presented data.

The H1 Collaboration at HERA reports the first measurement of groomed event shape observables in deep inelastic electron-proton scattering (DIS) at $\sqrt{s}=319$ GeV, using data recorded between the years 2003 and 2007 with an integrated luminosity of $351$ pb$^{-1}$. Event shapes provide incisive probes of perturbative and non-perturbative QCD. Grooming techniques have been used for jet measurements in hadronic collisions; this paper presents the first application of grooming to DIS data. The analysis is carried out in the Breit frame, utilizing the novel Centauro jet clustering algorithm that is designed for DIS event topologies. Events are required to have squared momentum-transfer $Q^2 > 150$ GeV$^2$ and inelasticity $ 0.2 < y < 0.7$. We report measurements of the production cross section of groomed event 1-jettiness and groomed invariant mass for several choices of grooming parameter. Monte Carlo model calculations and analytic calculations based on Soft Collinear Effective Theory are compared to the measurements.

The CMS experiment will operate at the Large Hadron Collider (LHC). A hybrid pixel detector located close to the interaction region of the colliding beams will provide high resolution tracking and vertex identification which will be crucial for b quark identification. Because of the radiation environment of the LHC, the performance of the sensors must be carefully evaluated up to a fluence of 6×1014 neq cm−2. We expect that the sensors will be operated partially depleted during their operation at the LHC and we have implemented an n+ on n sensor design. We have irradiated prototype sensors to a dose of 1×1015 neq cm−2. We present the results of our testing before and after irradiation.

Results are presented from a test in the CERN SPS North Area of a prototype of the DELPHI microvertex detector. Full-sized modules built up from prototype ac-coupled detectors and VLSI readout electronics were used. The spatial resolution of the detectors equipped with prototype VLSI chips was measured to be 6.5 μm. The system aspects, including the readout, were found to work well. Extrapolating to the final components we expect to achieve a measurement precision of 5 μm with the DELPHI microvertex detector.

A silicon microstrip detector has been developed with 50- mu m-pitch strips on both the p- and n-side, using the principle of capacitive coupling between p/sup +/ diode strips (respectively, n/sup +/ strips) and the metallization strips which connect to the front-end preamplifiers. The detector is biased on both sides via polysilicon resistors connecting each p/sup +/ or n/sup +/ line to a common bias bus. To allow ohmic separation at the n-side, the accumulation layer of electrons has to be disrupted between the n/sup +/ strips. This has been achieved in three different ways: by separate polysilicon lines on thick oxide between two adjacent n/sup +/ lines to break the conducting accumulation layer by externally induced field depletion or by using the metal lines of the n/sup +/ strips on thick oxide or on thin oxide. Results on 20*20-mm/sup 2/ test devices are presented. A preliminary analysis of the spatial resolution gives sigma =16 mu m on both sides. These results demonstrate that double-sided readout Si strip detectors can be used for experiments where spatial resolution in the 10 mu m range is needed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The CMS pixel detector is a complex device consisting of about 1400 modules. The control and the readout systems of this detector will be described. The detector modules have to be correctly set up before data taking can start. This means downloading of a very large number of parameters to the front-ends. During data taking the information from the detector has to be read out and various detector parameters have to be monitored. The readout system has to be very efficient to minimize dead time. A set of fast control signals will be used to reset and re-synchronize the detector.

The production of prompt photons is measured in the photoproduction regime of electron–proton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340 pb−1 collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range $6<\ensuremath{E_{T}^{\gamma}}<15$ GeV and −1.0<η γ <2.4, respectively. Cross sections for events with an additional jet are measured as a function of the transverse energy and pseudorapidity of the jet, and as a function of the fractional momenta x γ and x p carried by the partons entering the hard scattering process. The correlation between the photon and the jet is also studied. The results are compared with QCD predictions based on the collinear and on the k T factorization approaches.

Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic $$ep$$ scattering at HERA are presented as a function of the Feynman variable $$x_F$$ and of the centre-of-mass energy of the virtual photon-proton system $$W$$ . The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of $$131~\text {pb}^{-1}$$ . The measurement is restricted to photons and neutrons in the pseudorapidity range $$\eta >7.9$$ and covers the range of negative four momentum transfer squared at the positron vertex $$6<Q^2<100$$ GeV $$^2$$ , of inelasticity $$0.05<y<0.6$$ and of $$70<W<245~$$ GeV. To test the Feynman scaling hypothesis the $$W$$ dependence of the $$x_F$$ dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.

Abstract Exclusive photoproduction of $${{\rho ^0}} (770)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>ρ</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>770</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction $$\gamma p \rightarrow \pi ^{+}\pi ^{-}Y$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>γ</mml:mi> <mml:mi>p</mml:mi> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mi>Y</mml:mi> </mml:mrow> </mml:math> . Reactions where the proton stays intact ( $${{{m_Y}} {=}m_p}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>Y</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>p</mml:mi> </mml:msub> </mml:mrow> </mml:math> ) are statistically separated from those where the proton dissociates to a low-mass hadronic system ( $$m_p{&lt;}{{m_Y}} {&lt;}10~{{\text {GeV}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>p</mml:mi> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>Y</mml:mi> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:mn>10</mml:mn> <mml:mspace /> <mml:mtext>GeV</mml:mtext> </mml:mrow> </mml:math> ). The double-differential cross sections are measured as a function of the invariant mass $$m_{\pi \pi }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:mrow> <mml:mi>π</mml:mi> <mml:mi>π</mml:mi> </mml:mrow> </mml:msub> </mml:math> of the decay pions and the squared 4-momentum transfer t at the proton vertex. The measurements are presented in various bins of the photon–proton collision energy $${{W_{\gamma p}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>W</mml:mi> <mml:mrow> <mml:mi>γ</mml:mi> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> </mml:math> . The phase space restrictions are $$0.5\le m_{\pi \pi } \le 2.2~{{\text {GeV}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>0.5</mml:mn> <mml:mo>≤</mml:mo> <mml:msub> <mml:mi>m</mml:mi> <mml:mrow> <mml:mi>π</mml:mi> <mml:mi>π</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≤</mml:mo> <mml:mn>2.2</mml:mn> <mml:mspace /> <mml:mtext>GeV</mml:mtext> </mml:mrow> </mml:math> , $$\vert t\vert \le 1.5~{{\text {GeV}^2}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>|</mml:mo> <mml:mi>t</mml:mi> <mml:mo>|</mml:mo> </mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>1.5</mml:mn> <mml:mspace /> <mml:msup> <mml:mtext>GeV</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> , and $$20 \le W_{\gamma p} \le 80~{{\text {GeV}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>20</mml:mn> <mml:mo>≤</mml:mo> <mml:msub> <mml:mi>W</mml:mi> <mml:mrow> <mml:mi>γ</mml:mi> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≤</mml:mo> <mml:mn>80</mml:mn> <mml:mspace /> <mml:mtext>GeV</mml:mtext> </mml:mrow> </mml:math> . Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the $${m_{\pi \pi }}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:mrow> <mml:mi>π</mml:mi> <mml:mi>π</mml:mi> </mml:mrow> </mml:msub> </mml:math> dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the $${{\rho ^0}} (770)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>ρ</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>770</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> meson mass and width at $$m_\rho = 770.8{}^{+2.6}_{-2.7}~({\text {tot.}})~{{\text {MeV}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>ρ</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>770.8</mml:mn> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>2.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.6</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>tot.</mml:mtext> <mml:mo>)</mml:mo> </mml:mrow> <mml:mspace /> <mml:mtext>MeV</mml:mtext> </mml:mrow> </mml:math> and $$\Gamma _\rho = 151.3 {}^{+2.7}_{-3.6}~({\text {tot.}})~{{\text {MeV}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Γ</mml:mi> <mml:mi>ρ</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>151.3</mml:mn> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>3.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.7</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>tot.</mml:mtext> <mml:mo>)</mml:mo> </mml:mrow> <mml:mspace /> <mml:mtext>MeV</mml:mtext> </mml:mrow> </mml:math> , respectively. The model is used to extract the $${{\rho ^0}} (770)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>ρ</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>770</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> contribution to the $$\pi ^{+}\pi ^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> cross sections and measure it as a function of t and $${W_{\gamma p}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>W</mml:mi> <mml:mrow> <mml:mi>γ</mml:mi> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> </mml:math> . In a Regge asymptotic limit in which one Regge trajectory $$\alpha (t)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>α</mml:mi> <mml:mo>(</mml:mo> <mml:mi>t</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> dominates, the intercept $$\alpha (t{=}0) = 1.0654\ {}^{+0.0098}_{-0.0067}~({\text {tot.}})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>α</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>t</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>1.0654</mml:mn> <mml:mspace /> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>0.0067</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.0098</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>tot.</mml:mtext> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> and the slope $$\alpha ^\prime (t{=}0) = 0.233 {}^{+0.067 }_{-0.074 }~({\text {tot.}}) ~{{\text {GeV}^{-2}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>α</mml:mi> <mml:mo>′</mml:mo> </mml:msup> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>t</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>0.233</mml:mn> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>0.074</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.067</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace /> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>tot.</mml:mtext> <mml:mo>)</mml:mo> </mml:mrow> <mml:mspace /> <mml:msup> <mml:mtext>GeV</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> of the t dependence are extracted for the case $$m_Y{=}m_p$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>Y</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>p</mml:mi> </mml:msub> </mml:mrow> </mml:math> .

At the Paul Scherrer Institute a new synchrotron light source is currently under construction, the Swiss Light Source (SLS), which will be operational in summer 2001. Among the first beamlines is a high brightness, micro-focusing protein crystallography beamline. It will be equipped with a pixel detector, which has several features of interest for the next generation of protein crystallography detectors. The point spread function and the effect of charge sharing was measured with a prototype detector in a test experiment at the European Synchrotron Radiation Facility in Grenoble. The concepts of the SLS pixel detector is presented as well as test results from radiation hard prototype chips.

A search for excited electrons is performed using the full $e^{\pm}p$ data sample collected by the H1 experiment at HERA, corresponding to a total luminosity of 475 pb$^{-1}$. The electroweak decays of excited electrons ${e}^{*}\to{e}{\gamma}$, ${e}^{*}\to{e}Z$ and ${e}^{*}{\to}\nu W$ with subsequent hadronic or leptonic decays of the $W$ and $Z$ bosons are considered. No evidence for excited electron production is found. Mass dependent exclusion limits on $e^*$ production cross sections and on the ratio $f/{\Lambda}$ of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited electron searches. The $e^*$ production via contact interactions is also addressed for the first time in $ep$ collisions.

Processes leading to a final state with at least two high transverse momentum leptons (electrons or muons) are studied using the full e±p data sample collected by the H1 experiment at HERA. The data correspond to an integrated luminosity of 463 pb−1. Di-lepton and tri-lepton event classes are investigated. Cross sections of the production of e+e− and μ+μ− pairs are derived in a restricted phase space dominated by photon–photon collisions. In general, good agreement is found with Standard Model predictions. Events are observed with a total scalar sum of lepton transverse momenta above 100GeV where the Standard Model expectation is low. In this region, combining di-lepton and tri-lepton classes, five events are observed in e+p collisions, compared to a Standard Model expectation of 0.96±0.12, while no such event is observed in e−p data for 0.64±0.09 expected.

Events with high energy isolated electrons, muons or tau leptons and missing transverse momentum are studied using the full e^\pm p data sample collected by the H1 experiment at HERA, corresponding to an integrated luminosity of 474 pb^{-1}. Within the Standard Model, events with isolated leptons and missing transverse momentum mainly originate from the production of single W bosons. The total single W boson production cross section is measured as 1.14 \pm 0.25 (stat.) \pm 0.14 (sys.) pb, in agreement with the Standard Model expectation. The data are also used to establish limits on the WW\gamma gauge couplings and for a measurement of the W boson polarisation.

The cross section for $ep \rightarrow e\, b\bar{b} X$ in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel $b\bar{b} \rightarrow ee X'$ is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q 2≤1 GeV2, the inelasticity 0.05≤y≤0.65 and the pseudorapidity of the b-quarks $|\eta(b)|, |\eta(\bar{b})|\leq2$ . The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks 〈P T (b)〉 down to the threshold. The results are compared to next-to-leading-order QCD predictions.

It is proposed to combine the technology of fully depleted silicon microstrip detectors fabricated on n doped high resistivity silicon with the concept of the bipolar transistor. This is done by adding a n++ doped region inside the normal p+ implanted region of the reverse biased p+ n diode. Teh resulting structure has amplifying properties and is referred to as bipolar pixel transistor. The simplest readout scheme of a bipolar pixel array by an aluminium strip bus leads to the bipolar microstrip detector. The bipolar pixel structure is expected to give a better signal-to-noise performance for the detection of minimum ionizing charged particle tracks than the normal silicon diode strip detector and therefore should allow in future the fabrication of thinner silicon detectors for precision tracking.

The decay Jψ→γf(1270), f(1270)→π0π0 has been studied. The γf decay branching ratio is measured to be (1.48±0.25±0.30)×10−3. A fit to the f production and decay angular distributions yields the values A1A0=0.88±0.13 and A2A0=0.04±0.19, where Aλ are the f helicity amplitudes. These results disagree with the values predicted from a QCD two-gluon-exchange model.Received 14 December 1981DOI:https://doi.org/10.1103/PhysRevD.25.3065©1982 American Physical Society

A search for excited neutrinos is performed using the full $e^{-}p$ data sample collected by the H1 experiment at HERA at a centre-of-mass energy of 319 GeV, corresponding to a total luminosity of 184 pb$^{-1}$.The electroweak decays of excited neutrinos ${\nu}^{*}{\to}{\nu}{\gamma}$, ${\nu}^{*}{\to}{\nu}Z$ and ${\nu}^{*}{\to}eW$ with subsequent hadronic or leptonic decays of the $W$ and $Z$ bosons are considered. No evidence for excited neutrino production is found. Mass dependent exclusion limits on $\nu^*$ production cross sections and on the ratio of the coupling to the compositeness scale $f/{\Lambda}$ are derived within gauge mediated models. A limit on $f/{\Lambda}$, independent of the relative couplings to the SU(2) and U(1) gauge bosons, is also determined. These limits extend the excluded region to higher masses than has been possible in previous excited neutrino searches.

A search for excited quarks is performed using the full ep data sample collected by the H1 experiment at HERA, corresponding to a total integrated luminosity of 475 pb^-1. The electroweak decays of excited quarks q* -> q gamma, q* -> q Z and q* -> q W with subsequent hadronic or leptonic decays of the W and Z bosons are considered. No evidence for first generation excited quark production is found. Mass dependent exclusion limits on q* production cross sections and on the ratio f/Lambda of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited quark searches.

A search for second and third generation scalar and vector leptoquarks produced in ep collisions via the lepton flavour violating processes ep→μX and ep→τX is performed by the H1 experiment at HERA. The full data sample taken at a centre-of-mass energy s=319GeV is used for the analysis, corresponding to an integrated luminosity of 245 pb−1 of e+p and 166 pb−1 of e−p collision data. No evidence for the production of such leptoquarks is observed in the H1 data. Leptoquarks produced in e±p collisions with a coupling strength of λ=0.3 and decaying with the same coupling strength to a muon–quark pair or a tau–quark pair are excluded at 95% confidence level up to leptoquark masses of 712 GeV and 479 GeV, respectively.

The CMS experiment which is currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) will contain a pixel detector which provides in its final configuration three space points per track close to the interaction point of the colliding beams. Because of the harsh radiation environment of the LHC, the technical realization of the pixel detector is extremely challenging. The readout chip as the most damageable part of the system is believed to survive a particle fluence of 6×1014neq/cm2 (All fluences are normalized to 1MeV neutrons and therefore all components of the hybrid pixel detector have to perform well up to at least this fluence. As this requires a partially depleted operation of the silicon sensors after irradiation-induced type inversion of the substrate, an “n in n” concept has been chosen. In order to perform IV-tests on wafer level and to hold accidentally unconnected pixels close to ground potential, a resistive path between the pixels has been implemented by the openings in the p-stop implants surrounding every pixel cell. A prototype of such sensors has been produced by two different companies and especially the properties of these resistors have extensively been tested before and after irradiation.

First measurements are presented of the diffractive cross section σ ep→eXY at centre-of-mass energies $\sqrt{s}$ of 225 and $252\mathrm {\;GeV}$ , together with a precise new measurement at $\sqrt{s}$ of $319\mathrm {\;GeV}$ , using data taken with the H1 detector in the years 2006 and 2007. Together with previous H1 data at $\sqrt{s}$ of $301\mathrm {\;GeV}$ , the measurements are used to extract the diffractive longitudinal structure function $F_{L}^{D}$ in the range of photon virtualities $4.0 \leq Q^{2} \leq 44.0\mathrm {\;GeV}^{2}$ and fractional proton longitudinal momentum loss 5×10−4≤x ℙ≤3×10−3. The measured $F_{L}^{D}$ is compared with leading twist predictions based on diffractive parton densities extracted in NLO QCD fits to previous measurements of diffractive Deep-Inelastic Scattering and with a model which additionally includes a higher twist contribution derived from a colour dipole approach. The ratio of the diffractive cross section induced by longitudinally polarised photons to that for transversely polarised photons is extracted and compared with the analogous quantity for inclusive Deep-Inelastic Scattering.

Deep-inelastic positron-proton scattering events at low photon virtuality, Q 2, with a forward jet, produced at small angles with respect to the proton beam, are measured with the H1 detector at HERA. A subsample of events with an additional jet in the central region is also studied. For both samples, differential cross sections and normalised distributions are measured as a function of the azimuthal angle difference, Δϕ, between the forward jet and the scattered positron in bins of the rapidity distance, Y, between them. The data are compared to predictions of Monte Carlo generators based on different evolution approaches as well as to next-to-leading order calculations in order to test the sensitivity to QCD evolution mechanisms.

The inclusive photoproduction of D\ast mesons and of D\ast-tagged dijets is investigated with the H1 detector at the ep collider HERA. The kinematic region covers small photon virtualities Q2 < 2 GeV2 and photon-proton centre-of-mass energies of 100 < Wgp < 285 GeV. Inclusive D\ast meson differential cross sections are measured for central rapidities |eta(D\ast)| < 1.5 and transverse momenta pT (D\ast) > 1.8 GeV. The heavy quark production process is further investigated in events with at least two jets with transverse momentum pT (jet) > 3.5 GeV each, one containing the D\ast meson. Differential cross sections for D\ast-tagged dijet production and for correlations between the jets are measured in the range |eta(D\ast)| < 1.5 and pT (D\ast) > 2.1 GeV. The results are compared with predictions from Monte Carlo simulations and next-to-leading order perturbative QCD calculations.

The development and first results are described of a silicon strip detector telescope for the HERA experiment H1 designed to measure the polar angle of deep inelastic scattered electrons at small Bjorken x and low momentum transfers Q2.

2. Excellent point spread function of one pixel. 3. High quantum efficiency. At 8 keV the absorption of a 0.3 mm thick Si-Sensor is 100%, at 12 keV 75% of the incoming radiation. This exceeds the quantum-efficiency of direct-coupled CCDs.

Charged particle production in deep-inelastic ep scattering is measured with the H1 detector at HERA. The kinematic range of the analysis covers low photon virtualities, 5<Q 2<100 GeV2, and small values of Bjorken-x, 10−4<x<10−2. The analysis is performed in the hadronic centre-of-mass system. The charged particle densities are measured as a function of pseudorapidity (η ∗) and transverse momentum ( $p_{T}^{*}$ ) in the range 0<η ∗<5 and $0<p_{T}^{*} < 10\mbox{~GeV}$ in bins of x and Q 2. The data are compared to predictions from different Monte Carlo generators implementing various options for hadronisation and parton evolutions.

The production of photons at very small angles with respect to the proton beam direction is studied in deep-inelastic positron-proton scattering at HERA. The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of $126 \mathrm{pb}^{-1}$. The analysis covers the range of negative four momentum transfer squared at the positron vertex $6<Q^2<100$ GeV$^2$ and inelasticity $0.05<y<0.6$. Cross sections are measured for the most energetic photon with pseudorapidity $\eta>7.9$ as a function of its transverse momentum $p_T^{lead}$ and longitudinal momentum fraction of the incoming proton $x_L^{lead}$. In addition, the cross sections are studied as a function of the sum of the longitudinal momentum fraction $x_L^{sum}$ of all photons in the pseudorapidity range $\eta>7.9$. The cross sections are normalised to the inclusive deep-inelastic scattering cross section and compared to the predictions of models of deep-inelastic scattering and models of the hadronic interactions of high energy cosmic rays.