I. Golutvin

We present results on a high statistics study of the proton structure functions F2(x, Q2) and R=σL/σT measured in deep inelastic scattering of muons on a hydrogen target. The analysis is based on 1.8 × 106 events after all cuts, recorded at beam energies of 100, 120, 200 and 280 GeV and covering a kinematic range 0.06 ⩽ x ⩽ 0.80 and 7 GeV2 ⩽Q2 ⩽260 GeV2. At small x, we find R to be different from zero in agreement with predictions of perturbative QCD.

We present the final results of the spin asymmetries A 1 and the spin structure functions g 1 of the proton and the deuteron in the kinematic range 0.0008ϽxϽ0.7 and 0.2ϽQ 2 Ͻ100 GeV 2 .For the determination of A 1 , in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low x, we use a new method which minimizes the radiative background by selecting events with at least one hadron as well as a muon in the final state.We find that this hadron method gives smaller errors for xϽ0.02, so it is combined with the usual method to provide the optimal set of results.͓S0556-2821͑98͒07017-9͔

We present results on a high statistics study of the nucleon structure functions F2(x, Q2) and R=σL/σT measured in deep inelastic scattering of muons on a deuterium target. The analysis is based on 8×105 events after all cuts, recorded at beam energies of 120, 200 and 280 GeV in the kinematic range 0.06⩽ × ⩽0.80 and 8GeV2⩽Q2⩽260GeV2. Scaling violations observed in the data are in agreement with predictions of perturbative QCD and allow to determine the QCD mass scale parameter Λ.

New data is presented on the ratios of structure functions F2(x, Q2) measured in deep inelastic muon scattering with deuterium, nitrogen, and iron targets. The existence of nuclear effects at large Q2 is confirmed with improved systematic accuracy. The ratio F2Fe(x)F2D2(x) covers the range 0.20 ⩽ x ⩽ 0.70 and is in agreement with earlier measurements. The ratio F2N2(x)/F2D2(x) is measured over the range 0.08 ⩽ x ⩽ 0.70 and is compatible with unity below x = 0.3.

New Results are presented on nuclear effects in deep inelastic muon scattering on deuterium and iron targets at large Q2. The ratio FFe2(x)FD22(x) measured in the kinematic range 0.06⩽x⩽0.70, 14GeV2⩽Q2⩽70 GeV2 is in good agreement with earlier measurements in the region of x > 0.25. At lower x, the structure function ratio exhibits an enhancement of ≈5%.

At the CERN SPS we have measured a deep inelastic μ± cross section asymmetry at momentum transfers Q2 ranging from 15 to 180GeV2. The result is in quantitative agreement with the WS/GIM standard electroweak model and allows to determine the muon neutral current couplings.

We report on the test beam results and calibration methods using high energy electrons, pions and muons with the CMS forward calorimeter (HF). The HF calorimeter covers a large pseudorapidity region ( $3\leq|\eta|\leq5$ ), and is essential for a large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of forward tagging jets in weak boson fusion channels in Higgs production. The HF calorimeter is based on steel absorber with embedded fused-silica-core optical fibers where Cherenkov radiation forms the basis of signal generation. Thus, the detector is essentially sensitive only to the electromagnetic shower core and is highly non-compensating (e/h≈5). This feature is also manifest in narrow and relatively short showers compared to similar calorimeters based on ionization. The choice of fused-silica optical fibers as active material is dictated by its exceptional radiation hardness. The electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form as $\frac{a}{\sqrt{E}}\oplus{b}$ . The stochastic term a is 198% and the constant term b is 9%. The hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the electromagnetic case, a = 280% and b = 11%.

Inclusive electron and positron emission have been observed for θcm = 30° and s = 2800 GeV2 at the CERN Intersecting Storage Rings (ISR). Over the transverse momentum interval 0.2 GeV/c < pT < 1.5 GeV/c, electrons and positrons, which are equal in number within the experimental accuracies, appear to grow with respect to other particles (pions) approximately like 1/pT. We are unable to explain their number and pT-dependence in terms of “conventional” mechanisms.

We present results from a high statistics study of the nucleon structure function F2(x,Q2) measured in deep inelastic scattering of muons on carbon in the kinematic range 0.25⩽x⩽0.80 and Q2⩾25 GeV2. The analysis is based on 1.5×106 reconstructed events recorded at beam energies of 120, 200 and 280 GeV. R=σL/σT is found to be independent of x in the range 0.25⩽x⩽0.07 and 40 GeV2⩽Q2⩽200 GeV2 with a mean value R=0.015±0.013 (stat) ±0.026 (syst.).

We have searched for Theta+(1540) and Xi(--)(1862) pentaquark candidates in proton-induced reactions on C, Ti, and W targets at midrapidity and square root of s = 41.6 GeV. In 2 x 10(8) inelastic events we find no evidence for narrow (sigma approximately 5 MeV) signals in the Theta+ --> pK0(S) and Xi(--) --> Xi- pi- channels; our 95% C.L. upper limits (UL) for the inclusive production cross section times branching fraction B dsigma/dy/(y approximately 0) are (4-16) mub/N for a Theta+ mass between 1521 and 1555 MeV, and 2.5 mub/N for the Xi(--). The UL of the yield ratio of Theta+/Lambda(1520) < (3-12)% is significantly lower than model predictions. Our UL of B Xi(--)/Xi(1530)0 < 4% is at variance with the results that have provided the first evidence for the Xi(--).

Measurements of the kinematic distributions of J/ψ mesons produced in p–C, p–Ti and p–W collisions at $\sqrt{s}=41.6~\mathrm{GeV}$ in the Feynman-x region −0.34<x F <0.14 and for transverse momentum up to p T =5.4 GeV/c are presented. The x F and p T dependencies of the nuclear suppression parameter, α, are also given. The results are based on 2.4×105 J/ψ mesons reconstructed in both the e + e − and μ + μ − decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of x F for the first time. The average value of α in the measured x F region is 0.981±0.015. The data suggest that the strong nuclear suppression of J/ψ production previously observed at high x F turns into an enhancement at negative x F .

Deep inelastic scattering cross sections have been measured with the CERN SPS muon beam at incident energies of 120 and 200 GeV. Approximately 100 000 events at each energy are used to obtain the structure function F2(x, Q2) in the kinematic region 0.3<x<0.7 and 25 GeV2 <Q2<200 GeV2.

Extensive measurements have been made with pions, electrons and muons on four production wedges of the compact muon solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. The energy dependent time slewing effect was measured and tuned for optimal performance.

The HERA-B Outer Tracker is a large system of planar drift chambers with about 113000 read-out channels. Its inner part has been designed to be exposed to a particle flux of up to 2.10^5 cm^-2 s^-1, thus coping with conditions similar to those expected for future hadron collider experiments. 13 superlayers, each consisting of two individual chambers, have been assembled and installed in the experiment. The stereo layers inside each chamber are composed of honeycomb drift tube modules with 5 and 10 mm diameter cells. Chamber aging is prevented by coating the cathode foils with thin layers of copper and gold, together with a proper drift gas choice. Longitudinal wire segmentation is used to limit the occupancy in the most irradiated detector regions to about 20 %. The production of 978 modules was distributed among six different laboratories and took 15 months. For all materials in the fiducial region of the detector good compromises of stability versus thickness were found. A closed-loop gas system supplies the Ar/CF4/CO2 gas mixture to all chambers. The successful operation of the HERA-B Outer Tracker shows that a large tracker can be efficiently built and safely operated under huge radiation load at a hadron collider.

Ratios of the ψ′ over the J/ψ production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus interactions with the HERA-B detector at the HERA storage ring. The ψ′ and J/ψ states were reconstructed in both the μ+μ- and the e+e- decay modes. The measurements covered the kinematic range -0.35≤xF≤0.1 with transverse momentum pT≤4.5 GeV/c. The angular dependence of the ratio has been used to measure the difference of the ψ′ and J/ψ polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is Rψ′(μ)/Rψ′(e)=1.00±0.08±0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B′(μ)B(e))/(B(μ)B′(e)), of ψ′ and J/ψ in the two channels. The ψ′ to J/ψ production ratio is almost constant in the covered xF range and shows a slow increase with pT.

In this paper we describe the operation and performance of the HERA-B Outer Tracker, a 112674 channel system of planar drift tube layers. The performance of the HERA-B Outer Tracker system fullfilled all requirements for stable and efficient operation in a hadronic environment, thus confirming the adequacy of the honeycomb drift tube technology and of the front-end readout system. The detector was stably operated with a gas gain of 30000 in an Ar/CF4/CO2 (65:30:5) gas mixture, yielding a good efficiency for triggering and track reconstruction, larger than 95 % for tracks with momenta above 5 GeV/c. The hit resolution of the drift cells was 300 to 320 micrometers and the relative momentum resolution can be described as: sigma(p)/p (in %) = (1.61 +- 0.02) + (0.0051 +- 0.0006) p. At the end of the HERA-B running no aging effects in the Outer Tracker cells were observed.

A study of the angular distributions of leptons from decays of J/ψ's produced in p-C and p-W collisions at $\sqrt{s}=41.6\mbox{~GeV}$ has been performed in the J/ψ Feynman-x region −0.34<x F <0.14 and for J/ψ transverse momenta up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3×105 J/ψ's reconstructed in both the e + e − and μ + μ − decay channels, indicate that J/ψ's are produced polarized. The magnitude of the effect is maximal at low p T . For p T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises.

The HERA-B Outer Tracker consists of drift tubes folded from polycarbonate foil and is operated with Ar/CF4/CO2 as drift gas. The detector has to stand radiation levels which are similar to LHC conditions. The first prototypes exposed to radiation in HERA-B suffered severe radiation damage due to the development of self-sustaining currents (Malter effect). In a subsequent extended R&D program major changes to the original concept for the drift tubes (surface conductivity, drift gas, production materials) have been developed and validated for use in harsh radiation environments. In the test program various aging effects (like Malter currents, gain loss due to anode aging and etching of the anode gold surface) have been observed and cures by tuning of operation parameters have been developed.

We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.

The interference structure function xG3(x) has been measured for the first time scattering positive and negative muons of opposite helicity off a carbon target. The x dependence observed for Q2 between 40 and 180 (GeV/c2) is in good agreement with predictions of the quark-parton model. The measured ratio 2(auQu + adQd)/(Qu2 + Qd2 = 1.87 ± 0.25 (stat.) ± 0.24 (syst.) is consistent with the hypothesis of fractional quark charges and determines the sign of Qu − Qd to be positive.

A 50 m long magnetized iron torus enclosing a 40 m long target provides the luminosity and acceptance necessary for the study of deep inelastic muon scattering at high Q2. The construction and performance of this spectrometer and the associated trigger are described. Details of the data acquisition system and data analysis are also given.

The inclusive production cross sections of the strange vector mesons K*0, K*0bar, and phi have been measured in interactions of 920 GeV protons with C, Ti, and W targets with the HERA-B detector at the HERA storage ring. Differential cross sections as a function of rapidity and transverse momentum have been measured in the central rapidity region and for transverse momenta up to pT=3.5 GeV/c. The atomic number dependence is parametrised as sigma(pA) = sigma(pN)*A**alpha, where sigma(pN) is the proton-nucleon cross section. Within the phase space accessible, alpha(K*0) = 0.86+/-0.03, alpha(K*0bar) = 0.87+/-0.03, and alpha(phi) = 0.96+/-0.02. The total proton-nucleon cross sections, determined by extrapolating the differential measurements to full phase space, are sigma(pN->K*0) = 5.06+/-0.54 mb, sigma(pN->K*0bar) = 4.02+/-0.45 mb, and sigma(pN->phi) = 1.17+/-0.11 mb. The Cronin effect is observed for the first time for vector mesons containing strange quarks; compared to the measurements of Cronin et al. for K+- mesons, the measured values of alpha for phi mesons coincide with those of K- mesons for all transverse momenta, while the enhancement for K*0 / K*0bar mesons is smaller.

ψ F < 0.15 is presented.Both µ + µ - and e + e -J/ψ decay channels are observed with an overall statistics of about 15000 χc events, which is by far the largest available sample in pA collisions.The result is Rχ c = 0.188 ± 0.013st +0.024 -0.022 sys averaged over the different materials, when no J/ψ and χc polarisations are considered.The χc1 to χc2 production ratio R12 = Rχ c 1 /Rχ c 2 is measured to be 1.02 ± 0.40, leading to a cross section ratio σ(χ c1 ) σ(χ c2 ) = 0.57 ± 0.23.The dependence of Rχ c on the Feynman-x of the J/ψ, x J/ψ F , and its transverse momentum, p J/ψ T , is studied, as well as its dependence on the atomic number, A, of the target.For the first time, an extensive study of possible biases on Rχ c and R12 due to the dependence of acceptance on the polarization states of J/ψ and χc is performed.By varying the polarisation parameter, λ obs , of all produced J/ψ's by two sigma around the value measured by HERA-B, and considering the maximum variation due to the possible χc1 and χc2 polarisations, it is shown that Rχ c could change by a factor between 1.02 and 1.21 and R12 by a factor between 0.89 and 1.16.

Using data collected by the HERA-B experiment, we have measured the fraction of J/ψ's produced via radiative χc decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained Rχc=0.32±0.06stat±0.04sys for the fraction of J/ψ from χc decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions.

The measurements of the transmission regeneration amplitude on hydrogen in the momentum region of 14–42 GeV/c indicate that in accordance with the Pomeranchuk theorem its magnitude |ƒ° − ƒ°|/k decreases as energy increases and its phase is approximately constant and equal to arg (ƒ° − ƒ°) = (−118 ± 13)°.

Data from deep inelastic scattering of 200 GeV muons on a carbon target with squared four-momentum transfer 52 GeV2≤Q 2≤200 GeV2 were analysed in the region of the Bjorken variable close tox=1, which is the kinematic limit for scattering on a free nucleon. At this value ofx, the carbon structure function is found to beF 2 ≈1.2·10−4. Thex dependence of the structure function forx>0.8 is well described by an exponentialF 2 ∞exp(−sx) withs=16.5±0.6.

Using the HERA-B detector, the b-bbar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b-bbar production was tagged via inclusive bottom quark decays into J/psi, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction. Both $e^+e^-$ and $\mu^+\mu^-$ channels have been reconstructed and the combined analysis yields the cross section $\sigma(b \bar b) = 32 ^{+14}_{-12} (stat) ^{+6}_{-7} (sys) nb/nucleon$.

We report a large enhancement of 1.7 in deuteron polarization up to values of 0.6 due to frequency modulation of the polarizing microwaves in a two liters polarized target using the method of dynamic nuclear polarization. This target was used during a deep inelastic polarized muon-deuteron scattering experiment at CERN. Measurements of the electron paramagnetic resonance absorption spectra show that frequency modulation gives rise to additional microwave absorption in the spectral wings. Although these results are not understood theoretically, they may provide a useful testing ground for the deeper understanding of dynamic nuclear polarization.

The Outer Hadron Calorimeter (HCAL HO) of the CMS detector is designed to measure the energy that is not contained by the barrel (HCAL HB) and electromagnetic (ECAL EB) calorimeters. Due to space limitation the barrel calorimeters do not contain completely the hadronic shower and an outer calorimeter (HO) was designed, constructed and inserted in the muon system of CMS to measure the energy leakage. Testing and calibration of the HO was carried out in a 300 GeV/c test beam that improved the linearity and resolution. HO will provide a net improvement in missing E T measurements at LHC energies. Information from HO will also be used for the muon trigger in CMS.

A new measurement of the $b\overline{b}$ production cross section in 920 GeV proton-nucleus collisions is presented by the HERA-B Collaboration. The $b\overline{b}$ production is tagged via inclusive bottom quark decays into $J/\ensuremath{\psi}$ mesons by exploiting the longitudinal separation of $J/\ensuremath{\psi}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$ decay vertices from the primary proton-nucleus interaction point. Both ${e}^{+}{e}^{\ensuremath{-}}$ and ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ channels are reconstructed for a total of $83\ifmmode\pm\else\textpm\fi{}12$ inclusive $b\ensuremath{\rightarrow}J/\ensuremath{\psi}X$ events found. The combined analysis yields a $b\overline{b}$ to prompt $J/\ensuremath{\psi}$ cross section ratio of $\frac{\ensuremath{\Delta}\ensuremath{\sigma}(b\overline{b})}{\ensuremath{\Delta}{\ensuremath{\sigma}}_{J/\ensuremath{\psi}}}=0.032\ifmmode\pm\else\textpm\fi{}{0.005}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.004}_{\mathrm{sys}}$ measured in the ${x}_{F}$ acceptance ($\ensuremath{-}0.35&lt;{x}_{F}&lt;0.15$), extrapolated to $\ensuremath{\sigma}(b\overline{b})=14.9\ifmmode\pm\else\textpm\fi{}{2.2}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{2.4}_{\mathrm{sys}}\text{ }\text{ }\mathrm{\text{nb/nucleon}}$ in the total phase space.

In deep inelastic interactions of 200 GeV muons with a carbon target, we have found 17 events of the type μ±N→μ±μ∓μ∓X (“wrong-sign” dimuons). We derive upper limits of 1.2% (90% CL) on D0-D0 transitions (mixing) or, alternatively, of 9 pb (90% CL) cross section for BB pair production as possible sources of such events.

The HERA-B Outer Tracker is a large detector with 112 674 drift chamber channels.It is exposed to a particle flux of up to 2 • 10 5 cm -2 s -1 thus coping with conditions similar to those expected for the LHC experiments.The front-end readout system, based on the ASD-8 chip and a customized TDC chip, is designed to fulfil the requirements on low noise, high sensitivity, rate tolerance, and high integration density.The TDC system is based on an ASIC which digitizes the time in bins of about 0.5 ns within a total of 256 bins.The chip also comprises a pipeline to store data from 128 events which is required for a deadtime-free trigger and data acquisition system.We report on the development, installation, and commissioning of the front-end electronics, including the grounding and noise suppression schemes, and discuss its performance in the HERA-B experiment.

Plastic scintillators are often used as detectors in High Energy Physics (HEP), but have insufficient radiation hardness. Organization of better light collection inside a single detector may prolong operation life of scintillators. A finger-strip plastic scintillator option has many advantages to keep the excellent detector performance at high luminosity. Measurements assigned to show an advantage of a stripped detector vs. the un-stripped one in the range of increased absorbed doses and the smallest dose rates have been performed. This method has proved to be a good upgrade strategy.

A muon beam polarimeter was built for the SMC experiment at the CERN SPS, for beam energies of 100 and 190 GeV. The beam polarisation is determined from the asymmetry in the elastic scattering off the polarised electrons of a ferromagnetic target whose magnetisation is periodically reversed. At muon energies of 100 and 190 GeV the measured polarisation is Pμ=−0.80±0.03 (stat.)±0.02 (syst.) and Pμ=−0.797±0.011 (stat.)±0.012 (syst.), respectively. These results agree with measurements of the beam polarisation using a shape analysis of the decay positron energy spectrum.

A large toroidal iron spectrometer for the study of deep-inelastic muon scattering at the CERN SPS has been upgraded to extend the accessible kinematic range and to reduce the systematic errors on absolute cross-section measurements. The layout of the improved apparatus, the construction of new detectors and associated electronics, and the structure of a new data-acquisition system are described in detail.

The 10-probe NMR system for measuring the polarization in the deuterated butanol target of the Spin Muon Collaboration is presented. It is calibrated by determining the integrated spectrum in thermal equilibrium at 1 K. Thermal stabilization and control of electromagnetic interference were effective in reducing drift and electronic noise, so that high quality thermal equilibrium signals were obtained. The calibration constant was determined with a reproducibility of 2%. Systematic effects of circuit drift and of the magnetic field shift have been studied. The resulting 4.4% uncertainty of the calibration dominates the 5% overall error on the target polarization value which was typically 0.45.

The high precision straw chamber with cathode readout was constructed and investigated. The 10 mm diameter straws were made of aluminized Mylar with transparent longitudinal window. The X-coordinate information has been taken from cathode strips as induced charges and investigated with the centroid method. The spatial resolution σx = 103 μm was obtained at a signal-to-noise ratio of about 70. The possible ways to improve the signal-to-noise ratio are discussed.

The PMTs of the CMS Hadron Forward calorimeter were found to generate a large size signal when their windows were traversed by energetic charged particles. This signal, which is due to Čerenkov light production at the PMT window, could interfere with the calorimeter signal and mislead the measurements. In order to find a viable solution to this problem, the response of four different types of PMTs to muons traversing their windows at different orientations is measured at the H2 beam-line at CERN. Certain kinds of PMTs with thinner windows show significantly lower response to direct muon incidence. For the four anode PMT, a simple and powerful algorithm to identify such events and recover the PMT signal using the signals of the quadrants without window hits is also presented. For the measurement of PMT responses to Čerenkov light, the Hadron Forward calorimeter signal was mimicked by two different setups in electron beams and the PMT performances were compared with each other. Superior performance of particular PMTs was observed.

This paper is a summary of a research and development programme, conducted during the past 3 years on the CMS Preshower silicon sensors to define the specifications. The main purpose was to study the radiation hardness of these devices resulting from the specific design (metal lines wider than the p+ implants) and the production technology, a deep n+ layer on the ohmic side. An acceptable noise and a uniform charge collection were guaranteed by an appropriate choice of the interstrip region width. About 65 sensors, of different designs and produced by six manufacturers, were irradiated with neutrons and protons and thoroughly tested before and after irradiation. The results of the tests and the final specifications are presented.

A system of nine wire spark chambers having magnetostrictive readout, data acquisition electronics used on-line with the computer BESM-3M located at a 1 km distance from the experimental area has been designed and tested using a negative pion beam of the Dubna synchrophasotron.

Plastic scintillators are very often used as detecting media in sampling calorimeters of High Energy Physics (HEP). Many modern HEP experimental installations are already operating or proposed to work at high luminosity. Plastic scintillators are the most sensitive part of such setups in terms of their radiation hardness. Improving the light collection from the most irradiated scintillators will ensure their long-term use at high luminosity. The experimental results of the measurements for different assemblies (scintillator SCSN-81 and the WLS fiber Y-11 electron-irradiated (E≈4 MeV) were obtained. Calculations of the light yields for different samples based on our experimental results show the possibility of increasing the radiation hardness of plastic scintillators inside the sampling calorimeter up to 20 Mrad.

The experiments at the planned 14 TeV proton-proton collider LHC will need a good identification and measurement of muons with energies of up to about 800 GeV. The production of electromagnetic secondaries by muons of energy from 10 to 300 GeV has been measured at the RD5 experiment at CERN using various detector types proposed for LHC experiments. It is demonstrated that the detectors can recognize the presence of individual hits from em secondaries, and that the muon measurement would be seriously compromised if these hits are not suppressed.

We report on a search for the flavor-changing neutral current decay $D^0 \to \mu^+\mu^-$ using $50 \times 10^6$ events recorded with a dimuon trigger in interactions of 920 GeV protons with nuclei by the HERA-B experiment. We find no evidence for such decays and set a 90% confidence level upper limit on the branching fraction $Br(D^0 \to \mu^+\mu^-) <2.0 \times 10^{-6}$.

Four versions of a fast monolithic charge-sensitive preamplifier (CSP) were designed using microwave BJT-JFET technology. The best one has a 3.5 ns rise time for input detector capacitance Cd = 100 pF and approximately 8 mW power dissipation for 5 V supply voltage. The ENC performance at shaping time 30 ns is 1350 e + 17 e/pF for Cd up to 600 pF. Crosstalk in a four-channel amplifier made in the same chip was measured to be about −46 dB for Cd = 100 pF. The linear output voltage swing is 0.8 V for voltage supply 5 V. The IC has revealed good radiation hardness to neutron irradiation.

The energy-loss spectrum of high energy muons after traversal of a 10 meter iron degrader has been measured with an accuracy of better than 1%. Data taken at energies between 50 and 120 GeV are in agreement with predictions from a Monte Carlo program based on the most recent theoretical descriptions of all relevant processes. The stopping power calculated by this program deviates up to several percent from earlier calculations.

Inclusive doubly differential cross sections d 2 σ pA /dx F dp 2 as a function of Feynman-x (x F ) and transverse momentum (p T ) for the production of K 0 , Λ and $\bar{\varLambda}$ in proton-nucleus interactions at 920 GeV are presented. The measurements were performed by HERA-B in the negative x F range (−0.12<x F <0.0) and for transverse momenta up to p T =1.6 GeV/c. Results for three target materials: carbon, titanium and tungsten are given. The ratios of production cross sections are presented and discussed. The Cronin effect is clearly observed for all three V 0 species. The atomic number dependence is parameterized as σ pA =σ pN ⋅A α where σ pN is the proton-nucleon cross section. The measured values of α are all near one. The results are compared with EPOS 1.67 and PYTHIA 6.3. EPOS reproduces the data to within ≈20% except at very low transverse momentum.

A new segment building algorithm for the Cathode Strip Chambers in the CMS experiment is presented. A detailed description of the new algorithm is given along with a comparison with the algorithm used in the CMS software. The new segment builder was tested with different Monte-Carlo data samples. The new algorithm is meant to be robust and effective for hard muons and the higher luminosity that is expected in the future at the LHC.

New projective prototypes of a scintillator/lead sandwich type sampling calorimeter Shashlik with a silicon preshower detector have been constructed and tested with an electron beam at CERN-SPS. The energy resolution is measured to be 8.7%E(GeV) in stochastic term, 0.330/E(GeV) in noise term and 0.5% in constant term. The angular resolution is better than 70 mradE(GeV).

Silicon sensors designed for the CMS preshower detector must have a high breakdown voltage in order to be fully efficient after irradiation to 2/spl times/10/sup 14/ n/cm/sup 2/ expected during the ten years of Large Hadron Collider operation (CMS ECAL Group, Bloch et al.). Studies made by several groups (Bischoff et al., Evensen et al., Da Rold et al., Passeri et al., Li et al., Militaru et al.) have underlined the importance of the p/sup +/ side geometrical parameters, such as the metal width and the number and spacing of guard rings. We have in addition investigated the effects related to the ohmic side processing and found that the breakdown voltage depends strongly on the thickness of the effective "dead" n/sup +/ layer. By increasing this thickness from 1 to 2.5 /spl mu/m, the fraction of sensors with breakdown voltage higher than 500 V increased from 22% to more than 80%. In addition, a thick n/sup +/ layer protects against defects caused by the technological treatment during detector production and assembly.

In the Compact Muon Solenoid (CMS) experiment, muon detection in the forward direction is accomplished by cathode strip chambers (CSC). These detectors identify muons, provide a fast muon trigger, and give a precise measurement of the muon trajectory. There are 468 six-plane CSCs in the system. The efficiency of finding muon trigger primitives (muon track segments) was studied using 36 CMS CSCs and cosmic ray muons during the Magnet Test and Cosmic Challenge (MTCC) exercise conducted by the CMS experiment in 2006. In contrast to earlier studies that used muon beams to illuminate a very small chamber area (<0.01m2), results presented in this paper were obtained by many installed CSCs operating in situ over an area of ≈23m2 as a part of the CMS experiment. The efficiency of finding two-dimensional trigger primitives within six-layer chambers was found to be 99.93±0.03%. These segments, found by the CSC electronics within 800 ns after the passing of a muon through the chambers, are the input information for the Level-1 muon trigger and, also, are a necessary condition for chambers to be read out by the Data Acquisition System.

A detailed description of an original method used to measure the luminosity accumulated by the HERA-B experiment for a data sample taken during the 2002-2003 HERA running period is reported. We show that, with this method, a total luminosity measurement can be achieved with a typical precision, including overall systematic uncertainties, at a level of 5% or better. We also report evidence for the detection of delta-rays generated in the target and comment on the possible use of such delta rays to measure luminosity.

The high mass μ+μ− pairs produced by 280 GeV μ+ on a carbon target are studied in a search for the Y production. The high mass continuum in the region 2–18 GeV is interpreted in terms of QED pair production and of μ pairs originating from the decay of hidden and open charm particles as well as of hadrons (π, K) from deep inelastic interactions. The upper limit for the upsilon production by muons is found to be, at the 90% confidence level, σγ·(γ→μ+μ−)<13·10−39 cm2/nucleon.

A robust technique with a sub-optimal weight function (M-estimate) was applied to investigate track fitting in cathode strip chambers (CSCs) and determine the CSC spatial resolution. The comparative analysis with the conventional least squares method was made on simulated data and experimental data from the Dubna CSC prototype. The results obtained definitely prove a necessity of using robust track fitting for a reliable estimation of muon chamber spatial resolution.

The ME1/1 cathode strip chambers are the part of the CMS endcap muon system. They were designed and produced in Dubna. The chambers have been installed in the detector and commissioning has been completed. This paper describes chamber readout electronics and presents the results of the tests with cosmicray muons.

We present the results of measurements of the light yield dependencies for the plastic scintillators on magnetic field value and orientation. The magnetic field value was changed from 0 up to 3.8 T. Scintillators were irradiated by electrons (137Cs and 207Bi) and by alpha-particles (241Am). The detected light spectra in the electron irradiating cases show two dependencies: the first one is dependence on the magnetic field value only and the second-light output is dependent on the magnetic field orientation when the radioactive source is outside of the scintillator. The value and behavior of the first dependence agree with data published earlier. Under alpha-particle irradiation the light output does not depend on the magnetic field value and orientation practically.

Results are presented of a study of the accuracy in detecting relativistic particle coordinates in proportional chambers using the cathode information read-out. The width of the cathode strips was 2 mm and the anode to cathode distance 4 mm. For the tracks perpendicular to the chamber plane the detection accuracy was 50 μm. Two methods of calculation of the centre of the induced charge distribution on the cathode strips are described: by the centre of gravity and by fitting this distribution by a special formula. It is shown that for single-particle events the change of the width of the induced charge distribution does not exceed 1.2%.

Implanted silicon multistrip detectors with 50 and 100 μ m pitch have been developed, fabricated and tested. Each strip is read out by using charge sensitive preamplifiers. Results of efficiency, noise and resolution are presented and a system for use in an experiment is described.

CMS hadron calorimeters (HB, HE, HO) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The endcap calorimeter HE suffered more radiation damage than anticipated causing rapid degradation of scintillator segments (tiles) which have a higher radiation flux from secondary particles than HB and HO. A proposal to upgrade of HE calorimeter will provide a solution for survivability at future LHC higher luminosity. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements and simulations have been performed and this method is a good upgrade strategy. HE upgrade beyond phase 1. Finger scintillator option. S.V. Afanasiev, P. de Barbaro, A.Yu. Boyarintsev, I.F. Emeliantchik, I.A. Golutvin, B.V. Grinyov, Yu.V. Ershov, L.G. Levchuk , A.V. Litomin, A.I. Malakhov, P.V. Moisenz, V.F. Popov , N.M. Shumeiko, V.A. Smirnov, P.V. Sorokin, P.N. Zhmurin a Joint Institute for Nuclear Research, Dubna, Russia b National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine c Institute for Scintillation Materials National Academy of Sciences of Ukraine, Kharkov, Ukraine d National Center for Particle and High Energy Physics, Minsk, Belarus e University of Rochester, Rochester, USA Abstract CMS hadron calorimeters (HB, HE, HO) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The endcap calorimeter HE suffered more radiation damage than anticipated causing rapid degradation of scintillator segments (tiles) which have a higher radiation flux from secondary particles than HB and HO. A proposal to upgrade of HE calorimeter will provide a solution for survivability at future LHC higher luminosity. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements and simulations have been performed and this method is a good upgrade strategy.CMS hadron calorimeters (HB, HE, HO) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The endcap calorimeter HE suffered more radiation damage than anticipated causing rapid degradation of scintillator segments (tiles) which have a higher radiation flux from secondary particles than HB and HO. A proposal to upgrade of HE calorimeter will provide a solution for survivability at future LHC higher luminosity. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements and simulations have been performed and this method is a good upgrade strategy.

The results of the CMS experiment based on the LHC first-run data taken at c.m.s. energies of 7 and 8 TeV and on the first data taken in the second-run at the c.m.s. energy of 13 TeV are presented. The research prospects with the LHC running at high luminosity are discussed.

The CMS preshower detector contains 16m2 of silicon. The silicon sensors’ design is being finalized by taking into account their performance after five years of operation at high luminosity. Three detectors from different manufacturers were irradiated by neutrons and photons under bias and at low temperature. Their electrical parameters and their response to α and β particles were measured. The charge collection efficiency attains a plateau at around 300 V. The irradiation set-up and the results of the measurements are presented in this paper.

Abstract The effect of magnetic fields up to 15 kOe on the characteristics of spark chambers with magnetostrictive readout is discussed in this paper. The measurements were made in a magnetic field of 12.5 kOe. The efficiency and accuracy of particle detection are measured. The experimental equipment, described in paper 1 ), was used.

The production, installation, and testing of 468 cathode strip chambers for the endcap muon system of the CMS experiment played a critical role in the preparation of the endcap muon system for the final commissioning. Common testing procedures and sets of standard equipment were used at 5 international assembly centers. The chambers were then thoroughly retested after shipment to CERN. Final testing was performed after chamber installation on the steel disks in the CMS detector assembly building. The structure of the detector quality control procedure is presented along with the results of chamber performance validation tests.

We study the light output, light collection efficiency and signal timing of a variety of organic scintillators that are being considered for the upgrade of the hadronic calorimeter of the CMS detector. The experimental data are collected at the H2 test-beam area at CERN, using a 150 GeV muon beam. In particular, we investigate the usage of over-doped and green-emitting plastic scintillators, two solutions that have not been extensively considered. We present a study of the energy distribution in plastic-scintillator tiles, the hit efficiency as a function of the hit position, and a study of the signal timing for blue and green scintillators.

The first beam-test results for two- and three-bundle shashlik tower prototypes are described. We found that the spatial resolution, the uniformity of energy response, the calorimeter reliability and hermeticity and also two showers separation are improved in multi-bundle design approach.

Electrical and α-particle PHA damage tests for ELMA and SGS silicon detectors irradiated at two different fast neutron facilities, in the range of fluences from 1010 to 1015 n/cm2 are presented. Results on depletion voltage, α damage constants and self-annealing are discussed. Supplementary damage effects due to nuclear reactions are evaluated. The spread of the data in the self-annealing corrected α damage constant versus hardness parameter plot shows the difficulty in comparing the results obtained in different neutron environments. A systematics is however possible, in the framework of standardization of the “1 MeV equivalent” neutron spectrum.

The aim of this work is to estimate the shower leakage from the CMS Endcap Hadron calorimeter (HE) due to electromagnetic secondaries and punch-through in the region of the ME1/1 Forward Muon Station. Two configurations are considered: with and without the CMS Endcap Electromagnetic calorimeter (EE). The experimental data have been taken during the combined beam test of CMS subdetectors (HE, ME, RPC, DT) at the CERN H2 beam facility in 2004. Serial CSC chambers (ready for installation in CMS) fully equipped with readout electronics have been exposed. Simulation of a beam test setup has been performed using the GEANT4-based simulation software package OSCAR.

Abstract The first iteration step of a custom front-end readout integrated circuit design for muon spectrometer cathode strip chambers is reported. It was intended for the GEM experiment at the SSC supercollider (USA, Texas), however, it can be applied in CMS or ATLAS projects (the LHC supercollider, CERN, Switzerland). The IC was produced using BJT-JFET technology. It contains of a BJT-inputted charge-sensitive preamplifier followed by a slow shaper in a signal path and a fast shaper in a trigger path. A noise performance ENC = 1980 e + 7 e pF has been achieved for detector capacitance up to 600 pF at a peaking time of 300 ns and a power dissipation of 67 mW per channel. A low power comparator made with the same technology, when connected to the fast shaper output, has provided a time walk and jitter of approximately 2 ns. The IC appears to have good radiation tolerance for neutrons.

The centroid and charge-ratio methods are used to investigate the position resolutions of a new kind of gas detector: a straw chamber with a strip readout. The methods are simple and give the same resolution. The charge-ratio method is not sensitive to the pedestal subtraction and cross talks between the strips.

Arrays of limited streamer tubes of the Iarocci type were deployed in our experiment at CERN as part of a forward muon detector system with provisions for the beam to pass through the center of each panel in the array. A total of 16 4 m×4 m panels were assembled with inductive readout strips on both sides of each panel. An active feedback system was deployed to regulate the high voltage to the streamer tubes to insure a constant efficiency for minimum ionizing particles. The arrays were operated in this environment for over five years of data taking. Streamer tube track-reconstruction efficiencies and tube replacement rates are reported.

Sensors designed for the CMS preshower detector were irradiated with protons and neutrons to fluences equivalent up to 2/spl times/10/sup 14/ n/cm/sup 2/. The leakage current and the capacitance as well as the charge collection efficiency and the noise were measured, before and after the irradiation, for most of the detectors. We noticed, that for some detectors of a lower quality, the breakdown voltage increases after type inversion and that their leakage current, charge collection efficiency and noise are comparable to good detectors. We explain this phenomenon by two effects: a change of the distribution of the electric field and a decrease of the carrier lifetime. Defects on the p-side do much less harm after type inversion, because the maximum of the E-field is now on the n-side. Defects on the n-side still generate charge carriers, but their lifetime is much shorter and most of them recombine before reaching by diffusion the space charge volume. The article presents the measurements of the breakdown voltage, the charge collection efficiency and the noise before and after irradiation of such sensors compared with detectors of a high initial quality.

Two CMS Endcap hadron calorimeters (HE) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The HE calorimeter suffered more from the radiation than it had been anticipated because of rapid degradation of scintillator segments (tiles) which have a high radiation flux of secondary particles. Some investigations of scintillators have shown that the degradation of plastic scintillator increases significantly at low dose rates. A proposal to upgrade up-grade the HE calorimeter has been prepared to provide a solution for survivability of the future LHC at higher luminosity and higher energy. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements have been performed and this method has proved to be a good upgrade strategy.

The Compact Muon Solenoid (CMS) is a high-performance general-purpose detector at the Large Hadron Collider (LHC) at CERN.More than twenty institutes from Russia and Joint Institute for Nuclear Research (JINR) are involved in Russia and Dubna Member States (RDMS) CMS Collaboration.A proper computing grid-infrastructure has been constructed at the RDMS institutes for the participation in the running phase of the CMS experiment.Current status of RDMS CMS computing and plans of its development to the next LHC start in 2015 are presented.

Measurements of the kinematic distributions of $J/\psi$ mesons produced in $p-$C, $p-$Ti and $p-$W collisions at $\sqrt{s}=41.6 \mathrm{GeV}$ in the Feynman-$x$ region $-0.34 < x_{F} < 0.14$ and for transverse momentum up to $p_T = 5.4 \mathrm{GeV}/c$ are presented. The $x_F$ and $p_T$ dependencies of the nuclear suppression parameter, $\alpha$, are also given. The results are based on $2.4 \cdot 10^{5}$ $J/\psi$ mesons in both the $e^+ e^-$ and $\mu^{+}\mu^{-}$ decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of $x_{F}$ for the first time. The average value of $\alpha$ in the measured $x_{F}$ region is $0.981 \pm 0.015$. The data suggest that the strong nuclear suppression of $J/\psi$ production previously observed at high $x_F$ turns into an enhancement at negative $x_F$.

Characteristics of the gas ionisation electromagnetic (EM) calorimeters with 1.5 and 3mm lead absorbers has been studied using 6–30GeV electron beams of the IHEP accelerator. The calorimeters were filled with heavy freon C3F8. The results of the electronics noise measurements are presented. The dependencies of the average signal and the energy resolution on the beam energy, gas pressure and high voltage are discussed.

The Phase I upgrade of the CMS Hadron Endcap Calorimeters consists of new photodetectors (Silicon Photomultipliers in place of Hybrid Photo-Diodes) and front-end electronics. The upgrade will eliminate the noise and the calibration drift of the Hybrid Photo-Diodes and enable the mitigation of the radiation damage of the scintillators and the wavelength shifting fibers with a larger spectral acceptance of the Silicon Photomultipliers. The upgrade also includes increased longitudinal segmentation of the calorimeter readout, which allows pile-up mitigation and recalibration due to depth-dependent radiation damage. As a realistic operational test, the responses of the Hadron Endcap Calorimeter wedges were calibrated with a 60Co radioactive source with upgrade electronics. The test successfully established the procedure for future source calibrations of the Hadron Endcap Calorimeters. Here we describe the instrumentation details and the operational experiences related to the sourcing test.

We present an overview of the CALICE activities on calorimeter development for a future linear collider. We report on test beam analysis results, the status of prototype development and future plans.