E. Focardi

The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric standard model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses of neutral Higgs bosons.

The pion form factor has been measured in the space-like q2 region 0.014 to 0.26 (GeV/c)2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar results to the naive pole form, and conclude 〈r2π〉 = 0.438±0.008 fm2.

The Collider Detector at Fermilab (CDF) is a 5000 t magnetic detector built to study 2 TeV pp collisions at the Fermilab Tevatron. Event analysis is based on charged particle tracking, magnetic momentum analysis and fine-grained calorimetry. The combined electromagnetic and hadron calorimetry has approximately uniform granularity in rapidity-azimuthal angle and extends down to 2° from the beam direction. Various tracking chambers cover the calorimeter acceptance and extend charged particle tracking down to 2 mrad from the beam direction. Charged particle momenta are analyzed in a 1.5 T solenoidal magnetic field, generated by a superconducting coil which is 3 m in diameter and 5 m in length. The central tracking chamber measures particle momenta with a resolution better then δpT/pT2 = 2 × 10−3 (GeV/c)−1 in the region 40° < θ < 140° and δPT/pT2 ≤ 4 × 10−3 for 21° < θ < 40° and 140° < θ < 159°. The calorimetry, which has polar angle coverage from 2° to 178° and full azimuthal coverage, consists of electromagnetic shower counters and hadron calorimeters, and is segmented into about 5000 projective “towers” or solid angle elements. Muon coverage is provided by drift chambers in the region 56° < θ < 124°, and by large forward toroid systems in the range 3° < θ < 16° and 164° < θ < 177°. Isolated high momentum muons can be identified in the intermediate angular range by a comparison of the tracking and calorimeter information in many cases. A custom front-end electronics system followed by a large Fastbus network provides the readout of the approximately 100 000 detector channels. Fast Level 1 and Level 2 triggers make a detailed pre-analysis of calorimetry and tracking information; a Level 3 system of on-line processors will do parallel processing of events. This paper provides a summary of the aspects of the detector which are relevant to its physics capabilities, with references to more detailed descriptions of the subsystems.

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.

The full LEP-1 data set collected with the ALEPH detector at the Z pole during 1991–1995 is analysed in order to measure the τ decay branching fractions. The analysis follows the global method used in the published study based on 1991–1993 data, but several improvements are introduced, especially concerning the treatment of photons and π0's. Extensive systematic studies are performed, in order to match the large statistics of the data sample corresponding to over 300 000 measured and identified τ decays. Branching fractions are obtained for the two leptonic channels and 11 hadronic channels defined by their respective numbers of charged particles and π0's. Using previously published ALEPH results on final states with charged and neutral kaons, corrections are applied to the hadronic channels to derive branching ratios for exclusive final states without kaons. Thus the analyses of the full LEP-1 ALEPH data are combined to yield a complete description of τ decays, encompassing 22 non-strange and 11 strange hadronic modes. Some physics implications of the results are given, in particular related to universality in the leptonic charged weak current, isospin invariance in a1 decays, and the separation of vector and axial-vector components of the total hadronic rate. Finally, spectral functions are determined for the dominant hadronic modes and updates are given for several analyses. These include: tests of isospin invariance between the weak charged and electromagnetic hadronic currents, fits of the ρ resonance lineshape, and a QCD analysis of the non-strange hadronic decays using spectral moments, yielding the value αs(mτ2)=0.340±0.005exp±0.014th. The evolution to the Z mass scale yields αs(MZ2)=0.1209±0.0018. This value agrees well with the direct determination from the Z width and provides the most accurate test to date of asymptotic freedom in the QCD gauge theory.

The negative kaon electromagnetic form factor has been measured in the space-like q2 range 0.015–0.10 (GeV/c)2 by the direct scattering of 250 GeV kaons from electrons at the CERN SPS. It is found that the kaon mean square charge radius 〈r2K〉 = 0.34 ± 0.05 fm2. From data collected simultaneously for πe scattering, the difference between the charged pion and kaon mean square radii (which is less sensitive to systematic errors) is found to be 〈r2π〉 − 〈r2K = 0.1 0 ± 0.045 fm2.

We present measurements of the pseudorapidity (η) distribution of charged particles (dNchdη) produced within |η|≤3.5 in proton-antiproton collisions at √s of 630 and 1800 GeV. We measure dNchdη at η=0 to be 3.18±0.06(stat)±0.10(syst) at 630 GeV, and 3.95±0.03 (stat)±0.13(syst) at 1800 GeV. Many systematic errors in the ratio of dNchdη at the two energies cancel, and we measure 1.26±0.01±0.04 for the ratio of dNchdη at 1800 GeV to that at 630 GeV within |η|≤3. Comparing to lower-energy data, we observe an increase faster than ln(s) in dNchdη at η=0.Received 2 October 1989DOI:https://doi.org/10.1103/PhysRevD.41.2330©1990 American Physical Society

Measurements of inclusive transverse-momentum spectra for charged particles produced in proton-antiproton collisions at \ensuremath{\surd}2 of 630 and 1800 GeV are presented and compared with data taken at lower energies.

The CDF central and endwall hadron calorimeter covers the polar region between 30° and 150° and a full 2π in azimuth. It consists of 48 steel-scintillator central modules with 2.5 cm sampling and 48 steel-scintillator endwall modules with 5.0 cm sampling. A general description of the detector is given. Calibration techniques and performance are discussed. Some results of the test beam studies are shown.

We report a measurement of the negative pion electromagnetic form factor in the range of space-like four-momentum transfer 0.014 < q2 < 0.122 (GeV/c)2. The measurement was made by the NA7 collaboration at the CERN SPS, by observing the interaction of 300 GeV pions with the electrons of a liquid hydrogen target. The form factor is fitted by a pole form with a pion radius of 〈r2〈12 = 0.657 ± 0.012 fm.

An analysis of pp\ifmmode\bar\else\textasciimacron\fi{} collision events at \ensuremath{\surd}s =1.8 TeV with jets and large missing transverse energy finds no event with missing transverse energy &gt;40 GeV. This result yields a 90%-C.L. limit on the cross section for one-jet-event production of &lt;0.1 nb for events with the jet in the pseudorapidity range \ensuremath{\Vert}\ensuremath{\eta}\ensuremath{\Vert}&lt;1.0 and with jet ${E}_{T}$&gt;52 GeV. Limits on the masses of squarks and gluinos in a minimal supersymmetry model are also set. At the 90% C.L., ${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$&gt;74 GeV and ${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$&gt;73 GeV.

The EM form factor of the pion has been studied in the time-like region by measuring σ(e+e− → π+π−) normalized to σ(e+e− → μ+μ−). Results have been obtained for q2 down to the physical threshold.

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 analysis of ${Z}^{0}$\ensuremath{\rightarrow}${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ and ${Z}^{0}$\ensuremath{\rightarrow}${\ensuremath{\mu}}^{+}$${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$ data from the Collider Detector at Fermilab in p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s =1.8 TeV yields a mass of the ${Z}^{0}$ boson of ${M}_{Z}$=90.9\ifmmode\pm\else\textpm\fi{}0.3 (stat+syst)\ifmmode\pm\else\textpm\fi{}0.2 (scale) GeV/${c}^{2}$ and a width of ${\ensuremath{\Gamma}}_{z}$=3.8\ifmmode\pm\else\textpm\fi{}0.8\ifmmode\pm\else\textpm\fi{}1.0 GeV.

An asynchronous version of a binary pixel readout circuit has been implemented in an array with 16 columns at 500 mu m pitch and 63 rows at 75 mu m pitch. This readout chip has been bonded with solder bumps to a silicon detector with matching pixel elements. Event information in a pixel can be strobed into a local memory by a trigger signal and subsequently read out. Without a strobe the information in this memory is continuously cleared. The complete hybrid detector has been successfully tested with ionizing particles from a radioactive source. Three such devices have been used in the CERN heavy ion experiment WA94 in the Omega spectrometer where they recorded particle tracks from high multiplicity /sup 32/S interactions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Inclusive jet production at $\sqrt{s}=1.8$ TeV has been measured in the CDF detector at the Fermilab Tevatron $\overline{p}p$ Collider. Jets with transverse energies (${E}_{t}$) up to 250 GeV have been observed. The ${E}_{t}$ dependence of the inclusive jet cross section is consistent with leading-order quantum-chromodynamic calculations, and comparison with lower-energy data shows deviations from scaling consistent with QCD. A lower limit of 700 GeV (95% confidence level) is placed on the quark compositeness scale parameter ${\ensuremath{\Lambda}}_{c}$ associated with an effective contact interaction.

Mitochondrial fission and fusion control the shape, size, number, and function of mitochondria in the cells of organisms from yeast to mammals. The disruption of mitochondrial fission and fusion is involved in severe human diseases such as Parkinson's disease, Alzheimer's disease, metabolic diseases, and cancers. Agents that can real-time track the mitochondrial dynamics are of great importance. However, the short excitation wavelengths and rapidly photo-bleaching properties of commercial mitochondrial dyes render them unsuitable for tracking mitochondrial dynamics. Thus, mitochondrial targeting agents that exhibit superior photo-stability under continual light irradiation, deep tissue penetration and at intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds employ low-energy near-infrared light and have emerged as a non-invasive tool for real-time cell imaging. Here, cyclometalated Ir(III) complexes (Ir1–Ir5) are demonstrated as one- and two-photon phosphorescent probes for the real-time imaging and tracking of mitochondrial fission and fusion. The results indicate that Ir2 is well suited for two-photon phosphorescent tracking of mitochondrial fission and fusion in living cells and in Caenorhabditis elegans (C. elegans). This study provides a practical use for mitochondrial targeting two-photon phosphorescent Ir(III) complexes.

Large double-sided readout silicon strip detectors have been fabricated for the Aleph minivertex. We have tested them with a β-source and have observed charge collection and capacitive charge division both on the junction side and on the ohmic side. A charge correlation has been observed between the two faces and can be used to reduce ambiguities in the case of two particles crossing the same wafer.

A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb−1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, $ {\xi^2} = \frac{{\sigma \left( {{\text{e}^{+} }{\text{e}^{-} } \to {\text{Zh}}} \right)}}{{{\sigma_{\text{SM}}}\left( {{\text{e}^{+} }{\text{e}^{-} } \to {\text{Zh}}} \right)}} \times B\left( {h \to {\text{aa}}} \right) \times B{\left( {{\text{a}} \to {\tau^{+} }{\tau^{-} }} \right)^2} $ . For m h < 107 GeV/c 2 and 4 < m a < 10 GeV/c 2, ξ 2 > 1 is excluded at the 95% confidence level.

An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm−2 s−1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016 cm−2. The CERN-RD50 project “Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders” has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.

Deuteron and anti-deuteron production in Z decays has been observed in the ALEPH experiment at LEP. The production rate of anti-deuterons is measured to be 5.9+-1.8+-0.5 10^-6 per hadronic Z decay in the anti-deuteron momentum range 0.62 to 1.03 GeV/c. The coalescence parameter B_2, which characterizes the likelihood of anti-deuteron production, is measured to be 0.0033+-0.0013 GeV^2 in Z dedays. These measurements indicate that the production of anti-deuterons is suppressed in e+e- collisions compared to pp and photoproduction collisions.

Triple gauge-boson couplings γWW and ZWW involving single-photon, single-W and W-pair production are determined using data samples collected at LEP with the ALEPH detector at centre-of-mass energies between 183 and 209 GeV. The integrated luminosity used is 700 pb−1 for the single-photon measurement and 683 pb−1 for the W channels. Restricting the measurement to C- and P-conserving terms and applying local SU(2)L×U(1)Y gauge invariance, the measured values of the parameters g1Z, κγ and λγ are: g1Z=1.001±0.027(stat)±0.013(syst),κγ=0.971±0.055(stat)±0.030(syst),λγ=−0.012±0.027(stat)±0.011(syst) for single-parameter fits, where the two other parameters are fixed to their Standard Model values. Results are also presented for the cases where two or all three couplings are allowed to vary. An additional analysis using W-pair events is performed to measure the unconstrained real and imaginary parts of all 14 triple gauge-boson couplings and to perform an indirect search for a techni-ρ resonance. No deviations from the Standard Model expectations are observed and the lower limit on the techni-ρ mass is set to 600 GeV/c2 at 95% confidence level.

Cross sections, angular distributions and forward-backward asymmetries are presented, of two-fermion events produced in e+e- collisions at centre-of-mass energies from 189 to 209 GeV at LEP, measured with the ALEPH detector. Results for e+e-, μ+μ-, τ+τ-, qq̄, bb̄ and cc̄ production are in agreement with the standard model predictions. Constraints are set on scenarios of new physics such as four-fermion contact interactions, leptoquarks, Z′ bosons, TeV-scale quantum gravity and R-parity violating squarks and sneutrinos.

Charmed meson pairs have been photoproduced coherently on an active silicon target. Ninety-eight decays have been analyzed and the lifetime of charged D's has been measured.

The mass of the W boson is determined from the direct reconstruction of its decays into purely hadronic and semi-leptonic events in e+e- collisions at LEP. The data sample corresponds to an integrated luminosity of 683 inverse picobarns collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection a new procedure is adopted in which low energy particles are not considered in the mass determination from the purely hadronic channel. The combined result from all channels is Mw = 80.440+-0.043(stat.)+-0.024(syst.)+-0.009(FSI)+-0.009(LEP) GeV/c**2 where FSI represents the possible effects of final state interactions in the purely hadronic channel. From two-parameter fits to the W mass and width, the W width is found to be Gw = 2.14+-0.09(stat.)+-0.04(syst.)+-0.05(FSI)+-0.01(LEP) GeV

We present the dijet invariant-mass distribution in the region between 60 and 500 GeV, measured in 1.8-TeV $\overline{p}p$ collisions in the Collider Detector at Fermilab. Jets are restricted to the pseudorapidity interval $|\ensuremath{\eta}|&lt;0.7$. Data are compared with QCD calculations; axigluons are excluded with 95% confidence in the region $120&lt;{M}_{A}&lt;210$ GeV for axigluon width ${\ensuremath{\Gamma}}_{A}=\frac{N{\ensuremath{\alpha}}_{s}{M}_{A}}{6}$, with $N=5$.

The Compact Muon Solenoid (CMS) is one of the experiments at the Large Hadron Collider (LHC) under construction at CERN. Its inner tracking system consist of the world largest Silicon Strip Tracker (SST). In total it implements 24,244 silicon sensors covering an area of 206m2. To construct a large system of this size and ensure its functionality for the full lifetime of 10 years under LHC condition, the CMS collaboration developed an elaborate design and a detailed quality assurance program. This paper describes the strategy and shows first results on sensor qualification.

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 ϱ− radiative decay width has been measured by studying the production of ϱ− via the Primakoff effect by 200 GeV incident π− on Cu and Pb targets. This width was obtained by fitting the measured dσ/dt for ϱ production with the theoretical coherent differential cross section including both the electromagnetic and strong contributions. The measured radiative width value is 81 ± 4 ± 4 keV: it is consistent with the ratio Γ(ϱ → πγ)/Γ(ω → πγ) ∼ case:19 as expected from the vector dominance and the quark model.

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.

A detector has been developed in our laboratory for proposed use in high energy experiments. It works as a MWPC in which the ionizing medium consists of a thin layer of silicon crystal. The results of the test carried out at CERN show that the detector is ideally suited for the detection of minimum ionizing particles and can provide very high spatial resolution.

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.

The cross section for the production and subsequent decay to electron and neutrino of the W intermediate vector boson has been measured in 1.8-TeV p\ifmmode\bar\else\textasciimacron\fi{}p collisions at the Fermilab Tevatron Collider. An analysis of events with missing transverse energy greater than 25 GeV and with an electron of transverse energy greater than 15 GeV from a datum sample of 25.3 ${\mathrm{nb}}^{\mathrm{\ensuremath{-}}1}$ gives \ensuremath{\sigma}B=2.6\ifmmode\pm\else\textpm\fi{}0.6\ifmmode\pm\else\textpm\fi{}0.5 nb.

We report on the design, manufacturing and first characterisation of pad diodes, test structures and microstrip detectors processed with high resistivity magnetic Czochralski (MCz) p- and n-type Si. The pre-irradiation study on newly processed microstrip detectors and test structures show a good overall quality of the processed wafers. After irradiation with 24 GeV/c protons up to 4×1014 cm-2 the characterisation of n-on-p and p-on-n MCz Si sensors with the C–V method show a decrease of the full depletion voltage and no space charge sign inversion. Microscopic characterisation has been performed to study the role of thermal donors in Czochralski Si. No evidence of thermal donor activation was observed in n-type MCz Si detectors if contact sintering was performed at a temperature lower than 380 °C and the final passivation oxide was omitted.

The ALEPH silicon vertex detector is the first detector operating in a colliding beam environment that uses silicon strip detectors which provide readout on both sides and hence a three-dimensional point measurement for the trajectory of charged particles. The detector system was commissioned successfully at the e+e− collider LEP at the research centre CERN, Switzerland, during the year 1991 while taking data at the Z0 resonance. The achieved spatial resolution of the complete 73 728 channel device (intrinsic plus alignment) is 12 μm in the r-f view and 12 μm in the z view. The design and construction of the entire detector system are discussed in detail and the experience gained in running the detector will be described with special emphasis on the uses of this novel tracking device for the physics of short-lived heavy particles produced in the decays of the Z0 resonance.

Microstrip silicon detectors with orthogonal readout on opposite sides have been designed and fabricated. The active area of each device is 25 cm2 and the strip pitch is 25 μm on the junction side and 50 μm on the opposite ohmic side. A space resolution of 15 μm on the junction side (100 μm readout pitch) and 24 μm on the ohmic side (200 μm readout pitch) has been measured. We also report on AC-coupling chips, designed and fabricated in order to allow AC connection of the strips to the amplifiers. These chips are 6.4 × 5.0 mm2 and have 100 μm pitch. Both AC-couplers and detectors have been installed as part of the ALEPH minivertex.

The charged-particle fractional momentum distribution within jets, D(z), has been measured in dijet events from 1.8-TeV p\ifmmode\bar\else\textasciimacron\fi{}p collisions in the Collider Detector at Fermilab. As expected from scale breaking in quantum chromodynamics, the fragmentation function D(z) falls more steeply as dijet invariant mass increases from 60 to 200 GeV/${\mathit{c}}^{2}$. The average fraction of the jet momentum carried by charged particles is 0.65\ifmmode\pm\else\textpm\fi{}0.02(stat)\ifmmode\pm\else\textpm\fi{}0.08(syst).

A search was made for heavy stable charged particles produced in 1.8-TeV proton-antiproton collisions. No such particles were found in 26.2 ${\mathrm{nb}}^{\mathrm{\ensuremath{-}}1}$ of data. Cross-section limits are presented and mass limits of the order of 100 GeV are set for particles containing excited quarks in higher color representations.

We have measured dijet angular distributions at \ensuremath{\surd}s =1.8 TeV with the Collider Detector at Fermilab and the Tevatron p\ifmmode\bar\else\textasciimacron\fi{}p Collider and find agreement with leading-order QCD. By comparing the distribution for the highest dijet invariant masses with the prediction of a model of quark compositeness, we set a lower limit on the associated scale parameter ${\ensuremath{\Lambda}}_{c}$ at 330 GeV (95% C.L.).

Interstrip and backplane capacitances on silicon microstrip detectors with p+ strip on n substrate of 320μm thickness were measured for pitches between 60 and 240μm and width over pitch ratios between 0.13 and 0.5. Parametrisations of capacitance w.r.t. pitch and width were compared with data. The detectors were measured before and after being irradiated to a fluence of 4×1014protons/cm2 of 24GeV/c momentum. The effect of the crystal orientation of the silicon has been found to have a relevant influence on the surface radiation damage, favouring the choice of a 〈100〉 substrate. Working at high bias (up to 500 V in CMS) might be critical for the stability of detector, for a small width over pitch ratio. The influence of having a metal strip larger than the p+ implant has been studied and found to enhance the stability.

A new approach to monolithic pixel detectors, based on silicon on insulator (SOI) wafers with high resistivity substrate, is being pursued by the CERN RD19 collaboration. The fabrication methods and the results of the electrical evaluation of the SOI-MOSFET devices and of the detector structures fabricated in the bulk are reported. The leakage current of the high-resistivity PIN-diodes is kept of the order of 5 to 10 nA/cm/sup 2/. The SOI preparation processes employed-SIMOX (separation by implantation of oxygen) and ZMR (zone melting recrystallization)-produce working electronic circuits, and appear to be compatible with the fabrication of detectors of suitable quality.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Successive versions of high speed, active silicon pixel detectors with integrated readout electronics have been developed for particle physics experiments using monolithic and hybrid technologies. Various matrices with binary output as well as a linear detector with analog output have been made. The hybrid binary matrix with 1024 cells (dimension 75 μm×500 μm) can capture events at ∼5 MHz and a selected event can then be read out in < 10 μs. In different beam tests at CERN a precision of 25 μm has been achieved and the efficiency was better than 99.2%. Detector thicknesses of 300 μm and 150 μm of silicon have been used. In a test with a 109Cd source a noise level of 170 e− r.m.s. (1.4 keV fwhm) has been measured with a threshold non-uniformity of 750 e− r.m.s. Objectives of the development work are the increase of the size of detecting area without loss of efficiency, the design of an appropriate readout architecture for collider operation, the reduction of material thickness in the detector, understanding of the threshold non-uniformity, study of the sensitivity of the pixel matrices to light and low energy electrons for scintillating fiber detector readout and last but not least, the optimization of cost and yield of the pixel detectors in production.

Results of tests performed on a series of prototype silicon detectors with double side readout are presented. Electrical characteristics and particle data analysis indicate that these detectors can be operated in capacitive charge division with good spatial resolution on two orthogonal coordinates.

A telescope made up of thin silicon detectors was built and used as a live target in a high-energy photoproduction experiment at the CERN Super Proton Synchrotron. Its working principles, construction technique, and the results of tests are reported. This telescope will allow measurement of the decay path in the range 300–10000 μm.

Vertex detectors allow high precision reconstruction of particle tracks and therefore make possible the investigation of the decay topology of short-lived particles in collider experiments. In the ALEPH experiment at LEP a minivertex detector will be installed. It consists of silicon microstrip detectors arranged on two concentric “cylindrical” surfaces around the interaction point. With this geometry it will be possible to measure the r − ϕ − z coordinates of particles traversing the detector. The expected position resolution is 10 μm in r − ϕ and 20 μm in r − z. For optimum signal processing monolithic CMOS readout electronics are under development. Each chip consists of 60 charge sensitive preamplifiers, multiplexed into one output channel. Fast power switching will reduce heat dissipation. Details about construction and expected device performance will be described.

Measurements of inclusive transverse-momentum spectra for ${K}_{S}^{0}$ mesons produced in proton-antiproton collisions at $\sqrt{s}$ of 630 and 1800 GeV are presented and compared with data taken at lower energies. The ratio, as a function of ${p}_{T}$, of the cross section for ${K}_{S}^{0}$ to that for charged hadrons is very similar to what is observed at lower energies. At 1800 GeV, we calculate the strangeness-suppression factor $\ensuremath{\lambda}=0.40\ifmmode\pm\else\textpm\fi{}0.05$.

The ALEPH collaboration, in view of the importance of effective vertex detection for the Higgs boson search at LEP 2, decided to upgrade the previous vertex detector. Main changes were an increased length (+/- 20 cm), a higher granularity for r phi view (50 mu m), a new preamplifier (MX7 rad hard chip), a polymide (upilex) fan-out on z side to carry the signals from the strips to the front-end electronics outside the fiducial region reducing consequently the passive material in the central region by a factor of two. The detector, the running experience and its performance will be described. (C) 1998 Elsevier Science B.V. All rights reserved.

The paper describes the technology used for the fabrication of a set of prototypes of microstrip silicon detectors matching the requirements of the CMS inner tracking system. The detectors are single and double-sided devices featuring integrated AC coupling on both sides. Polysilicon resistors are used as bias elements and individual p-stop patterns provide isolation in between the strips on the ohmic side. The design is such that the performance of these detectors will be marginally affected by the heavy irradiation correlated to several years of running at LHC. Different dielectric layers have been used to study rigidity and yield in the integrated capacitors. Different polysilicon implant doses have been used to optimise the uniformity and to increase the reproducibility of the poly resistors. The paper describes the design choices and the results of laboratory tests on a series of devices.

The two-jet differential cross section ${\mathit{d}}^{3}$\ensuremath{\sigma}(p\ifmmode\bar\else\textasciimacron\fi{}p\ensuremath{\rightarrow}jet 1+jet 2+X)/${\mathit{dE}}_{\mathit{t}}$d${\mathrm{\ensuremath{\eta}}}_{1}$d${\mathrm{\ensuremath{\eta}}}_{2}$, averaged over -0.6\ensuremath{\le}${\mathrm{\ensuremath{\eta}}}_{1}$\ensuremath{\le}0.6, at \ensuremath{\surd}s =1.8 TeV, has been measured in the Collider Detector at Fermilab. The predictions of leading-order quantum chromodynamics for most choices of structure functions show agreement with the data.

The first observation of neutral pion production in πe inelastic scattering is presented. The cross section at 300 GeV for |t‖>62;10−3 (GeV / c)2 is 2.11 ± 0.47 nb, in good agreement with the theory of PCAC anomalies with 3 quark colours.

The luminosity upgrade of the CERN Large Hadron Collider (SLHC) imposes severe requirements on the radiation hardness of the tracking systems. The CERN RD50 collaboration as well as the Italian INFN SMART project (fifth commission) are focused on the study of new radiation hard materials and devices in view of this upgrade. Preliminary studies on irradiated high resistivity n- and p-type magnetic Czochralski silicon are described in this paper. Electrical characterization and microscopic defect studies were performed on a wide set of diodes made with both n- and p-type float zone and magnetic Czochralski silicon irradiated up to a nominal fluence of 3×1015 cm−2 1 MeV equivalent neutrons. The annealing behavior was studied in detail and a first evaluation of the damage-related parameters is shown.

We report the results of two beam tests performed in July and September 1995 at CERN using silicon microstrip detectors of various types: single sided, double sided with small angle stereo strips, double sided with orthogonal strips, double sided with pads. For the read-out electronics use was made of Preshape32, Premux128 and VA1 chips. The signal to noise ratio and the resolution of the detectors was studied for different incident angles of the incoming particles and for different values of the detector bias voltage. The goal of these tests was to check and improve the performances of the prototypes for the CMS Central Detector.

Measurements of the cosmic ray response of the CDF central calorimeters have been performed. For the electromagnetic calorimeter, fine grained response maps were obtained for 46 modules, and the similarity of the individual maps has been studied. For the hadron calorimeter, several basic parameters were calibrated with the use of minimum ionizing particles. In both cases the correspondence between cosmic ray results and test beam results was established.

The production rate of charged D* mesons in jets has been measured in 1.8-TeV p¯p collisions at the Fermilab Tevatron with the Collider Detector at Fermilab. In a sample of approximately 32 300 jets with a mean transverse energy of 47 GeV obtained from an exposure of 21.1 nb−1, a signal corresponding to 25.0±7.5(stat)±2.0(syst) D*±→K∓π±π± events is seen above background. This corresponds to a ratio N(D*++D*−)/N(jet) =0.10±0.03±0.03 for D* mesons with fractional momentum z greater than 0.1.Received 10 October 1989DOI:https://doi.org/10.1103/PhysRevLett.64.348©1990 American Physical Society

Resolution and linearity of the position measurement of Pisa multi-electrode silicon detectors are presented. The detectors are operated in slightly underdepleted mode and take advantage of their intrinsic resistivity for resistive charge partition between adjacent strips. 22 μm resolution is achieved with readout lines spaced 300 μm. Possible applications in colliding beam experiments for the detection of secondary vertices are discussed.

The results of the pre- and post-irradiation characterization of n- and p-type magnetic Czochralski silicon micro-strip sensors are reported. This work has been carried out within the INFN funded SMART project aimed at the development of radiation-hard semiconductor detectors for the luminosity upgrade of the large Hadron collider (LHC). The detectors have been fabricated at ITC-IRST (Trento, Italy) on 4 in wafers and the layout contains 10 mini-sensors. The devices have been irradiated with 24 GeV/c and 26 MeV protons in two different irradiation campaigns up to an equivalent fluence of 3.4×1015 1-MeV n/cm2. The post-irradiation results show an improved radiation hardness of the magnetic Czochralski mini-sensors with respect to the reference float-zone sample.

A large system of silicon strip detectors with double sided readout has been successfully commissioned over the course of the last year at the e+e− collider LEP. The readout of this 73 728 channel system is performed with custom designed VLSI charge sensitive amplifier chips (CAMEX64A). An overall point resolution of 12 μm on both sides has been acheived for the complete system. The most important difficulties during the run were beam losses into the detector, and a chemical agent deposited onto the electronics; however, the damage from these sources was understood and brought under control. This and other results of the 1991 data-taking run are described with special emphasis on the operational experience.

A measurement of the QCD jet-broadening parameter ⟨QT⟩ is described for high-ET jet data in the central calorimeter of the Collider Detector at Fermilab. As an alternate approach to clustering analysis, this method involves the use of a global event parameter which is free from the ambiguities associated with the definition and separation of individual clusters. The parameter QT is defined as the scalar sum of the transverse momentum perpendicular to the transverse thrust axis. Parton-level QCD predictions are made for ⟨QT⟩ as a function of ET, the total transverse energy in the events, and suggest that a measurement would show a dependence on the running of the strong coupling constant αs. Comparisons are made to first-order QCD parton-level calculations, as well as to fully evolved and hadronized leading-log simulations. The data are well described by the QCD predictions.Received 25 January 1991DOI:https://doi.org/10.1103/PhysRevD.44.601©1991 American Physical Society

Describes the germanium monlithic detector and discusses its performance. The detector is a parallelepiped 5 x 5 x 20 mm in volume with 48 electrodes 20 mm long, 50 microns wide and spaced 50 microns one from the other deposited on one face. Presents a sketch of the detector and its working principle. To obtain a finer granularity, a telescope of 40 layers of silica was substituted with a target made out of a single block of germanium followed by a silicon telescope.

A new GeSi active target is presently used in the NA1 experiment at CERN to study photoproduction of charmed particles and to measure their lifetimes. Some general comments on the active target technique are made.

Due to their low depletion voltage, even after high particle fluences, improved tracking precision and momentum resolution, and reduced material budget, thin substrates are one of the possible choices to provide radiation hard detectors for future high energy physics experiments. In the framework of the CERN RD50 Collaboration, we have developed PIN diode detectors on membranes obtained by locally thinning the silicon substrate by means of TMAH etching from the wafer backside. Diodes of different shapes and sizes have been fabricated on 50-/spl mu/m and 100-/spl mu/m thick membranes and tested, showing a low leakage current (of 300 nA/cm/sup 3/) and a very low depletion voltage (in the order of 1 V for the 50 /spl mu/m membrane) before irradiation. Radiation damage tests have been performed with 58 MeV lithium (Li) ions up to the fluence of 10/sup 14/ Li/cm/sup 2/ in order to determine the depletion voltage and leakage current density increase after irradiation. Charge collection efficiency tests carried out with a /spl beta//sup -/ particle source have been performed on both nonirradiated devices and samples irradiated up to 1.8/spl times/10/sup 13/ Li/cm/sup 2/. Results reported here confirm the advantages of thinned diodes with respect to standard 300-/spl mu/m thick devices in terms of low depletion voltage and high charge collection efficiency.

Hadronic Z decays into three jets are used to test QCD models of colour reconnection (CR). A sensitive quantity is the rate of gluon jets with a gap in the particle rapidity distribution and zero jet charge. Gluon jets are identified by either energy-ordering or by tagging two b-jets. The rates predicted by two string-based tunable CR models, one implemented in JETSET (the GAL model), the other in ARIADNE, are too high and disfavoured by the data, whereas the rates from the corresponding non-CR standard versions of these generators are too low. The data can be described by the GAL model assuming a small value for the R0 parameter in the range 0.01-0.02.

We report on the processing and characterization of microstrip sensors and pad detectors produced on n- and p-type Magnetic Czochralski (MCz), Epitaxial (EPI) and Float Zone (FZ) silicon within the SMART project to develop radiation-hard silicon position sensitive detectors for future colliders. Each wafer contains 10 microstrip sensors with different geometries, several diodes and test structures. The isolation in the strip detectors produced on p-type material has been achieved by means of a uniform p-spray implantation, with doping of 3×1012 cm−2 (low-dose p-spray) and 5×1012 cm−2 (high-dose p-spray). The samples have undergone irradiations with 26 MeV protons and reactor neutrons up to ∼1016 cm−2 1 MeV equivalent neutrons (neq/cm2), and have been completely characterized before and after irradiation in terms of leakage current, depletion voltage and breakdown voltage. The current damage parameter α has been determined for all substrates. MCz diodes show less pronounced dependence of effective doping concentration Neff on the fluence when compared to standard FZ silicon, giving results comparable to diffusion oxygenated FZ devices for all irradiation sources. The observed increase of Neff with fluence can be interpreted in EPI material as a net donor introduction process, overcompensating the usual acceptor introduction process. This effect is stronger for 26 MeV proton irradiation than for neutron irradiation.

A description of the ALEPH Vertex Detector (VDET 91), including the mechanical structure and the improved data acquisition system, is given. The apparatus consists of two complete layers of silicon detectors with double-sided readout which provide a full x, y, z information of the impact points of charged particles. The authors show results on signal-to-noise ratio for minimum ionizing particles and efficiency in hit/track matching. Results on position, impact parameter, and momentum resolution are also shown as measured using high momentum muons. The first preliminary study on vertexing techniques and their impact on physics analysis is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Several 5*5 cm/sup 2/ double-sided readout silicon strip detectors have been fabricated using planar technology. Electrical characteristics (I-V and C-V curves interstrip resistance versus bias voltage) have been measured. Some detectors have been tested with a scanning electron microscope to investigate defects due to the fabrication process. A few of them have been tested with a beta source and with a 50-GeV electron beam. A strong correlation is observed between charges collected on the ohmic side and on the junction side. Preliminary results on capacitive charge division studies are also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A measurement of the lifetime of theΛ c baryon photoproduced coherently off a Germanium-Silicon target is presented. A signal ofΛ c →ΔK*→pKππ0 has been observed and the two different decay diagrams for this process are compared. A sample of 9Λ c decays gives a lifetime of 1.1 −0.4 +0.8 10−13 s.

A search for short-life isomers in $^{98}\mathrm{Tc}$ has been made with the reaction $^{98}\mathrm{Mo}(p, n)^{98}\mathrm{Tc}$ and a pulsed proton beam. Three new isomeric transitions have been identified in addition to the known one of 14.6 ns half-life. The mean lives measured for the three $\ensuremath{\gamma}$ rays of 47.8, 57.0, and 65.2 keV come out to be ${\ensuremath{\tau}}_{\mathrm{m}}=(11.6\ifmmode\pm\else\textpm\fi{}0.3), (11.6\ifmmode\pm\else\textpm\fi{}0.9), \mathrm{and} (11.4\ifmmode\pm\else\textpm\fi{}2.8)$ (11.6 \ifmmode\pm\else\textpm\fi{} 0.9), and (11.4 \ifmmode\pm\else\textpm\fi{} 2.8) ns, respectively. These transitions have been attributed to the decay of the 138.6 keV level. Two new levels at 73.4 keV and at 90.8 keV have been identified and are suggested as possible candidates for the 14.6 \ensuremath{\mu}s isomer. An upper limit (${\ensuremath{\tau}}_{\mathrm{m}}&lt;2$ ns) has also been obtained for the mean life of the levels at 65.4, 81.6, 152.0, 190.3, and 203.9 keV.NUCLEAR REACTIONS $^{98}\mathrm{Mo}(p, n\ensuremath{\gamma})$, ${E}_{p}=4\ensuremath{-}5$ MeV, pulsed beam; measured ${E}_{\ensuremath{\gamma}}$, delayed $\ensuremath{\gamma}$. $^{98}\mathrm{Tc}$ isomer observed, deduced lifetime. Enriched target.

A search for Higgs bosons produced in association with a fermion pair, and decaying to WW, is performed with the data collected by the ALEPH detector at centre-of-mass energies ranging from 191 to 209 GeV. The data correspond to an integrated luminosity of 453.2 pb-1. Thirteen exclusive selections are developed according to the different final state topologies. No statistically significant evidence for a Higgs boson decaying into a WW pair has been found. An upper limit is derived, as a function of the Higgs boson mass, on the product of the e+e-→Hff̄ cross section and the H→WW branching ratio. The data on the search for H→WW are combined with previously published ALEPH results on the search for H→γγ, to significantly extend the limits on the mass of a fermiophobic Higgs boson.

The aim of this work is the development of radiation hard detectors for very high luminosity colliders. A growing interest has been recently focused on Czochralski silicon as a potentially radiation-hard material. We report on the processing and characterization of micro-strip sensors and pad detectors produced by ITC-IRST on n- and p-type magnetic Czochralski and float zone silicon. Part of the samples has been irradiated using 24 GeV/c protons (CERN-Geneva), while another part has been irradiated with 26 MeV protons (FZK-Karlsruhe) up to a fluence of 5×1015 1 MeV-neutron-equivalent/cm2. All the samples have been completely characterized before and after irradiation. Their radiation hardness as a function of the irradiation fluence has been established in terms of breakdown voltage, leakage current and evaluating the more relevant mini-sensor parameter variation. Moreover, the time evolution of depletion voltage, leakage current and inter-strip capacitance has been monitored in order to study their annealing behavior and space charge sign inversion effects.

The Compact Muon Solenoid (CMS) detector is one of the two largest and most powerful particle physics detectors ever built. CMS is installed in P5 at CERN's Large Hadron Collider (LHC) and as of early 2011 has completed nearly a year of operation in which it recorded products of interactions produced in protonproton collisions at a center of mass energy of 7 TeV. The proton-proton run 2010 lasted 7 months and was followed by Pb-Pb ion collisions in November. During the first few months of 2011 the LHC has delivered higher luminosity. The LHC machine is performing extremely well, allowing CMS to record enough data to perform a large number of studies of the Standard Model (SM) of particle physics in this new energy domain for the first time and to search for evidence of new physics in regions of phase space that have never before been entered. The CMS detector components, the operational experience and the performance with colliding beams will be described.

We present results obtained with full-size wedge silicon microstrip detectors bonded to APV6 (Raymond et al., Proceedings of the 3rd Workshop on Electronics for LHC Experiments, CERN/LHCC/97-60) readout chips. We used two identical modules, each consisting of two crystals bonded together. One module was irradiated with 1.7×1014neutrons/cm2. The detectors have been characterized both in the laboratory and by exposing them to a beam of minimum ionizing particles. The results obtained are a good starting point for the evaluation of the performance of the “ensemble” detector plus readout chip in a version very similar to the final production one. We detected the signal from minimum ionizing particles with a signal-to-noise ratio ranging from 9.3 for the irradiated detector up to 20.5 for the non-irradiated detector, provided the parameters of the readout chips are carefully tuned.

The Aleph silicon vertex detector at the LEP e+e− collider at CERN is described. A detailed information on the various components of the detector is given. Preliminary results obtained during 1990 LEP running are presented.

The major reason for building a vertex detector for CDF is the tagging of decay vertices of particles with lifetime in the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> 3/10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> 2 sec. range. This is a complementary approach to heavy flavour physics with respect to missing E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> and large P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> leptons. The method can be best applied to tag hadronic decays of heavy flavours, which have the largest branching ratios, but have eluded any specific tagging until now. It also works, although with somewhat reduced efficiency, in events with a semileptonic decay. All in all it promises to be a powerful tool in the search of rather elusive processes like Higgs, top, or fourth generation quark production [1]. The additional information provided by the vertex detector will also improve significantly the resolution of the CDF central tracking system [2].

A proposal for a pixel-based Level 1 trigger for the Super-LHC is presented. The trigger is based on fast track reconstruction using the full pixel granularity exploiting a readout which connects different layers in specific trigger towers. The trigger will implement the current CMS high level trigger functionality in a novel concept of intelligent detector. A possible layout is discussed and implications on data links are evaluated.

The Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) is equipped with four gas systems, one per each of the muon detectors (i.e. Cathode Strip Chambers, Drift Tube and Resistive Plate Chambers) and one for the inner detectors neutral gas flushing (pixel, tracker, Electromagnetic and Hadron calorimeters). Each gas detector is suitable operated with a well defined gas mixture and also the levels of contaminants (commonly O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O, etc.) that can affect the detector performances are well defined. Therefore, the necessity of a tool able to verify the gas mixture composition was always considered as a fundamental requirement. Moreover, after three years of operation few critical points have been identified and this allowed to define the requirement of a new analysis station already installed that will soon monitor the mixture composition for all the detectors. The analysis station is based on a gas chromatograph with a system of three multi-ways valves that will allow to analyze almost automatically up to 48 gas stream coming from different detectors and also from several region of the experiment subjected to different level of radiation.

The ALEPH Silicon Vertex Detector (VDET) is operational inside the apparatus since 1991. The novel technology of double-sided silicon strip detectors has been demonstrated a powerful tool in reconstructing vertices in 3D with LEP running at Z0 c.m. energy; some results from this running experience will be presented. Due to the VDET key role for b-tagging in the Higgs boson search at LEP200 the detector has been upgraded to improve the performance. An overall description of the VDET II will be given and the results obtained in the first run of LEP at Ecm = 131 GeV will be discussed.

This paper describes the main achievements in the development of radiation resistant silicon detectors to be used in the CMS tracker. After a general description of the basic requirements for the operation of large semiconductor systems in the LHC environment, the issue of radiation resistance is discussed in detail. Advantages and disadvantages of the different technological options are presented for comparison. Laboratory measurements and test beam data are used to check the performance of several series of prototypes fabricated by different companies. The expected performance of the final detector modules are presented together with preliminary test beam results on system prototypes.

Multi-electrode germanium detectors are being used as an active target for decay path measurements of charmed mesons. The procedure used to fabricate such detectors is described and a brief analysis of their performance is given.

In the silicon tracker for the Compact Muon Solenoid experiment at the forthcoming Large Hadron Collider of CERN, each silicon sensor is connected to the front-end electronics by a pitch adapter, the structure of which consists of a fan of very thin chromium strips coated with a few microns aluminium deposition, on a glass support. The absence of contaminants in the depositions is of crucial importance for the electrical and mechanical reliability of the micro-bonding connections. The PIXE set-up of the Florence external micro-beam facility appeared to be suitable to analyse the metal deposition of an adapter, on which the micro-bonds had shown mechanical and electrical problems. Our measurements pointed out a significant copper contamination of the metal deposition on the faulty adapter, while no copper was detected in another one, which showed a correct behaviour at bonding. This suggests a possible role of Cu impurities in the encountered problems during micro-bonding.

One “wedge” Double Sided Silicon Detector prototype for the CMS forward inner tracker has been tested both in laboratory and on a high energy particle beam. The results obtained indicate the most reliable solutions for the strips geometry of the junction side. Three different designs of “wedge” Double Sided detectors with different solutions for the ohmic side strip geometry are presented.

Abstract In the framework of the CERN detector R&D effort in view of future high luminosity colliders, several pixel detector prototypes, both hybrid and monolithic, are being developed. A hybrid matrix of 16 × 64 pixels with a new readout cell is described here, and it will be first used for a test in a heavy-ion experiment. Preliminary results from the application of SOI processes on high resistivity silicon are also presented.

The authors describe the performance of surface barrier silicon detectors with x,y readout electrodes which have been fabricated and tested with minimum ionizing particles. The impact points of the incoming particles are reconstructed with an accuracy of 52 mu m and 300 mu m, respectively, for the two coordinates, and each detector provides a fully two-dimensional plot of the beam profile. Global efficiency, edge effects, and two-particle resolution in both coordinates are reported. It is concluded that the strong correlation between the charges collected on the two sides is helpful in solving ambiguities in about 80% of the events with two particles.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The CMS experiment at the LHC will comprise a large silicon strip tracker. This article highlights some of the results obtained in the R&D studies for the optimization of its silicon sensors. Measurements of the capacitances and of the high voltage stability of the devices are presented before and after irradiation to the dose expected after the full lifetime of the tracker.

The ALEPH experiment [1] at LEP is equipped with a vertex detector [2] using two layers of double-sided silicon strip detectors. These detectors allow a real two-dimensional measurement of charged particle tracks. The present (1991) detector has the inner layer at a radius of 6.5 cm and the outer layer at 11.5 cm. The theta angle coverage is ±33° for the inner layer and ±50° for the outer layer. The inner layer is made out of 9 faces with four silicon detectors each, the outer layer has 15 such faces. We use silicon detectors of 5 × 5 cm2 and 300 μm thickness. The readout pitch is 100 μm at both sides and using capacitive charge division a resolution in the order of 10 μm can be achieved. The signals from 256 readout strips are integrated, amplified and multiplexed using four CAMEX64 chips. An early version of this detector was already installed in spring 1990. Although the detector was not complete and in addition was accidentally damaged by malfunctions of the external electronics, it took data during the 1990 ALEPH run. For the first time double sided silicon detectors were used in a physics experiment. In 1991 the beampipe was replaced by a smaller one. This allowed us to move the inner layer to a radius of 6.5 cm. A completely new detector has been built. This new detector has been installed in spring 1991. Most of the results quoted in this paper refer to this detector.

Due to their low depletion voltage, even after high particle fluences, improved tracking precision and momentum resolution and reduced material budget, thin substrates are one of the possible choices to provide radiation hard detectors for future high energy physics experiments. In the framework of the CERN RD50 Collaboration, we have developed p-n diode detectors on membranes obtained by locally thinning the silicon substrate by means of TMAH etching from the wafer back-side. Diodes of different shapes and sizes have been fabricated on 50-/spl mu/m and 100-/spl mu/m thick membranes and tested, showing a low leakage current (about 300 nA/cm/sup 3/) and, as expected, a very low depletion voltage (in the order of 1 V for the 50-/spl mu/m membrane). Radiation damage tests have been performed with 58-MeV Li ions at the SIRAD Irradiation Facility of the INFN National Laboratory of Legnaro, Italy, up to a fluence of 1.83 /spl times/ 10/sup 13/ Li/cm/sup 2/. Moreover, charge collection efficiency tests performed at INFN Firenze with a /spl beta/ particle source have been performed on both non-irradiated and irradiated samples. Results here reported confirm the advantages of thinned diodes with respect to standard ones in terms of low depletion voltage and charge collection efficiency even after the highest ion fluence.

A measurement of the lifetime of D0-mesons photoproduced coherently off a germanium target is presented. Signals have been observed for the production of D0 into several channels and for D*+ → D0π+. A sample of 58 D0 decays gives a lifetime of (3.4−0.5+0.6 ± 0.3) · 10−13 s.

The most recent developments in fabrication and performance of double-sided microstrip silicon detectors are described in view of applications for beauty physics at e+e− and hadron colliders.

The monolithic integration of electronics and high-resistivity silicon detectors is reported. The approach is based on CMOS circuit integration in the top layer of high-resistivity SOI (silicon-on-insulator) wafers. In a preliminary feasibility study, high-resistivity wafers were subjected to SOI layer fabrication methods and evaluated with a simple diode process for two main characteristics: diode leakage and possible dopant concentration increase. In the second phase of the project, a full SOI-on-H Omega process was executed. MOSFET behavior was then evaluated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In the last years several hundreds of large (∼25 cm2) double-sided silicon strip detectors have been designed and tested in our Pisa-INFN laboratory. These detectors are currently used in ALEPH and L3 vertices, and in other field of applications as well. We present the tests performed on a single detector, and we discuss some results on the test structures inserted in each wafer in order to measure the relevant, process-dependent, quantities which determine the detector performances.

A prototype of the barrel Tracking Detector of the Compact Muon Solenoid (CMS) experiment proposed for LHC was built and tested in a beam and in a magnetic field of up to 3 T. It contained six microstrip gas chambers, 25 cm long, and three double-sided silicon microstrip detectors, 12.5 cm long. We report some preliminary results on the performance of the chambers.

Detectors with very high space resolution have been built in our laboratory and tested at CERN in order to investigate their possible use in high energy physics experiments. These detectors consist of thin layers of silicon crystals acting as ionization chambers. Thin electrodes, structured in strips or in more fancy shapes are applied to their surfaces by metal coating. The space resolution which could be reached is of the order of a few microns. An interesting feature of these solid state detectors is that they can work under very high or low external pressure or at very low temperature. The use of these detectors would strongly reduce the dimensions and the cost of high energy experiments.

Four position sensitive silicon detectors have been tested inside the Tevatron beam pipe at Fermilab. The system is the prototype of the small angle silicon spectrometer designed to study primarily pp elastic and diffractive cross-sections at the Collider of Fermilab (CDF). Particles in the beam halo during p-p storage tests were used to study the performance of the detectors. Efficiency, linearity of response and spatial resolution are shown. Measurements performed at different distances from the beam axis have shown that the detectors could be operated at 8.5 mm from the beam with low rates and no disturbance to the circulating beams. This distance corresponds to about 11 times the standard half-width of the local beam envelope. The behaviour of the detectors with the radiation dose has also been investigated.

The CMS Silicon tracker consists of 70m2 of microstrip sensors which design will be finalized at the end of 1999 on the basis of systematic studies of device characteristics as function of the most important parameters. A fundamental constraint comes from the fact that the detector has to be operated in a very hostile radiation environment with full efficiency. We present an overview of the current results and prospects for converging on a final set of parameters for the silicon tracker sensors.

Abstract Radiation effects on silicon microstrip detectors have been investigated on sensors similar to the ones that will be installed in the forward tracker of CMS. Sensors have been built starting from a high resistivity (about 6 kΩ cm ) n-type substrate, 〈1 1 1〉 crystal lattice orientation. Some of the wafers have been exposed to a neutron beam with a 1 MeV equivalent neutron fluence of 1.1×10 14 neutron / cm 2 . Depletion voltage, reverse current, bulk and interstrip capacitance have been measured in laboratory before and after irradiation, directly on the full size structures. Detectors built with these structures have then been tested with a 90 Sr source in laboratory. Device properties and performances with respect to signal to noise ratio are presented, emphasizing their dependence on irradiation.

For the construction of the silicon microstrip detectors for the Tracker of the CMS experiment, two different substrate choices were investigated: A high-resistivity (6 k cm) substrate with (111) crystalorientation and a low-resistivity (2k cm) one with (100) crystalorientation. The interstrip and backplane capacitances were measured before and after the exposure to radiation in a range of strip pitches from 60 μm to 240 μm and for values of the width-over-pitch ratio between 0.1 and 0.5.

A new Silicon Vertex Detector was developed for the ALEPH experiment and first installed for the high energy run at 130 GeV at the end of 1995. The detector has an active length of 40 cm and consists of two concentric layers of silicon wafers with double-sided readout. It extends the angular coverage, has only half the passive material as the former detector in the tracking volume and is radiation hard to cope with the higher level of radiation background expected for the LEP2 phase. The construction and the performance of the detector is described.

Abstract A large quantity of silicon microstrip detectors is foreseen to be used as part of the CMS tracker. A specific research and development program has been carried out with the aim of defining layouts and technological solutions suitable for the use of silicon detectors in high radiation environment. Results presented here summarise this work on many research areas such as techniques for device manufacturing, pre- and post-irradiation electrical characterization, silicon bulk defects analysis and simulations, system performance analytical calculations and simulations and test beam analysis. As a result of this work we have chosen to use single-sided, AC-coupled, poly silicon biased, 300 μm thick, p + on n substrate detectors. We feel confident that these devices will match the required performances for the CMS tracker provided they can be operated at bias voltages as high as 500 V. Such high-voltage devices have been succesfully manufactured and we are now concentrating our efforts in enhancing yield and reliability.