Roberto Dell’Orso

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.

We present a precise measurement of the left-right cross section asymmetry ($A_{LR}$) for $Z$ boson production by $\ee$ collisions. The measurement was performed at a center-of-mass energy of 91.26 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (63.0$\pm$1.1)%. Using a sample of 49,392 $\z0$ decays, we measure $A_{LR}$ to be 0.1628$\pm$0.0071(stat.)$\pm$0.0028(syst.) which determines the effective weak mixing angle to be $\swein=0.2292\pm0.0009({\rm stat.})\pm0.0004({\rm syst.})$.}

We have measured the differential production cross sections as a function of scaled momentum x_p=2p/E_cm of the identified hadron species pi+, K+, K0, K*0, phi, p, Lambda0, and of the corresponding antihadron species in inclusive hadronic Z0 decays, as well as separately for Z0 decays into light (u, d, s), c and b flavors. Clear flavor dependences are observed, consistent with expectations based upon previously measured production and decay properties of heavy hadrons. These results were used to test the QCD predictions of Gribov and Lipatov, the predictions of QCD in the Modified Leading Logarithm Approximation with the ansatz of Local Parton-Hadron Duality, and the predictions of three fragmentation models. Ratios of production of different hadron species were also measured as a function of x_p and were used to study the suppression of strange meson, strange and non-strange baryon, and vector meson production in the jet fragmentation process. The light-flavor results provide improved tests of the above predictions, as they remove the contribution of heavy hadron production and decay from that of the rest of the fragmentation process. In addition we have compared hadron and antihadron production as a function of x_p in light quark (as opposed to antiquark) jets. Differences are observed at high x_p, providing direct evidence that higher-momentum hadrons are more likely to contain a primary quark or antiquark. The differences for pseudoscalar and vector kaons provide new measurements of strangeness suppression for high-x_p fragmentation products.

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.

The strong coupling αs(M2Z) has been measured using hadronic decays of Z0 bosons collected by the SLD experiment at SLAC. The data were compared with QCD predictions both at fixed order O(α2s) and including resummed analytic formulas based on the next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, and angular energy flow, and checked the consistency between αs(M2Z) values extracted from these different measures. Combining all results we obtain αs(M2Z)= 0.1200±0.0025 (expt) ±0.0078 (theor), where the dominant uncertainty is from uncalculated higher order contributions.Received 19 September 1994DOI:https://doi.org/10.1103/PhysRevD.51.962©1995 American Physical Society

We present measurements of ${\mathit{R}}_{\mathit{b}}$ using the SLD at the SLC. The analyses use 2D and 3D impact parameter tags and a displaced 3D vertex tag which all exploit the small size and stability of the ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ interaction point and the precision 3D CCD pixel vertex detector to achieve high bb\ifmmode\bar\else\textasciimacron\fi{}-tagging efficiencies and purities. The combined measurement yields ${\mathit{R}}_{\mathit{b}}$=0.229\ifmmode\pm\else\textpm\fi{}0.011 and is consistent with standard model predictions. \textcopyright{} 1996 The American Physical Society.

We present the first measurement of the left-right cross section asymmetry (${\mathit{A}}_{\mathit{L}\mathit{R}}$) for Z boson production by ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ collisions. The measurement was performed at a center-of-mass energy of 91.55 GeV with the SLD detector at the SLAC Linear Collider which utilized a longitudinally polarized electron beam. The average beam polarization was (22.4\ifmmode\pm\else\textpm\fi{}0.6)%. Using a sample of 10 224 Z decays, we measure ${\mathit{A}}_{\mathit{L}\mathit{R}}$ to be 0.100\ifmmode\pm\else\textpm\fi{}0.044(stat)\ifmmode\pm\else\textpm\fi{}0.004(syst), which determines the effective weak mixing angle to be ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathit{W}}^{\mathit{e}\mathit{f}\mathit{f}}$=0.2378 \ifmmode\pm\else\textpm\fi{}0.0056(stat)\ifmmode\pm\else\textpm\fi{}0.0005(syst).

We present a new measurement of the left-right cross section asymmetry $({A}_{\mathrm{LR}})$ for $Z$ boson production by ${e}^{+}{e}^{\ensuremath{-}}$ collisions. The measurement was performed at a center-of-mass energy of 91.28 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was $(77.23\ifmmode\pm\else\textpm\fi{}0.52)%$. Using a sample of 93 644 $Z$ decays, we measure the pole value of the asymmetry, ${A}_{\mathrm{LR}}^{0}$, to be $0.1512\ifmmode\pm\else\textpm\fi{}0.0042(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0011(\mathrm{syst})$, which is equivalent to an effective weak mixing angle of $\mathrm{sin}{}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.23100\ifmmode\pm\else\textpm\fi{}0.00054(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.00014\left(\mathrm{syst}\right)$.

The purpose of this work is to study layout solutions aimed at increasing the breakdown voltage in silicon micro-strip detectors. Several structures with multiple floating guards in different configurations have been designed and produced on high-resistivity silicon wafers. The main electrical characteristics of these devices have been measured before and after irradiation. Both radiation-induced surface and bulk damage effects were considered as well. The highest breakdown voltage was found on devices featuring p/sup +/ guards without field plates. A simulation study has been carried out on simplified structures to evaluate the distribution of the breakdown field as a function of the guard layout. The aim was design optimization.

We report on the 3-year INFN ATLAS–CMS joint research activity in collaboration with FBK, started in 2014, and aimed at the development of new thin pixel detectors for the High Luminosity LHC Phase-2 upgrades. The program is concerned with both 3D and planar active-edge pixel sensors to be made on 6" p-type wafers. The technology and the design will be optimized and qualified for extreme radiation hardness (2×1016 neq cm−2). Pixel layouts compatible with present (for testing) and future (RD53 65 nm) front-end chips of ATLAS and CMS are considered. The paper covers the main aspects of the research program, from the sensor design and fabrication technology, to the results of initial tests performed on the first prototypes.

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.

We present the first experimental study of the ratio of cumulant to factorial moments of the charged-particle multiplicity distribution in high-energy particle interactions, using hadronic Z$^0$ decays collected by the SLD experiment at SLAC. We find that this ratio, as a function of the moment-rank $q$, decreases sharply to a negative minimum at $q=5$, which is followed by quasi-oscillations. These features are insensitive to experimental systematic effects and are in qualitative agreement with expectations from next-to-next-to-leading-order perturbative QCD.

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.

We have measured the distributions of the jet energies in ${e}^{+}$${e}^{\ensuremath{-}}$\ensuremath{\rightarrow}qq\ifmmode\bar\else\textasciimacron\fi{}g events, and of the three orientation angles of the event plane, using hadronic ${Z}^{0}$ decays collected in the SLD experiment at SLAC. We find that the data are well described by perturbative QCD incorporating vector gluons. We have also studied models of scalar and tensor gluon production and find them to be incompatible with our data.

Using an impact parameter tag to select an enriched sample of Z0→bb¯ events, and the net momentum-weighted track charge to identify the sign of the charge of the underlying b quark, we have measured the left-right forward-backward asymmetry for b quark production as a function of polar angle. Based on 1.8pb−1 of Z0 decay data produced with a mean electron beam polarization of Pe=63%, this yields a direct measurement of the extent of parity violation in the Zbb coupling of Ab=0.87±0.11(stat)±0.09(syst).Received 3 October 1994DOI:https://doi.org/10.1103/PhysRevLett.74.2890©1995 American Physical Society

Within the family of the Micro Strip Gas Detectors (MSGD), the intrinsic characteristics of the bulk Micro-Megas (MM) device represent the most promising features for the construction of a new instrument to be operated as a TPC gas chamber in a low-pressure regime. In this study, we present the main properties of a low-pressure bulk MM detector in which the amplification gap was slightly increased to improve the gas gain. Two configurations have been deeply studied: the first one with a gap of 128μm and a second one with a 192μm gap, both filled and operated with a gas mixture (Ar-CO2) at pressures below 100 mbar. The dependence of the gain and the energy resolution on the amplification field, gas pressure and drift field have been evaluated. The reliability of the measured performance, combined with the simple and robust structure of the detector even with an increased length of amplification gap, make it an attractive choice for applications where the track length of low energy particles is detected by using a low-pressure filling gas.

The parity-violating parameters Ab and Ac are directly measured by the SLD experiment at the SLAC Linear Collider in e+e− collisions with polarized electrons at the Z0 resonance. Leptons with distinctive total and transverse momenta are used to select and analyze Z0→bb¯ and Z0→cc¯ events. Ab and Ac are extracted by forming the left-right forward-backward asymmetry in electron beam polarization and quark polar angle. From our 1993 sample of 1.8 pb–1 of Z0 decay data with an average electron beam polarization of 63% we find Ab=0.91±0.14 (stat) ±0.07 (syst) and Ac=0.37±0.23 (stat) ±0.21 (syst).Received 4 October 1994DOI:https://doi.org/10.1103/PhysRevLett.74.2895©1995 American Physical Society

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 lifetimes of B 1 and B 0 mesons are measured using a sample of 150 000 hadronic Z 0 decays collected by the SLD experiment at the SLAC Linear Collider between 1993 and 1995.Two analyses are presented in which the decay length and charge of the B meson are reconstructed.The first method uses a novel topological vertexing technique while the second uses semi-inclusively reconstructed semileptonic decays.The topological analysis yields a sample of 6033 ( 3665) charged (neutral) vertices with good charge purity, whereas the semileptonic analysis yields a smaller sample of 634 ( 584) charged (neutral) decays with excellent charge purity.Combining the results from both analyses, we find t B 1 1.66 6 0.06͑stat͒ 6 0.05͑syst͒ ps, t B 0 1.64 6 0.08͑stat͒ 6 0.08͑syst͒ ps, and t B 1 ͞t B 0 1.01 6 0.07͑stat͒ 6 0.06͑syst͒.[S0031-9007(97)

Bhabha scattering with polarized electrons at the ${Z}^{0}$ resonance has been measured with the SLD experiment at the SLAC Linear Collider. The first measurement of the left-right asymmetry in Bhabha scattering is presented, yielding the effective weak mixing angle of ${sin}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.2245\ifmmode\pm\else\textpm\fi{}0.0049\ifmmode\pm\else\textpm\fi{}0.0010$. The effective electron couplings to the ${Z}^{0}$ are extracted from a combined analysis of polarized Bhabha scattering and the left-right asymmetry previously published: ${\ensuremath{\upsilon}}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.0414\ifmmode\pm\else\textpm\fi{}0.0020$ and ${a}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.4977\ifmmode\pm\else\textpm\fi{}0.0045$.

Abstract A large hadron calorimeter and muon tracking device using plastic streamer tubes has been constructed in the iron flux-return structure for the SLD detector at SLAC. Various studies of the operating characteristics of the streamer tubes of this system are presented. Emphasis is placed on the tracking capabilities of the device and on the optimization of the high voltage and readout electronics.

Using an impact parameter tag to select an enriched sample of ${\mathit{Z}}^{0}$\ensuremath{\rightarrow}bb\ifmmode\bar\else\textasciimacron\fi{} events, we have measured the difference between the average charged multiplicity of ${\mathit{Z}}^{0}$\ensuremath{\rightarrow}bb\ifmmode\bar\else\textasciimacron\fi{} and ${\mathit{Z}}^{0}$\ensuremath{\rightarrow} hadrons to be n${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{b}}$-n${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathrm{had}}$=2.24\ifmmode\pm\else\textpm\fi{}0.30 ( stat )\ifmmode\pm\else\textpm\fi{}0.33 ( syst ) tracks per event. From this, we have derived n${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{b}}$-n${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{u}\mathit{d}\mathit{s}}$=3.31\ifmmode\pm\else\textpm\fi{}0.41\ifmmode\pm\else\textpm\fi{}0.79. Comparing this measurement with those at lower center-of-mass energies, we find no evidence that n${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{b}}$-n${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{u}\mathit{d}\mathit{s}}$ depends on energy. This result is in agreement with a precise prediction of perturbative QCD, and supports the notion that QCD remains asymptotically free down to the scale ${\mathit{M}}_{\mathit{b}}^{2}$.

Average charged multiplicities have been measured separately in b, c and light quark (u, d, s) events from Z0 decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of b and light quark events, and reconstructed charmed mesons were used to select c quark events. We measured the charged multiplicities: nuds= 20.21 ± 0.10(stat.) ± 0.22(syst.), nc= 21.28 ± 0.46(stat.)−0.36+0.41syst.) and nb= 23.14 ± 0.10(stat.)−0.37+0.38(syst.), from which we derived the differences between the total average charged multiplicities of c or b quark events and light quark events: Δnc= 1.07 ± 0.47(stat.)−0.30+0.36(syst.) and Δnb= 2.93 ± 0.14(stat.)−0.29+0.30(syst.). We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.

We present direct measurements of the ${Z}^{0}$-lepton coupling asymmetry parameters ${A}_{e}$, ${A}_{\ensuremath{\mu}}$, and ${A}_{\ensuremath{\tau}}$, based on a data sample of 12 063 leptonic ${Z}^{0}$ decays collected by the SLD detector. The $Z$ bosons are produced in collisions of beams of polarized ${e}^{\ensuremath{-}}$ with unpolarized ${e}^{+}$ at the SLAC Linear Collider. The couplings are extracted from the measurement of the left-right and forward-backward asymmetries for each lepton species. The results are ${A}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.152\ifmmode\pm\else\textpm\fi{}0.012(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.001(\mathrm{syst})$, ${A}_{\ensuremath{\mu}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.102\ifmmode\pm\else\textpm\fi{}0.034\ifmmode\pm\else\textpm\fi{}0.002$, and ${A}_{\ensuremath{\tau}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.195\ifmmode\pm\else\textpm\fi{}0.034\ifmmode\pm\else\textpm\fi{}0.003$.

We have determined the strong coupling ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$ from measurements of jet rates in hadronic decays of ${\mathit{Z}}^{0}$ bosons collected by the SLD experiment at SLAC. Using six collinear and infrared safe jet algorithms we compared our data with the predictions of QCD calculated up to second order in perturbation theory, and also with resummed calculations. We find ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$(${\mathit{M}}_{\mathit{Z}}^{2}$)=0.118\ifmmode\pm\else\textpm\fi{}0.002(stat)\ifmmode\pm\else\textpm\fi{}0.003(syst)\ifmmode\pm\else\textpm\fi{}0.010(theory), where the dominant uncertainty is from uncalculated higher order contributions.

The iron flux-return structure for the SLC Large Detector (SLD) has been instrumented with plastic streamer tubes covering an area of about 4500 m2, to provide muon identification plus energy measurement of hadron showers. A description is given of the production techniques used to construct this large detector system, with an emphasis on the methods by which high reliability and a small number of defects in the completed assembly were ensured.

The CDF Associative-Memory device (AM), proven technology developed for the Silicon-Vertex-Trigger at the CDF experiment, is one of the proposed solutions at the LHC for track reconstruction at level-1 in the HL-LHC upgrade, for very high-luminosity conditions (hundreds proton-proton collisions every 25 ns, at 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">- 2</sup> sec <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">- 1</sup> ). This luminosity requires a drastic revision of the existing trigger strategies. In the CMS experiment, one of the identified challenges for future upgrades is the capability of using already at L1 the tracker information to trigger events. Simulation studies show that this can be achieved by correlating hits on two closely spaced silicon strip sensors. This strategy requires massive computing power, to minimize the online execution time of complex tracking algorithms and the “combinatorial challenge.” The AM allows to compare the tracker information of each event to pre-calculated “expectations” (pattern matching) in a so short time that tracks can contribute to the trigger decision. One of the main challenges for the CMS tracker is the latency due to the tracker data distribution to the AM processors. A very parallelized readout architecture and a possible layout are discussed.

We designed, realized, and tested a 2.5-Gb/s optical wireless communication (OWC) system prototype, that should be employed in high energy physics (HEP) experiments, such as the compact muon solenoid (CMS). The system consists of off-the-shelf components, mainly a vertical cavity surface emitting laser (VCSEL) and a PIN photodiode with a proper ball lens. Since it should be used to transmit data among particle sensors in neighboring rings of the CMS, its target distance is 10 cm. Its most attractive feature is that it does not require a (complex) active tracking system because its measured tolerance to misalignment is around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 1 mm (at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-12}$</tex-math></inline-formula> bit error rate). We also report the X-rays irradiation tests of all components (Quartz lens, VCSEL, and PIN photodiode): None of them showed any degradation up till 238-Mrad (Si) dose. These results indicate that the designed OWC can be a viable solution for future HEP experiments.

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.

We present the first measurement of the left-right charge asymmetry AQobs in hadronic Z boson decays. This was performed at Ec.m.=91.27GeV with the SLD at the SLAC Linear Collider with a polarized electron beam. Using 89 838 events we obtain AQobs=0.225±0.056±0.019, which leads to a measurement of the electron left-right asymmetry parameter, Ae=0.162±0.041±0.014, and sin2θWeff=0.2297±0.0052±0.0018. Also, the AQobs measurement combined with the left-right cross section asymmetry determines Ae independent of the value of the electron-beam polarization.Received 30 August 1996DOI:https://doi.org/10.1103/PhysRevLett.78.17©1997 American Physical Society

We present a direct measurement of Ac=2vcac(vc2+ac2) from the left-right forward-backward asymmetry of D*+ and D+ mesons in Z0 events produced with the longitudinally polarized SLAC Linear Collider beam. These Z0→cc¯ events are tagged on the basis of event kinematics and decay topology from a sample of hadronic Z0 decays recorded by the SLAC Large Detector. We measure Ac0=0.73±0.22(stat)±0.10(syst).Received 10 April 1995DOI:https://doi.org/10.1103/PhysRevLett.75.3609©1995 American Physical Society

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.

One of the proposed solutions for a transverse momentum (pT) based trigger at SLHC for the CMS experiment is based on the concept known as the "cluster width" approach, in which clusters produced by low pT tracks are rejected based on the width of the cluster shape, made either on a single strip sensor or a doublet of strip sensors by a suitable electronics logic at the level of the front-end. This information can then be used in many ways to provide first level trigger primitives. These kinds of modules are inexpensive, and coupled high-speed opto-electronic components this concept provides the simplest solution to the first level trigger for SLHC trackers. We will present the simulation studies aimed to optimize the concept, as well as the basic building blocks of the module and their connectivity. Finally we will provide the experimental validation of it by using data collected by the CMS Tracker during the Cosmic runs in 2008 and 2009 as well as the first collision data from the LHC.

We have searched for signatures of polarization in hadronic jets from $Z^0 \to q \bar{q}$ decays using the ``jet handedness'' method. The polar angle asymmetry induced by the high SLC electron-beam polarization was used to separate quark jets from antiquark jets, expected to be left- and right-polarized, respectively. We find no evidence for jet handedness in our global sample or in a sample of light quark jets and we set upper limits at the 95% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing power of the method proposed by Efremov {\it et al.}

We report a measurement of the average $B$-hadron lifetime using data collected with the SLD detector at the SLC in 1993. An inclusive analysis selected three-dimensional vertices with $B$-hadron lifetime information in a sample of 50k $Z^{0}$ decays. A lifetime of $1.564\pm0.030\,(\rm stat)\pm 0.037\,(\rm syst)$~ps was extracted from the decay length distribution of these vertices using a binned maximum-likelihood method.

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>

Based on a sample of approximately 500 000 hadronic Z0 decays accumulated between 1993 and 1998, the SLD experiment has set limits on 24 fully charged two-body and quasi-two-body exclusive charmless hadronic decays of B+, B0, and B0s mesons. The precise tracking capabilities of the SLD detector provided for the efficient reduction of combinatoric backgrounds, yielding the most precise available limits for ten of these modes.Received 27 October 1999DOI:https://doi.org/10.1103/PhysRevD.62.071101©2000 American Physical Society

We have determined the strong coupling alpha-s from a comprehensive study of energy-energy correlations (EEC) and their asymmetry (AEEC) in hadronic decays of Z0 bosons collected by the SLD experiment at SLAC. The data were compared with all four available predictions of QCD calculated up to O(alpha-s**2) in perturbation theory, and also with a resummed calculation matched to all four of these calculations. We find large discrepancies between alpha-s values extracted from the different O(alpha-s**2) calculations. We also find a large renormalization scale ambiguity in alpha-s determined from the EEC using the O(alpha-s**2) calculations; this ambiguity is reduced in the case of the AEEC, and is very small when the matched calculations are used. Averaging over all calculations, and over the EEC and AEEC results, we obtain alpha-s(MZ)=0.124+0.003-0.004(exp.) +-0.009(theory).

The paper describes the role of the n+ edge implants in the breakdown process of p+ on n-bulk silicon diodes. Laboratory measurements and simulation studies are presented on a series of test structures aimed at an optimization of the design in the edge region. The dependence of the breakdown voltage on the geometrical parameters of the devices is discussed in detail. Design rules are extracted for the use of n+-layers along the scribe line to avoid surface conduction of current generated by the exposed edges. The effect of neutron irradiation has been studied up to a fluence of 1.8×1015 cm−2.

The subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15\,\% of the final silicon strip detector, and over 4.7~million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.

A measurement of the lifetime of the τ lepton has been made using a sample of 1671 Z0→τ+τ− decays collected by the SLD detector at the SLC. The measurement benefits from the small and stable collision region at the SLC and the precision pixel vertex detector of the SLD. Three analysis techniques have been used: decay length, impact parameter, and impact parameter difference methods. The combined result is ττ=297±9 (stat)±5(syst) fs.Received 7 June 1995DOI:https://doi.org/10.1103/PhysRevD.52.4828©1995 American Physical Society

Abstract The gas mixtures presently used in plastic limited streamer tubes (“Iarocci tubes” or LSTs) have a high hydrocarbon content and are very flammable when mixed with air, posing a potential safety hazard in modern large underground experiments. The SLD Warm Iron Calorimeter group has therefore made an extensive investigation of nonflammable ternary mixtures based on CO 2 . Ar and various hydrocarbons. We present here brief results of this research. In particular, we describe a detailed study of a nonflammable gas mixture (2.5% Ar: 9.5% iC 4 H 10 : 88% CO 2 ) which indicates that this mixture has properties comparable to those of the two commonly used gases (25% Ar: 75% iC 4 H 10 and 21% Ar: 37% nC 5 H 12 : 42% CO 2 ) and could successfully replace these mixtures in LST-based tracking devices and hadron calorimeters.

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.

We present the exploratory approach of Project FOCS (Free Space Optical communications for Space), which aims at proposing and demonstrating new applications of Visible Light Communications (VLC) for satellites. The first selected application scenario that will be investigated deals with transmission of Gbit/s signals on very small satellites, e.g. CubeSats. The second selected research line will be about low-bit-rate communication between satellites over > 100 m distances.

Abstract Optical Wireless Communication (OWC) system for particles detector can be a viable solution for reducing the complexity of the optical fibre network used to extract the data from the detector. In this work we present the initial study of the tolerance to misalignment for the OWC system under investigation. We observed that using collimators of beam waist from 0.35 mm to 3.5 mm we can obtain tolerance in range from ± 0.25 mm to ± 0.8 mm . We also observed using ray trace simulation that both transmitting power and tolerance can be improved by using optimized lens at the receiver having VCSEL as transmitting source.

High speed optical fiber or copper wire communication systems are frequently deployed for readout data links used in particle physics detectors. Future detector upgrades will need more bandwidth for data transfer, but routing requirements for new cables or optical fiber will be challenging due to space limitations. Optical wireless communication (OWC) can provide high bandwidth connectivity with an advantage of reduced material budget and complexity of cable installation and management. In a collaborative effort, Scuola Superiore Sant'Anna and INFN Pisa are pursuing the development of a free-space optical link that could be installed in a future particle physics detector or upgrade. We describe initial studies of an OWC link using the inner tracker of the Compact Muon Solenoid (CMS) detector as a reference architecture. The results of two experiments are described: the first to verify that the laser source transmission wavelength of 1550 nm will not introduce fake signals in silicon strip sensors while the second was to study the source beam diameter and its tolerance to misalignment. For data rates of 2.5 Gb/s and 10 Gb/s over a 10 cm working distance it was observed that a tolerance limit of ±0.25 mm to ±0.8 mm can be obtained for misaligned systems with source beam diameters of 0.38 mm to 3.5 mm, respectively.

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.

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 development of new instruments for low-energy atoms is becoming of considerable interest in various research fields, such as the direct detection of dark matter, micro-dosimetry, the study of the atmospheres of the Solar System bodies, as well as in the direct measurement of low-energy cosmic rays.In the last few years, our working group, at INFN Pisa Laboratory, has been involved in the development of a gas detector based on a Micro-Megas (MM) device working in a lowpressure regime.Within the Micro-Pattern Gas Detector family, the intrinsic characteristics of the MM device represent the most promising features for constructing a new detector to be operated as an imaging device gas chamber.The main goal of the experimental activity was the development of an electrode configuration optimizing the instrument performance for atoms in the energy range of 1-100 keV, with good energy and angular resolution in a single compact instrument.The dependence of the gain, the energy resolution from the amplification field, gas pressure, and drift field have been deeply investigated, both with x-rays sources and ionized helium beams.Here a summary of a measurements campaign devoted to a technical characterization of a MM bulk filled with a gas mixture maintained at low pressure is presented.

We realized a high-speed Optical Wireless Communication (OWC) system for short distances, and then tested its transmitter and receiver boards against the most challenging issues that the devices can face in the space environment. As the system is made of commercially available optoelectronic components, operating at 850 nm, there was no specific preliminary indication that they can survive in the space environment. Thus, we thoroughly tested our OWC boards against strong acceleration and typical mechanical vibrations (up to 7.5g, 850 Hz), then over a wide temperature range (−40°C<T<80 °C) and finally against X-ray irradiation (1 Mrad). In all tests, the OWC system suffered no relevant issue. This is clear evidence that OWC technology, realized by Commerical Off-the-Shelf components, can be suitable for space applications.

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.

We have measured the $B$ hadron energy distribution in ${Z}^{0}$ decays using a sample of semileptonic $B$ decays recorded in the SLD experiment at SLAC. The energy of each tagged $B$ hadron was reconstructed using information from the lepton and a partially reconstructed charm-decay vertex. We compared the scaled energy distribution with several models of heavy quark fragmentation. The average scaled energy of primary $B$ hadrons was found to be $〈{x}_{{E}_{B}}〉=0.716\ifmmode\pm\else\textpm\fi{}0.011(\mathrm{stat}{)}_{\ensuremath{-}0.022}^{+0.021}(\mathrm{syst})$.

We present a direct measurement of the parity-violating asymmetry ${A}_{b}$ in the ${Z}^{0}$ to $b\overline{b}$ coupling using a new technique to distinguish the $b$ and $\overline{b}$ quarks using charged kaons from $B$ decays. The ${Z}^{0}$ bosons are produced in ${e}^{+}{e}^{\ensuremath{-}}$ collisions at the SLC with longitudinally polarized electrons. $b\overline{b}$ events are selected using a secondary vertex mass tag and ${A}_{b}$ is determined from the left-right forward-backward asymmetry. From the 1994--1995 data sample, selected from 100 000 hadronic ${Z}^{0}$ decays, we obtain ${A}_{b}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.855\ifmmode\pm\else\textpm\fi{}{0.088}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.102}_{\mathrm{syst}}$.

The front-end digital electronics and the Fastbus readout and data reduction module for limited streamer tube strips of the SLD warm iron calorimeter and muon tracker are described. A special high-sensitivity front-end hybrid has been developed to read strip information from limited streamer tubes working well below the limited streamer voltages. An MC68020-based Fastbus module to perform fast readout, zero suppression, cluster searching and apparatus monitoring has also been designed, built and tested.

The SLD detector at the Stanford Linear Accelerator Center is a general purpose device for studying e{sup +}{epsilon}{sup {minus}} interaction at the Z{sup 0}. The SLD calorimeter system consists of two parts: a lead Liquid Argon Calorimeter (LAC) with both electromagnetic (22 radiation lengths) and hadronic sections (2.8 absorption lengths) housed inside the coil, and the Warm Ion limited streamer tubes Calorimeter (WIC) outside the coil which uses as radiator the iron of the flux return for the magnetic field. The WIC completes the measurement of the hadronic shower energy ({approximately}85% on average is contained in the LAC) and it provides identification and tracking for muons over 99% of the solid angle. In this note we report on the construction, test and commissioning of such a large system.

A study has been made of the properties of the SGS D779-based readout electronics for limited streamer tubes, both with pulses from a pulse generator and with strip pulses from the actual chambers to be used in the SLD detector. To accommodate the special requirements of the SLD detector, a hybrid circuit has been developed and tested that is capable of operating with pulses from the strips of tubes operated below the limited-streamer-node voltages.< <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.

Experience at high luminosity hadron collider experiments shows that tracking information enhances the trigger rejection capabilities while retaining high efficiency for interesting physics events [F. Palla and G. Parrini, Tracking in the trigger: from the CDF experience to CMS upgrade, 2007. Published in PoS VER-TEX2007:034, 2007]. The design of a tracking based trigger for Super LHC (S-LHC), the already envisaged high luminosity upgrade of the LHC collider, is an extremely challenging task, and requires the identification of high-momentum particle tracks as a part of the Level 1 Trigger. Simulation studies show that this can be achieved by correlating hits on two closely spaced silicon strip sensors. This work focuses on the design and development of micro-strip stacked prototype modules and will also discuss the technical challenges in the construction and the final detector performance. Studies of possible sensor geometries and wire-bonding techniques will be also presented. The prototypes have been built with the silicon sensors and electronics used to equip the present CMS Tracker [CMS Collaboration, The CMS experiment at the CERN LHC, JINST 3:S08004:26-89, 2008]. Correlation of signals collected from sensors are processed off detector. We will present the results of tests performed on the prototype modules in terms of the noise performance of the proposed stack geometry. Preliminary results in terms of signal over noise and tracking performance with cosmic rays will also be shown.

The SLD detector consists of five major subsystems, each with associated front-end electronics and an integrated FASTBUS control and data acquisition system. This paper highlights the choices among electronic technologies that have been developed for the SLD detector electronics. The common control, calibration, and data acquisition architectures are described. The functions of selected SLD integrated circuits, standard cells, gate arrays, and hybrids are summarized, and the integration of these functions into the common data acquisition path is described. Particular attention is directed to four areas of electronic technology developed for the SLD detector: (1) the preamplifier hybrid designs are compared and their performance and implementation examined; (2) the application of full custom CMOS digital circuits in SLD is compared to gate array and EPLD (electrically programmable logic device) implementations; (3) the fiber optic signal transmission techniques in SLD are examined and the data rates and link topology are presented; and (4) finally, the packaging, power consumption, and cooling requirements for system functions resident inside the detector structure are explored. The rationale for the implementation choices in the SLD electronics is presented so that others might benefit from our experience.

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.

A brief description is given of the SLD calorimeter system, with emphasis on the iron calorimeter/muon identifier. Design choices and expected performance are summarized.

Experience at high luminosity hadrons collider experiments shows that tracking information enhances the trigger rejection capabilities while retaining high efficiency for interesting physics events.The design of a tracking based trigger for Super LHC (S-LHC), the already envisaged high luminosity upgrade of the LHC collider, is an extremely challenging task, and requires the identification of high-momentum particle tracks as a part of the Level 1 Trigger.Simulation studies show that this can be achieved by correlating hits on two closely spaced silicon strip sensors.The progresses on the design and development of this micro-strip stacked prototype modules and the performance of few prototype detectors will be presented.The prototypes have been built with the silicon sensors and electronics used to equip the present CMS[1] Tracker.Preliminary results of a simulated tracker layout equipped with stacked modules are discussed in terms of p T resolution and triggering capabilities.The study of real prototypes in terms of signal over noise and tracking performance with cosmic rays and a dedicated beam test experiment will also be shown.©2011 CERN, for the benefit of CMS Collaboration.

Experience at high luminosity hadron collider experiments shows that tracking information enhances the trigger rejection capabilities while retaining high efficiency for interesting physics events [1]. The design of a tracking based trigger for Super LHC (S-LHC), the high luminosity upgrade of the LHC collider [2], is an extremely challenging task requiring the identification of high-momentum tracks as a part of the Level 1 trigger decision. Simulation studies show that this can be achieved by correlating hits on two closely spaced silicon strip sensors. This paper focuses on the design and development of micro-strip stacked prototype modules and their performance. The prototypes have been built with the silicon sensors and electronics used to equip the present CMS Tracker [3]. Correlation of signals collected from sensors are processed off detector. Preliminary results in terms of signal over noise and tracking performance with cosmic rays will be also shown.

High-voltage operation can be a solution to obtain full charge collection in strongly irradiated silicon detectors. The maximum bias voltage which can be applied is limited by the breakdown point of the junction. We show how multiguard structures can enhance the breakdown voltage in p+–n silicon devices designed for applications in the LHC environment.

We present a comparison of the strong couplings of light (u, d, and s), c, and b quarks determined from multijet rates in flavor-tagged samples of hadronic Z0 decays recorded with the SLC Large Detector at the SLAC Linear Collider. Flavor separation on the basis of lifetime and decay multiplicity differences among hadrons containing light, c, and b quarks was made using the SLD precision tracking system. We find αudssαalls=0.987±0.027(stat)±0.022(syst)±0.022(theory), αcsαalls=1.012±0.104±0.102±0.096, and αbsαalls=1.026±0.041±0.041±0.030.Received 16 December 1994DOI:https://doi.org/10.1103/PhysRevD.53.R2271©1996 American Physical Society

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.

This paper reports the unique results of a high dose test on an Optical Wireless Communication (OWC) system designed for High Energy Physics (HEP). The 10 Gbit/s optical link under test is composed by a Vertical Cavity Surface Emitting Laser (VCSEL) and a PIN Photo-Diode (PD) with the proper ball lenses. This architecture does not require a complex active tracking due to the system misalignment tolerance of ±3 mm at Bit Error Ratio (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> and 20 cm distance. The reported OWC system aims at removing the massive wire harness in HEP experiments tracking structures. We experimentally explore the limits of our prototype components under strong radiation conditions, in order to validate the compatibility of HEP experiments. Both VCSEL and PD performance are strongly reduced after 1 h of proton irradiation and the components can tolerate a total fluence of ~1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> p/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

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.

The paper presents the results of an extensive set of measurements performed on silicon microstrip sensors produced by STMicroelectronics for the CMS Tracker. 5″ and 6″ technologies were used to process several series of detector prototypes. Detectors 300μm thick were produced on 5″ wafers and fully characterized. A new design on 500μm thick wafers with 6″ technology has been recently implemented. The performance of three different layouts has been investigated in terms of macroscopic electrical parameters and radiation resistance.

We present the first measurement of the left-right cross-section asymmetry (A LR ) in Z-boson production observed at the SLAC Linear Collider. In 1992 the SLD detector recorded 10 224 Z events produced by the collision of longitudinally polarized electrons with an unpolarized positron beam at a center-of-mass energy of 91.55 GeV. The average electron beam polarization during the run was (22.4 ± 0.6)%. We measure A LR to be 0.100 ± 0.0440 (stat.) ±0.004 (syst.) , which determines the effective weak mixing angle to be [Formula: see text].

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.

The ALEPH Silicon Vertex Detector features an optical fibre laser system to monitor its mechanical stability. The operating principle and the general performance of the laser system are described. The experience obtained during 1997 and 1998 operations confirms the important role that such a system can have with respect to the detector alignment requirements. In particular, the laser system has been used to monitor short-term temperature-related effects and long-term movements. These results and a description of the laser-based alignment correction applied to the 1998 data are presented.

The breakdown performance of CMS barrelmodule prototype detectors and test devices with single and multi-guard structures were studied before and after neutron irradiation up to 2·1014 1 MeV equivalent neutrons. Before irradiation avalanche breakdown occurred at the guard ring implant edges. We measured 100–300 V higher breakdown voltage values for the devices with multi-guard than for devices with single-guard ring. After irradiation and type inversion the breakdown was smoother than before irradiation and the breakdown voltage value increased to 500–600 V for most of the devices.

The entire data acquisition chain, from the custom made front-end electronics to the Fastbus readout and data reduction module, for the digital readout of the SLD (see ref. [1]: SLD design report, SLAC-Report 73 (1984)) limited streamer tube Warm Iron Calorimeter and Muon Identifier is described. Also described is a Fastbus cosmic logic unit being developed to achieve the capability of reading cosmic ray events, also during the intercrossing time, for apparatus monitoring and calibration purposes.

The entire data-acquisition chain, from the custom-made front-end electronics to the Fastbus readout and data-reduction module, for the digital readout of the SLD limited streamer tube Warm Iron Calorimeter and Muon Identifier is described. Also described is a Fastbus Cosmic Logic Unit being developed to achieve the capability of reading cosmic ray events, also during the inter-crossing time, for apparatus monitoring and calibration purposes. 9 refs., 9 figs.

The paper reports on a detailed study of the radiation resistance of p/sup +/ on n silicon microstrip detectors for the CMS tracking system. From this study, it is seen that the use of low-resistivity substrates with <100> crystal lattice orientation promises excellent performance of the Inner Tracker after heavy irradiation in the Large Hadron Collider environment. Furthermore, the advantage of using detectors thicker than 300 /spl mu/m in the Outer Tracker is discussed together with experimental measurements on prototypes.

The decision taken by the CMS experiment to build a tracker entirely based on silicon detectors has made necessary the use of thicker sensors instead of the usual 300-/spl mu/m sensors for the outer part of the detector. We first present results on the performance of 500-/spl mu/m-thick detectors, before and after neutron irradiation, bonded to the CMS tracker front-end electronics. Laboratory measurements show that the total collected charge scales linearly with thickness when compared with a 300-/spl mu/m module, and the measured noise is in good agreement with expectations. The results obtained confirm the feasibility of large-area silicon trackers.

Prototype silicon microstrip modules meant to generate Level 1 trigger information in future tracker implementations at super-high luminosity accelerators have been built using spare components from the current CMS Tracker and tested on a 120 GeV muon beam at the CERN SPS North Area. Tracking information from a silicon microstrip beam telescope has also been used in order to precisely reconstruct tracks and incidence angles. Data has been collected from prototypes with different geometries and interconnection schemes and at different angles of beam incidence, simulating the effect of a solenoidal magnetic field on particles of different transverse momentum p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⊥</sub> .

Double-sided silicon detector prototypes produced for the CMS inner tracker are described which divide the n-side into pads rather than strips. The signal routing to the readout electronics is made on a separate flexible z-print which is glued on the detector and then wire-bonded to the pads.

This paper investigates the performance of 500μm thick silicon microstrip detectors before and after heavy irradiation. Prototype sensors, produced by STMicroelectronics, have been extensively studied using laboratory measurements, a radioactive source and a beam of minimum ionising particles. The comparison with a standard 300μm sensor shows that the collected charge in thick devices scales linearly with thickness. By over-depleting the irradiated devices, the pre-irradiated charge collection efficiency is fully recovered. The measured noise is in good agreement with expectations. Although more work is needed, the paper shows that 500μm thick devices are a promising technology for very large tracking systems.

This paper describes the Silicon microstrip Tracker of the CMS experiment at LHC. It consists of a barrel part with 5 layers and two endcaps with 10 disks each. About 10 000 single-sided equivalent modules have to be built, each one carrying two daisy-chained silicon detectors and their front-end electronics. Back-to-back modules are used to read-out the radial coordinate. The tracker will be operated in an environment kept at a temperature of T=−10°C to minimize the Si sensors radiation damage. Heavily irradiated detectors will be safely operated due to the high-voltage capability of the sensors. Full-size mechanical prototypes have been built to check the system aspects before starting the construction.

Experience at high luminosity hadron collider experiments shows that tracking information enhances the trigger rejection capabilities while retaining high efficiency for interesting physics events. The design of a tracking based trigger for Super LHC (S-LHC), the already envisaged high luminosity upgrade of the LHC collider, is an extremely challenging task, and requires the identification of high-momentum particle tracks as a part of the Level 1 Trigger. Simulation studies show that this can be achieved by correlating hits on two closely spaced silicon strip sensors. This work focuses on the design and development of micro-strip stacked prototype modules and will also discuss the technical challenges in the construction and final detector performance. Studies of possible sensor spacing and wire-bonding techniques will be also presented. The prototypes have been built with the silicon sensors and electronics used to equip the present CMS Tracker. Correlation of signals collected from sensors are processed off detector. We will present the results of tests performed on the prototype modules in terms of the noise performance of the proposed stack geometry. Preliminary results in terms of signal over noise and tracking performance with cosmic rays will also be shown.

We demonstrated low cost and power-efficient a 2.5 Gb/s optical wireless transmission system at 10 cm distance, which should be employed in high-energy physics experiments such as Compact Muon Solenoid. The system uses an off-the-shelf VCSEL and a PIN photodiode with proper ball lens. Its most attractive feature is that it does not need a complex active tracking system because its measured tolerance to misalignment is around +/-1mm at Bit Error Rate of 10^-12. The experimental results show that this can be a viable solution for future HEP experiments.

The inner portion of the CMS microstrip Tracker consists of 3540 silicon detector modules; its construction has been under full responsibility of seven INFN (Istituto Nazionale di Fisica Nucleare) and University laboratories in Italy. In this note procedures and strategies, which were developed and perfected to qualify the Tracker Inner Barrel and Inner Disks modules for installation, are described. In particular the tests required to select highly reliable detector modules are illustrated and a summary of the results from the full Inner Tracker module test is presented. 1) INFN sez. di Catania and Universita di Catania, Italy 2) INFN sez. di Perugia and Universita di Perugia, Italy 3) INFN sez. di Pisa and Scuola Normale Superiore di Pisa, Italy 4) INFN sez. di Pisa and Universita di Pisa, Italy 5) INFN sez. di Pisa, Italy 6) INFN sez. di Torino and Universita di Torino, Italy 7) INFN sez. di Torino, Italy 8) INFN sez. di Firenze, Italy 9) INFN sez. di Bari and Dipartimento Interateneo di Fisica di Bari, Italy 10) INFN sez. di Bari, Italy 11) INFN sez. di Padova, Italy 12) INFN sez. di Firenze and Universita di Firenze, Italy 13) INFN sez. di Padova and Universita di Padova, Italy 14) INFN sez. di Perugia, Italy a) On leave from ISS, Bucharest, Romania b) On leave from IFIN-HH, Bucharest, Romania c) Corresponding Author

Abstract A large use of silicon microstrip detectors is foreseen for the intermediate part of the CMS tracker. A specific research and development program has been carried out with the aim of finding design layouts and technological solutions for allowing silicon microstrip detectors to be reliably used on a high radiation level environment. As a result of this work single sided, AC-coupled, polysilicon biased, 300 μ m thick, p + on n substrate detectors were chosen. Irradiation tests have been performed on prototypes up to fluence 2×10 14  n/cm 2 . The detector performances do not significantly change if the detectors are biased well above the depletion voltage. S / N is reduced by less than 20%, still enough to insure a good efficiency and space resolution. Multiguard structures has been developed in order to reach high voltage operation (above 500 V).

The structure of e ϩ e Ϫ →bb ¯g events was studied using Z 0 decays recorded in the SLC Large Detector experiment at SLAC.Three-jet final states were selected and the charge-coupled device-based vertex detector was used to identify two of the jets as b or b ¯.Distributions of the gluon energy and polar angle were measured over the full kinematic range for the first time, and compared with perturbative QCD predictions.The energy distribution is potentially sensitive to an anomalous b chromomagnetic moment .We measured to be consistent with zero and set the first limits on its value: Ϫ0.17ϽϽ0.11at 95% C.L.

Abstract We present the results of a systematic study of three-component gas mixtures containing argon, isobutane, and carbon dioxide. The study used production-type chambers from the SLD Warm Iron Calorimeter (WIC), instrumented with standard plastic streamer tubes, and triggered by cosmic-ray muons. Pulse height spectra are presented as a function of high voltage, over a wide range of mixtures of these three gases. Various features and similarities observed throughout this three-dimensional mixture space are important clues to an understanding of the underlying physics of discharge mechanisms in wire detectors.

We have compared a new QCD calculation by Clay and Ellis of energy-energy correlations (EEC's) and their asymmetry (AEEC's) in ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ annihilation into hadrons with data collected by the SLD experiment at SLAC. From fits of the new calculation, complete at O(${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}^{2}$), we obtained ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$(${\mathit{M}}_{\mathit{Z}}^{2}$)=0.1184\ifmmode\pm\else\textpm\fi{}0.0031(expt)\ifmmode\pm\else\textpm\fi{}0.0129(theory) (EEC) and ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$(${\mathit{M}}_{\mathit{Z}}^{2}$)=0.1120\ifmmode\pm\else\textpm\fi{}0.0034(expt)\ifmmode\pm\else\textpm\fi{}0.0036(theory) (AEEC). The EEC result is significantly lower than that obtained from comparable fits using the O(${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}^{2}$) calculation of Kunszt and Nason.