P. Lariccia

We report on the results at ADONE to study the properties of the newly found 3.1-BeV particle.Received 18 November 1974DOI:https://doi.org/10.1103/PhysRevLett.33.1408©1974 American Physical Society

A study has been made of the decays W → ev and Z → e+e−, using the UA2 detector at the CERN p̄p Collider. The data correspond to an integrated luminosity of 142 nb−1 at a centre-of-mass collision energy √s=546 GeV, and 768 nb−1 at √s=630 GeV. Measurements of the standard model parameters from samples of 251 W decay and 39 Z decay candidates are compared with expectations of the standard electroweak model.

A fourth state in the upsilon energy region has been seen in ${e}^{+}{e}^{\ensuremath{-}}$ collisions at the Cornell Electron Storage Ring. A resonance is observed with a mass 1112\ifmmode\pm\else\textpm\fi{}5 MeV above the lowest upsilon state. The 9.6-MeV rms width is greater than the 4.6-MeV energy resolution of the ${e}^{+}{e}^{\ensuremath{-}}$ beams. The observed characteristics of the new state make it a likely candidate for the $4^{3}S$ state of the $b\overline{b}$ system, lying above the threshold for the production of $B$ mesons.

The two-jet invariant mass spectrum as measured in the UA2 experiment is used to search for additional heavy vector bosons decaying to two-jets. The mass of an additional W boson that couples to fermions with a V+A form is constrained to be greater than 261 GeV to the 90% confidence level. A limit on the production cross section of additional W and Z bosons is given as a function of the boson mass. A limit on the production of excited quarks is also given as a function of the excited quark mass.

The W and Z bosons masses, mw and mz, are measured using saing samples of W→ev and Z→e+e− decays observed in pp collisions at √s=630 GeV. The ration is found to be mwmz=0.8813±0.0036 ± 0.0019. This gives a value sin2 θw = 0.2234 ± 0.0064 ± 0.0033, and in combination with precise mz measurements from LEP yields mw=80.35±0.33±0.17 GeV. This result is in good agreement with other experiments, and with the standard model for a top quark mass lighter than 250 GeV.

Three narrow resonances have been observed in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into hadrons at total energies between 9.4 and 10.4 GeV. Measurements of mass spacing and ratios of lepton pair widths support the interpretation of these "$\ensuremath{\Upsilon}$" states as the lowest triplet-$S$ levels of the $b\overline{b}$ quark-antiquark system.

An enhancement has been observed in the inclusive cross section for direct single electrons produced in ${e}^{+}{e}^{\ensuremath{-}}$ annihilations at the $\ensuremath{\Upsilon}(4S)$. This is interpreted as evidence for a new weakly decaying particle, the $B$ meson. A branching ratio for $B\ensuremath{\rightarrow}\mathrm{Xe}\ensuremath{\nu}$ of [13\ifmmode\pm\else\textpm\fi{}3 (\ifmmode\pm\else\textpm\fi{}3)]% is inferred, where the first set of errors is statistical and the estimated systematic error is enclosed in parentheses.

A search has been made with the upgraded UA2 experiment at the CERN pp Collider at s=630 GeV for multi-jet events with large transverse momentum imbalance in a data sample corresponding to an integrated luminosity of 7.4 pb−1. Under the assumption that the photino is the lightest stable supersymmetric (SUSY) particle, the data have been used to deduce lower limits in a minimal SUSY model for the squark (mq) and the gluino (mg) masses. The 90% CL bounds are mg> 74 GeV independent of mg, mg> 79 GeV independent of mg, and and m> 106 GeV for mq=mq=m.

The UA2 experiment has collected large samples of W and Z events during recent runs at the CERN pp Collider at s = 630 GeV. These samples have been used to perform precise measurements of the masses of the W and Z bosons. After a careful analysis of systematic errors, an improved result is obtained for the mass ratio mwmz. This provides a new value for the weak mixing parameter sin2θw. Furthermore, it can be combined with recent measurements of the Z mass from e+e− colliders to give an absolute measurement of the W mass, leading to the result mw=80.49±0.43 (stat) ± 0.24 (syst) GeV.

An enhancement in the inclusive cross section for single muons produced in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at the $\ensuremath{\Upsilon}(4S)$ is observed, confirming the interpretation that a new bare flavor ($B$ mesons) is produced at the $\ensuremath{\Upsilon}(4S)$. A branching ratio for $B\ensuremath{\rightarrow}X\ensuremath{\mu}\ensuremath{\nu}$ of (9.4\ifmmode\pm\else\textpm\fi{}3.6)% is obtained. The two-muon decay, $B\ensuremath{\rightarrow}X{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ is not observed, providing a 90%-confidence-level upper limit for the branching ratio for that decay of 1.7%. Combining this with our previously reported limit of 5% for $B\ensuremath{\rightarrow}X{e}^{+}{e}^{\ensuremath{-}}$, we obtain 1.3% as an upper limit for $B\ensuremath{\rightarrow}X{l}^{+}{l}^{\ensuremath{-}}$.

A study of the two-jet mass spectrum measured with the UA 2 calorimeter has revealed a signal from hadronic decays ofW andZ bosons above a large background. Production and decay properties of the signal have been measured. The combined production cross-section σ·B(W, Z → two jets) is 9.6±2.3 (stat.)±1.1 (syst.) nb, compared with an expectation of 5.8 nb calculated to order α s 2 . A limit on the production cross-section of additional heavy vector bosons decaying into two jets is given as a function of the boson mass.

The process pp→evγ+X is studied as √s=630 GeV. The observed signal is used to extract a direct measurement of the parameters κ and λ which define the magnetic dipole and electric quadrupole moments of the W boson and therefore the WWγ coupling. We find κ=1+2.6−2.2 and λ=0+1.7−1.8 and their 95% confidence limits −3.5<κ<5.9 and −3.6<λ<3.5. The results are model indepedent and in good agreement with the standard model values, κ=1 and λ=0.

Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦P T ≦6 GeV/c and center-of-mass rapidity −0.4≦y *≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.

The inclusive jet cross-section has been measured at the CERN pp Collider (s = 630 GeV) as a function of the jet transverse momentum (pT) and pseudorapidity (η) for pT values up to 180 GeV and for−2<η<2. The results are consistent with leading order QCD calculations, and a lower limit Λc>825 GeV (95% CL) is set on the quark compositeness scale Λc.

The total UA2 data sample at the CERN pp̄ Collider corresponds to an integrated luminosity of 910 nb−1. Limits on various hypothetical processes, such as production of excited electrons, additional charged or neutral vector bosons, or supersymmetric particles, are presented from the analysis of this sample.

The large sample of W→eν events collected by the UA2 experiment at the CERN pp̄ collider between 1988 and 1990 has been used to determine the strong coupling constant αs. From a measurement of the ratio of the production rate of W events with one jet to that with no jets, αs has been extracted to second order in the MS̄ scheme: αs(M2w)=0.123±0.0.18(stat.)±0.017 (syst.).

The decays W → ev and Z → e+e− are studied in [ovbar|p]p collisions at √s=630 GeV. The products of production cross section and branching ratio are measured as σew=682±12±40 pb and σew=65.6±4.0±3.8 pb. The results are in good agreement with O(α2s) calculations of the production cross sections. Many systematic effects cancel in the ratio, R=10.4±0.70.6±0.3, which can be used to give an indirect measurement of the total width of the W boson: Γw=2.10±0.13±0.09 GeV. The width gives a limit on the top quark mass, mtop>53 GeV (95% CL), which is independent of the top decay mode.

A sensitive search has been done for the production of new long-lived and penetrating particles by 300 GeV/c negative pions. No new state —decaying into at least two charged known particles —has been detected with mass above 1 GeV/c2 and lifetime in the range 5·10−11 s to 5·10−7s. We give upper limits on production cross sections, and consequences on the existence of heavy “axion-like” particles, heavy neutrinos and supersymmetric particles. In particular, this experiment excludes the existence of light gluinos with lifetime in the range 5·10−11 to 10−8s: this closes the last “window of opportunity” for gluinos withM<2 GeV/c2 and lifetime measurable in particle physics experiments.

A measurement of the inclusive cross-section for production of direct photons in p̄p collisions at a centre of mass energy of 630 GeV is presented as a function of the photon transverse momentum. The data correspond to a total integrated luminosity of 7.4 pb−1. The results support predictions from QCD theory.

The invariant mass distribution of jet pairs observed in the UA2 central calorimeter is examined in the search for an excess of events in the region of the W± and Z bosons, which would reveal their decays into quark-antiquark pairs. We give a detailed account of the methods of analysis used to optimize the mass resolution achieving ≅±10%. A structure is observed at the level of ≅ 3 standard deviations in the mass region of W± and Z with shape and position consistent with expectation from their qq̄decays. It contains 632 ± 190 events, 1.4 standard deviations above the standard model prediction of 340 ± 80 events.

We have observed the decay of the $\ensuremath{\Upsilon}(2S)$ into the $\ensuremath{\Upsilon}(1S)$, obtaining a branching ratio of 19.1\ifmmode\pm\else\textpm\fi{}3.1\ifmmode\pm\else\textpm\fi{}2.9% for the mode $\ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}+\ensuremath{\Upsilon}(1S)$. The di-pion mass spectrum peaks at large invariant mass, and the angular distribution of the di-pion system is consistent with $s$-wave production.

Results on the production cross sections ofW andZ bosons detected in the UA2 experiment are given based on a large sample ofW→eν andZ→e + e − decays. The measured cross sections are σ = 660±15(stat)±37(syst)pb, σ = 70.4±5.5(stat)±4.0(syst)pb and their ratioR=9.38 −0.72 +0.82 (stat)±0.25(syst). In the framework of the Standard Model, the measured value ofR is used to determine the total width of theW, Γ(W)=2.30±0.19(stat)±0.06(syst) GeV.

We present the characteristics and the performance of a large area silicon hodoscope in the upgraded UA2 experiment. The main purpose of this detector is to provide an energy loss measurement, thus helping to identify single electrons against a background of unresolved e+e− pairs from photon conversions and π0 Dalitz decays. We also describe a second layer of silicon counters at a close distance from the beam which will be used in conjunction with the first layer for fast pattern recognition purposes.

A measurement of the cross-sections for single and double prompt photon production in pp interactions at s = 630GeV is presented. The data sample corresponds to an integrated luminosity of 13.2 pb−1. The results are in good agreement with the predictions of perturbative QCD. The signal from double prompt photon production has a statistical significance of 4.3 standard deviations.

The upgraded UA 2 detector has collected data corresponding to a total integrated luminosity of 7.5 pb−1 from $$\bar pp$$ collisions at a centre of mass energy of 630 GeV during 1988 and 1989. A search has been performed for the production and decay of the top quark (t) or a member of a hypothetical fourth family (b′). No evidence has been found for such processes. Using the expected rates for production and decay branching ratios from the Standard Model, this implies that the top quark mass is greater than 69(71) GeV/c2, and that theb′ mass is greater than 54(57) GeV/c2, at 95(90)% confidence.

A measurement of the direct production of photons with high transverse momentum from $$\bar pp$$ collisions at $$\sqrt s = 630$$ GeV is presented. The structure of events containing a high transverse momentum photon is studied. The results support predictions from QCD theory.

We present experimental evidence for a resonant behaviour of the hadron production from e+e− annihilations at the e+e− storage ring ADONE. A Breit-Wigner fit to the enhancement present between 1800 and 1850 MeV gives the following parameters M = 1812−13+7 MeV, Γ = 34−15+21 MeV.

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.

The process t→H+b, H+→τ+v, τ+→hadrons+v and its charge conjugate are investigated by seeking an excess in number of observed τ's beyond that expected from the standard model under the assumption of e-τ universality. No such excess is found and new regions of the mH−mt plane are excluded for B(H+→τv) = 0.5 and 1.0. In addition, the ratio of couplings of the τ and e to the W is precisely measured as gwτ/gwe = 1.02 ± 0.04(stat.)±0.04(syst.).

The transverse momentum distributions ofW andZ bosons produced in $$\bar pp$$ collisions at $$\sqrt s = 630 GeV$$ are examined. Comparisons are made with QCD predictions, and good agreement is found. The fraction ofW bosons produced withp T >25 GeV is found to be 3.8±0.6(stat) −1.3 +0.9 (syst)%.

The UA2 experiment at the CERN pp Collider has identified a total sample of 251 W→eν events. Among this sample 221 events are found without jets and 29 with one jet. The yield of one-jet events relative to that of zero-jet events provides a measurement of the strong coupling constant: αs(Mw2)=0.13±0.03(stat)±0.03±(syst1)±0.02(syst2), where syst1 represents the experimental systematic error and syst2 is an estimate of the theoretical uncertainty.

We analyze the energy density distribution in harronic final states as a function of their total transverse energy measured in the segmented central calorimeter of the UA2 detector. The energy dependence of collective shape variables is investigated. The data, collected at the CERN $$\bar p$$ p Collider at $$\sqrt s = 630$$ GeV, exhibit strong variations in all these variables over the transverse energy range between 15 and 210 GeV, corresponding to substantial modifications in the structure of multihadronic final states. The evolution of the energy density distribution and of the collective shape variables shows a clear transition between two extreme dynamical regimes, respectively dominated byp T -limited phase space and by collimated two-jet configurations. A study of the relative populations of two-and three-jet systems reveals two different sources of configurations having three distinct lobes in the pattern of the energy-flow. A first component, steeply falling with energy, receives substantial contributions from soft parton collisions at lower transverse energies. Above 60 GeV a new hard component emerges, characterized by an approximately constant rate with respect to the dominant two-jet structures.

A search has been made for scalar leptoquark pair production with the upgraded UA2 detector at the CERN pp Collider at √s = 630 GeV, investigating decays of the leptoquark into a quark and either an electron or an electron neutrino. From an event sample corresponding to an integrated luminosity of 13 pb−1 a lower limit has been determined for the mass of first generation leptoquarks, yielding 67 GeV (95% CL) for a scalar leptoquark decaying with a 50% branching ratio into a quark and an electron.

The UA2 jet vertex detector, a drift chamber with jet geometry, was successfully operated during the 1987 and 1988 CERN pp̄ Collider runs. A description of the chamber and a comparison between test-beam results and the chamber's performance during the Collider runs are given.

Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦PT≦6 GeV/c and center-of-mass rapidity −0.4≦y*≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.

Abstract The total cross section for electron-positron annihilation into three or more hadrons has been measured for centre of mass energies between 1.4 and 2.0 GeV. The data were obtained at ADONE by the BB experiment.

A measurement of the gluon structure fusion using direct photon events observed with the UA2 detector in pp collisions at √s=630 GeV is presented. The x-range covered by this analysis is between 0.049 and 0.207 and the Q2 range is between 280 GeV2 and 3670 GeV2. The data sample corresponds to an integrated luminosity of 7.14 pb−1. The results are found to be in good agreement with the gluon distributions measured in deep inelastic scattering experiments extrapolated to the UA2 Q2 values.

A prototype electromagnetic calorimeter containing 180 litres of liquid krypton has been tested in electron and muon beams at the CERN SPS. The main features of this detector are its active shower medium, a granularity of 2 cm with tower readout, and the use of the initial current readout technique with an effective shaping time of about 60 ns. An energy resolution for electrons of 4.1%√E[GeV] with a constant term of 0.4% and a noise contribution of 50 MeV has been achieved. The calorimeter has a spatial resolution of 4.5 mm√E[GeV] with a constant term of 0.3 mm and a time resolution of about 0.5 ns for energies larger than 10 GeV.

Different experimental spectra relevant to inelastic protonproton interactions, at incident energies between 1 and 10 GeV, are compared with the predictions of the one-pion-exchange (OPE) model, by taking into account the production of one and two pions. This analysis gives a further confirmation of the validity of the OPE model below 3 GeV; with increasing energy, it is found that the model deteriorates rapidly, and that other effects have to be taken into account. However, the behaviour of the spectra at high energy seems to depend critically on the isospin of the exchanged system, and may be difficult to describe in terms of the pictures currently used for high-energy inelastic interactions.

The ratio of branching fractions of theW decaying to τ ande leptons is measured using $$\bar pp$$ collisions at $$\sqrt s = 630$$ GeV. The ratio of the electroweak charged current couplings to theW is then determined to beg /g =0.997±0.056 (stat.)±0.042 (syst.). The decay modeZ→τ+→τ+ is observed and also found to be consistent withe-τ universality.

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 have measured the inclusive cross-section for π0 production at large transverse momentum by 200 GeV/c positive and negative hadron beams on Carbon targets (2.9<P T <6 GeV/c; −0.4<y *<1.2). We used the NA3 spectrometer at the CERNSPS.

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.

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 present the beam test results of single-sided silicon microstrip detectors, with different substrate resistivities. The effects of radiation damage are studied for a detector irradiated to a fluence of 2.4×1014n/cm2. The detectors are read out with the APV6 chip, which is compatible with the 40MHz LHC clock. The performance of different detectors and readout modes are studied in terms of signal-to-noise ratio and efficiency.

We report results of a search for narrow resonances in e+e− annihilation at center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR detector at the VEPP-4M e+e− collider. The upper limit on the leptonic width of a narrow resonance ΓeeR⋅Br(R→hadr)<120 eV has been obtained (at 90% C.L.).

(l) J . J . AUBERT, U. BECKER, J . P . BIGGS, J . BURGER, M. CHEN, G. EVERHART, P . GOLDHAGEN, J . LEONQ, T. Me CORRISTON, T. G. RHOADES, M. •OHDE, S. C. C. TING, SAW LAN WU a n d Y. Y. LEE: Iok~8. Rev. Lett., 33, 1404 (1974). (l) J . E . AUGUSTIN, A. ~ . BOYARSKI, M. BREIDENBACH, 1~. BULOS, J . T. DAKIN, G. J . FELDMAN, G. E. FISCHER, D. FRYBERGER, G. HANSON, B. JEAN-1VIARIE, R . 1~. LARSEN, V. LUTH, H . L. LYNCH, D. LYON, C. C. ~r J . ~r PATERSON, ~[. L. PERL, B. RICHTER, P . RAPIDIS, R . F. SCHWITTERS, W. ~ . TANENBAUM, F. VANN~rCCI, G. S. ABRAMS, D. BRIGGS, W . CHINOWSKY, C. ]~. I~RIEDBERG, G. GOLDHABER, R . J . •OLLEBEEK, J . A. I~ADYK, B. LULU, F. PIERRE, G. H. TRILLING, J . 8. WHITAKER, J. Wiss and J. E. ZIPSE: IOh~8. ReV. Let t . , 33, 1406 (1974). (3) C. ]3ACCI, R . BALDINI-CELIO, M. BERNA.RDINI, G. CAPOI~, l~. DEL FABBRO, 1VL GRILLI, E. IAROCCI, L. H . JONES, M. LOCCI, C. MENCUCCINI, G. P . ~URTAS, G. PENSO, G. SALVINI, ~r SPINETTI, M. SPA~O, B. STELLA, V. VALENTE, B. BARTOLI, D. BISELLO, B. ESPOSITO, F. FELICETrI, P . ~ONACELLI, M. NIGRO, L. PAOLUZI, I . PERUZZI, G. PIANO ~ORTARI, 1~. PICCOLO, F. ~ONGA, F. SEBASTIA~I, L. TRASATTI, F. VANOLI, G. BARBARINO, G. BARBIELLINI, C. BEMPORAD, R . BIANCASTELLI, M. CASTELLANO, F. CEVENII~I, ~[. CALVETTI, F. COSTANTINI, P . LARICCIA, P . PARASCANDOLO, 8. PATRICELLI, E. BASSI, C. SPENCER, L. TORTORA, U. TROYA a n d S. VITALE: Phys. Rev. Left., 33, 1408 (1974).

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.

Results on the cross section for the production of electron pairs in pp collisions at √s = 630 GeV are presented. The measured value is σ = 405 ± 51 (syst.) ± 84 (syst.) pb, in the invariant mass interval 10 < m< 70 GeV. The results are compared to recent theoretical calculations which include O(αs2) QCD contributions. The comparison of these data with those of lower energy experiments show approximate scaling as a function of the variable √τ =m√s.

A search for supersymmetric decays of the Z boson into a pair of scalar electrons or winos (partners of the electron and W boson) has been made with the upgraded UA2 experiment at the CERN pp collider at s= 630GeV. The analysis of the sample of electron pairs, corresponding to an integrated luminosity of 7.4 pb−1, shows no evidence for such exotic decays. The 90% confidence level lower mass limits obtained exclude selectron masses up to e40 GeV/c2 in the case of a light photino, and wino masses up to 45 GeV/c2 in the case of a light scalar neutrino.

Results are given on a search for the decay W±→π±γ with the UA2 detector in pp collisions at √s=630 GeV. No signal for such a process is observed and upper limits on the ration R=Γ(W±→π±γ)/Γ(W±→e±v)<4.9×10−3 and on the branching ratio BR(W±→π±γ)<5.4×10−4 are derived at 95% confidence level.

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.

A second inner layer of 192 silicon pad counters, covering 0.1 m2, has been built, directly surrounding the interaction region in the UA2 apparatus. Using the AMPLEX readout chips, a compact detector could be realized which uses less than 5 W of power for 3072 detecting elements. It was successfully operated during a 4 months physics run in 1988 at the CERN pp-collider.

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.

We have constructed a triplet of cylindrical proportional chambers with anode and cathode strip read out that now forms the innermost element of the CLEO detector. The double read out allows tracking in both the axial and longitudinal views. Center of charge calculation on the cathode strips provides an accuracy of about 0.3 mm on the longitudinal coordinate. We describe the construction and the initial performance of the chambers and discuss their use in the trigger system, in rejecting cosmic rays and beam-gas and beam-wall interaction and in selecting specific final states.

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 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.

This paper is constituted by two rather distinct sections: in the fi rst section we will summarize the overall situation of standards and formats applied to develop an «Exchange Platform» for Learning Objects, educational material and courseware. In the second section we will describe our activities in progress to implement an experimental CourseWare portal based on Plone and EduCommons. Specifi cally we report our activities of Plone products testing within the EduCommons platform and the developing of a couple of specifi c tools, «KMap Semantic Search» that should support Semantic queries on the courseware modules and «Web-Learning Object Reviewing tool» that should enable a web-assisted peer-reviewing activity in a «multi-body-multiportal» academic environment. Our goal is to produce a model of such a tool and to prototype it on EduCommons, a Learning Management System based on the Python/Zope/Plone stack, that recently made its appearance in the university environment; thanks to the development effort of the Utah State University, it is available under GPL-style license. Within the framework of the EduCommons initiative, we plan to experiment «Object reviewing» in collecting, classifying, and distributing reusable Learning Objects, in order to allow the end-user to build his/her own paths of investigation on a selected subject.

The final design of the NA48 tagging system is described and a discussion of the 1992 test run results for the detector prototype is presented. A time resolution of about 90 ps is obtained with standard electronics, and a light yield of 300–400 p.e. is measured. A 450 MHz 6 bit FADC system has been designed and tested. This system has shown an intrinsic time resolution of 50 ps, and a double pulse resolution of 7 ns. A high precision alignment procedure allows to achieve a detector efficiency consistent with 100%. The technical and mechanical features of the design are well suited for the purpose of the experiment.

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.

We searched for new narrow resonances in the mass region from 1.42 to 1.75 GeV/c2 at ADONE. No evidence was found for states having an integrated hadronic cross section larger than 8% of the J/ ψ (3100) one (at 90% C.L.)

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).

A triplet of low mass cylindrical PWC's form the innermost element of the CLEO detector at the Cornell Electron Storage Ring (CESR). Each PWC has 2 cathodes of 144 azimuthal rings. Analogue signals from each ring enable center of charge reconstruction of the longitudinal (z) position of each avalanche. Structural elements are ρ = .06 g/cm3 polyurethane foam cylinders 1.2 cm thick. Each of the 720 anode wires and 864 cathode strips is instrummented with a charge integrator, ADC, and provision for read out to a computer. Preliminary observed z resolution of an individual PWC is ~ 300 μ for avalanches from e+e- annihilation events. The PWC's are also an important element in the fast trigger to discriminate against cosmic rays, and are used to identify beam-gas and beam-wall background events.

We report the results of test beams performed at CERN using irradiated microstrip silicon detectors. The detectors were single- and double-sided devices, produced by different manufacturers and irradiated with neutrons at various fluences up to 3.6 × 1013 n/cm2. Signal-to-noise ratio, resolution and efficiency were studied for different values of the incidence angle, of the detector temperature and of the read-out pitch, as a function of the detector bias voltage. The goal of these tests was to optimize the design of the final prototypes for the CMS Silicon Strip Tracker.

An important tool for the discovery of new physics at LHC is the design of a low level trigger with an high power of background rejection. The contribution of pixel detector to the lowest level trigger at CMS is studied focusing on low-energy jet identification, matching the information from calorimeters and pixel detector. In addition, primary vertex algorithms are investigated. The performances are evaluated in terms of, respectively, QCD rejection and multihadronic jets final states efficiency.

We present a measurement of the particle flux punching through tungsten and iron beam dumps; the NA3 spectrometer was used. Momentum spectra and spatial distributions were determined for pions above GeV/c and for strange particles (K±, Ks0, Λ, Ξ; 15 < p < 50 GeV/c). Information on the effective attenuation length for strange particles was obtained by comparing the results from dumps of different lengths (200 and 220 cm).

We report selected results of laboratory measurements and beam tests of heavily irradiated microstrip silicon detectors. The detectors were single-sided devices, produced by different manufacturers and irradiated with different sources, for several total ionizing doses and fluences up to 4 /spl times/10/sup 14/ 1-MeV-equivalent neutrons per cm/sup 2/. Strip resistance and capacitance, detector leakage currents and breakdown performance were measured before and after irradiations. Signal-to-noise ratio and detector efficiency were studied in beam tests, for different values of the detector temperature and of the read-out pitch, as a function of the detector bias voltage. The goal of these test is to optimise the design of the final prototypes for the Silicon Strip Tracker of the CMS experiment at the CERN LHC collider.

Author(s): Bettini, A.; Cresti, M.; Mazzucato, M.; Peruzzo, L.; Sartori, S.; Zumerle, G.; Alston-Garnjost, M.; Huesman, R.; Ross, R.; Soljaitz, F.F.; Bigi, A.; Carrara, R.; Casali, R.; Lariccia, P.; Pazzi, R.; Borreani, G; Quassiati, B.; Rinaudo, G.; Vigone, M.; Werbrouck, A.

Abstract The new silicon tracker layout (V4) is presented. The system aspects of the construction are discussed together with the expected tracking performance. Because of the high radiation environment in which the detectors will operate, particular care has been devoted to the study of the characteristics of heavily irradiated detectors. This includes studies on performance (charge collection, cluster size, resolution, efficiency) as a function of the bias voltage, integrated fluence, incidence angle and temperature.

The CMS silicon strip tracker involves about 70 m2 of instrumented silicon, with approximately 18500 microstrip detectors read out by 5 × 106 electronics channels. It has to satisfy a set of stringent requirements imposed by the environment and by the physics expected at the LHC: low cell occupancy and good resolution, radiation hardness aided by adequate cooling, low mass combined with high stability. These conditions have been incorporated in a highly modular design of the detector modules and their support structures, chosen to facilitate construction and to allow for easy assembly and maintenance.

The paper describes the Silicon Tracking System of the Compact Muon Solenoid (CMS) experiment that is foreseen to collect events from p–p collision at the Ecm=14 TeV at the CERN future Large Hadron Collider (LHC). The proposed system consists of four layers of silicon microstrip detectors placed between the two inner layers of the pixel detector and the outer microstrip gas chamber system. The barrel part covers the η region up to 1.8, instrumenting the central radial region between 20 and 50 cm. The forward–backward disks extend the coverage up to η=2.6. This paper will review the main characteristics and performances of the system, the actual status of the R&D activities that we are carrying on, and the status of the milestones we have to fulfill in view of the Technical Design Report expected at the end of the year.

This paper describes the silicon microstrip tracker of the CMS experiment at the future LHC. The silicon tracker consists of a barrel part with 5 layers and two endcaps with 10 disks each. About 6500 modules will have to be built, each one carrying two daisy-chained silicon sensors and their front-end electronics. The modules have been designed to be as simple and robust as possible. Radiation damage in the silicon sensors is minimized by cooling the whole system down to -10°C. Safe operation after heavy irradiation will be possible due to the high-voltage capability of the sensors. We expect the sensors to have a signal-to-noise ratio of 10 at the end of 10years of LHC running, which still gives an efficiency of almost 100%.