R. Castaldi

We present the first results of a measurement of the total cross-section σT in proton-proton collisions at equivalent laboratory momenta between 291 and 1480 GeV/c at the CERN Intersecting Storage Rings (ISR). The method is based on the measurement of the ratio of the total interaction rate and the machine luminosity. The data show an increase of about 10% in σT in this energy interval.

The proton-antiproton total cross section was measured at the CM energy √s = 546 GeV. The result is σtot = 61.9± 1.5 mb. The ratio of the elastic to the total cross section is σeℓ/σtot = 0.215±0.005. A comparison to the lower energy data shows that the increase of the total cross section with energy is very close to a log2s behaviour.

Proton-antiproton elastic scattering was measured at the CERN SPS Collider at the centr-of-mass energy s=546 GeV in the Coulomb interference region. The data provide information on the phase of the hadronic amplitude in the forward direction. The conventional analysis gives for the ratio ϱ of the real to the imaginary part of the hadronic amplitude the result ϱ=0.24±0.04.

Proton-antiproton elastic scattering was measured at the CM energy √s = 546 GeV in the four-momentum transfer range 0.03<−t<0.32GeV2 For −<0.15GeV2 the data are well described by a simple exponential form exp(bt) with slope parameter b=15.2±0.2GeV−2. This value is significantly larger than the one measured in the region 0.21<−t<0.50 GeV2.

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 $\swein=0.2292\pm0.0009({\rm stat.})\pm0.0004({\rm syst.})$.}

Proton-antiproton elastic scattering was measured at the center-of-mass energy s=546 GeV in the four-momentum transfer range 0.45⩽−⩽1.55GeV2. The shape of the t-distribution is quite different from that observed in proton-proton scattering at the ISR. Rather than a dip-bump structure, a kink is present at − ≈0.9GeV2 followed by a shoulder. The cross section at the second maximum is more than one order of magnitude higher than at the ISR.

Single diffraction dissociation was measured in the reaction p¯p→p¯X at the centre-of-mass energy √s = 546 GeV. The mass M of the system X was deduced from the pseudorapidity distribution of the observed charged tracks. The cross section of single diffraction dissociation for M2/s⩽0.05isσsd=9.4 ± 0.7 mb. Comparison to the ISR data shows that σsd increases with energy less fast than the total and the elastic cross sections.

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.

First results on the measurement of the elastic and total cross section at the CERN pp̄ Collider are presented. Combining the measurement of elastic scattering at low momentum transfer with the rate of inelastic interactions, a value of the total cross section of 66 mb with a 10% statistical error was obtained.

We present data on two-particle distributions in the approximate rapidity variable η = −1n tan θ/2 for secondaries produced in proton-proton collisions at the CERN Intersecting Storage Rings (ISR). The data at centre-of-mass energies of 23 and 62 GeV show the existence of energy-independent positive, short-range correlations between secondaries within the central region. Deviations from short-range correlation exist when one (or both) of the particles is near the boundary of the available phase space. In part, such deviations are interpreted as the effect of a diffractive-like component in multiparticle production.

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.

Following a major shortage of 99Mo in the 2009–2010 period, concern grew that the aging reactor production facilities needed to be replaced. Most producers were using highly enriched 235U (HEU) as the target material. The Organisation for Economic Co-...Read More

Proton-antiproton elastic scattering was measured at the centre-of-mass energy s = 630 GeV in the four-momentum transfer range 0.7 ⩽ − t ⩽ 2.2 GeV2. The new data confirm our previous results at s = 546 GeV on the presence of a break in the t-distribution at −t ≃ 0.9 GeV2 which is followed by a shoulder, and extend the momentum transfer range to larger values. The t-dependence of the differential cross section beyond the break is discussed.

The reaction pp → pX was studied at a centre-of-mass energy s = 540 GeV by measuring the momentum spectrum of the antiproton. Data are presented in the four-momentum transfer range 05 < −t < 1.2GeV2. The shape of the mass distribution of the system X shows a diffractive component as already observed at lower energies. The differential cross section scales approximately with energy when compared to the ISR data.

Measurements of $\mathrm{pp}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}+X$ at $\sqrt{s}=44 \mathrm{and} 62$ GeV are compared. The data are taken under identical conditions utilizing clean proton-proton collisions from the CERN intersecting storage rings and confirm scaling to 5%. The observed ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ yield is a factor of 1.6\ifmmode\pm\else\textpm\fi{}0.2 larger than estimated from a simple parton model but is consistent with QCD. The ${p}_{T}$ dependence of the muon pairs agrees well with expectations from QCD.

Measurements of the proton-proton total cross section have been made with increased precision (±0.6%) over the ISR energy range s=23.5−62.7 GeV. Two different experimental methods gave consistent results, showing that the total cross section increases 10% over the ISR range and in addition that the absolute value of the ISR luminosity can be measured to ±0.9%.

The measurement of the proton-proton total cross section performed by the CERN-Pisa-Rome-Stony Brook Collaboration at the CERN ISR is discussed in detail. The total interaction rate, the elastic scattering rate in the forward direction, and the machine luminosity were measured simultaneously to obtain three different determinations of the total cross section. Consistent results were found, which made it possible to prove the reliability of the Van der Meer luminosity calibration within +-0.9% and to achieve a precision of +-0.6% in the measurement of the total cross section.

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).

The reaction pp → pX was studied as a function of the mass M of the system X at the centre-of-mass energy s = 546 GeV in the kinematical region where diffraction dissociation dominates. The pseudorapidity distribution of charged tracks, produced in the fragmentation of the system X, is well described within the limits of cylindrical phase space. The fragments of the X-system behave very similarly to the products of non-diffractive inelastic collisions at s = M.

We report the results of a study of the mechanism of inclusive dimuon production from the reaction $p+p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}+X$ at the CERN intersecting storage rings. The present experiment was done at the center-of-mass energies $\sqrt{s}=62 \mathrm{and} 44$ GeV and in the dimuon pair invariant-mass region $m=3\ensuremath{-}25$ GeV. The dependence on the Feynman variable $x$ has been measured. The average transverse momentum is found to increase with $\sqrt{s}$ and with mass and reaches $〈{p}_{T}〉\ensuremath{\simeq}1.9$ GeV, compatible with predictions from quantum-chromodynamic gluon processes.

Proton-antiproton elastic scattering was measured at a centre of mass energy s = 540 GeV. In the four-momentum transfer range 0.21 < −t < 0.50 GeV2 the t-distribution of about 7000 events is well represented by the exponential shape exp (bt) with slope parameter b = 13.7 ± 0.3 GeV−2. A new measurement of the slope for −t < 0.19 GeV2 confirms our earlier result, giving evidence for a change of slope of about 4 GeV−2 around −l̷ ≈ 0.15 GeV2.

Prompt dimuon production has been measured. Events with mass up to 25 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$ are observed, as well as the $J$ and $\ensuremath{\Upsilon}$ resonances. Cross sections are given for $J$ and $\ensuremath{\Upsilon}$ production. For the continuum, the scaling function $F(\ensuremath{\tau})$ is measured at very small values of $\sqrt{\ensuremath{\tau}}=\frac{m}{\sqrt{s}}$ covering the range $0.05&lt;\sqrt{\ensuremath{\tau}}&lt;0.20$.

Proton-antiproton elastic scattering at a centre-of-mass energy of 540 GeV was measured in the four-momentum transfer range 0.05 < −t < s.19 GeV2. The t-distribution can be fitted by the exponential exp(b) with b=17.2±1.0 GeV−2. This result indicates a rapid decrease of the width of the diffraction peak between ISR and Collider energies.

We present data on the semi-inclusive distributions of rapidities of secondary particles produced in pp collisions at very high energies. Our experiment was performed at the CERN Intersecting Storage Rings (ISR). The data given here, at centre-of-mass energies of √s=23 and 62 GeV, include the single-particle distributions and two-particle correlations. The semi-inclusive correlations show pronounced short-range correlation effects which have a width considerably narrower than in the case of inclusive correlations. We show that these short-range effects can be understood empirically in terms of three parameters whose energy and multiplicity dependence are studied. The data support the picture of multiparticle production in which clusters of small multiplicity and small dispersion are emitted with subsequent decay into hadrons.

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 $\mathrm{sin}{}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.23100\ifmmode\pm\else\textpm\fi{}0.00054(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.00014\left(\mathrm{syst}\right)$.

We have measured the behaviour or charged-particle multiplicities as a function of the transverse momentum of photons produced at 90° in proton-proton collisions. The data were obtained at the CERN Intersecting Storage Rings (ISR) at a centre-of-mass energy of 53 GeV and cover the transverse momentum range 0 < p⊥ < 4.5 GeV/c. The total associated charge multiplicity increases with p⊥ and most of the increase is found in a very wide cone opposite the detected photons. Partial multiplicities in the direction of the photons vary only slightly with p⊥. However, multiplicities at small angles with respect to the beams decrease sharply with increasing p⊥.

We present direct tests of the hypothesis of limiting fragmentation from an experiment at the CERN Intersecting Storage Rings at centre-of-mass energies between 31 and 53 GeV. Single-particle inclusive distributions and partial multiplicity distributions are observed for the case in which the energy of one beam is fixed while varying the energy of the other beam. Within cones around the beam, limiting fragmentation is shown to be valid.

We describe the apparatus used in experiment UA4 to study proton-antiproton elastic and inelastic interactions at the CERN SPS Collider. Elastically scattered particles, travelling at very small angles, are observed by detectors placed inside movable sections (“Roman pots”) of the SPS vacuum chamber. The deflection in the field of the machine quadrupoles allow the measurement of the particle momentum. Inelastic interactions are observed by a left-right symmetric system of trigger counter hodoscopes and drift-chamber telescopes. The apparatus reconstructs the interaction vertex and measures the pseudorapidity η of charged particles in the range 2.5 < ‖η‖ < 5.6.

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.

The ${\ensuremath{\pi}}^{0}$ inclusive cross section for c.m. production angles $\ensuremath{\theta}=90\ifmmode^\circ\else\textdegree\fi{}$ and $22\ifmmode^\circ\else\textdegree\fi{}&gt;~\ensuremath{\theta}&gt;~5\ifmmode^\circ\else\textdegree\fi{}$ at c.m. energies of $\sqrt{s}=23 \mathrm{and} 53$ GeV has been measured. This cross section is strongly dependent on both $\ensuremath{\theta}$ and $\sqrt{s}$ at small angles. The hypothesis of radial scaling is shown to be incapable of incorporating both $\ensuremath{\theta}$ and $\sqrt{s}$ dependence of the cross section. A recent quantum-chromodynamics calculation is in qualitative agreement with our results.

We report on an experiment of ω-photoproduction from nuclei (C, Al, Zn, Ag, Ta, Pb; 5.7 GeV mean photon energy) performed at DESY. The experimental apparatus detects the πoγ decay of the produced ω-mesons. Results about the ω-photon coupling γω2/4π and about the ω-nucleon total cross section σω are derived. The dependence of these results on the different possible models of analysis is discussed.

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

Abstract The vertex detector built by the Pisa Group for the CERN Intersecting Storage Rings muon pair experiment R 209 is described. A modular system of 136 small drift chambers, assembled around the ISR intersection region, measures the entrance directions of the muon pairs into the magnetized iron spectrometer, and the directions of the charged hadrons produced in association. Each module contains two doublets of sense wires, each doublet being associated with one delay line to determine directly the space points without left-right ambiguities. The mechanical structure is rather unconventional, having been designed with the aim of minimizing any dead space in the assembly of the modules. Space resolution is ≈ ± 0.2 mm in the drift coordinate and ≈ ± 2mm in the delay coordinate.

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 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.

We have measured the charged-particle multiplicities of events containing a large-transverse-momentum (${p}_{\ensuremath{\perp}}$) photon produced near center-of-mass polar angles ($\ensuremath{\theta}$) of 90\ifmmode^\circ\else\textdegree\fi{}, 17.5\ifmmode^\circ\else\textdegree\fi{}, and 8\ifmmode^\circ\else\textdegree\fi{} in proton-proton collisions. The data were obtained at the CERN Intersecting Storage Rings at center-of-mass energies of 23, 31, 45, 53, and 62 GeV and for the transverse-momentum range $0\ensuremath{\le}{p}_{\ensuremath{\perp}}\ensuremath{\le}4.5$ GeV/c. When the photons are detected near $\ensuremath{\theta}=90\ifmmode^\circ\else\textdegree\fi{}$, the associated multiplicity in the hemisphere away from the observed photon is found to increase with increasing photon transverse momentum. In the hemisphere containing the photon, the associated multiplicity decreases at the lowest energy and is approximately constant at the highest energies. The data at $\ensuremath{\theta}=17.5\ifmmode^\circ\else\textdegree\fi{} \mathrm{and} 8\ifmmode^\circ\else\textdegree\fi{}$ are similar, with the exception that the particle multiplicities near the detected photon are found to decrease with increasing photon ${p}_{\ensuremath{\perp}}$ at all energies. No strong back-to-back structure is observed in the data; however, as the photon emission angle is changed, some shift of the multiplicity distributions in the direction opposite the photon is observed. The data at all three polar angles show a broad peak in the azimuthal angular distributions at $\ensuremath{\varphi}=180\ifmmode^\circ\else\textdegree\fi{}$ (opposite the detected photon). Finally, the data are compared to a simplified picture for particle production in high-${p}_{\ensuremath{\perp}}$ events, and to the various classes of high-${p}_{\ensuremath{\perp}}$ models that have been proposed.

We report on an experimental performed at DESY to search for the πo + γ decay of the φ mesons, photoproduced at 5.5 GeV on a Zn target. From the known production cross-section and the calculated detection efficiency, an upper limit for the branching ratio B = Γ(φ → πo + γ)Γ(φ → all) of 0.35% was obtained.

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

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.

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).

We have measured at √s=62GeV, at the CERN Intersecting Storage Rings, the associated charged hadrons with massive μ pairs, employing a vertex detector of ∼ 4π coverage. The experiment has provided the first data on hadron multiplicity, angular distributions, and correlations in lepton pair events at ISR energies. The average associated charged multiplicity 〈nch〉 is found to increase as the invariant mass of the hadronic system Mh increases, similarly to the observed √s dependence in e+e− annihilation into hadrons at high energies. The multiplicity also increases with pT in the hemisphere opposite to the transverse momentum pT of the dimuon. Small clusters appear to be produced, whose correlation with the μ-pair can be explained in a simple Monte Carlo model incorporating the production of a weakly collimated jet of low multiplicity, recoiling against the dimuon.

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

The parity violation parameters Ab and Ac of the Zbb¯ and Zcc¯ couplings have been measured directly, using the polar angle dependence of the Z0-pole polarized cross sections. Bottom and charmed hadrons were tagged via semileptonic decays. Both the muon and electron identification algorithms take advantage of new multivariate techniques, incorporating for the first time information from the SLD Čerenkov Ring Imaging Detector. Based on the 1993–1995 SLD sample of 150 000 Z0 decays produced with highly polarized electron beams, we measure Ab=0.910±0.068(stat)±0.037(syst), Ac=0.642±0.110(stat)±0.063(syst).Received 4 May 1999DOI:https://doi.org/10.1103/PhysRevLett.83.3384©1999 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.

Abstract Data obtained from p-p collisions at centre-of-mass energies between 31 and 63 GeV are presented on correlations between momentum analysed forward π−, K− and p and charged particles observed in an omnidirectional hodoscope. The data show that significant correlations are present over the whole rapidity range for all three types of negative particles. The dependence on various kinematic variables suggests a cluster mechanism for the production of particles. In this picture, pions would be produced in clusters emitted in the fragmentation region while K− and p emanate from non-leading clusters.

A prototype hadron calorimeter, of similar design to the Warm Iron Calorimeter (WIC) planned for the SLD experiment, has been built and its performance has been studied in a test beam. The WIC is an iron sampling calorimeter whose active elements are plastic streamer tubes similar to those used for the Mont-Blanc proton decay experiment. The construction and operation of the tubes will be briefly described together with their use in an iron calorimeter - muon tracker. Efficiency, resolution and linearity have been measured in a hadron/muon beam up to 11 GeV. The measured values correspond to the SLD design goals.

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.

A set of CMS MicroStrip Gas Chambers (MSGC) was exposed to a high-intensity 3GeV/c pion beam at a CERN PS facility for a period of two weeks. The performance of the detectors is reported in terms of stability of efficiency and response to minimum ionising particles as well as to more heavily ionising fragments generated by nuclear interactions.

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 $〈{x}_{{E}_{B}}〉=0.716\ifmmode\pm\else\textpm\fi{}0.011(\mathrm{stat}{)}_{\ensuremath{-}0.022}^{+0.021}(\mathrm{syst})$.

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 FF-LYNX project aims at the definition of a flexible protocol that can handle both the distribution of Timing, Trigger and Control (TTC) signals and the data acquisition in future High Energy Physics (HEP) experiments. The implementation of this protocol in digital interfaces designed and produced in standard CMOS technologies (130 and/or 90 nm) and available as “IP cores” is also foreseen.

The FF-LYNX protocol provides an innovative solution for the integrated distribution of Timing, Trigger and Control signals and the data readout in future High Energy Physics experiments. Transmitter and receiver interfaces implementing the FF-LYNX protocol have been simulated with a high-level simulator and in an FPGA based emulator. The design of the interfaces in a commercial CMOS technology as radiation tolerant and low power modules is ongoing and the submission of a test circuit is foreseen in fall 2010. The key features of the protocol are described in this paper as well as its possible application for the transmission from Silicon Trackers to trigger processors with short and constant latency of data to be used for the L1 trigger generation.

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.

The FF-LYNX project aims at the definition of a flexible protocol for the distribution of Timing, Trigger and Control (TTC) signals and for the readout in future High Energy Physics (HEP) experiments and its implementation in radiation tolerant and low power interfaces designed and developed in standard CMOS technologies (130 nm-90 nm) and available as IP cores to designers of integrated circuits. The results of the first year of activity and future plans are here presented.

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.

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.

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.

A FASTBUS module has been designed for the acquisition and preliminary elaboration of digital data coming from limited streamer-tube strip readout electronics. The module is based on the Motorola MC68020 microprocessor and will perform fast readout with zero suppression, cluster searching, and apparatus monitoring on calorimeter cathode strip data. A description is given of the readout system architecture, the front-end processor, and the FASTBUS interface.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

We present the first study of rapidity gaps in e+e- annihilations using Z0 decays collected by the SLD experiment at SLAC. Our measured rapidity gap spectra fall exponentially with increasing gap size over five decades, and we observe no anomalous class of events containing large gaps. This supports the interpretation of the large-gap events measured in pp and ep collisions in terms of exchange of color-singlet objects. The presence of heavy flavors or additional jets does not affect these conclusions.

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

The FF-LYNX project, aimed at the design of an innovative data transmission protocol for high energy physics experiments and its implementation in rad-hard, low-power interfaces, is described in this document. An outline of the present project status and results is presented, as well as the foreseen future activity.

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.

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.

Data, obtained from p-p collisions at centre-of-mass energies between 31 and 63 GeV, are presented on inclusive and semi-inclusive correlations between forward emitted neutrons and charged particles observed in an omnidirectional hodoscope. A total absorption spectrometer was used to detect the neutrons and to measure their energy. Significant correlations are observed over the whole rapidity range. The data suggest that neutrons result from the decay of clusters emitted in the fragmentation region.

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.

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.

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.

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.

Studying the reaction Studyingpp → μ+ μ−X at the Intersecting Storage Rings (ISR),a special class of events was found for which no hadrons are seen associated with the muon pair in a large solid angle vertex detector. The origin of these events can be most naturally explained as arising from the two-photon process in pp collisions. It is emphasized that this process becomes increasingly interesting at higher hadron colliding facilities.