V. Karimäki

We report the results of two searches made on data recorded at the CERN SPS Proton-Antiproton Collider: one for isolated large-ET electrons, the other for large-ET neutrinos using the technique of missing transverse energy. Both searches converge to the same events, which have the signature of a two-body decay of a particle of mass ∼80 GeV/c2. The topology as well as the number of events fits well the hypothesis that they are produced by the proces p̄+p→W±+X, with W± →e±+ν; where W± is the Intermediate Vector Boson postulated by the unified theory of weak and electromagnetic inter- actions.

The general characteristics of inelastic proton-antiproton collisions at the CERN SPS Collider are studied with the UA1 detector using magnetic and calorimetric analysis. Results are presented on charged particle multiplicities and transverse and longitudinal momenta, and on total transverse energy distributions at centre of mass energies ranging from 0.2 to 0.9 TeV.

We report the observation of five events in which a missing transverse energy larger than 40 GeV is associated with a narrow hadronic jet and of two similar events with a neutral electromagnetic cluster (either one or more closely spaced photons). We cannot find an explanation for such events in terms of backgrounds or within the expectations of the Standard Model.

A sample of 52 Intermediate Vector Boson decays in the (vee) channel is described. They were produced at the CERN SPS Collider for an integrated luminosity of 0.136 pb−1. Both production and decay properties fit well with expectations from the Standard Model of weak interactions. An improved value for the W mass is given and compared with the previously published value for the Z0 mass.

We report on a search for B0↔B¯0 oscillations (mixing) using events with two identified muons from data collected at the CERN p¯p collider. In the absence of B0↔B¯0 oscillations, dimuons coming directly from decays of beauty-antibeauty paris must have opposite signs. Like-sign dimuons are expected from events where one muon arises from beauty decay and the other from the charm decay of the associated beauty-charm cascade. Taking these processes into account, together with the contribution from charm production, the predicted ratio of like-sign to unlike-sign muon pairs is 0.26±0.03. Experimentally we measure 0.42±0.07±0.03. A natural explanation for the excess of like-sign events is the existence of a significant amount of B0↔B¯0 transitions. The fraction of beauty particles that produce first-generation decay muons with the opposite electric charge from that expected without mixing is deduced to be: χ = 0.121±0.047. Combined with the null result from searches for B0↔B¯0 oscillations at e+e− colliders, our results are consistent with transitions inthe B0s system, as favoured theoretically.

With a segmented total absorption calorimeter of large acceptance, we have measured the total transverse energy spectrum for pp̄ collisions at s12 = 540 GeV up to ΣET= 130 GeV in the pseudo-rapidity range |η|< 1.5. Using two different algorithms, we have looked for localized depositions of transverse energy (jets). For ΣET > 40 GeV, the fraction of events with two jets increases with ΣET; this event structure is dominant for ΣET > 100 GeV. We measure the inclusive jet cross section up to ET(jet) = 60 GeV and the two-jets mass distribution to 120 GeV/c2. The measured cross sections are compatible with the predictions of hard scattering models based on QCD.

The production of transverse energy clusters in minimum bias proton-antiproton collisions at the CERN SPS Collider is studied with the UA1 detector over a new range of centre of mass energies (√s = 0.2−0.9 TeV). This study is intended to investigate how low in transverse momentum perturbative QCD is able to describe the dynamics of hadron collisions. We observe that clusters with transverse energy in excess of a few GeV exhibit properties in agreement with QCD expectations for parton scattering, supporting their interpretation in terms of jet production. We find that the jet-event rate represents a sizeable fraction of the inelastic rate and is increasing with √s over the measured energy range.

An extensive study of production and decay properties of charged and neutral Intermediate Vector Bosons (IVB) at the CERN proton-antiproton collider is presented. Intermediate Vector Bosons were detected in the electron, muon, and tau decay modes at centre-of-mass energies of 0.546 and 0.630 TeV. This paper is a summary, based on all the available data from the UA1 experiment from the running periods 1982–1985. Results are presented and compared with expectations of the Standard Eletroweak Model and QCD-improved Drell-Yan annihilation processes. The general conclusion is that there is an excellent agreement between the predictions of the Standard Model and our measurements.

A sample of events with large missing transverse energy from 715 nb−1 of data from the UA1 experiment at the CERN proton-antiproton collider is used to search for evidence of supersymmetric particle production. Assuming that the photino is the lightest supersymmetric particle and that it is massless, we find a limit on the squark mass of mq>45 GeV/c2 at 90% CL, independently of the gluino mass. Similarly, we find a limit on the gluino mass of mg>53 GeV/c2 (at 90% CL) independently of the squark mass, provided that the gluino is not long-lived (i.e. provided that the squark is not too heavy, mq⪅1 TeV/c2). For equal squark and gluino masses we find a limit mq=mg>75 GeV/c2 at 90% CL. The effect of a non-zero photino mass on these limits is studied.

We report evidence for beauty particle production through the observation of dimuon events from proton-antiproton collisions at energies of √s=546 GeV and √s=630 GeV at the CERN collider. Our data indicate that semi-leptonic decays of beauty particles are the dominant source of pairs of high-pT muons. The beauty flavour creation (gg or q¯q→b¯b) cross-section needed to explain the dimuon rate is σ{p¯p→b¯b+X, pbT5 GeV/c, |η|<2.0}=(1.1±0.1±0.4) μb, which is in good agreement with QCD calculations. We also observe clear signals for ϒ→μ+μ− (hidden beauty) and high-pT J/ψ→μ+μ−, well above the backgraound of continuum muon pairs from the Drell-Yan mechanism.

We present a detailed study of hadronic jets obtained in a data sample taken in the UA1 detector with a localized transverse energy trigger. We discuss the average shape of jets in terms of energy and charged particle content, and compare this to data generated in Monte Carlo programs. We further extend the previously reported inclusive jet cross section to the region of ET = 100 GeV. A comparison with theoretical models of cross sections for events with more than two jets is also given.

The two-jet cross section measured in the UA1 apparatus at the CERN pp Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x1 and x2. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x2 and x2, as expected in vector gluon theories (QCD). The differential cross section in x1 and x2 is consistent with factorization and provides a measurement of the proton structure function F(x) = G(x) + 49[Q(x) + Q(x)] at values of the four-momentum transfer squared, -t̂ ≈ 2000 GeV2. Over the range x = 0.10−0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (−9.5x).

We report measurements of b-quark and B-hadron production in pp̄ collisions at √s=630 GeV. We use muon samples to extract beauty production cross-sections over a wide range of transverse momentum in the central rapidity range |y| < 1.5. We compare our results to an O(αs3) QCD prediction and find good agreement over the measured b-quark transverse momentum range 6 GeV/c to 54 GeV/c. Using the shape of the pT and y distribution predicted by QCD to extrapolate our data, we infer a total cross-section for b-quark production at √s=630GeV ofσ(pp̄→bb̄+X)=19.3±7(exp.)±9(th.μb.

Track information from the central detector in the UA1 experiment at the CERN proton-antiproton collider (√s = 540 GeV) is used to determine the charged particle multiplicity distribution for the pseudorapidity range ∣η∣ < 1.3. The mean value for this multiplicity per unit of η is 3.9 ± 0.3 for events having at least one track in this range. Data from the central electromagnetic and hadron calorimeters are used to examine the correlation between the transverse energy measured in the collisions and the multiplicity in the central region.

Proton-antiproton elastic scattering at CM energy 540 GeV has been studied in the t-range 0.04 < −t < 0.45 GeV2. The data are well fitted by the form exp (bt) with b = 17.1 ± 1.0 GeV−2 for |t| = 0.04 − 0.18 GeVsu2 and b = 13.7 ± 0.2 ± 0.2 GeV−2 for |t| = 0.21−0.45 GeV2. A luminosity measurement combined with the optical theorem gives σtot = 67.6 ± 5.9 ± 2.7 mb and σe1/σtot = 0.209 ± 0.018 ± 0.008.

The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e- collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Standard Model physics, in particular Higgs and top-quark measurements. Subsequent stages will focus on measurements of rare Higgs processes, as well as searches for new physics processes and precision measurements of new states, e.g. states previously discovered at LHC or at CLIC itself. In the 2012 CLIC Conceptual Design Report, a fully optimised 3 TeV collider was presented, while the proposed lower energy stages were not studied to the same level of detail. This report presents an updated baseline staging scenario for CLIC. The scenario is the result of a comprehensive study addressing the performance, cost and power of the CLIC accelerator complex as a function of centre-of-mass energy and it targets optimal physics output based on the current physics landscape. The optimised staging scenario foresees three main centre-of-mass energy stages at 380 GeV, 1.5 TeV and 3 TeV for a full CLIC programme spanning 22 years. For the first stage, an alternative to the CLIC drive beam scheme is presented in which the main linac power is produced using X-band klystrons.

We report on a search for new heavy quarks using data collected by the UA1 experiment during 1983, 1984 and 1985 at the CERN proton-antiproton collider, corresponding to an integrated luminosity of approximately 700 nb−1. Studying events with a muon or an isolated electron, accompanied by one or more jets, we find good agreement between our data and Monte Carlo predictions for the production of charm and beauty, without the need for a new quark. A top quark model, involving the decayW→t $$\bar b$$ and directt $$\bar t$$ production via the strong interaction, is used to determine our detection efficiency for top. This allows us to place an upper limit on the cross section for producing top quarks as a function of the top quark mass. Our analysis is not sensitive to theW→t $$\bar b$$ process alone. By comparing our limit with a calculation of thet $$\bar t$$ cross section, added to theW→t $$\bar b$$ cross section derived from our own measurements ofW →lv, we are able to place a lower limit on the mass of the top quark. From the lowest order (α 2 ) calculation, using the choice of structure functions andQ 2 scale that give the lowest cross section, we find: $$m_{top} > 44GeV/c^2 \left( {95\% c.l.} \right).$$ Including an estimate of the next higher order (α 2 ) and calculating the cross section with the EUROJET QCD Monte Carlo program using a less extreme choice for the structure functions andQ 2 scale gives: $$m_{top} > 56GeV/c^2 \left( {95\% c.l.} \right).$$ A search has also been made for a fourth generation, charge 1/3 quark (b'). Assuming that theb' mass is smaller than that of the top quark and that it can-not be produced inW decays, the mass limits, using the above procedures, are respectivelym b' >32 GeV/c2 andm b' >44 GeV/c2, both at 95% confidence level.

We present a fast method for circular trajectory fitting. Our method is based on an explicit solution of an nonlinear least-squares problem to fit the circle curvature, direction and position parameters. The advantage with respect to previously published methods is that these parameters are Gaussian behaved which implies more reliable error estimation of the fitted parameters. We present formulae for error estimation as well as for propagation of parameters and error matrix to another point of reference.

The properties of a sample of 172 charged intermediate vector bosons decaying in the (eve) channel and 16 neutral intermediate vector bosons decaying in the (e+e−) channel are summarized. Masses, decay widths, decay angular distributions, and production cross sections are given, and a limit is put on the number of light neutrino types Nv ⩽ 10 at 90% CL.

We summarize the results obtained in the UA1 experiment on the production of bottom quarks in proton-antiproton collisions at √s=0.63 TeV. Independent muon data samples are used to determine the bottom quark production cross section in different transverse momentum ranges from 6 to 30 GeV. A recent theoretical calculation to O(αs3) of the inclusive bottom quark transverse momentum spectrum in hadronic collisions shows reasonable agreement with the data. We extrapolate the integral PT distribution to PT=0 and in rapidity to estimate the total cross section forthe production of bottom quark pairs. Assuming the shape in PT and rapidity given by the O(αs3) calcultaion, we obtain σ(pp→bb+X) = 10.2 ±3.3 μb.

We report on further analysis of events with large missing transverse energy from 715 nb−1 of data from the UA1 experiment at the CERN proton-antiproton collider. Measured W and Z0 rates and heavy flavour cross sections are used to predict rates of missing transverse energy event from all known standard model process. Limits are derived on two possible new sources, namely: (1) semi-hadronic decays of a fourth sequential charged heavy lepton coupling to the W boson, (2) Z0 decays into additional pairs of non-interacting particles. After taking into additional pairs of non-interacting particles. After taking into account all known sources of missing transverse energy events, we find a mass limit on a fourth-generation charged lepton of mL>41 GeV/c2 (90% CL) and a limit on the number of additional neutrino species of n⩽7 (90% CL).

We present updated results from the UA1 experiment on cross sections times leptonic branching ratios for intermediate vector bosons produced in proton-antiproton collisions at a centre-of-mass energy of 0.630 TeV. We find that σ·B(W→lβn)=0.63±0.04±0.10nb and σ·B(Z0→l+l−=0.071±0.011nb where l denotes an average of electron and muon channels. An average over all data (electron and muon channels at 0.546 and 0.630 TeV) gives a ratio of R≡σ·(W→lν)/σ·B(Z0→l+l−) = 9.1+1.7−1.2. Using current theoretical predictions for this quantity, limits are extracted on the number of light neutrino types. Combining UA1 and UA2 data and imposing the bound Nν⩾3 we find that Nν⩽5.9 at 90% CL. Constraints on the mass of the top quark are also discussed.

Results on charged particle production in pp̄ collision at s12 = 540 GeV are presented. The data were obtained at the CERN pp̄ collider using the UA1 detector, operated without magnetic field. The central particle density is 3.3 + - 0.2 per unit o pseudo-rapidity for non-diffractive events. KNO scaling of the multiplicity distributions withresults from ISR energies is observed.

We report on the first observation of the beauty baryon Λb in an exclusive decay channel at the CERN pp collider. Using 4.7 pb−1 of muon data collected in the 1988/89 collider runs we reconstruct 16±5 Λb's in the decay mode Λb→JψΛ above a background of 9±1 events, corresponding to a significance of about five standard deviations. We measure the Λb mass to be mΛb=5640±50±30 MeV/c2. Using the beauty cross-section measured by UA1 we deduce for the product of the production fraction and branching ratio fΛb Br (Λb→JψΛ)=(1.8±1.0)×10-10. Our sample contains three-muon event in which the beauty particle opposite to the Λb is tagged by the third muon. We also observe an indication of a signal in the decay channel B0→JψK0∗ with a significance of three standard deviations.

A significant intermittency signal is observed in 630 GeV pp collisions measured in the UA1 central detector. It occurs with similar magnitude in different variables: pseudorapidity, rapidity and azimuthal angle. The signal increases with decreasing charged particle multiplicity in the event. Its strength in a sample of low p⊥ tracks and its multiplicity dependence are not reproduced by commonly used Monte Carlo models of high energy interactions.

Isolated photons, produced directly by a scattering process, have been observed in the UA1 experiment at the CERN pp collider at centre-of-mass energies √=546 GeV and √=630 GeV. Single and double photon differential cross sections have been determined and found to be consistent with the expectations of QCD.

Results are presented on two-jet and three-jet cross sections, measured in the UA1 experiment at the CERN Super Proton Synchrotron (SPS) pp̄ Collider, at the highest available subprocess cms energies (ŝ>150 GeV). Precise measurements of the two-jet angular distribution are consistent with previous results but show significant scale-breaking effects. The three-jet Dalitz plot and the three-jet angular distributions show evidence for final- and initial-state bremsstrahlung processes, in agreement with the leading-order QCD predictions. A comparison of the yield of wide-angle three-jet events with the yield of two-jet events at smaller scattering angles gives for the strong interaction coupling constant: αs(K3JK2J)=0.16±0.02±0.03 at Q2≈4000 GeV2, where the factor K3JK2J may plausibly be assumed to be close to unity.

We report results based on a sample of events with large missing transverse energy corresponding to 715 nb−n of data from the UA1 experiment at the CERN proton-antiproton collider. High transverse-momentum tau-leptons from W decays are observed for the first time through their semi-hadronic decay modes and associated missing transverse energy. The measured relative rates of W→eν, W→μν, and W→τν provide the first direct tests of the electron-muon-tau universality of the weak charged couplings at Q2=mw2. We determine gτge=1.01±0.09±0.05 and gμge=1.05±0.07±0.08.

Angular distributions of high-mass jet pairs (180<m2J<350 GeV) have been measured in the UA1 experiment at the CERN pp̄ Collider (s=630GeV). We show that angular distributions are independent of the subprocess centre-of-mass (CM) energy over this range, and use the data to put constraints on the definition of the Q2 scale. The distribution for the very high mass jet pairs (240<m 2J<300 GeV) has also been used to obtain a lower limit on the energy scale Λc of compositeness of quarks. We find Λc>415 GeV at 95% confidence level.

We have measured the production cross-section times branching ratio for J/ψ→μ+μ− in pp̄ interactions at √s = 630 GeV in the kinematic range |y|<2.0 and pT>5 GeV/c, BR(J/ψ→μ+μ−)σ(pp̄→J/ψ)=6.18±0.24±0.81 nb. The data sample collected in 1988 and 1989 for an integrated luminosity of 4.7 pb−1 represents a fivefold improvement over the statistics in our earlier study of the J/ψ production process, and the pT distribution which is measured extends to 28 GeV/c. Using event topology we show that the rate for the direct production of J/ψ, via radiative decays of χ states, is larger than that for production via B-hadrons. Production of ψ′ is also studied using the decay modes <ψ′→μ+μ− and ψ′→J/ψπ+ψ−.

We report on a search for the decays B0→ μ+μ−, B→ μ+ μ−X and Bd0 → μ+ μ−K0∗, which are expected to be rare if mediated by flavor changing neutral currents. Using data collected during the 1984–1989 CERN pp̄ Collider runs, the UA1 search was carried out using μ+ μ− events with 3.9<Mμμ < 5.5 GeV/c2. We find 90% confidence level upper limits on the branching for BR → μ+μ− of 8.3 × 10−6, for B → μ+μ−X of 5.0 × 10−5, and for B0d→μ+μ−K0∗ of of 2.3 × 10−5. Implicatitions for upper limits on the t-quark mass are discussed.

Bose-Einstein correlations have been measured at the SPS collider at centre-of-mass energies from √s=0.2 to 0.9 TeV. The size and the incoherence parameter of the particle emitting region have been determined as a function of charged particle density in pseudorapidity Δn/Δη, centre-of-mass energy and the direction of emission of the charged particles. For fixed values of Δn/Δη the size of the interaction region and the incoherence parameter remain constant with rising √s. At fixed √s, the size of the interaction region increases with rising charged particle density while the incoherence parameter decreases.

Two-jet mass distributions have been measured as a function of centre-of-mass scattering angle for high-mass jet pairs produced in proton-antiproton collisions at the CERN collider operating at a centre-of-mass energy of 630 GeV. The agreement between QCD expectations and the experimental measurements has been used to place limits on the production cross section of an object X decaying into two jets. In particular we consider the existence of a massive colour octet of vector gauge bosons (axigluons). We exclude axigluons with a width ΛA < 0.4mA and a mass mA in the range 150 < mA < 310 GeV/c2 (95% CL).

The electronics systems for the readout of a large drift chamber (25 m3, 6110 sense wires) with image readout, to be used at the CERN p-p collider, is described. The system uses a flash analog-to-digital converter and is able to measure directly the drift time, the charge division, and the energy losses for many tracks on each wire. The results obtained with chamber and electronics prototypes are reported.

We have measured the W transverse momentum distribution (pTW) using a sample of 323 W → eν and W → μν events produced in proton-antiproton collisions at the CERN collider. In the present letter we extend the study of the distribution up to pTW ∼- m W and compare to leading and higher order QCD. This comparison is a precise test of QCD with hadron colliders and the inclusive spectrum gives good agreement over a large range of pTW. However we observed two events at very large pTW (∼- 100 GeV/c) in which the W candidate recoils against an energetic di-jet system. Both events have a very large missing transverse energy and a jet-jet mass compatible with the W mass. In a separate analysis, a topologically similar event has been observed in which a high-mass di-jet system is balanced by a large missing transverse energy which could be interpreted as Z0 → νν decay. We cannot easily explain these three events in terms of explicit second-order QCD calculations. However we cannot exclude at this stage the possibility that they are the result of non-gaussian fluctuations in the response of UA1 calorimetry or a statistical fluctuation in the data.

We present a study of low mass dimuon events [m(μμ) < 6 GeV/c2] from the UA1 experiment at the CERN pp collider. Contributions from semileptonic decays of heavy flavour particles, Drell-Yan type processes, J/ψ decays and leptonic decays of light mesons are extracted, and cross sections for high pT beauty and Drell-Yan production are derived. A limit for the branching fraction for the exotic decay B0→μ+μ− is also obtained. The cross section for section for low mass, high pT Drell-Yan prod uction is compared to the measured direct photon cross section using QED and QCD derived relationship. This relationship is used to infer a measurement of the single photon cross section at lower values of transverse momentum, where photons cannot be unambigously identified.

We have studied high transverse momentum J/ψ production in pp interactions at s=630 GeV. The measured cross section times branching fraction for J/ψ→μ+μ− production with pT⩾5 GeV/c and |y|<2.0 is 7.5±0.7±1.2 nb. The event topology is used to establish that there is J/ψ production from both the direct production of cc bound states and the decay of B hadrons. The inferred yield of J/ψ from beauty decays is compatible with our estimates of beauty production in other channels.

We report the observation of five muonic Z0 decays. The mass and cross section times branching ratio is consistent with the previous measurements of Z0→e+e−. Three of the muonic decays have unexpected features. One event is of the type Z0→μ+μ−γ. Two of the Z0→μ+μ− decays are accommpanied by several (>4) energetic (ET > 10 GeV) jets which are difficult to explain within the framework of standard QCD corrections.

The properties of a sample of 172 charged intermediate vector bosons decaying in the (eνe) channel and 16 neutral intermediate vector bosons decaying in the (e+e-) channel are described. Masses, decay widths, decay angular distributions, and production cross-sections are given; they are shown to be in excellent agreement with the expectations of the SU2 ⊗ U1 standard model. A limit is put on the number of light-neutrino types Nν ⩽ 10 at 90% c.l.

A sample of two-jet events from the UA1 experiment at the CERN pp̄ Collider has been used to study the fragmentation of high-energy quark and gluon jets into charged hadrons. Compared with lower-energy jets observed in e+e− and pp collisions, the fragmentation function measured in the present experiment is softer (i.e. peaked to smaller values of z) and the mean internal transverse momentum is larger, mainly because of the effects of the QCD scaling violations. Using our knowledge of the quark and gluon structure functions in the proton, together with the QCD matrix elements, a statistical separation of quark and gluon jets is achieved within the present experiment. The fragmentation function for the gluon jets is found to be softer, and the angular spread of the fragmentation products larger, than is the case for quark jets.

The production properties of a sample of 172 charged intermediate vector bosons produced at the CERN Super Proton Synchrotron Collider are described. The production cross-section, the longitudinal- and transverse-momentum distributions and the properties of hadronic jet activity produced in association with the weak bosons are in agreement with the expectations of the QCD-improved Drell-Yan mechanism.

Charged particle multiplicity cross sections for 100 GeV/c π−p inelastic interactions are presented and compared with results at other energies. The results for multiplicities n ⪖ 4 show a consistent trend in their energy dependence. The two-prong cross section curve differs as it tends to flatten off at the higher energies. The zero-prong cross section values decrease steeply as plab−1.1. The results for n ⩾ 2 for π−p and pp reactions appear to lie on a “universal” curve if nσn/σinel is plotted against 〈n〉/n. This “scaling” rule is equivalent to KNO scaling, but the plot suggested here is more useful in studying low multiplicities. An interpretation in terms of a two-component model and a possible extrapolation to higher energies are proposed.

The production of KS0, Λ and Λ is measured in π+p reactions at 16 GeV/c. The total strange particle cross section is found to be 4.0 ± 0.3 mb, about 20% of the inelastic cross section. Cross sections for single strange particles and for strange particle pairs are determined, both inclusively and as functions of the charged multiplicity. Relative production rates for different strange particle combinations are compared with the prediction of the isospin statistical model. Inclusive spectra for single particles are studied and it is found the KS0 are produced mostly in the forward hemisphere, most probably by fragmentation of the incident pion into KKπ. The Λ are mostly backwards, probably deriving from fragmentation of the proton into ΛK pairs. The Λ tend to be produced forwards, but evidence is found for central ΛΛ production. Distributions in rapidity of the Λ particles from π+p interactions are compared in terms of the factorisation hypothesis. Results are given on the Λ transversal polarisation.

We have analysed a sample of 2.36 million minimum bias events produced in pp collisions at s=630 GeV in the UA1 experiment at the CERN collider. We have studied the production of charged particles with transverse momenta (pT) up to 25 GeV/c. The results are in agreement with QCD predictions. The rise of 〈pT〉 with charged particle multiplicity may be related to changing production of low pT particles.

Higher order Bose-Einstein correlations up to fifth order, of particles produced in proton-antiproton collisions, are presented using UA1 data at √s=630 and 900 GeV. The results are compared with theoretical calculations to investigate the primary assumptions for the parametrization of the correlation functions.

An analysis of W and Z boson production at UA1, using 4.66 pb−1 of data from the 1988 and 1989 CERN pp Collider runs at s=0.63 TeV, yields R≡σWBr(W→μv)/σzBr(Z→μμ)=10.4−1.5+1.8stat.±0.8(syst.) We find R=9.5−1.0+1.1(stat.+syst.) when combining all available UA1 data, in both the electron and muon channel, taken in the period 1983–1989. In the framework of the standard model, the value of R is used to infer the total width of the W boson, ΓWtot=2.18−0.24+0.26 (exp.)±0.04(theory) GeV/c2.

Inclusive cross sections are presented for strange-particle production in proton-proton interactions at 19 GeV/c for the pairs (K0K0C=+1, K0Λ, K+Λ, K0Σ+, K0Σ− and for Λ, Ks0, Σ+, Σ− and Ξ−. The KK, the KY and the total strange particle cross sections have been found to be 1.40 ± 0.10 mb, 2.69 ± 0.09 mb and 4.23 ± 0.20 mb, respectively. The charged multiplicity distributions for events with Ks0, Λ, (K0K0)C=+1 or K0 Λ are shown to follow a modified KNO curve, whereas K+ Λ does not. For the inclusive reactions pp→(K0K0)C=+1 + X++, pp→K0Λ + X++ and pp → Λ + X++, we find that the average charged multiplicity of the remainder system X++ is the same as when X++ is produced in other reactions with the same system energy and quantum numbers.

Simple inclusive cross sections for pp interactions at 12 GeV/c are given. The data cover prong cross sections, V0 production and resonances. Separation has been made into annihilation and non-annihilation modes. Some implications of the data are discussed. It is pointed out that the ratios of cross sections for ϱ0π− production are independent of incident antiproton momentum in pp annihilation processes, and that data at the highest available pp energies (ISR) tend to the same value.

Inclusive fragmentation of jets into charged particles has been studied in the UA1 experiment at the CERN Super Proton Synchrotron (SPS) pp̄ Collider at s = 540 GeV for jets having a transverse energy above 30 GeV. The observed fragmentation function is very similar to that seen in e+e−jets and is therefore indicative of similar hadronization processes for gluons and quarks. Scaling with the energy of the jet is valid to a good approximation, although slight deviations are suggested by the data. The average transverse momentum with respect to the jet axis for jets with ET > 30 GeV is 600 MeV/c for particles having z > 0.1 and increases slowly with the jet energy.

We have analysed a sample of 2.36 million minimum bias events produced in pp collisions at s=630 GeV in the UA1 experiment at the CERN SppS collider. We have studied the production of KS0, Λ and Λ particles with transverse momenta (pt) up to 7 GeV/c and K± up to 2 GeV/c. The kaon data are compared with a recent QCD prediction and are found to be in good agreement. The <pt> for KS0, Λ and Λ is seen to increase as a function of the charged particle multiplicity and is compared with charged particle production.

We report evidence for the production of the charged D∗ mesons in pp̄ collisions at s = 540 GeV. The search was confined to the charged particle fragments of hadronic jets, which are expected to be predominantly gluon jets in this experiment. The fragmentation function and production rate for D∗ in jets of average transverse momentum of 28 GeV/c are given.

3roton-antiproton elastic scattering at cm energy 540 GeV has been studied in the t range 0.14 ⩽ −t ⩽ 0.26 GeV2. The data is well fitted by an exponential form exp(bt) with b = 13.3 ± 1.5 GeV−2.

We report on a new measurement of B0−B0 mixing at the CERN Spp̄S collider. Mixing is measured in the non-isolated high mass dimoun sample using data from the 1988–1989 collider runs. The measured value of the mixing parameter, χ, is 0.145±0.035(stat.) ± 0.014(syst.). The average of this measurement and that from our 1984–1985 data is ξ= 0.14 ± 0.029 (stat.) ± 0.017 (syst.) assuming fully correlated errors. Using the measurement of ξd from ARGUS and CLEO , we obtain χ = 0.50 ± 0.20, which gives a limit of χs > 0.17 (0.12) at 90% (95%) CL. Including the measurements of χ from the ALEPH and L3 experiments gives χs = 0.53 ± 0.15, and a limit of χs > 0.27 (0.23) at 90% (95%) CL.

We report on a search for new heavy quarks decaying semileptonically into muons, using 4.7 pb−1 of data taken during the CERN $$p\bar p$$ collider runs in 1988 and 1989. The properties of isolated muons accompanied by jets are consistent with the predictions from the Standard Model but do not show a signal for a new heavy quark. Combining all the UA1 data (5.4 pb−1), lower mass limits are obtained at 60 GeV/c2 (95% CL) for thet-quark and 43 GeV/c2 (95% CL) for a fourth-generation charge-1/3 quark (b′-quark).

We report on measurements of correlated $$b\bar b$$ production in $$p\bar p$$ collisions at $$\sqrt s = 630GeV$$ , using dimuon data to tag both theb and $$\bar b$$ quarks. Starting from an inclusive dimuon sample we obtain improved cross-sections for single inclusive beauty production and confirm our earlier results on $$B^0 - \bar B^0$$ mixing. From a study of $$b\bar b$$ correlations we derive explicit cross-sections for semi-differential $$b\bar b$$ production. We compare the measured cross-sections and correlations to $$\mathcal{O}\left( {\alpha _s^3 } \right)$$ QCD predictions and find good quantitative agreement. From the measured angular distributions we establish a size-able contribution from higher order QCD processes with a significance of about seven standard deviations. A large nonperturbative contribution to these higher order corrections is excluded.

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 report the observation of 21 dimuon events at the CERN pp Collider with the UA1 detector. The events range in invariant dimuon mass from 2 to 22 GeV / c2. The properties of these events are given. The bulk of the events are consistent with heavy-flavour production (mainly bb) with a few candidates for Drell-Yan production. There remain a few events which are difficult to interpret in terms of these processes, in particular two events with isolated, like-sign muons.

Results on K∗(890) production in K−p → NKπ reactions at 16 GeV/c are presented. Total cross sections, differential cross sections and density matrix elements are determined. It is found that: (i) The cross section for K∗−(890) p is consistent with containing two components, one due to natural parity exchange, falling slowly with increasing energy, the other, due to unnatural parity exchange, vanishing rapidly with increasing energy. For K∗o(890)n, the cross section decreases steadily as the energy increases. (ii) Natural spin-parity exchange dominates in the K∗−(890) p channel, the unnatural exchange contribution being approximately (5±4)%. In K∗o(890)n, natural spin-parity exchange is only about (30±10)%. (iii) The reacton K−p → K∗−(890)p is dominated (95±5)% by isoscalar exchange. (iv) The effective trajectory involved in the I = 0 natural parity exchange is consistent with the ω-f trajectory. (v) Interference terms between exchanges with positive (f, πo,…) and negative (ϱo, ω,…) C-conjugation amount to (23±12) μb at 16 GeV/c.

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field values. The value of the field at a given point of a volume is obtained by interpolation from a regular grid of values resulting from a TOSCA calculation or, when available, from a parameterization. The results of the measurements and calculations are presented, compared and discussed.

We derive explicit and precise formulae for 3×3 error matrix of particle transverse momentum, direction and impact parameter. The error matrix elements are expressed as functions of up to fourth order statistical moments of the measured coordinates. The formulae are valid for any curvature and track length in case of negligible multiple scattering. The calculation is compared with formulae derived by Gluckstern for curvature and direction. We show that Gluckstern formulation is valid at the limit of small L/R, ratio between the track length and radius of curvature.

We present a study of heavy flavour (charm and beauty) production using data collected with the UA1 detector at the CERN Proton-Antiproton collider at a centre-of-mass energy of 630 GeV for an integrated luminosity of 556 nb−1. This follows our earlier study ofb $$\bar b$$ andc $$\bar c$$ production in dimuon events and the evidence for mixing betweenB 0 and $$\bar B^0 $$ states. Properties of an inclusive sample of events containing a muon withp T >6 GeV/c are compared with QCD predictions for heavy flavour production, using the ISAJET Monte Carlo program. The predicted largep T muon yield from heavy flavour production and decay agrees with the data to within 30%. For events with a muon ofp T >10 GeV/c and at least one jet withE T >10 GeV, we measure the ratio charm/(charm+beauty) to be (24±8±9)%. We also show that the correlations observed between the two heavy quark jets expected by flavour conservation are consistent with the mixture of lowest and higher order QCD processes. We study in detail the topological and kinematic properties of a subsample of events containing a highp T muon and one or more jets. The good agreement of the theoretical predictions with our data in a region dominated by the production of charm and beauty shows that one of the main background sources to a new heavy quark signature is well understood.

The Central Detector of the UA1 experiment at the CERN proton-antiproton Collider underwent a first physics run at the end of 1981. The detector consists of a large drift chamber assembly (25 m3, ~ 6000 sense wires). An electronics readout with multi-hit capability simultaneously digitizes the time and the analog information used for charge division and energy measurement. The initial performance of the readout and control system will also be presented. The detector was tested in two cosmic-ray runs, and is now fully operational for the second physics run; this started at the beginning of October 1982.

Abstract Data are presented on inclusive single particle distributions in the proton fragmentation region for the reactions K + p → π ± X at 8.2 and 16 GeV/ c and K − p → π ± X at 10 and 16 GeV/ c . The energy dependence is studied and compared with the dual Regge model predictions for approach to scaling. None of the existing models is in full agreement with the data. The model of Chan and his collaborators is consistent with our results under the additional assumption of equality of vector and meson coupling constants in the p π + vertex in the Mueller diagram.

During summer 2006 a fraction of the CMS silicon strip tracker was operated in a comprehensive slice test called the Magnet Test and Cosmic Challenge (MTCC). At the MTCC, cosmic rays detected in the muon chambers were used to trigger the readout of all CMS sub-detectors in the general data acquisition system and in the presence of the 4 T magnetic field produced by the CMS superconducting solenoid. This document describes the operation of the Tracker hardware and software prior, during and after data taking. The performance of the detector as resulting from the MTCC data analysis is also presented.

The influence of Bose-Einstein correlations on the rise of factorial moments is small in the 1-dimensional phase space given by the pseudorapidity η, where the 2-body correlation function is dominated by unlike-sign particle correlations. Contraily, the influence is dominant in the higher dimensional phase space. This is shown by using correlation integrals. They exhibit clear power law dependences on the four-momentum transferQ 2 for all orders investigated (i=2–5). When searching for the origin of this behaviour, we found that the Bose-Einstein ratio itself shows a steep rise forQ 2→0, compatible with a power law.

A search for multifractal structures, in analogy with multifractal theories, is performed on UA1 minimum bias events. A downward concave multifractal spectral function,f(α) (where α is the Lipschitz-Hölder exponent), indicates that there are self-similar cascading processes, governing the evolution from the quark to the hadron level, in the final states of hadronic interactions.f(α) is an accurate measure of the bin to bin fluctuations of any observable. It is shown that the most sensitive comparison between data and the Monte Carlo models, GENCL and PYTHIA 4.8 can be made usingf(α). It is found that these models do not fully reproduce the behaviour of the data.

A beam telescope providing precision track measurements as reference for other detectors has been upgraded in the CERN H2 test beam. The apparatus was completely rebuilt from the detector wafers and front-end electronics to the data acquisition system. The new detector setup consists of eight 5.6×5.6cm2 sized DC coupled silicon microstrip detectors. Typical position resolution values of about 7.5μm were measured. Details of the setup are described and results from the recent beam tests are reported.

From a sample of 2.36 million minimum bias events produced in pp collisions at s=630GeV in the UA1 experiment and from other published data at the CERN SppS collider we have estimated the relative production of π±, π0, K±, KS0, Λ, Λ, p and p. We obtain a meson over baryon ratio MB= 6.4 ± 1.1. From the KS0π± ratio we measure the strangeness suppression factor λ = 0.29 ± 0.02 ± 0.01 which, combining with other available data provides a new world average of 0.29 ± 0.015. Both the KS0π± ratio and the strangeness suppression factor λ as a function of s are investigated, and an extrapolation to the LHC energy is performed.

Strip detectors with an area of 16cm2 were processed on high resistivity n-type magnetic Czochralski silicon. In addition, detectors were processed on high resistivity Float Zone wafers with the same mask set for comparison. The detectors were irradiated to several different fluences up to the fluence of 3×10151MeVneq/cm2 with protons or with mixed protons and neutrons. The detectors were fully characterized with CV- and IV-measurements prior to and after the irradiation. The beam test was carried out at the CERN H2 beam line using a silicon beam telescope that determines the tracks of the incoming particles and hence provides a reference measurement for the detector characterization. The n-type MCz-Si strip detectors have an acceptable S/N at least up to the fluence of 1×1015neq/cm2 and thus, they are a feasible option for the strip detector layers in the SLHC tracking systems.

A search for t-quark decay into charged Higgs, t→H+b, with the charged Higgs decaying via the H+→τ+vτ mode, has been done in proton-antiproton collisions at √2 = 0.63 TeV with the UA1 experiment. No evidence for this decay das been observed. Mass limits at 95% and 90% CL for the t-quark and the charged Higgs are presented. The results have also been interpreted in terms of the tan β parameter of a two-doublet Higgs sector.

We study the multiplicity distributions and the correlations of charged particles produced forward and backward in the centre-of-mass system. The correlations are small but significant. This type of analysis shows clearly the presence of the diffractive component of the inelastic cross section, amounting to about 15% of it. It is also apparent that KNO multiplicity scaling is not satisfied.

The UA1 Collaboration has recently improved its measurement of the beauty production cross-section by including explicit measurements of bb correlations. Using these data we have determined the strong coupling constant αs. The comparison of the measured cross-section for 2-body final states with O(αs3) QCD predictions yields a measurement of αs(20 GeV) = 0.145−0.010 exp −0.016 th+0.012 +0.013, corresponding to αs(Mz) = 0.113−0.006 exp −0.009 th+0.007 +0.008. This is the first theoretically well-defined measurement of αs from a purely hadronic production process. Evaluating αs from cross-sections at different Q2-values we find that the running of αs is needed for internal consistency of the UA1 data.

This is the first full solid angle analysis of large transverse energy events in $$p\bar p$$ collisions at the CERN collider. Events with transverse energies in excess of 200 GeV at $$\sqrt s = 630 GeV$$ are studied for any non-standard physics and quantitatively compared with expectations from perturbative QCD Monte Carlo models. A corrected differential cross section is presented. A detailed examination is made of jet profiles, event jet multiplicities and the fraction of the transverse energy carried by the two jets with the highest transverse jet energies. There is good agreement with standard theory for events with transverse energies up to the largest observed values $$( \approx \sqrt {s/2} )$$ and the analysis shows no evidence for any non-QCD mechanism to account for the event characteristics.

In March 2007 the assembly of the Silicon Strip Tracker was completed at the Tracker Integration Facility at CERN. Nearly 15% of the detector was instrumented using cables, fiber optics, power supplies, and electronics intended for the operation at the LHC. A local chiller was used to circulate the coolant for low temperature operation. In order to understand the efficiency and alignment of the strip tracker modules, a cosmic ray trigger was implemented. From March through July 4.5 million triggers were recorded. This period, referred to as the Sector Test, provided practical experience with the operation of the Tracker, especially safety, data acquisition, power, and cooling systems. This paper describes the performance of the strip system during the Sector Test, which consisted of five distinct periods defined by the coolant temperature. Significant emphasis is placed on comparisons between the data and results from Monte Carlo studies.

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15 °C to −15 °C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) μm RMS in the outer (inner) part of the barrel.

Abstract Performance of single-sided DC-coupled silicon strip detectors is studied in the CERN H2 test beam. A great emphasis is put on the calibration of the detector response as well as on the geometric alignment of the detector planes. Performance results are presented for different angles of incidence for the particles.

The total punchthrough probability of showers produced by negatively charged pions of momenta 30, 40, 50, 75, 100, 200 and 300 GeV/c, has been measured in the RD5 experiment at CERN using a toroidal spectrometer. The range of the measurement extends to 5.3 m of equivalent iron. Our results have been obtained by two different analysis methods and are compared with the resutls of a previous experiment.

Abstract Single layer honeycomb strip chambers have been constructed for the tracking calorimeter TRACAL. This detector is a component of the RD5 experimental test setup at CERN, where aspects of muon detection in LHC conditions are studied. The construction of the chambers is described and the excellent spatial resolution obtained from strip signals (σ

Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly ionising particles (HIPs) and deposit as much energy within the sensor bulk as several hundred minimum ionising particles. The large signals generated by these ‘HIP events’ can momentarily saturate the APV25 front-end readout chip for the silicon strip tracker (SST) sub-detector of the compact muon solenoid (CMS) experiment, resulting in deadtime in the detector readout system. This paper presents studies of this phenomenon through simulation, laboratory measurements and dedicated beam tests. A proposed change to a front-end component to reduce the APV25 sensitivity to HIP events is also examined. The results are used to infer the expected effect on the performance of the CMS SST at the future large hadron collider. The induced inefficiencies are at the percent level and will have a negligible effect on the physics performance of the SST.

We test the usage of a Toolkit for Multivariate Data Analysis (TMVA) in b tagging. Tagging b jets associated with heavy neutral MSSM Higgs bosons at the LHC can be used to extract the Higgs bosons from the Drell-Yan background, for which the associated jets are mainly light quark and gluon jets. Achievable b tagging efficiency is studied with more than ten MVA classifiers at 1% mistagging rate. Most classifiers were found to perform better than the simple track counting algorithm.

We have measured the rate of D∗± meson production inside the jets produced in pp collisions at √s = 630 GeV. For jets in the transverse energy range 15<ET<60 GeV we find a production rate of 0.10±0.04±0.03 D∗± per jet, which is in good agreement with perturbative QCD calculations. In addition, we find that the D∗± fragmentation distribution is strongly peaked towards low z consistent with gluon splitting as the dominant production mechanism.

Parity conserving decays yield incomplete information about the spin state of a decaying resonance. Using the cascade decay Y∗ (1385) → Λπ (Λ → pπ), where the second decay does not comserve parity, one finds all the parameters necessary to specify the spin state of Y∗ resonances. In this paper Y∗ resonances produced in π+p reactions at 8 GeV/c and K−p reactions at 10 GeV/c are studied. It is found that the experimental results are, with one exception, in resonable agreement with the predictions of the additive quark model.

We present a fast code to fit circular arcs to measured points. Our algorithm is based on an explicit solution of a non-linear least-squares problem to fit the circle curvature, direction and position parameters. The code includes error estimation of the circle parameters as well as the transformation of parameters and error matrix to another point of reference. The formalism is valid for any arc lenght up to a full circle.

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.

Inclusive production of ϱ0,K *±(892), andf is studied in $$\bar p$$ p interactions at 12 GeV/c. The inclusive cross sections for ϱ0,K *±(892), andf are found to be 6.7±0.3 mb, 1.0±0.2 mb, and 1.4±0.3 mb, respectively. The differential cross sections are presented as a function of c.m. rapidity, Feynmanx and square of the transverse momentump 2 . Comparison with the correspondingpp data shows some interesting differences which can be attributed to the $$\bar p$$ p annihilation. The results are compared with the predictions of the quark fusion model.

Five-body final states from K−p interactions at 6, 10 and 16 GeV/c are separated into sub-reactions depending upon which particles go forward in the c.m. system. The relative population and energy dependence of the various sub-reactions are shown to be closely related to the quantum numbers exchanged between the forward and backward going particles. In particular the energy dependence is the same as that found for the production of two-body final states involving exchange of the same quantum numbers. Single diffraction dissociation of the incident kaon and proton are shown to be important processes in these five-body states. We refer to this technique of separating events as binary LPS.

A method is presented for deriving channel cross sections for all multiplicities, considering both charged and neutral particles, for K−p reactions of pion production, Thus the “true”, rather than charged, multiplicity is obtained. The input data are the channel cross sections measured with four- and one-constraint fits. The model employed is the two-component one, so that for each reaction channel, separate cross sections are derived for kaon diffraction, proton diffraction and for non-diffractive processes. Results are obtained up to the highest energies at which data of channel cross sections are available, i.e. up to 16 GeV/c incoming momentum, and some extrapolation is also made towards higher energies. It is found that the cross section for single kaon diffraction dissociation is equal to that for single proton diffraction dissociation. In the energy range considered, the sum of kaon and proton single diffraction processes has a cross section of (2.4 ± 0.3) mb, i.e., about 75% of the elastic cross section. The cross section for kaon diffraction dissociation into (Kπ) is consistent with zero.

The problem of how much of the correlations observed between the longitudinal momenta of the two leading particles can be explained by facts already known from single particle distributions is studied in the reaction K−+p→Ko+p+ anything at 10 GeV/c. It is argued that the correlation function of variables related to the momentum is strongly distorted because of the non-rectangular boundaries imposed by energy-momentum conservation. It is shown that the exponential decrease of the transverse momentum for porduced pions and of the four-momentum transfer for leading particles are sufficient to describe the main features of the experimental correlation function.

Good geometrical calibration is essential in the use of high resolution detectors. The individual sensors in the detector have to be calibrated with an accuracy better than the intrinsic resolution, which typically is of the order of 10 um. We present an effective method to perform fine calibration of sensor positions in a detector assembly consisting of a large number of pixel and strip sensors. Up to six geometric parameters, three for location and three for orientation, can be computed for each sensor on a basis of particle trajectories traversing the detector system. The performance of the method is demonstrated with both simulated tracks and tracks reconstructed from experimental data. We also present a brief review of other alignment methods reported in the literature.

We report on test beam results obtained with a 32.5 cm2 microstrip detector processed on an n-type 380 μm thick magnetic Czochralski (MCZ) grown silicon substrate with 1200 Ωcm effective resistivity. The full depletion voltage of the as-processed detector was 420 V with a leakage current of 2 μA. The AC coupled detector had 1024 p+ strips, 10 μm by width and 6.154 cm by length with a pitch of 50 μm. The detector was irradiated with 10 MeV protons to 1.6×1014 1 MeV neutron equivalent fluence and annealed for 345 days at room temperature. The post-irradiation full depletion voltage of the detector was 225 V. The leakage current at the full depletion measured at −10 °C was 261 μA. The beam tests were carried out at the CERN H2 area using a Silicon Beam Telescope, which consists of pairs of horizontal and vertical position sensitive silicon detectors. This telescope determines the tracks of incoming particles and hence provides a reference measurement for the detector characterization. In the beam test an average signal to noise ratio of 3 with a spatial resolution of 20 μm and a particle detection efficiency of 36% were measured. These results show that the MCZ device detected particles, which encourages further investigations of MCZ silicon as a detector material. The poor performance of the MCZ detector may be explained by the problems observed in the reference telescope.

We present rst results of a track based alignment procedure applied to test beam data recorded with Cosmic Rack, a test setup which mimicks the outer barrel of the CMS Tracker. The Hits and Impact Points alignment method is used within the CMS reconstruction software framework to align this telescope-like device. These results were compared to results obtained with manual alignment and to results obtained with the Millepede algorithm. This study demonstrates that the software implementation of the recently developed alignment tools works properly and also represents the rst track based alignment results in CMS using real data.

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.

Three- and four-body final states with strange particles are studied in π+p and π−p interactions at 16 GeV/c. We present cross sections and investigate their energy dependence. Production mechanism, resonance production and quantum number transfer are discussed. Strong Y∗(1385) production is found in the reaction π+p → ΛK+π+, while the corresponding π−p reaction is dominated by production of K∗(890). In the NKKπ channels, the K and K are produced mainly at the same vertex, i.e. non-strangeness exchange ΔS = 0 is dominant (about 75% of the cases), whereas in the ΛKππ channels, the Λ and K are more frequently produced at opposite vertices, i.e. |ΔS| = 1 exchange is important (about 60% of the cases). Results on the polarization of the lambdas produced in the π+p reactions are given.

We have tested the detection performance of a strip detector processed on silicon wafer grown by magnetic Czochralski (MCZ) method. This is the first time a full size Czochralski detector has been tested in a beam, although the advantages of CZ silicon have been known before. Prior to test beam measurements, the electrical characteristics of the Czochralski silicon detectors were found to be appropriate for particle detection. Using the Helsinki Silicon Beam telescope at CERN H2 test beam, the performance of the Czochralski silicon detector was shown to be comparable with the existing silicon strip detectors.

Single particle distributions as functions of the scaled variables pT/⟨pT⟩ and pL/⟨pL⟩ have been studied for neutral strange particles produced in proton-proton interactions at 19 GeV/c. For pp → Ks0+X++ the distributions in both variables for different charged particle multiplicities show approximate scaling, while for pp → Λ+X++ only the distribution in the transverse variable shows this behaviour.