R. Kinnunen

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.

Physics at the Large Hadron Collider (LHC) and the International e+e- Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC/ILC Study Group so far is summarized in this report. Possible topics for future studies are outlined.

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.

For an intermediate mass Higgs boson with SM-like couplings the CERN LHC allows observation of a variety of decay channels in production by gluon fusion and weak boson fusion. Cross section ratios provide measurements of various ratios of Higgs couplings, with accuracies of order 15% for 100 ${\mathrm{fb}}^{\ensuremath{-}1}$ of data in each of the two LHC experiments. For Higgs boson masses above 120 GeV, minimal assumptions on the Higgs sector allow for an indirect measurement of the total Higgs boson width with an accuracy of 10 to 20 %, and of the $\stackrel{\ensuremath{\rightarrow}}{H}\mathrm{WW}$ partial width with an accuracy of about 10%.

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.

This work summarizes and puts in an overall perspective studies done within the compact muon solenoid (CMS) concerning the discovery potential for squarks and gluinos, sleptons, charginos and neutralinos, supersymmetric (SUSY) dark matter, lightest Higgs, sparticle mass determination methods and the detector design optimization in view of SUSY searches. It represents the status of our understanding of these subjects as of summer 1997. As a benchmark we used the minimal supergravity-inspired supersymmetric standard model (mSUGRA) with a stable lightest supersymmetric particle (LSP). Discovery of supersymmetry at the large hadron collider should be relatively straightforward. It may occur through the observation of large excesses of events in missing ET plus jets, or with one or more isolated leptons. An excess of trilepton events or isolated dileptons with missing ET, exhibiting a characteristic signature in the l+l− invariant mass distribution, could also be the first manifestation of SUSY production. Squarks and gluinos can be discovered for masses in excess of 2 TeV. Charginos and neutralinos can be discovered from an excess of events in dilepton or trilepton final states. Inclusive searches can give early indications from their copious production in squark and gluino cascade decays. Indirect evidence for sleptons can also be obtained from inclusive dilepton studies. Isolation requirements and a jet veto would allow detection of both the direct chargino/neutralino production and the directly produced sleptons. Squark and gluino production may also represent a copious source of Higgs bosons through cascade decays. The lightest SUSY Higgs h → b may be reconstructed with a signal/background ratio of order 1 thanks to hard cuts on ETmiss justified by escaping LSPs. The LSP of SUSY models with conserved R-parity represents a very good candidate for cosmological dark matter. The region of parameter space where this is true is well covered by our searches, at least for tanβ = 2.

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.

The inclusive jet cross section has been measured in the UA1 experiment at the CERN pp Collider at centre-of-mass energies √s = 546 GeV and √s = 630 eV. The cross sections are found to be consistent with QCD predictions, The observed change in the cross section with the centre-of-mass energy √s is accounted for in terms of xT scaling.

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 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.

Muons of high transverse momentum pμT have been observed in the large drift chambers surrounding the UA1 detector at the CERN 540 GeV pp̄ collider. For an integrated luminosity of 108 nb−1, 14 isolated muons have been found with pT > 15 GeV/c. They are correlated with a large imbalance in total transverse energy, and show a kinematic behaviour consistent with the muonic decay of the Intermediate Vector Boson W± of weak interactions. The partial cross section is in agreement with previous measurements for electronic decays and with muon-electron universality. The W mass is determined to be mW = 81+6−7 GeV/c2.

This work summarizes the studies for the Higgs boson searches in CMS at the LHC collider. The main discovery channels are presented and the potential is given for the discovery of the SM Higgs boson and the Higgs bosons of the MSSM. The phenomenology, detector, trigger and reconstruction issues are briefly discussed.

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).

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.

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.

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.

The search for MSSM Higgs bosons will be an important goal at the LHC. We analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs bosons with an integrated luminosity of 30 or 60 fb-1. This is done by combining the latest results for the CMS experimental sensitivities based on full simulation studies with state-of-the-art theoretical predictions of the MSSM Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios in terms of the parameters tan β and the Higgs-boson mass scale, MA. We study the dependence of the 5σ discovery contours in the MA–tan β plane on variations of the other supersymmetric parameters. The largest effects arise from a change in the higgsino mass parameter μ, which enters both via higher-order radiative corrections and via the kinematics of Higgs decays into supersymmetric particles. While the variation of μ can shift the prospective discovery reach (and correspondingly the ”LHC wedge” region) by about Δtan β=10, we find that the discovery reach is rather stable with respect to the impact of other supersymmetric parameters. Within the discovery region we analyze the accuracy with which the masses of the heavy neutral Higgs bosons can be determined. We find that an accuracy of 1–4% should be achievable, which could make it possible in favorable regions of the MSSM parameter space to experimentally resolve the signals of the two heavy MSSM Higgs bosons at the LHC.

In grand-unified theories (GUT), non-universal boundary conditions for the gaugino masses may arise at the unification scale and may affect the observability of the neutral MSSM Higgs bosons (h/H/A) at the LHC. The implications of such non-universal gaugino masses are investigated for Higgs boson production in the SUSY cascade decay chain $\tilde{g}\rightarrow \tilde{q}q$ , $\tilde{q}\rightarrow \tilde{\chi_{2}}q$ , $\tilde{\chi_{2}}\rightarrow \tilde{\chi_{1}}h/H/A$ , $h/H/A\rightarrow b\bar{b}$ produced in pp interactions. In the singlet representation with universal gaugino masses only the light Higgs boson can be produced in this cascade with the parameter region of interest for us, while with non-universal gaugino masses heavy neutral MSSM Higgs boson production may dominate. The allowed parameter space in the light of the WMAP constraints on the cold dark-matter relic density is investigated in the above scenarios for gaugino mass parameters. We also demonstrate that combination of representations can give the required amount of dark matter in any point of the parameter space. In the non-universal case we show that heavy Higgs bosons can be detected in the cascade studied in parameter regions with the WMAP preferred neutralino relic density.

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.

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.

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 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.

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

The search for MSSM Higgs bosons will be an important goal at the LHC. In order to analyze the search reach of the CMS experiment for the charged MSSM Higgs bosons, we combine the latest results for the CMS experimental sensitivities based on full simulation studies with state-of-the-art theoretical predictions of MSSM Higgs-boson production and decay properties. The experimental analyses are done assuming an integrated luminosity of 30 fb^-1 for the two cases M_H+- &lt; m_t and M_H+- &gt; m_t. The results are interpreted as 5 sigma discovery contours in M_H+- - tan_beta planes of the MSSM for various benchmark scenarios. We study the dependence of the 5 sigma contours on the variation of the relevant SUSY parameters. Particular emphasis is put on analyzing the variation of the discovery contours with the Higgs mixing parameter mu. The variation of mu can shift the prospective discovery reach in tan_beta by up to Delta tan_beta = 40.

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.

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 have done a fast simulation analysis of the H± signal at LHC in 1 and 3 prong hadronic τ-jet channels along with a tt̄ background. The τ polarization was effectively used to suppress the background in both channels. Combining this with appropriate cuts on pT of the τ-jet, the missing ET and the azimuthal angle between them reduces the background below the signal level. Consequently, one gets a viable H± signal up to a mass range of 600–700 GeV at moderate to large tanβ.

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.

The achievable precision of the cross section times branching ratio measurement from the event rates is estimated for the MSSM H/A -> tau tau decay in the associated production process gg -> b bbar H/A at large tan beta in CMS. This work demonstrates that the above production and decay process exhibit a large sensitivity to tan beta and thus add as a significant observable to a global fit of the SUSY parameters. To illustrate this potential an example is given concerning the achievable tan beta determination accuracy that could be reached from the event rates and for a given set of SUSY parameters and uncertainties.

This work summarises the present understanding of the expected MSSM SUSY Higgs reach for CMS. Many of the studies presented here result from detailed detector simulations incorporating final CMS detector design and response. With 30 fb-1 the h -&gt; gamma,gamma and h -&gt; bb channels allow to cover most of the MSSM parameter space. For the massive A,H,H+ MSSM Higgs states the channels A,H -&gt; tau,tau and H+ -&gt; tau,nu turn out to be the most profitable ones in terms of mass reach and parameter space coverage. Consequently CMS has made a big effort to trigger efficiently on taus. Provided neutralinos and sleptons are not too heavy, there is an interesting complementarity in the reaches for A,H -&gt; tau,tau and A,H -&gt; chi,chi.

We discuss the QCD corrections to the Drell-Yan production mechanism of weak bosons in pp reactions. Both soft and hard corrections are taken into account. Comparison with the recent UA1 data is made.

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

Production of the lightest minimal supersymmetric standard model (MSSM) Higgs boson h is studied at the LHC. Isorate contours for the h → γγ and h → τ+τ− decay channels are shown in the (mA, tan β) parameter space. Effects of the SUSY parameters, in particular the stop mixing and stop quark mass, are investigated. Search strategies at the LHC are discussed and the discovery potential is calculated for the CMS experiment. The MSSM parameter space for mA⪆ 150–200 GeV/c2 is expected to be covered with at least one decay channel with an integrated luminosity of 60 fb−1. A light stop quark with large stop mixing can affect seriously the discovery potential in the h → γγ and h → ZZ* decay channels.

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

The experiments at the planned 14 TeV proton-proton collider LHC will need a good identification and measurement of muons with energies of up to about 800 GeV. The production of electromagnetic secondaries by muons of energy from 10 to 300 GeV has been measured at the RD5 experiment at CERN using various detector types proposed for LHC experiments. It is demonstrated that the detectors can recognize the presence of individual hits from em secondaries, and that the muon measurement would be seriously compromised if these hits are not suppressed.

Report of the Higgs working group for the Workshop "Physics at TeV Colliders", Les Houches, France 8-18 June 1999. It contains 6 separate sections: 1. Measuring Higgs boson couplings at the LHC. 2. Higgs boson production at hadron colliders at NLO. 3. Signatures of Heavy Charged Higgs Bosons at the LHC. 4. Light stop effects and Higgs boson searches at the LHC. 5. Double Higgs production at TeV Colliders in the MSSM. 6. Programs and Tools for Higgs Bosons.

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.

Report of the Higgs working group for the Workshop `Physics at TeV Colliders', Les Houches, France, 21 May - 1 June 2001. It contains 7 separate sections: A. Theoretical Developments B. Higgs Searches at the Tevatron C. Experimental Observation of an invisible Higgs Boson at LHC D. Search for the Standard Model Higgs Boson using Vector Boson Fusion at the LHC E. Study of the MSSM channel $A/H \to ττ$ at the LHC F. Searching for Higgs Bosons in $t\bar t H$ Production G. Studies of Charged Higgs Boson Signals for the Tevatron and the LHC

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.

Polarization effects for the leptonic decays of W± and Z0 are calculated and discussed in pp collisions with longitudinally polarized proton beams. Numerical examples are given for the CERN pp collider and Fermilab Tevatron.

In this paper we evaluate the potential of the CMS detector for the measurement of CP violation in the B system at the initial low luminosity of LHC (~10 33 cm −2 s −1 ). The sensitivity to the unitarity triangle angle β obtained from the [Formula: see text] channel is given by δ ( sin 2β) = 0.046, whilst the sensitivity to a from the [Formula: see text] channel is given by δ ( sin 2α) = 0.082. We also discuss the possibilities of observing semi-inclusive B → μ + D (s) final states, to measure [Formula: see text] oscillations and to observe some B baryon modes.

Main features of the CMS detector relevant for B-physics studies are described. A detailed simulation study of the channel Bos → μ+μ- is presented. Results for some rare FCNC Bod,s decay modes and sensitivity to the forbitten τ → 3μ decay are also discussed. Expected CMS reach for the χs measurement in the Bos - ¯Bos oscillations is also shown.

We present a search for the decay W±→π±γ, using data taken at the CERN proton-antiproton Collider with the UA1 detector and corresponding to an integrated luminosity of 0.7 pb−1. We do not observe a signal for such a process: hence we obtain an upper limit on the π±γ decay width of 5.8×10−2Γ (W±→e±v) (95%CL).

Report of the Higgs working group for the Workshop Physics at TeV Colliders, Les Houches, France 8-18 June 1999. It contains 6 separate sections: 1. Measuring Higgs boson couplings at the LHC. 2. Higgs boson production at hadron colliders at NLO. 3. Signatures of Heavy Charged Higgs Bosons at the LHC. 4. Light stop effects and Higgs boson searches at the LHC. 5. Double Higgs production at TeV Colliders in the MSSM. 6. Programs and Tools for Higgs Bosons.

The possibility to detect the massive charged Higgs boson H using the hadronic decay channel H -> tb in the associated production pp -> tH + X in the CMS experiment at LHC is studied. There is a large background from ttbb events which makes the observation difficult. Detection of a Higgs signal in this channel requires an excellent b-tagging performance. Good calorimeter mass resolution is also necessary for the full event reconstruction.

In a study of 12 GeV/c pp interactions in the CERN 2 m HBC, we have searched for a narrow K3π state. Contrary to an investigation of 12 GeV/c pp interactions in the CERN BEBC, we find no support for such a state.

A study of a possible layout of a Silicon tracker has been done. The design is based on simulations done in the context of the Compact Muon Solenoid (CMS) detector for the LHC. The high granularity of the silicon strip detectors yields to low occupancies. New type of a silicon strip detector, single sided stereo angle detector (SSSD), has been designed to match the requirements of a LHC tracker. This detector allows a z-coordinate measurement without increasing the number of channels i.e. power consumption and it facilitates a tracker design with reasonable complicity.

The achievable precision of the cross section times branching ratio measurement from the event rates is estimated for the MSSM H/A → ττ decay in the associated production process gg → b¯/A at large tanβ in CMS. This work demonstrates that the above production and decay process exhibit a large sensitivity to tanβ and thus add as a significant observable to a global fit of the SU SY parameters. To illustrate this potential an example is given concerning the achievable tanβ determination accuracy that could be reached from the event rates and for a given set of SUSY parameters and uncertainties.