D. Denegri

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.

We report the observation of four electron-positron pairs and one muon pair which have the signature of a two-body decay of a particle of mass ∼ 95 GeV/c2. These events fit well the hypothesis that they are produced by the process p̄+ p→Z0+X(with Z0→ ℓ++ ℓ−), where Z0 is the Intermediate Vector Boson postulated by the electroweak theories as the mediator of weak neutral currents.

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 have measured transverse momentum spectra up to 10 GeV/c for charged particles produced centrally in proton-antiproton collisions at 540 GeV in the centre of mass at the CERN collider. Our results are compared with data at ISR energies and with the predictions of a QCD model. The charged particle spectrum shows a clear dependence on charged track multiplicity.

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 clear signal is observed for the production of an isolated large-transverse-momentum lepton in association with two or three centrally produced jets. The two-jet events cluster around the W± mass, indicating a novel decay of the Intermediate Vector Boson. The rate and features of these events are not consistent with expectations of known quark decays (charm, bottom). They are, however, in agreement with the process W→ tb followed by t → bℓv, where t is the sixth quark (top) of the weak Cabibbo current. If this is indeed so, the bounds on the mass of the top quark are 30 GeV/c2 < mt <550 GeV/c2.

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.

We studied the Kπ scattering from threshold to mKπ = 1200 MeV using the Chew-Low extrapolation method in the reactions K+p→Ko←πo−Δ++. In addition to an analysis using only the data at 5.43 GeV/c incident momentum, we also present the results using the world data compiled from experiments with momenta from 3.0 to 12.7 GeV/c. The extrapolated cross section for the elastic K+π−→K+π− scattering exceeds the p-wave isospin-12 unitary limit in the K∗ (890) region. The phase shift δ11 (notation δl2I) shows the expected Breit-Wigner behavior which suggests that δ13⋍0 in the mass region studied. Solutions for the s-wave phase shifts δo1 and δo3 are obtained from the extrapolated differential cross sections. We obtain a unique set of solutions for δo1 and δo3 by requiring the calculated cross sections to agree with those extrapolated from K+π− elastic scattering and with those for K−π− scattering obtained in other experiments. We find δo1 increasing slowly from 0° at threshold and approaching 80° at mKπ⋍1150 MeV with no evidence of passing through 90° in the mass range studied. The phase shift δo3 decreases slowly from 0° at threshold to ⋍ − 30° at mKπ ⋍ 1200 MeV.

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.

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.

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

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).

The observation of an apparent excess of radiative Z0 decays into e+e−γ and μ+μ−γ has prompted the search for massive eνγ and μνγ final states containing an energetic photon. No events were found other than those consistent with QED radiative effects in leptonic W decays. The data sample corresponds to an integrated luminosity of 0.136 pb−1 produced at the CERN super proton synchrotron (SPS) collider. An upper limit on the occurrence of such events is given.

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 search for events having the characteristics of cosmic ray Centauros has been made in 540 GeV centre of mass proton-antiproton collisions, using information on charged particle multiplicities and transverse momenta from our central detector image chamber, together with energy deposition in our calorimeters. No such events were found in 48 000 low bias events.

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.

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.

We have studied the Kππ system in the 14.3 GeV/c reactions K−p → K−π+π−p, K−p → K0π−π0 and K−p → K0π+π−n. The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (Kππ) ∼ 1.75 GeV. The reaction cross sections are compared to K−p data at other energies. We discuss the Kππ mass dependence of the diffractive production slope. Evidence is presented for a Q−p versus Q+p differential cross section cross-over around |t| = 0.17 GeV2. A t-channel isospin analysis for the KN → K∗(890)πN channels in the Q-region shows that the I = 1 exchange amplitude is ⋍ 10% of the dominant I = 0 exchange amplitude. The Kππ decay distributions indicate a predominant JP = 1+ state in the Q-region, and an important JP = 2− contribution in the L-region. We find neither s-channel nor t-channel helicity conservation at the meson vertex in the Q- or L-regions. The Kπ angular correlation moments within the Kππ diffractive system are characteristic of Kπ elastic scattering, suggesting a π-exchange Deck-type production mechanism. There is evidence for a Kf0 and κπ contribution (where κ is the JP(Kπ) = 0+ state) to the diffractive Kππ system. A fit to the K−π+π− and K0π−π0 Dalitz-plot distributions for the Q-re gion indicates that the ratio of Kϱ to K∗π decay amplitudes decreases with increasing Kππ mass.

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.

Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated.

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.

Inclusive production of vector and tensor mesons is studied in a K−p experiment at 32 GeV/c in the MIRABELLE bubble chamber. The K∗0(890), ϱ0 and ω cross sections are comparable, about 4 mb each. The K∗0(1420 and cross sections are also comparable, about 1 mb each. The K∗ö+(890), Φ, K∗ö−(1420) and f cross sections beam fragmentation; ϱ production is almost forward-backward symmetric in the c.m.s. The pT production slopes of K∗ö−(890) and ϱ are similar, the Φ slope is shallower. Vector and tensor mesons alone are responsible for ≅50% (≅60%) of final-state pions

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.

In events at centre of mass energy 540 GeV from the CERN pp collider, we have found clear evidence for correlations in rapidity and azimuthal angle between high transverse momentum charged particles. These correlations increase with transverse momentum and are much stronger than the general two-particle correlations in minimum bias events. By analogy to ISR results, a qualitative interpretation in terms of hard scattering and fragmentation of partons is discussed.

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).

Abstract We investigate the main features of the reaction pp → ppπ+π− at 69 GeV/c from data obtained in the Mirabelle bubble chamber at Serpukhov. A search for a double pomeron exchange mechanism contribution leads to an upper limit of ⋍20 μ b for M(π + π − ) ⩽ 0.7 GeV under reasonable assumptions. The four-body final state is dominated by proton diffractive dissociation p → pπ+π− (mostly Δ++π−). The cross section for this process, as well as the t production slope and the decay distributions (of the Δ++) show little variation in comparison with lower energy data.

Ensuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.

Abundant production of the established $L$ meson and also of the possible $Q$ meson are observed in coherent production, ${K}^{\ensuremath{-}}d\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}d$, at 12.6 BeV/c. This is the first observation of $L$-meson production on nuclei. The $Q$ and $L$ isospins are unambiguously determined to be \textonehalf{}. The $L$ is observed to be produced polarized. A striking resemblance between the final states ${K}^{*}(890)\ensuremath{\pi}d$ and ${K}^{*}(1400)\ensuremath{\pi}d$ is observed with these final states being related to the $Q$ and $L$ mesons, respectively.

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.

Longitudinal invariant structure functions Edσdx for a number oflow pt hadronic fragments produced in K+- interactions at 32 GeV/c are presented. Data were obtained in the Mirabelle bubble chamber. The fragmentation modes investigated are K± → K0, K̄0, K∗0,+(890), K̄∗0,−(890), ϕ, ϱ0, π+-, Λ, ḡL, and p → pinel, Δ++(1236), Λ, ḡL, π±, K0, ϱ0. These various fragmentation spectra clearly fall into a definite hierarchy, the invariant cross sections being more suppressed at large |x| the bigger the difference between initial and final state hadron quantum numbers. Invariant cross sections in the fragmentation regions are adequately fitted by a power law Edσ/dx ∝ (1 − |x|)n as suggested by dimensional or Regge counting The values of n are in general consistent with values obtained at FNAL and ISR energies for comparable data. They are in good overall agreement with the quark counting rules as recently reformulated, and the deviations observed suggest corrections due to strange (s) and light (u, d) quark mass differences. The power laws governing the kaon valence quark structure functions behave at large x as sKV(x)x→+1 ∼ (1 − x)0.5 and ūKV(x)x→+1 ∼ (1 − x) 1.5.

From a 2.5 events gmb K−d exposure of the BNL 80″ bubble chamber we obtained 351 events which successfully fit the reaction K−d → K−π−pps. The (pπ−) mass spectrum exhibits a strong enhancement, centered at 1400 MeV and 400 MeV wide, which cannot be clearly resolved into individual resonances. The reaction is analyzed with a diffraction dissociation model and the relevant cross sections are given. From a study of the low K−π− mass region we find that the Kπ elastic scattering cross section in the isospin 32 state is of the order of 2 mb.

This note summarizes many detailed physics studies done by the ATLAS and CMS Collaborations for the LHC, concentrating on processes involving the production of high mass states. These studies show that the LHC should be able to elucidate the mechanism of electroweak symmetry breaking and to study a variety of other topics related to physics at the TeV scale. In particular, a Higgs boson with couplings given by the Standard Model is observable in several channels over the full range of allowed masses. Its mass and some of its couplings will be determined. If supersymmetry is relevant to electroweak interactions, it will be discovered and the properties of many supersymmetric particles elucidated. Other new physics, such as the existence of massive gauge bosons and extra dimensions can be searched for extending existing limits by an order of magnitude or more.

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.

We have studied the reactions K−p → K−π+π−p and K−p → K0π−π0p at 14.3 GeV/c using respectively 15 992 and 3723 events. Partial-wave analysis of the region 1.0 < m(Kππ) < 1.7 GeV have been made using a modified version of the method developed at the University of Illinois. We have measured the cross section as a function of mass for each spin-parity state of the Kππ system. Results from the two reactions are in excellent agreement and indicate an overall isospin of 12. We find that the Q enhancement is predominantly JP = 1+ but that the partial-wave substates have very different branching ratios into Kϱ and K∗π, the K∗π component of the 1+ state being similar to the 1+ state of the 3π system produced in the reaction πp → (3π)p.

The performance of electromagnetic calorimeter modules made of proton-irradiated PbWO4 crystals has been studied in beam tests. The modules, similar to those used in the Endcaps of the CMS electromagnetic calorimeter (ECAL), were formed from 5×5 matrices of PbWO4 crystals, which had previously been exposed to 24 GeV protons up to integrated fluences between 2.1× 1013 and 1.3× 1014 cm−2. These correspond to the predicted charged-hadron fluences in the ECAL Endcaps at pseudorapidity η = 2.6 after about 500 fb−1 and 3000 fb−1 respectively, corresponding to the end of the LHC and High Luminosity LHC operation periods. The irradiated crystals have a lower light transmission for wavelengths corresponding to the scintillation light, and a correspondingly reduced light output. A comparison with four crystals irradiated in situ in CMS showed no significant rate dependence of hadron-induced damage. A degradation of the energy resolution and a non-linear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The latter is interpreted, through comparison with simulation, as a side-effect of the degradation in light transmission. The experimental results obtained can be used to estimate the long term performance of the CMS ECAL.

The authors review the methods used before the operation of the high energy Stanford and CERN ${e}^{+}{e}^{\ensuremath{-}}$ colliders to determine the number of neutrino species ${N}_{\ensuremath{\nu}}$, or an upper limit on this number, within the framework of the Standard Model of light stable neutrinos interacting according to the SU(2)\ifmmode\times\else\texttimes\fi{}U(1) universal couplings. The astrophysical limit based on the neutrino burst from supernova 1987A is discussed first, followed by a discussion of the cosmological constraint based on the observed He/H abundance ratio. Finally, the particle physics methods based on single-photon production in ${e}^{+}{e}^{\ensuremath{-}}$ collisions, on the production of monojets in $p\overline{p}$ collisions, and on the determination of ${N}_{\ensuremath{\nu}}$ from the ratio of the $W\ensuremath{\rightarrow}l\overline{\ensuremath{\nu}}$ to ${Z}^{0}\ensuremath{\rightarrow}l\overline{l}$ partial cross sections in $p\overline{p}$ collisions are discussed. The various sources of uncertainty and the experimental backgrounds are presented, as well as an idea of what may be expected on this subject in the future. There is a remarkable agreement between the various methods, with central values for ${N}_{\ensuremath{\nu}}$ between 2 and 3 and with upper limits ${N}_{\ensuremath{\nu}}&lt;6$. Combining all determinations, the authors obtain a central value ${N}_{\ensuremath{\nu}}={2.1}_{\ensuremath{-}0.4}^{+0.6}$ for ${m}_{\mathrm{top}}=50$ GeV/${\mathit{c}}^{2}$ and ${N}_{\ensuremath{\nu}}={2.0}_{\ensuremath{-}0.4}^{+0.6}$ if ${m}_{\mathrm{top}}\ensuremath{\ge}{m}_{W}$. The results are perfectly compatible with the a priori knowledge that at least three families of neutrinos should exist. The observed consistency between this a priori knowledge, the laboratory determinations of ${N}_{\ensuremath{\nu}}$, and determinations from SN 1987A and cosmology represent an astounding success for the Standard Model and for the current descriptions of stellar collapse and the Big-Bang primordial nucleosynthesis. These results, however, severely limit the number of additional families. Although the consistency is significantly worse, four families still provide a reasonable fit. In the framework of the Standard Model, a fifth light neutrino is, however, unlikely. A noted added in proof summarizes the results recently obtained at the Fermilab $\overline{p}p$ and the Stanford and CERN ${e}^{+}{e}^{\ensuremath{-}}$ colliders which confirm these conclusions.

Abstract We present the first evidence for K ∗ (1780) production in a non-exchange channel. This comes from a study of the reaction K − p → K° π − p at 14.3 GeV/ c . We also present evidence for K ∗ ° (1780) production in the charge exchange channel K − p → K − π + n. No significant K ππ , K ω and K η decay modes are found. The decay angular distribution, the spin-parity assignments and the production mechanism are discussed. With plausible assumptions on the production mechanism, the J P = 3 − spin-parity is favoured.

We compare some aspects of the N→Nπ, N→Nππ and N → ΛK diffractive fragmentation systems induced by 14.3 GeV/c incident K− mesons with those obtained in pp interactions at ISR energies. The similarity between the low-mass Nπ and Nππ systems produced by different incident particles at c.m. energies differing by an order of magnitude is very striking. The shapesof the mass spectra (not the M2/s spectra) are approximately independent of s, both in the resonant and non-resonant diffractive dissociation components. These findings, as well as features of the differential cross sections and decay angular distributions, indicate that the (asymptotic) diffractive dynamics operative at ISR energies is already dominant at 10–20 GeV/c, remains essentially unchanged over this broad energy range, and has approximate vertex factorization properties.

Data from a high statistics Mirabelle bubble chamber K−p experiment at 32 GeV/c are used to study inclusive single and double diffraction dissociation. From the reaction K−p → K− + X we find a total proton single dissociation cross section of 1040 ± 120 μb, with comparable contributions from proton dissociations into 1 and 3 charged particles. There is evidence for double dissociation in K−p → (K−π+π−) + X+, with cross section of 64 ± 20 μb. Cross sections and dσdt′ distributions are in qualitative agreement with the factorization hypothesis. With the results from a companion K+p experiment, the total diffractive cross section (elastic + SD + DD) is estimated. It amounts to ≅4.75 mb, i.e., about 25% of the total KN cross section and about 50% of Pumplin's upper bound for the diffractive cross section. A comparison with ISR data suggests that the total DD cross section increases by ∼2 mb over the c.m. energy range from ∼10 to ∼50 GeV.

Abstract We report on coherent interactions in a 2.5 event/μb K−d exposure. The predominant channel studied is K−d → K−π+gp−d (415 events). We find strong Q- and L-production in the (Kππ) system. The production mechanism determines I = 1 2 for both enhancements and a spin-parity in the series 0−, 1+,2−… . A spin-parity analysis shows the Q to be a 1+ object, while the L is 1+ or 2−, although a higher spin cannot be excluded. The cross sections for Q and L production and other final states are presented.

A highly peripheral $p{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ enhancement centered near 1450 MeV, observed in ${K}^{+}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}p$ at 5.5 BeV/c, is shown to be consistent with a ${\ensuremath{\Delta}}^{++}{\ensuremath{\pi}}^{\ensuremath{-}}$ system with $I=\frac{1}{2}$. We observe a large asymmetry in the ${\ensuremath{\Delta}}^{++}{\ensuremath{\pi}}^{\ensuremath{-}}$ angular distribution which is not consistent with a pure resonant effect. Dissociation-type models fit the data reasonably well when cuts are made on the ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ mass, and this is interpreted as evidence for diffractive ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ virtual scattering in this ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ mass region.

A study of the ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay mode of the ${K}^{*}(1400)$ produced with an ${N}^{*++}$ has been made using the reaction ${K}^{+}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}p$ at 5.5 BeV/c. We have fitted the ${K}^{*}(1400)$ angular distributions using a model involving interference between ${1}^{\ensuremath{-}}$ and ${2}^{+}$ ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ states. In this model a considerable amount of ${1}^{\ensuremath{-}}$ is needed in the ${K}^{*}(1400)$ mass region, suggesting that there is a ${J}^{P}={1}^{\ensuremath{-}}$ resonance under the ${K}^{*}(1400)$. Such a ${J}^{P}={1}^{\ensuremath{-}}$ resonance could be the first daughter of the ${K}^{*}(1400)$.

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 dependence on $\mathrm{tan}\ensuremath{\beta}$ of the event kinematics of final states with ${e}^{+}{e}^{\ensuremath{-}}/{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}{/e}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\mu}}^{\ensuremath{\mp}}{+E}_{T}^{\mathrm{miss}}+\mathrm{jets},$ as expected in $\mathrm{pp}$ collisions at CERN LHC, within the framework of the minimal supergravity model. With an increase of $\mathrm{tan}\ensuremath{\beta},$ the third generation sparticle masses ${m}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\tau}}}_{1}}$ and ${m}_{{b}_{1}}$ decrease due to the increase of the tau and bottom Yukawa couplings. As a result, the gluino, top squark, sbottom, chargino, and neutralino decays to third generation particles and sparticles are enhanced. With $\mathrm{tan}\ensuremath{\beta}$ rising, we observe a characteristic change in the shape of the dilepton mass spectra in ${e}^{+}{e}^{\ensuremath{-}}/{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}{+E}_{T}^{\mathrm{miss}}+\mathrm{jets}$ versus ${e}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\mu}}^{\ensuremath{\mp}}{+E}_{T}^{\mathrm{miss}}+\mathrm{jets}$ final states, reflecting the presence of the decays ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{l}_{L,R}^{\ifmmode\pm\else\textpm\fi{}}{l}^{\ensuremath{\mp}}\ensuremath{\rightarrow}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}{l}^{+}{l}^{\ensuremath{-}}, {\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}{l}^{+}{l}^{\ensuremath{-}},$ and ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\tau}}}_{1}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\tau}}^{\ensuremath{\mp}}\ensuremath{\rightarrow}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}},$ ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0},$ respectively. We exploit this effect for constraining the value of $\mathrm{tan}\ensuremath{\beta}.$

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.

Search for the Higgs Boson is one of the prime goals of the LHC. Higgs bosons lighter than 130 GeV /c 2 decay mainly to a b-quark pair. While the detection of a directly produced Higgs boson in the bchan- nel is impossible because of the huge QCD background, the channel t ¯ 0 → l ± νq¯ qb¯¯ b is very promising in the Standard Model and the MSSM. We discuss an event reconstruction and selection method based on likelihood functions. The CMS detector response is performed with parametrisations obtained from detailed simulations. Various physics and detector performance scenarios are investigated and the results are presented. It turns out that excellent b-tagging performance and good mass resolution are essential for this channel.

We discuss some consequences of the production of a top quark of mass comparable to Mw. Such a top quark decays into an on-shell W plus a b-quark. For mtop~Mw, the QCD tt production cross section, already sizeable at SppS energies, increases rapidly with √s. This, combined with the peculiar kinematics of the top decay for mtop~Mw, results in the production of apparent WW pairs at a rate overwhelming the electroweak WW cross section. This WW production mechanism would also represent an important contribution to the inclusive high-PtW production tail, even for masses of top (or higher generation t', b' quarks) substantially larger than Mw.

We present results on a number of non-diffractive two-body channels contributing to reactions K+p→K0π+p and K+p→K+π−π+p. The data come from an exposure of the Mirabelle bubble chamber to an r.f. separated K+ beam of 32 GeV/c at the Serpukhov accelerator. Total cross sections are given for the final states K∗+(890)p, K∗+(1420)p, K0 Δ++(1232), K∗+(890)p, Δ++(1232), K∗0(1420) Δ++(1232), K∗0(1780) Δ++(1232) and K∗0(890) Δ++(1950). The differential cross sections are given for all channels with sufficient statistics. The energy dependence of the total and differential cross sections is studied.

We present evidence for the double dissociation process K−p → QN12∗ → (K∗0π−)(nπ+) at 14.3 GeV/c. The cross section for this process is of the order of 10 μb. The production differential cross section is steep (for near-threshold excitation masses), as typical of diffractive processes, and exhibits a strong correlation between the production slope and the masses of the dissociated systems. The spin-parity composition and states of the two dissociation systems closely resemble those found in single dissociation, indicating that a common diffraction-like mechanism is responsible for both processes. The mass variations of the differential cross-section slope, the decay angular correlations and the total cross section of the double dissociation component are consistent with the predictions of a factorisable pomeron exchange model.

We analyze the events with two same-flavor, $\mathrm{o}\mathrm{p}\mathrm{p}\mathrm{o}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{e}\ensuremath{-}\mathrm{s}\mathrm{i}\mathrm{g}\mathrm{n}\mathrm{}\mathrm{leptons}{+E}_{T}^{\mathrm{miss}}+(\mathrm{jets})$ as expected in $\mathrm{pp}$ collisions at the CERN LHC within the framework of the minimal supergravity model. The objective is the determination of the parameters ${m}_{0}$ and ${m}_{1/2}$ of this model (for a given value of $\mathrm{tan}\ensuremath{\beta}$). The signature ${l}^{+}{l}^{\ensuremath{-}}{+E}_{T}^{\mathrm{miss}}+(\mathrm{jets})$ selects the leptonic decays ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}{l}^{+}{l}^{\ensuremath{-}},$ ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{l}_{L,R}^{\ifmmode\pm\else\textpm\fi{}}{l}^{\ensuremath{\mp}}\ensuremath{\rightarrow}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1}^{0}{l}^{+}{l}^{\ensuremath{-}}$ of ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0},$ produced in $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}/\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}$ decays. We exploit the fact that the invariant dilepton mass distribution has a pronounced structure with a sharp edge at the kinematical end point even in such an inclusive final state over a significant part of parameter space. We determine the domain of parameter space where the edge is expected to be visible. We show that a measurement of this edge already constrains the model parameters essentially to three lines in the ${(m}_{0}{,m}_{1/2})$ parameter plane. We work out a strategy to discriminate between the three-body leptonic decays of ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{2}^{0}$ and the decays into sleptons ${l}_{L,R}.$ This procedure may make it possible to get information on SUSY particle masses already with low luminosity, ${\mathcal{L}}_{\mathrm{int}}{=10}^{3}{\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}.$

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 briefly discuss the genesis of the CERN antiproton–proton collider project aimed at discovering the intermediate vector bosons W and Z, describe the main features of the UA1 and UA2 experiments, as well as the initial search and discovery of the W and Z. We also review the subsequent improvements in the determination of the basic electroweak parameters of the W and Z and of their QCD production properties as they evolved over the ten years of operation of the CERN antiproton–proton collider.

We present experimental results on a number of K−p reactions at 14.3 GeV/c that have three bodies in the final state. The final states are K−ωp, K−πp, Λπ+π−, ΛK+K−, Λpp, K∗−ωp, Λ(1520)K+K− and Λ(1520) pp. Whenever, with one exception explained by the Zweig rule, there is a K− or a proton in the final state, there is a diffractive-like threshold enhancement in the mass spectrum of the two recoiling particles. These enhancements account for a large fraction of the events in all but the Λπ+π− final state, where they cannot occur, and which is dominated by resonance production. We find evidence for the Q1(1300) decaying into K−ω.

In a 3.5 event/ub exposure of the BNL 80″ bubble chamber we have observed the following reactions: pd → pdφ+φ−, pd → ppnφ+φ−, pd → pdφ+φ−φ0. The incident p momentum was 7.0 GeV/c. We give cross sections for the reactions, as well as for other reactions involving production of Λ We give detailed descriptions of the coherent final states (1) and (3). It is observed that reactions (1)-(3) are dominated by production of Δ−−(1236). We apply a Deck model, both in Reggeized and non-Reggeized form, to the reaction pd → Δ−−π+d and obtain satisfactory fits to the distributions of all kinematic variables. In particular, the π+d mass spectrum, which shows a prominent peak (the “d∗”) at a mass M(πd) ≈ 2170 MeV, is well reproduced by the predictions of the model without introducing a resonant interpretation for this effect. Modified versions of this model are applied to the reactions pd → Δ−−π+ pn, and pd → Δ−−πOπ+d, which occur as sub-samples of the final states (2) and (3) respectively. Here also, prominent peaks are observed in the π+pn mass spectrum (in the former reaction) and in the π+d and πOd mass spectrum (in the latter reaction). Again the predictions of the model agree well with the observed distributions of all the kinematic variables.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

We discuss the structure of the momentum transfer distributions for the diffractive dissociation processes p → nπ+, p → Δ++π− and K− → K890∗0π−. In the near-threshold mass region a clear break of slope is found around t′KK ∼ 0.25 GeV2 for the two baryonic channels, whereas no comparable structure is seen for the mesonic system. The K → K∗π differential cross section exhibits a nearly exponential behaviour up to t′pp ∼ 0.6 GeV2, falling over three orders of magnitude. The slope variations and breaks are strongly correlated both to the mass region considered and to the decay angle of the fragmentation system.