[en] The result of a search for gaugino pair production with a trilepton signature is reinterpreted in the framework of minimal supergravity (MSUGRA) with R-parity violation via leptonic λ Yukawa couplings. The search used 95 pb^-1 of pp(bar sign) collisions at √(s)=1.8 TeV recorded by the DOe detector at the Fermilab Tevatron. A large domain of the MSUGRA parameter space is excluded for λ₁₂₁, λ₁₂₂≥10^-4. (c) 2000 The American Physical Society

[en] 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 fb^-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 H→WW partial width with an accuracy of about 10%. (c) 2000 The American Physical Society

[en] Events in p(bar sign)p collisions at √(s)=1.8 TeV with total transverse energy exceeding 500 GeV are used to set limits on quark substructure. The data are consistent with next-to-leading order QCD calculations. We set a lower limit of 2.0 TeV at 95% confidence on the energy scale Λ_LL for compositeness in quarks, assuming a model with a left-left isoscalar contact interaction term. The limits on Λ_LL are found to be insensitive to the sign of the interference term in the Lagrangian. (c) 2000 The American Physical Society

[en] We show that the cross section of the diffractive production of b bar b can be described as the sum of two contributions: the first is proportional to the probability of finding a small size b bar b color dipole in the fast hadron wave function before the interaction with a target, while the second is the b bar b production after or during the interaction with the target. The formulas are presented as well as the discussion of the interrelation between these two contributions and the Ingelman-Schlein and coherent diffraction mechanisms. The main prediction is that the coherent diffraction mechanism dominates, at least at the Fermilab Tevatron energies, giving the unique possibility to study it experimentally. copyright 1997 The American Physical Society

[en] We present the results of a search for the production of light elements in p(bar sign)p collisions at the Fermilab Tevatron collider. Momentum, time of flight, and dE/dx measurements are used to distinguish nuclei from elementary particles. A production ratio for deuterium to hydrogen is calculated and compared to the primordial value of the big bang model. Some evidence for tritium is found and none for helium isotopes. (c) 2000 The American Physical Society

[en] In a generic supersymmetric extension of the standard model, there will be lepton flavor violation at a neutral gaugino vertex due to misalignment between the lepton Yukawa couplings and the slepton soft masses. Sleptons produced at the CERN LHC through the cascade decays of squarks and gluinos can give a sizable number of events with 4 leptons. This channel could give a clean signature of supersymmetric lepton flavor violation under conditions which are identified. (c) 2000 The American Physical Society

[en] We calculate the transverse momentum distribution for the production of massive lepton pairs in longitudinally polarized proton-proton reactions at collider energies within the context of perturbative quantum chromodynamics. For values of the transverse momentum Q_T greater than roughly half the pair mass Q, Q_T>Q/2, we show that the differential cross section is dominated by subprocesses initiated by incident gluons, provided that the polarized gluon density is not too small. Massive lepton-pair differential cross sections should be a good source of independent constraints on the polarized gluon density, free from the experimental and theoretical complications of photon isolation that beset studies of prompt photon production. We provide predictions for the spin-averaged and spin-dependent differential cross sections as a function of Q_T at energies relevant for the Relativistic Heavy Ion Collider at Brookhaven, and we compare these with predictions for real prompt photon production. (c) 2000 The American Physical Society

[en] We estimate the Fermilab Tevatron run II potential for top and bottom squark searches. We find an impressive reach in several of the possible discovery channels. We also study some new channels which may arise in nonconventional supersymmetry models. In each case we rely on a detailed Monte Carlo simulation of the collider events and the CDF detector performance in run I. (c) 2000 The American Physical Society

[en] The prospects for detecting trilepton events (l=e or μ) from chargino-neutralino (χ₁^±χ₂⁰) associated production are investigated for the upgraded Fermilab Tevatron Collider in the context of the minimal supergravity model (MSUGRA). In some regions of parameter space, χ₁^± and χ₂⁰ decay dominantly into final states with τ leptons and the contributions from τ-leptonic decays enhance the trilepton signal substantially when soft cuts on lepton transverse momenta are used. Additional sources of the MSUGRA trilepton signal and dominant irreducible backgrounds are discussed. The dilepton (l⁺l^-) invariant mass distribution near the end point is considered as a test of MSUGRA mass relations. Discovery contours for pp(bar sign)→3l+X at 2 TeV with an integrated luminosity of 2-30 fb^-1 are presented in the MSUGRA parameter space of (m₀,m_1/2) for several choices of tan β. (c) 1999 The American Physical Society

[en] We study J/ψ production at fixed-target energies, including the color-octet production mechanisms predicted by NRQCD. In an earlier paper, we found that the octet components were crucial in understanding p_T-integrated forward (x_F>0) cross sections. Here we make a detailed comparison of the theoretical predictions with measured x_F distributions from fixed-target experiments. We find that the model predictions agree well with data. Taking into account higher orders in NRQCD, we argue that σ(χ₁)/σ(χ₂)=0.6, in excellent agreement with data. Similiar arguments also predict that σ(χ)/σ(J/ψ) is roughly equal in photo- and hadroproduction. copyright 1997 The American Physical Society