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Abstract:

First measurements of cross sections for isolated prompt photon production in deep inelastic ep scattering have been made using the ZEUS detector at the HERA electron-proton collider using an integrated luminosity of 121 pb -1. A signal for isolated photons in the transverse energy and rapidity ranges 535GeV2. Cross sections are presented for inclusive prompt photons and for those accompanied by a single jet in the range ETjet≥6GeV and -1. 5≤ηjet<1.8. Calculations at order α 3αs describe the data reasonably well. © 2004 Elsevier B.V. All rights reserved.

Abstract:

This biennial Review summarizes much of Particle Physics. Using data from previous editions, plus 1726 new measurements from 512 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 119 reviews are many that are new or heavily revised including those on neutrino mixing, CP violation in K, D, and B mesons, Vcb, the new exotic Θ(1540) particle, extra-dimensions, grand unified theories, cosmic background radiation, dark matter, cosmological parameters, and big bang cosmology. A booklet is available containing the Summary Tables and abbreviated versions ofsome of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http//pdg.lbl.gov. ©2004 Regents of the University of California.

Abstract:

The photoproduction of bottom quarks in events with two jets and a muon has been measured with the ZEUS detector at HERA using an integrated luminosity of 110 pb-1. The fraction of jets containing b quarks was extracted from the transverse momentum distribution of the muon relative to the closest jet. Differential cross sections for bottom production as a function of the transverse momentum and pseudorapidity of the muon, of the associated jet and of xγjets, the fraction of the photon's momentum participating in the hard process, are compared with MC models and QCD predictions made at next-to-leading order. The latter give a good description of the data.

Abstract:

A resonance search has been made in the K⁰Sp and K⁰Sp̄ invariant-mass spectrum measured with the ZEUS detector at HERA using an integrated luminosity of 121 pb^-1. The search was performed in the central rapidity region of inclusive deep inelastic scattering at an ep centre-of-mass energy of 300-318 GeV for exchanged photon virtuality, Q², above 1 GeV². Recent results from fixed-target experiments give evidence for a narrow baryon resonance decaying to K⁺n and K⁰Sp, interpreted as a pentaquark. The results presented here support the existence of such state, with a mass of 1521.5±1.5(stat.)^+2.8-1.7(syst.) MeV and a Gaussian width consistent with the experimental resolution of 2 MeV. The signal is visible at high Q² and, for Q²>20 GeV², contains 221±48 events. The probability of a similar signal anywhere in the range 1500-1560 MeV arising from fluctuations of the background is below 6×10^-5. © 2004 Elsevier B.V. All rights reserved.