Professor Brian Foster OBE, FRS

Abstract:

A search for excited quarks is performed using the full e ^± p data sample collected by the H1 experiment at HERA, corresponding to a total integrated luminosity of 475   pb ^{- 1}. The electroweak decays of excited quarks q ^* → q γ, q ^* → q Z and q ^* → q W with subsequent hadronic or leptonic decays of the W and Z bosons are considered. No evidence for first generation excited quark production is found. Mass dependent exclusion limits on q ^* production cross sections and on the ratio f / Λ of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited quark searches. © 2009 Elsevier B.V.

Abstract:

The dissociation of virtual photons, γ^{{star operator}} p → X p, in events with a large rapidity gap between X and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities Q² > 2   GeV² and γ^{{star operator}} p centre-of-mass energies 40 < W < 240   GeV, with MX > 2   GeV, where MX is the mass of the hadronic final state, X. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of t, the squared four-momentum transfer at the proton vertex and Φ, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of Q² and xP, the fraction of the proton's momentum carried by the diffractive exchange, as well as β, the Bjorken variable defined with respect to the diffractive exchange. © 2009 Elsevier B.V.

Abstract:

Beauty production in events containing two muons in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb-1. A low transverse-momentum threshold for muon identification, in combination with the large rapidity coverage of the ZEUS muon system, gives access to almost the full phase space for beauty production. The total cross section for beauty production in ep collisions at (s)1/2 = 318 GeV has been measured to be σtot(ep bX) = 13.9 1.5(stat.)+4.0-4.3(syst.)nb. Differential cross sections and a measurement of b correlations are also obtained, and compared to other beauty cross-section measurements, Monte Carlo models and next-to-leading-order QCD predictions. © 2009 SISSA.

Abstract:

Measurements of the cross sections for charged current deep inelastic scattering in e ^- p collisions with longitudinally polarised electron beams are presented. The measurements are based on a data sample with an integrated luminosity of 175 pb^-1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is given for positively and negatively polarised electron beams. The differential cross-sections d σ/dQ ², d σ/dx and d σ/dy are presented for Q ²>200 GeV². The double-differential cross-section d ² σ/dxdQ ² is presented in the kinematic range 2802<30∈000 GeV² and 0.015

More details from the publisher