Multi-lepton production at high transverse momentum at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 680:1 (2009) 13-23
Abstract:
A search for events containing two or more high-transverse-momentum isolated leptons has been performed in ep collisions with the ZEUS detector at HERA using the full collected data sample, corresponding to an integrated luminosity of 480 pb -1. The number of observed events has been compared with the prediction from the Standard Model, searching for possible deviations, especially for multi-lepton events with invariant mass larger than 100 GeV. Good agreement with the Standard Model has been observed. Total and differential cross sections for di-lepton production have been measured in a restricted phase space dominated by photon-photon collisions. © 2009 Elsevier B.V.Measurement of D ± and D 0 production in deep inelastic scattering using a lifetime tag at HERA
European Physical Journal C 63:2 (2009) 171-188
Abstract:
The production of D ±- and D 0-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb-1. The measurements cover the kinematic range 5Measurement of high-Q 2 neutral current deep inelastic e - P scattering cross sections with a longitudinally polarised electron beam at HERA
European Physical Journal C 62:4 (2009) 625-658
Abstract:
Measurements of the neutral current cross sections for deep inelastic scattering in e - p collisions at HERA with a longitudinally polarised electron beam are presented. The single-differential cross-sections d σ/dQ 2, d σ/dx and d σ/dy and the double-differential cross sections in Q 2 and x are measured in the kinematic region y<0.9 and Q 2>185∈GeV 2 for both positively and negatively polarised electron beams and for each polarisation state separately. The measurements are based on an integrated luminosity of 169.9∈pb -1 taken with the ZEUS detector in 2005 and 2006 at a centre-of-mass energy of 318∈GeV. The structure functions F3 and xF 3γ Z are determined by combining the e - p results presented in this paper with previously measured e + p neutral current data. The asymmetry parameter A - is used to demonstrate the parity violating effects of electroweak interactions at large spacelike photon virtuality. The measurements agree well with the predictions of the Standard Model. © 2009 Springer-Verlag / Società Italiana di Fisica.Search for excited quarks in ep collisions at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 678:4 (2009) 335-343
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.Deep inelastic scattering with leading protons or large rapidity gaps at HERA
Nuclear Physics B 816:1-2 (2009) 1-61