Study of the azimuthal asymmetry of jets in neutral current deep inelastic scattering at HERA
Physics Letters Section B Nuclear Elementary Particle and High Energy Physics 551:3-4 (2003) 226-240
Abstract:
The azimuthal distribution of jets produced in the Breit frame in high-Q2 deep inelastic e+p scattering has been studied with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. The measured azimuthal distribution shows a structure that is well described by next-to-leading-order QCD predictions over the Q2 range considered, Q2 > 125 GeV2. © 2002 Elsevier Science B.V. All rights reserved.Measurement of proton-dissociative diffractive photoproduction of vector mesons at large momentum transfer at HERA: The ZEUS collaboration
European Physical Journal C 26:3 (2003) 389-409
Abstract:
Diffractive photoproduction of vector mesons, γp → VY, where Y is a proton-dissociative system, has been measured in e+p interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb-1. The differential cross section, dσ/dt, is presented for 1.2 < -t < 12 GeV2, where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, dσ/dt ∝ (-t)-n. The slope of the effective Pomeron trajectory, measured from the W dependence of the ρ0 and φ cross sections in bins of t, is consistent with zero. The ratios dσγp→φY/dt to dσγp→ρ0Y/dt and dσγp→J/ψY/dt to dσγp→ρ0Y/dt increase with increasing -t. Decay-angle analyses for ρ0, φ and J/ψ mesons have been carried out. For the ρ0 and φ mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models.Search for resonance decays to lepton+jet at DESY HERA and limits on leptoquarks
Physical Review D Particles Fields Gravitation and Cosmology 68:5 (2003) 520041-5200415
Abstract:
A search for narrow-width resonances that decay into electron+jet or neutrino+jet has been performed with the ZEUS detector at the DESY ep collider HERA operating at center-of-mass energies of 300 and 318 GeV. An integrated e+p luminosity of 114.8 pb-1 and e-p luminosity of 16.7 pb-1 were used. No evidence for any resonance was found. Limits were derived on the Yukawa coupling λ as a function of the mass of a hypothetical resonance that has arbitrary decay branching ratios into eq or vq. These limits also apply to squarks predicted by R-parity-violating supersymmetry. Limits for the production of leptoquarks described by the Buchmüller-Rückl-Wyler model were also derived for masses up to 400 GeV. For λ = 0.1, leptoquark masses up to 290 GeV are excluded.Measurement of event shapes in deep inelastic scattering at HERA
EUROPEAN PHYSICAL JOURNAL C 27:4 (2003) 531-545
Measurement of high-Q2 e-p neutral current cross sections at HERA and the extraction of xF3
EUROPEAN PHYSICAL JOURNAL C 28:2 (2003) 175-201