An NLO QCD Analysis of Inclusive Cross-section Data and Jet Production Data from the ZEUS Experiment at HERA-I
ArXiv hep-ph/0407309 (2004)
Evidence for a narrow baryonic state decaying to KS 0p and KS 0p̄ in deep inelastic scattering at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 591:1-2 (2004) 7-22
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.Search for contact interactions, large extra dimensions and finite quark radius in ep collisions at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 591:1-2 (2004) 23-41
Abstract:
A search for physics beyond the Standard Model has been performed with high-Q2 neutral current deep inelastic scattering events recorded with the ZEUS detector at HERA. Two data sets, e+p→e +X and e-p→e-X, with respective integrated luminosities of 112 pb-1 and 16 pb-1, were analyzed. The data reach Q2 values as high as 40000 GeV2. No significant deviations from Standard Model predictions were observed. Limits were derived on the effective mass scale in eeqq contact interactions, the ratio of leptoquark mass to the Yukawa coupling for heavy leptoquark models and the mass scale parameter in models with large extra dimensions. The limit on the quark charge radius, in the classical form factor approximation, is 0.85×10 -16 cm. © 2004 Published by Elsevier B.V.Photoproduction of D*± mesons associated with a leading neutron
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 590:3-4 (2004) 143-160
Abstract:
The photoproduction of D*±(2010) mesons associated with a leading neutron has been observed with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 80 pb-1. The neutron carries a large fraction, xL>0.2, of the incoming proton beam energy and is detected at very small production angles, θn< 0.8 mrad, an indication of peripheral scattering. The D* meson is centrally produced with pseudorapidity η<1.5, and has a transverse momentum pT>1.9 GeV, which is large compared to the average transverse momentum of the neutron of 0.22 GeV. The ratio of neutron-tagged to inclusive D* production is 8.85±0.93(stat.) +0.48-0.61(syst.)% in the photon-proton center-of-mass energy range 130Measurement of beauty production in deep inelastic scattering at HERA
ArXiv hep-ex/0405069 (2004)