Search

Abstract: The first observation of (anti)deuterons in deep inelastic scattering at HERA has been made with the ZEUS detector at a centre-of-mass energy of 300–318 GeV using an integrated luminosity of 120 pb−1. The measurement was performed in the central rapidity region for transverse momentum per unit of mass in the range . The particle rates have been extracted and interpreted in terms of the coalescence model. The (anti)deuteron production yield is smaller than the (anti)proton yield by approximately three orders of magnitude, consistent with the world measurements. [Copyright &y& Elsevier]

Abstract: Inclusive dijet and trijet production in deep inelastic ep scattering has been measured for and low Bjorken x, . The data were taken at the HERA ep collider with centre-of-mass energy using the ZEUS detector and correspond to an integrated luminosity of . Jets were identified in the hadronic centre-of-mass (HCM) frame using the cluster algorithm in the longitudinally invariant inclusive mode. Measurements of dijet and trijet differential cross sections are presented as functions of , , jet transverse energy, and jet pseudorapidity. As a further examination of low- dynamics, multi-differential cross sections as functions of the jet correlations in transverse momenta, azimuthal angles, and pseudorapidity are also presented. Calculations at generally describe the trijet data well and improve the description of the dijet data compared to the calculation at . [Copyright &y& Elsevier]

Abstract: Deep inelastic scattering and its diffractive component, , have been studied at HERA with the ZEUS detector using an integrated luminosity of . The measurement covers a wide range in the c.m. energy W (37–245 GeV), photon virtuality Q 2 (2.2–80 GeV2) and mass (0.28–35 GeV). The diffractive cross section for rises strongly with W; the rise is steeper with increasing Q 2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single pomeron. The ratio of diffractive to total cross section is constant as a function of W, in contradiction to the expectation of Regge phenomenology combined with a naive extension of the optical theorem to scattering. Above of 8 GeV, the ratio is flat with Q 2, indicating a leading-twist behaviour of the diffractive cross section. The data are also presented in terms of the diffractive structure function, , of the proton. For fixed β, the Q 2 dependence of changes with in violation of Regge factorisation. For fixed , rises as , the rise accelerating with increasing Q 2. These positive scaling violations suggest substantial contributions of perturbative effects in the diffractive DIS cross section. [Copyright &y& Elsevier]