Professor Amanda Cooper-Sarkar

Abstract:

Inclusive KS0KS0 production in ep collisions at the DESY ep collider HERA was studied with the ZEUS detector using an integrated luminosity of 0.5fb-1. Enhancements in the mass spectrum were observed and are attributed to the production of f2(1270)/a20(1320), f2′(1525) and f0(1710). Masses and widths were obtained using a fit which takes into account theoretical predictions based on SU(3) symmetry arguments, and are consistent with the Particle Data Group values. The f0(1710) state, which has a mass consistent with a glueball candidate, was observed with a statistical significance of 5 standard deviations. However, if this state is the same as that seen in γγ→KS0KS0, it is unlikely to be a pure glueball state. © 2008 The American Physical Society.

Abstract:

Deep inelastic scattering and its diffractive component, e p → e^′ γ^* p → e^′ X N, have been studied at HERA with the ZEUS detector using an integrated luminosity of 52.4 pb^-1. The MX method has been used to extract the diffractive contribution. A wide range in the centre-of-mass energy W (37-245 GeV), photon virtuality Q² (20-450 GeV²) and mass MX (0.28-35 GeV) is covered. The diffractive cross section for 2 < MX < 15 GeV rises strongly with W, the rise becoming steeper as Q² increases. The data are also presented in terms of the diffractive structure function, F2^{D (3)}, of the proton. For fixed Q² and fixed MX, xP F2^{D (3)} shows a strong rise as xP → 0, where xP is the fraction of the proton momentum carried by the pomeron. For Bjorken-x < 1 × 10^-3, xP F2^{D (3)} shows positive log Q² scaling violations, while for x ≥ 5 × 10^-3 negative scaling violations are observed. The diffractive structure function is compatible with being leading twist. The data show that Regge factorisation is broken. © 2008 Elsevier B.V. All rights reserved.