ATLAS

Abstract:

In January 2007 the CERN director general announced the plan for the staged upgrade of the LHC luminosity. The plan foresees a phase 1 upgrade reaching a peak luminosity of $3 \times 10^{34}$ cm$^{-2}$s$^{-1}$ followed by phase reaching up to $ 10^{35}$ cm$^{-2}$s$^{-1}$. We discuss the physics potential and the experimental challenges of an upgraded LHC running. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are also discussed.

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.