Radiative corrections to the Drell-Yan process at large dilepton invariant masses
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EMENTARY PARTICLES AND FIELDS Theory
Radiative Corrections to the Drell–Yan Process at Large Dilepton Invariant Masses V. A. Zykunov* Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia Gomel State Technical University, pr. Oktyabrya 48, Gomel, 246746 Republic of Belarus Received November 8, 2005; in final form, March 28, 2006
Abstract—Electroweak radiative corrections to the neutral-current Drell–Yan process at large dilepton invariant masses are calculated. Asymptotic expressions are obtained for diagrams involving two-boson exchange, which represent one of the most significant contributions to the reaction being studied. The contributions of vertex diagrams and “soft” bremsstrahlung are also taken into account. A numerical analysis of electroweak effects with allowance for experimental constraints at the CMS facility is given. The result obtained from this analysis makes it possible to ensure a high precision in the region of high energies; therefore, it is applicable to future experiments at LHC. PACS numbers : 12.15.Lk, 13.75.Cs, 13.85.Qk DOI: 10.1134/S1063778806090109
1. INTRODUCTION The Standard Model, which, for more than two decades, has had the status of a consistent theory confirmed by experimental data, does not rule out the possible existence of new physics that may manifest itself as some deviation from Standard Model predictions in nonstandard experiments or, more probably, with increasing energy scale. It may turn out that supersymmetry, the existence of extra spatial dimensions [1] or extra neutral bosons [2], and a composite character of leptons and quarks [3] are traces of new physics. It is expected that experiments planned at the Large Hadron Collider (LHC), which is under construction at CERN, will shed light on at least some of the allied problems. Investigation of the neutral-current Drell–Yan process pp → γ, Z → l+ l− X
(1)
at large dilepton invariant masses is one of the powerful tools for revealing traces of new physics in experiments prepared at LHC, since the dilepton continuum is highly sensitive to any modifications to the Standard Model that are induced by new physics. Naturally, investigation of new-physics effects is impossible without precisely knowing Standard Model predictions, including those that concern QCD corrections, which are not considered here, and those *
E-mail: [email protected],Uladzimir.Zykunou@ cern.ch
that concern electroweak radiative corrections, which are the subject of the present study. Let us first specify the place of the present calculation among numerous studies devoted to this topic. By convention, we will break down electroweak corrections to the process in (1) into the following three classes: (i) electroweak corrections associated with boson self-energies, (ii) other electromagnetic corrections (that is, radiative corrections induced by at least one extra photon, a virtual or a real one), and (iii) other weak corrections (that is, corrections caused by at least one extra heavy boson, a Z or a W boson). The first and the second
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