Next-to-leading order QCD corrections to the Drell–Yan cross section in models of TeV-scale gravity

Abstract

The first results on next-to-leading order QCD corrections to graviton-induced processes in hadron collisions in models of TeV-scale gravity are presented focusing on the case of dilepton pair production inpp and pp collisions. Distributions in the invariant mass Q, the longitudinal fraction x F , the rapidity Y and the forward-backward asymmetry of the lepton pair are studied. The quantitative impact of the QCD corrections for searches of extra dimensions at hadron colliders is investigated. It turns out that at the LHC ( √ S = 14 TeV) the K-factor is rather large (K = 1.6) for large invariant mass Q of the lepton pair, indicating the importance of accounting for these QCD corrections in the experimental search for TeV-scale gravity. At the Tevatron, the K-factor does not substantially deviate from the Standard Model value. However, its inclusion is necessitated to make the cross-section stable with respect to scale variations.PACS numbers: 11.10. Kk, 13.60.Hb. contributions to SM processes strongly suggests that the LO corrections at hadronic colliders are quiet unreliable [6,7]. The standard Drell-Yan (DY) processes and Higgs production at hadron colliders, for example, not only get large corrections but the theoretical uncertainties get reduced significantly from NLO corrections.It is with this motivation that the present paper presents the results of the computation of NLO-QCD corrections to the DY process, P 1 + P 2 → µ + µ − + X, where P 1 , P 2 are initial hadrons and X is an arbitrary hadronic final state. This process takes place via the exchange of γ, Z and graviton. These NLO results are used to study the impact of the QCD correction for this process at the present Tevatron collider and the future LHC which is planned to operate at centre-of-mass energies around 14 TeV. This process had been considered earlier to LO [8,9] in the ADD model.The results we present here are for the ADD model, but since the QCD corrections, presented here, are model-independent they may equally be used for studying the Randall-Sundrum model of warped compactification [10].This paper is organised as follows. In Sec. 2 we describe additional graviton vertices needed to perform the NLO QCD corrections. We study the distributions in the invariant mass Q (Sec. 3), the longitudinal fraction x F (Sec. 4), the rapidity Y (Sec. 5) and the forward-backward asymmetry (Sec. 6) of lepton pair. Finally in Sec. 7 we present the discussion and summarise the results. In Appendix A and B we present the detailed expressions needed for x F and Y distributions in Sec. 4 and Sec. 5 respectively.

DiffractiveZboson pair production at the LHC in the large extra dimensions scenario

“…For comparison we also present the diffractive SM prediction which consider the next-to-leading-order gg → ZZ subprocess via a quark loop diagram [17]. The LED predictions dominate the distribution at larger values of the invariant mass, as expected from previous studies for the inclusive production of different final states [7]. In particular, we obtain that the LED prediction for the total cross section in central inclusive processes is one order of magnitude larger than the SM one for M S = 3.5 TeV and n = 2.…”

“…From the theoretical side, many studies on the virtual KK graviton effects up to the NLO exist [7]. These include the processes of fermion-pair, multijet, and diboson production.…”

Diphoton production in the ADD model to NLO+parton shower accuracy at the LHC

“…di-lepton [7], di-gauge boson (γγ [8], ZZ and W + W − [9]), which in extra dimension models could result from the exchange of a virtual KK mode in addition to the usual SM contribution. The real emission of KK modes lead to large missing E T signals viz.…”

Quark and gluon spin-2 form factors to two loops in QCD

“…In the theoretical context, the scales resulting from renormalisation and factorisation in the hadronic cross-sections provide estimates of uncertainties of the uncalculated higher order corrections. Next-to-leading order (NLO) QCD calculations are known for di-lepton [5], di-photon [6] and di-electroweak gauge boson [7] production via virtual KK modes in addition to the SM contributions. In the AMC@NLO framework, the results to NLO+PS accuracy are also available [8].…”