Measurement of the high-mass Drell–Yan differential cross-section in pp collisions at s=7 TeV with the ATLAS detector

Abstract

This Letter reports a measurement of the high-mass Drell-Yan differential cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. Based on an integrated luminosity of 4.9 fb −1 , the differential cross-section in the Z /γ * → e + e − channel is measured with the ATLAS detector as a function of the invariant mass, m ee , in the range 116 < m ee < 1500 GeV, for a fiducial region in which both the electron and the positron have transverse momentum p T > 25 GeV and pseudorapidity |η| < 2.5.A comparison is made to various event generators and to the predictions of perturbative QCD calculations at next-to-next-to-leading order.© 2013 CERN. Published by Elsevier B.V. All rights reserved. IntroductionAt hadron colliders, the Drell-Yan (DY) process [1], proceeding at tree level via the s-channel exchange of a virtual photon or Z boson, can produce charged lepton pairs over a wide range of invariant mass. The differential cross-section as a function of the invariant mass is described by perturbative QCD (pQCD) calculations at next-to-next-to-leading order (NNLO). Given the simple experimental signature and the low backgrounds, a small experimental uncertainty can be achieved on the measured invariant mass distribution allowing for a precision test of pQCD. The mass spectrum is also sensitive to the parton distribution functions (PDFs), in particular to the poorly known distribution of antiquarks at large x [2], where x can be interpreted, at leading order, as the fraction of the proton momentum carried by the interacting parton. Additionally, the production of DY dilepton pairs is a source of background for other Standard Model (SM) measurements, and the mass spectrum may be modified by new physics phenomena giving rise to, e.g., narrow resonances or an excess of high-mass pairs inconsistent with the known PDFs.The differential cross-section for DY dilepton pair production in the high-mass range has been reported previously by the CMS [3], CDF [4] and D0 [5] Collaborations. With the ATLAS detector, total and differential cross-sections in a mass window of 66-116 GeV have been measured using the 2010 dataset [6]. In addition, searches for new physics in the high-mass range have been performed [7][8][9] and no deviations from the SM expectation were observed. This Letter reports an extension of these previous ✩ © CERN for the benefit of the ATLAS Collaboration.E-mail address: atlas.publications@cern.ch.analyses by providing a measurement of the DY cross-section, fully corrected for detector effects, in the dielectron channel as a function of the e + e − invariant mass, m ee , up to 1500 GeV. To minimise model-dependent theoretical uncertainties, the cross-section is not extrapolated to the full phase space but is reported in a phase space only slightly extended with respect to the fiducial acceptance of the e + and e − . The results are compared to NNLO pQCD calculations with next-to-leading-order (NLO) electroweak corrections from the FEWZ 3.1 [10,11] framework and to the predictions from ...

HERAFitter

“…This list includes several LHC analyses of SM processes, namely inclusive Drell-Yan and W and Z production [99,100,[141][142][143], inclusive jet production [97,144], and inclusive photon production [145]. The results of QCD analyses using HERAFitter were also published by HERA experiments for inclusive [21,146] and heavy-flavour production measurements [147,148].…”

Standard Model Physics Results From Atlas and CMS

“…The Drell-Yan di↵erential cross section at 7 TeV was measured 18 by the ATLAS Collaboration in the range of 116<m ee <1500 GeV. The Monte Carlo (MC) predictions are consistent with the shape of measured m ee distribution.…”

PDFs and LHC data: current and future constraints

“…1 a comparison of the kinematic coverage of the new LHC data compared to that of the data included in the previous analysis is shown. New LHC data include: the ATLAS high-mass Drell-Yan production data [49], based on an integrated luminosity of 4.9 fb −1 , which carries important [9]. Comparison of the down (top row) and gluon (bottom row) NNPDF3.0 NNLO PDFs at Q = 100 GeV to PDFs obtained using the same dataset, but with all LHC data excluded information on the large-x quark-antiquark separation; the transverse momentum distribution of W bosons [62] measured by ATLAS, which provides a complementary constraint on the gluon in the medium-x region; the CMS charged W muon asymmetry based on the full statistics (5 fb −1 ) of the 7 TeV run [50], which displays substantially reduced statistical and systematic uncertainties with respect to the previous measurement in the electron channel; the 7 TeV double differential Drell-Yan cross sections [50], which cover a large range of lepton pair invariant mass and provide an important handle on quark-flavor separation for a wide range of x; the W production in association with charm quarks measured by CMS, [51], and the 940 pb −1 forward Z → e + e − production data taken at LHCb in 2011 [52].…”