Measurement of the Drell-Yan forward-backward asymmetry at high dilepton masses in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

Abstract

A measurement of the forward-backward asymmetry of pairs of oppositely charged leptons (dimuons and dielectrons) produced by the Drell-Yan process in proton-proton collisions is presented. The data sample corresponds to an integrated luminosity of 138 fb−1 collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV. The asymmetry is measured as a function of lepton pair mass for masses larger than 170 GeV and compared with standard model predictions. An inclusive measurement across both channels and the full mass range yields an asymmetry of 0.612 ± 0.005 (stat) ± 0.007 (syst). As a test of lepton flavor universality, the difference between the dimuon and dielectron asymmetries is measured as well. No statistically significant deviations from standard model predictions are observed. The measurements are used to set limits on the presence of additional gauge bosons. For a Z′ boson in the sequential standard model the observed (expected) 95% confidence level lower limit on the Z′ mass is 4.4 TeV (3.7 TeV).

Impact of high invariant-mass Drell-Yan forward-backward asymmetry measurements on SMEFT fits

“…We note that in the special case of data set IV, the "true" AFB with dynamic scale µ 0 = m ll significantly deviates from the aMC@NLO simulation in Ref. [24] as shown in Figure 2. Therefore, we also consider the case of µ 0 = H T , where H T is the sum of transverse masses of all final state particles.…”

“…13 TeV [22], and two AFB measurements at 8 TeV [23] and 13 TeV [24], respectively. These data sets are chosen specifically for their high luminosities and high di-lepton invariant mass (up to 7 TeV).…”

“…To mimic this we manually pick out the quark and anti-quark directions in our prediction 1 . In this work, we denote the former definition of AFB as A * FB , while the latter, often referred to as the "true" AFB in the literature [24,29], is denoted as A FB . We comment later on several aspects of A FB .…”

On Drell-Yan production of scalar leptoquarks coupling to heavy-quark flavours

“…Let us finally add that measurements of the DY forward-backward asymmetry (A FB ) at high dilepton invariant masses such as [5] might also be used to set limits on the presence of LQs and their interactions [8]. The forward (backward) DY cross section thereby includes all events with cos θ > 0 (cos θ < 0) where θ denotes the angle between the incoming quark and the outgoing negatively charged lepton in the Collins-Soper frame [88].…”

“…These searches are possible owing to the clean and well reconstructable experimental signature with excellent detection efficiency. While in the context of physics beyond the Standard Model (SM) both ATLAS and CMS have mostly investigated resonant dilepton signatures, recently also searches for non-resonant phenomena leading to dilepton final states [1][2][3][4][5][6] have been performed.…”