Measurement of the weak mixing angle with the Drell-Yan process in proton-proton collisions at the LHC

TL;DR

This paper presents a multivariate likelihood method to measure the weak mixing angle using the Drell-Yan process in proton-proton collisions at the LHC, applying it to CMS data to obtain a precise measurement consistent with the Standard Model.

Contribution

The paper introduces a novel multivariate likelihood approach that resolves decay angle ambiguities and measures the weak mixing angle from LHC data for the first time.

Findings

Measured sin^2(theta[eff]) = 0.2287 +/- 0.0020 (stat.) +/- 0.0025 (syst.)

Result is consistent with other Standard Model measurements

Method improves electroweak coupling measurements at the LHC

Abstract

A multivariate likelihood method to measure electroweak couplings with the Drell-Yan process at the LHC is presented. The process is described by the dilepton rapidity, invariant mass, and decay angle distributions. The decay angle ambiguity due to the unknown assignment of the scattered constituent quark and antiquark to the two protons in a collision is resolved statistically using correlations between the observables. The method is applied to a sample of dimuon events from proton-proton collisions at sqrt(s) = 7 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 1.1 inverse femtobarns. From the dominant u-ubar, d-dbar to gamma*/Z to opposite sign dimuons process, the effective weak mixing angle parameter is measured to be sin^2(theta[eff]) = 0.2287 +/- 0.0020 (stat.) +/- 0.0025 (syst.). This result is consistent with measurements from other processes, as expected within the standard model.