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.
Highlights
The main goal of the Large Hadron Collider (LHC) [1] is to explore physics at the TeV energy scale via protonproton collisions
This annihilation process could reveal the existence of a new neutral gauge boson [3,4] or uncover deviations from the standard model of particle physics (SM) in elementary fermion couplings to the known neutral electroweak bosons
We present a multivariate analysis that uses the full information about the Drell–Yan process qq" ! Ã=Z ! ‘À‘þ, parameterized as a function of the dilepton rapidity Y, invariant mass squared s^, and decay angle Ã
Summary
The main goal of the Large Hadron Collider (LHC) [1] is to explore physics at the TeV energy scale via protonproton collisions. The interference of the axial-vector and vector couplings leads to an asymmetry in the distribution of the polar angle of the lepton with respect to the direction of the constituent quark from the incoming proton in the quark-antiquark annihilation This type of ‘‘forward-backward’’ asymmetry has been the primary measurement used to extract the couplings and sin2W at the LEP, SLC, and Tevatron experiments. ‘À‘þ, parameterized as a function of the dilepton rapidity Y, invariant mass squared s^, and decay angle à This process offers a relatively simple environment for the development of the matrix-element analysis techniques for resonance polarization studies at the LHC. The angle à is defined as the angle between the lepton momentum and a z0-axis that bisects the angle between the direction
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