A simple event weighting technique for optimizing the measurement of the forward-backward asymmetry of Drell-Yan dilepton pairs at hadron colliders

TL;DR

This paper introduces a straightforward event weighting method to improve the measurement of the forward-backward asymmetry in Drell-Yan dilepton production at hadron colliders, reducing statistical errors and aiding new physics searches.

Contribution

It proposes a simple event weighting technique based on rapidity and decay angle to optimize asymmetry measurements, enhancing precision over traditional count methods.

Findings

Reduces statistical errors by 20% in p-pbar collisions

Reduces statistical errors by 40% in p-p collisions

Provides expressions for QCD angular coefficients in Drell-Yan events

Abstract

We describe a simple technique for optimizing the extraction of the forward-backward asymmetry ($A_{fb}$) of Drell-Yan lepton pairs ($e^+e^-$,$ \mu^+\mu^-$) produced in $\bar{p}p$ and $pp$ collisions at hadron colliders. The method employs simple event weights which are functions of the rapidity and $cos\theta$ decay angle of the lepton pair. It yields the best estimate of the acceptance corrected parton level ($\bar{q}q$) forward backward asymmetry as a function of final state dilepton mass ($M_{\ell\ell}$). Typically, when compared to the simple count method, the technique reduces the statistical errors by 20% for $\bar{p}p$, and 40% for $pp$ collisions, respectively. The technique can be used to search for new high mass and large width Z' bosons which may be best detected through the observation of deviations from the Standard Model expectation for the forward-backward asymmetry. In addition, we derive expressions for the QCD angular coefficients for Drell-Yan events.