Measuring the W-Boson mass at a hadron collider: a study of phase-space singularity methods

TL;DR

This paper explores an advanced phase-space singularity method to improve the measurement of the W-Boson mass at hadron colliders, offering a potentially more statistically optimal approach by incorporating an additional variable.

Contribution

It introduces a novel phase-space singularity mass variable that enhances W-Boson mass measurement accuracy by utilizing both longitudinal and transverse lepton momentum data.

Findings

The new variable is statistically optimal for mass measurement.

Graphical phase-space analysis resembles an extended Dalitz plot.

Method demonstrates advantages in simple realistic decay processes.

Abstract

The traditional method to measure the W-Boson mass at a hadron collider (more precisely, its ratio to the Z-mass) utilizes the distributions of three variables in events where the W decays into an electron or a muon: the charged-lepton transverse momentum, the missing transverse energy and the transverse mass of the lepton pair. We study the putative advantages of the additional measurement of a fourth variable: an improved phase-space singularity mass. This variable is statistically optimal, and simultaneously exploits the longitudinal- and transverse-momentum distributions of the charged lepton. Though the process we discuss is one of the simplest realistic ones involving just one unobservable particle, it is fairly non-trivial and constitutes a good "training" example for the scrutiny of phenomena involving invisible objects. Our graphical analysis of the phase space is akin to that of a Dalitz plot, extended to such processes.