Mass biases in reconstructing exclusive radiative hadronic decays of W bosons at the LHC

TL;DR

This paper investigates the challenges in reconstructing exclusive radiative hadronic decays of W bosons at the LHC, highlighting biases that affect mass measurements and the potential for new W mass determination methods.

Contribution

It identifies and discusses three key issues—particle misidentification, partial reconstruction, and interference effects—that bias the W boson mass measurement in these decay channels.

Findings

Particle misidentification causes significant mass shifts.

Partial reconstruction impacts the accuracy of decay measurements.

Interference with QCD processes shifts the reconstructed mass peak.

Abstract

The search for exclusive hadronic vector boson decays is an ongoing part of the LHC programme where, to date, no such decays have been observed. In addition to the intrinsic interest in the branching ratios, there is potential for a measurement of the $W$ boson mass quite distinct from the usual methods. The radiative decay modes offer good potential channels for this search; however, we highlight three issues with it not previously discussed: particle misidentification, partial reconstruction and the impact of interference with QCD. These issues cause shifts in the peak position of tens or hundreds of MeV/c$^2$.