Singular ways to search for the Higgs boson

TL;DR

This paper introduces and analyzes singularity variables derived from phase-space techniques to improve the search for the Higgs boson, aiding in signal-background separation and mass measurement at hadron colliders.

Contribution

It develops a set of invariant and non-invariant singularity variables for Higgs searches, enhancing analysis techniques with a focus on boost invariance and kinematic optimality.

Findings

Singularity variables help distinguish Higgs signals from background.

Boost-invariant variables are derived and shown to be effective.

Simulation of distributions benefits from understanding parton distribution functions.

Abstract

The discovery or exclusion of the fundamental standard scalar is a hot topic, given the data of LEP, the Tevatron and the LHC, as well as the advanced status of the pertinent theoretical calculations. With the current statistics at the hadron colliders, the workhorse decay channel, at all relevant H masses, is H to WW, followed by W to light leptons. Using phase-space singularity techniques, we construct and study a plethora of "singularity variables" meant to facilitate the difficult tasks of separating signal and backgrounds and of measuring the mass of a putative signal. The simplest singularity variables are not invariant under boosts along the collider's axes and the simulation of their distributions requires a good understanding of parton distribution functions, perhaps not a serious shortcoming during the boson hunting season. The derivation of longitudinally boost-invariant variables, which are functions of the four charged-lepton observables that share this invariance, is quite elaborate. But their use is simple and they are, in a kinematical sense, optimal.