W-jet Tagging: Optimizing the Identification of Boosted Hadronically-Decaying W Bosons

TL;DR

This paper introduces a multivariate W-jet tagging method that significantly improves the identification of boosted hadronically decaying W bosons over previous techniques, enhancing search sensitivity at the LHC.

Contribution

The paper presents a novel multivariate approach incorporating new jet shape discriminants, achieving a fivefold improvement in signal significance over traditional methods.

Findings

Multivariate approach outperforms previous filtering/mass-drop methods.

Discrimination is enhanced for longitudinally polarized W's.

Sensitivity to underlying event effects varies among variables.

Abstract

A method is proposed for distinguishing highly boosted hadronically decaying W's (W-jets) from QCD-jets using jet substructure. Previous methods, such as the filtering/mass-drop method, can give a factor of ~2 improvement in S/sqrt(B) for jet pT > 200 GeV. In contrast, a multivariate approach including new discriminants such as R-cores, which characterize the shape of the W-jet, subjet planar flow, and grooming-sensitivities is shown to provide a much larger factor of ~5 improvement in S/sqrt(B). For longitudinally polarized W's, such as those coming from many new physics models, the discrimination is even better. Comparing different Monte Carlo simulations, we observe a sensitivity of some variables to the underlying event; however, even with a conservative estimates, the multivariate approach is very powerful. Applications to semileptonic WW resonance searches and all-hadronic W+jet searches at the LHC are also discussed. Code implementing our W-jet tagging algorithm is publicly available at http://jets.physics.harvard.edu/wtag