Jet substructures of boosted polarized hadronic tops

TL;DR

This paper analyzes the substructure of boosted polarized top quarks in QCD, showing that the differential energy profile can distinguish top quark helicity, aiding the search for new physics.

Contribution

It introduces a factorization framework for jet substructures of polarized top quarks and demonstrates the differential energy profile as a helicity discriminator.

Findings

Differential energy profile differs for left- and right-handed top jets.

Right-handed top jets show a rapid decrease in energy profile with increasing cone radius.

The method can potentially reveal chiral structures of new physics.

Abstract

We study jet substructures of a boosted polarized top quark, which undergoes the hadronic decay $t\to b u\bar d$, in the perturbative QCD framework, focusing on the energy profile and the differential energy profile. These substructures are factorized into the convolution of a hard top-quark decay kernel with a bottom-quark jet function and a $W$-boson jet function, where the latter is further factorized into the convolution of a hard $W$-boson decay kernel with two light-quark jet functions. Computing the hard kernels to leading order in QCD and including the resummation effect in the jet functions, we show that the differential jet energy profile is a useful observable for differentiating the helicity of a boosted hadronic top quark: a right-handed top jet exhibits quick descent of the differential energy profile with the inner test cone radius $r$, which is attributed to the $\mbox{V-A}$ structure of weak interaction and the dead-cone effect associated with the $W$-boson jet. The above helicity differentiation may help to reveal the chiral structure of physics beyond the Standard Model at high energies.