On the spin and parity of a single-produced resonance at the LHC

TL;DR

This paper develops a comprehensive method using angular and mass distributions of decay products to determine the spin, parity, and tensor structure of a new boson discovered at the LHC, accounting for all spin correlations and couplings.

Contribution

It introduces a detailed Monte Carlo simulation framework for analyzing the spin and parity of a resonance, including all spin correlations and general couplings, verified against analytic calculations.

Findings

Potential to distinguish spin and parity hypotheses with 99% confidence after the 8 TeV LHC run.

Method enables optimal background rejection using angular and mass distributions.

Applicability to various resonance models, including non-parity eigenstates.

Abstract

The experimental determination of the properties of the newly discovered boson at the Large Hadron Collider is currently the most crucial task in high energy physics. We show how information about the spin, parity, and, more generally, the tensor structure of the boson couplings can be obtained by studying angular and mass distributions of events in which the resonance decays to pairs of gauge bosons, $ZZ, WW$, and $\gamma \gamma$. A complete Monte Carlo simulation of the process $pp \to X \to VV \to 4f$ is performed and verified by comparing it to an analytic calculation of the decay amplitudes $X \to VV \to 4f$. Our studies account for all spin correlations and include general couplings of a spin $J=0,1,2$ resonance to Standard Model particles. We also discuss how to use angular and mass distributions of the resonance decay products for optimal background rejection. It is shown that by the end of the 8 TeV run of the LHC, it might be possible to separate extreme hypotheses of the spin and parity of the new boson with a confidence level of 99% or better for a wide range of models. We briefly discuss the feasibility of testing scenarios where the resonances is not a parity eigenstate.