Angular observables for spin discrimination in boosted diboson final states

Abstract

We investigate the prospects for spin determination of a heavy diboson resonance using angular observables. Focusing in particular on boosted fully hadronic final states, we detail both the differences in signal efficiencies and distortions of differential distributions resulting from various jet substructure techniques. We treat the 2 TeV diboson excess as a case study, but our results are generally applicable to any future discovery in the diboson channel. Scrutinizing ATLAS and CMS analyses at 8 TeV and 13 TeV, we find that the specific cuts employed in these analyses have a tremendous impact on the discrimination power between different signal hypotheses. We discuss modified cuts that can offer a significant boost to spin sensitivity in a post-discovery era. Even without altered cuts, we show that CMS, and partly also ATLAS, will be able to distinguish between spin 0, 1, or 2 new physics diboson resonances at the 2σ level with 30 fb −1 of 13 TeV data, for our 2 TeV case study.

SMEFT, a theory for SM deviations

“…pole observables vs. tail of distributions, and c) a measurement of the gluon fusion vs ttH production rates. Unfortunately, explicit threshold effects in boosted Higgs production are too small to be observable in the near future [27]. Global analyses including kinematic information in all Higgs channels cannot rely on the kappa framework, but they can be based on SMEFT.…”

Identifying a new particle with jet substructures

“…In our numerical study, we focus on S → ZZ which subsequently decay semileptonically, i.e., q q + − . One reason for this choice is that the q q + − final state is expected to offer a better handle in inferring the underlying decay mode than the fully hadronic decay channel in which there exists non-negligible chance to misidentify observed events as S → W + W − due to the issue of jet mass resolution [28,45]. 4 Compared to the fully leptonic channel, the semileptonic channel certainly enjoys higher statistics due to the larger branching fraction of Z into quark pairs, allowing us to have better signal sensitivity.…”

“…We first point out that rather precise identification of the features is viable in some controlled environment, despite the presence of realistic effects. Motivated by the spinparity determination of the SM Higgs boson [26] and the diboson resonance [27,28] through massive bosonic intermediary states in relevant decay processes, we focus on the analysis of W/Z-induced two-prong jets and examine well-motivated angular variables formed with reconstructed subjets. In the case of production of a new, bosonic heavy resonance, the jet substructure techniques are relevant to the channels of W W , ZZ, and Zγ in which the associated final state is, at least, partially hadronic.…”