The Higgs-like boson spin from the center-edge asymmetry in the diphoton channel

TL;DR

This paper proposes using the center-edge asymmetry of photon angles in the diphoton rest frame to distinguish the spin-parity of the 125 GeV Higgs-like boson from a potential spin-2 resonance, with high discrimination power.

Contribution

The study introduces the center-edge asymmetry A_{CE} as a novel observable to differentiate between spin-0 and spin-2 hypotheses for the Higgs-like boson in diphoton decays.

Findings

A_{CE} effectively discriminates between spin hypotheses.

High confidence level (CL_s<10^{-6}) for f_{qq}=0.

Potential to outperform existing analyses for certain quark-antiquark fractions.

Abstract

We discuss the discrimination of the 125 GeV spin-parity 0^+ Higgs-like boson observed at the LHC, decaying into two photons, H\to\gamma\gamma, against the hypothesis of a minimally coupled J^{P}=2^+ narrow diphoton resonance with the same mass and giving the same total number of signal events under the peak. We apply, as the basic observable of the analysis, the center-edge asymmetry A_{CE} of the cosine of the polar angle of the produced photons in the diphoton rest frame to distinguish between the tested spin hypotheses. We show that the center-edge asymmetry A_{CE} should provide strong discrimination between the possibilities of spin-0 and spin-2 with graviton-like couplings, depending on the fraction of q\bar{q} production of the spin-2 signal, reaching a {CL}_s<10^{-6} for f_{qq}=0. Indeed, the A_{CE} has the potential to do better than existing analyses for f_{qq}<0.4.