Does the `Higgs' have Spin Zero?

TL;DR

This paper investigates whether the observed 125 GeV excess in collider experiments is consistent with a spin-zero Higgs boson, analyzing angular distributions to distinguish between spin-zero and spin-two hypotheses.

Contribution

It provides theoretical calculations of angular distributions for spin-two bosons in gamma gamma and W W* decays, offering methods to confirm the Higgs spin in experiments.

Findings

Gamma gamma angular distribution for spin-two is distinct from spin-zero.

W W* decay distributions differ significantly between spin-zero and spin-two.

Event selection efficiency for spin-two in W W* channel is reduced, affecting experimental analysis.

Abstract

The Higgs boson is predicted to have spin zero. The ATLAS and CMS experiments have recently reported of an excess of events with mass ~ 125 GeV that has some of the characteristics expected for a Higgs boson. We address the questions whether there is already any evidence that this excess has spin zero, and how this possibility could be confirmed in the near future. The excess observed in the gamma gamma final state could not have spin one, leaving zero and two as open possibilities. We calculate the angular distribution of gamma gamma pairs from the decays of a spin-two boson produced in gluon-gluon collisions, showing that is unique and distinct from the spin-zero case. We also calculate the distributions for lepton pairs that would be produced in the W W* decays of a spin-two boson, which are very different from those in Higgs decays, and note that the kinematics of the event selection used to produce the excess observed in the W W* final state have reduced efficiency for spin two.