MEASUREMENT OF THE HIGGS BRANCHING RATIO BR(H → γγ) AT 3 TeV CLIC

In this paper we address the potential of a 3 TeV center-of-mass energy Compact Linear Collider (CLIC) to measure the Standard Model (SM) Higgs boson decay to two photons. Since photons are massless, they are not coupled to the Higgs boson at tree level, but they are created in a loop exchange of heavy particles either from the Standard Model or beyond. Any deviation of the effective H → γγ branching ratio and consequently of the Higgs to photon coupling may indicate New Physics. The Higgs decay to two photons is thus an interesting probe of the Higgs sector, both at the running and future experiments. A similar study has been performed at 1.4 TeV CLIC, where the statistical uncertainty is determined to be 15% for an integrated luminosity of 1.5 ab−1 with unpolarized beams. This study is performed using a full simulation of the detector for CLIC and by considering all relevant physics and beam-induced processes in a full reconstruction chain. The meas- urement is simulated on 5000 pseudo-experiments and the relative statistical uncertainty is extracted from the pull distribution. It is shown that the Higgs production cross-section in W+W− fusion times the branching ratio BR(H → γγ) can be measured with a relative statistical accuracy of 8.2%, assuming an integrated luminosity of 5 ab−1 with unpolarized beams.