Search for a standard model-like Higgs boson in the mu+ mu- and e+ e- decay channels at the LHC

TL;DR

This paper reports a search for Higgs boson decays to muon and electron pairs at the LHC, setting upper limits on their production rates and branching fractions, and providing insights into the lepton-flavor couplings of the Higgs.

Contribution

The study provides the first upper limits on Higgs decays to muons and electrons at the LHC, testing lepton-flavor universality in Higgs couplings.

Findings

Upper limit on H→μ+μ− branching fraction is 0.0016.

Upper limit on H→e+e− branching fraction is 0.0019.

Results suggest non-universality of lepton couplings in the Higgs sector.

Abstract

A search is presented for a standard model-like Higgs boson decaying to muon pair or electron pair final states based on proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to integrated luminosities of 5.0 inverse femtobarns at a centre-of-mass energy of 7 TeV and 19.7 inverse femtobarns at 8 TeV for the muon search, and of 19.7 inverse femtobarns at 8 TeV for the electron search. Upper limits on the production cross section times branching fraction at the 95% confidence level are reported for Higgs boson masses in the range from 120 to 150 GeV. For a Higgs boson with a mass of 125 GeV decaying to muons, the observed (expected) upper limit on the production rate is found to be 7.4 (6.5 +2.8 -1.9) times the standard model value. This corresponds to an upper limit on the branching fraction of 0.0016. Similarly, for electrons, an upper limit of 0.0019 is placed on the branching fraction, which is about 3.7 E5 times the standard model value. These results, together with recent evidence of the 125 GeV boson coupling to tau-leptons with a larger branching fraction consistent with the standard model, confirm that the leptonic couplings of the new boson are not flavour-universal.