Evidence for Higgs boson decay to a pair of muons

Abstract

Evidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded by the CMS experiment at the CERN LHC. An excess of events over the back- ground expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at $$ \sqrt{s} $$ s = 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb−1, respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is $$ {1.19}_{-0.39}^{+0.40}{\left(\mathrm{stat}\right)}_{-0.14}^{+0.15}\left(\mathrm{syst}\right) $$ 1.19 − 0.39 + 0.40 stat − 0.14 + 0.15 syst . This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date.

Light quark Yukawas in triboson final states

“…We currently have firm evidence [1,2] that the Higgs couples to the 3 rd generation fermions (top, bottom, tau) with the strength predicted by the SM, within O(10%) accuracy. There is also preliminary evidence for the Higgs decays to muons [3,4], which is the first experimental verification of the SM Higgs mechanism at the level of the 2 nd generation fermions.…”

“…It is clear that the current 2 SS CMS analysis is not tailored to search for deviations in the light-quark Yukawa couplings from their SM values. Large improvements in the sensitivity to δy q can be obtained by a more stringent event selection, as illustrated in figure 3 for the normalized p 1 T , p 2 T , E miss T and p jj T (transverse momentum of the leading 4 Here and in all of the following, the bounds implicitly refer to the magnitude of δyq, that is δyq ≡ |δyq|.…”

Radiative muon mass models and (g − 2)μ

“…A naive combination of the CMS [1] and ATLAS [2] results for the Higgs-muon signal strength yields µ = 1.2 ± 0.3. Figure 3 shows that this measurement currently only constrains the parameter space of the Y ψ = 0 model, and only for small masses and large trilinear coupling.…”

“…i=1 Q i is the average of the charges of the mixed scalar states. 1 In deriving this expression we have used eq. (2.5), with the result that the leading contribution to a µ ≡ 1 2 (g − 2) µ is independent of the couplings y φ , y η , and the SU(3) representation of the exotics.…”

“…This relation, which does not hold in radiative mass generation models, is being directly tested by Higgs measurements at the LHC. Until recently, these measurements were restricted to the thirdfamily fermions; however, with the first evidence that the Higgs decays to muons [1,2], the mass generation mechanism of the second family is now being directly probed as well. For both families, the current data are consistent with the SM, but, as we shall see, also leave open the possibility of radiative mass generation.…”