CMS-PAS-HIG-23-010

CMS-PAS-HIG-23-010
Search for Higgs boson production in association with a charm quark in the diphoton decay channel
CMS Collaboration
23 July 2024

Abstract: This note presents the first search for the associated production of a Higgs boson with a charm quark (cH), focusing on the diphoton decay channel of the Higgs boson. This process provides a unique opportunity to probe the Higgs boson-charm quark coupling. The analysis results are based on the full Run 2 data set of proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Assuming the Standard Model (SM) cross sections times branching ratios for the non-cH processes, the observed (expected) upper limit at 95% confidence level on the cH signal strength is 243 (355) times the SM prediction. In the same assumption, the observed (expected) allowed interval on $ \kappa_{\mathrm{c}} $, the Higgs boson-charm quark coupling modifier, is $ \|\kappa_{\mathrm{c}}\| < $ 38.1 ($ \|\kappa_{\mathrm{c}}\| < $ 72.5) at 95% confidence level.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Leading order Feynmann diagrams that contribute to $ pp \rightarrow \mathrm{Hc} $, red dots correspond to vertices where the Yukawa coupling $ y_{\mathrm{c}} $ enters (left and center), while the blue vertex corresponds to the SM-like top loop, integrated out (right).
png pdf	Figure 2: Distributions of CvsL score for the leading jet in cH, resonant background and sideband data events. Sideband data removes events with 120 GeV $ < m_{\gamma\gamma} < $ 130 GeV. Error bars representing statistical uncertainties on the data are too small to be displayed. Events with CvsL score values below the vertical line are not included in the signal region.
png pdf	Figure 3: Distributions of BDT1 output (left) and BDT2 output (right), in cH, resonant background and sideband data events. Sideband data removes events with 120 GeV $ < m_{\gamma\gamma} < $ 130 GeV. Error bars represent statistical uncertainties.
png pdf	Figure 3-a: Distributions of BDT1 output (left) and BDT2 output (right), in cH, resonant background and sideband data events. Sideband data removes events with 120 GeV $ < m_{\gamma\gamma} < $ 130 GeV. Error bars represent statistical uncertainties.
png pdf	Figure 3-b: Distributions of BDT1 output (left) and BDT2 output (right), in cH, resonant background and sideband data events. Sideband data removes events with 120 GeV $ < m_{\gamma\gamma} < $ 130 GeV. Error bars represent statistical uncertainties.
png pdf	Figure 4: Invariant mass distribution for the selected events in all categories weighted by S/(S + B), where S (B) is the numbers of expected signal (background) events in the smallest mass window containing 68.3% of the expected signal events. Curves for the fitted signal + background (red), for the fitted background (black) and for the fitted continuous background (blue), as well as bands covering the $ \pm$1$\sigma $ and $ \pm$2$\sigma $ uncertainties of the fitted background, are overlaid. The lower panel shows the $ m_{\gamma\gamma} $ distribution subtracting the continuous background and overlaying the curve for the fitted signal (purple).

Tables
png pdf	Table 1: Number of expected signal cH ($ H \rightarrow \gamma\gamma $) events, resonant background events, and continuous background events, as well as signal-over-background ratio (S/B), in the mass window [122.88, 127.88] GeV for all categories. The fraction of different production processes contributing to the resonant background (ggH, ttH, VBF, and bH) is also reported.
png pdf	Table 2: Impacts of several systematic uncertainty groups divided by the total uncertainty in the signal strength measurement.

Summary

To conclude, we present the first search for the associated production of a charm quark and the Higgs boson. Assuming the mean value of the signal strengths of non-cH Higgs processes in the diphoton decay channel to be at the SM prediction, the observed (expected) upper limit at 95% confidence level on the cH signal strength is 243 (355) times the SM prediction. This search provides additional sensitivity to the Yukawa coupling between the Higgs boson and the charm quark. In the same assumption, the observed (expected) allowed interval on $ \kappa_{\mathrm{c}} $, the Higgs-charm coupling strength modifier, is $ |\kappa_{\mathrm{c}}| < $ 38.1 ($ |\kappa_{\mathrm{c}}| < $ 72.5) at 95% confidence level.

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