CMS-EXO-17-019

CMS-EXO-17-019 ; CERN-EP-2018-200
Search for narrow $\mathrm{H}\gamma$ resonances in proton-proton collisions at $\sqrt{s} = $ 13 TeV
CMS Collaboration
3 August 2018
Phys. Rev. Lett. 122 (2019) 081804
Abstract: A search for heavy, narrow resonances decaying to a Higgs boson and a photon (${\mathrm{H}\gamma} $) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$ collected with the CMS detector at the LHC in 2016. Events containing a photon and a Lorentz-boosted hadronically decaying Higgs boson reconstructed as a single, large-radius jet are considered, and the $\gamma$+jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether or not the large-radius jet can be identified as a result of the merging of two jets originating from b quarks. Results in both categories are found to agree with the predictions of the standard model. Upper limits on the production rate of ${\mathrm{H}\gamma}$ resonances are set as a function of their mass in the range of 720-3250 GeV, representing the most stringent constraints to date.
Links: e-print arXiv:1808.01257 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Signal acceptance times efficiency ($A \epsilon $) after the final selection, shown for the b-tagged and untagged categories.
png pdf	Figure 2-a: The observed ${\mathrm {J} {\gamma}}$ invariant mass spectra in the signal region, shown along with the background fit and a few selected signals, for the b-tagged category. Signal samples are plotted with arbitrary normalizations and are shown for illustration purposes. The green and yellow bands correspond to the one and two standard deviation uncertainties in the background-only fit. For bins with a low number of data entries, the error bars correspond to the Garwood confidence intervals [62]. Shown in the lower panel are the differences between the number of events in data and the nominal background prediction from the fit, divided by the combined statistical uncertainty in the data and the background fit. The error bars correspond to the statistical uncertainty in the data alone.
png pdf	Figure 2-b: The observed ${\mathrm {J} {\gamma}}$ invariant mass spectra in the signal region, shown along with the background fit and a few selected signals, for the untagged category. Signal samples are plotted with arbitrary normalizations and are shown for illustration purposes. The green and yellow bands correspond to the one and two standard deviation uncertainties in the background-only fit. For bins with a low number of data entries, the error bars correspond to the Garwood confidence intervals [62]. Shown in the lower panel are the differences between the number of events in data and the nominal background prediction from the fit, divided by the combined statistical uncertainty in the data and the background fit. The error bars correspond to the statistical uncertainty in the data alone.
png pdf	Figure 3: Upper limits at 95% CL on the product of the signal cross section and the branching fraction to ${{\mathrm {H}} {\gamma}}$ for the b-tagged and untagged categories, as well as the statistical combination of the two categories.

Summary

In summary, a search for heavy, narrow resonances decaying to a Higgs boson and a photon ($ \mathrm{H}\gamma $) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$ collected with the CMS detector at the LHC in 2016. Events in which a photon and a Lorentz-boosted Higgs boson that decays hadronically and is reconstructed as a single, large-radius jet are considered, and the $\gamma$+jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether the large-radius jet can be identified as a result of the merging of two jets originating from b quarks. The backgrounds, dominated by standard model $\gamma$+jet production, are estimated directly from data, without reliance on simulation. Results in both categories are found to agree with the predictions of the standard model. Upper limits on the production cross section of $ \mathrm{H}\gamma $ resonances ranging from 25 to 0.4 fb are set as a function of the resonance mass in the range of 720--3250 GeV. These are the most stringent constraints on narrow, spin-1 $ \mathrm{H}\gamma $ resonances to date in the entire mass range, and the first limits available below 1000 GeV and above 3000 GeV.

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