CMS-PAS-EXO-16-035

CMS-PAS-EXO-16-035
Search for high-mass resonances in $\mathrm{Z}(\mathrm{q}\bar{\mathrm{q}})\gamma$ final state in pp collisions at $ \sqrt{s} = $ 13 TeV with 12.9 fb$^{-1}$
CMS Collaboration
August 2016

Abstract: A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, using jet substructure and advanced b tagging techniques. Results are based on a sample of proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC corresponding to an integrated luminosity of 12.9 fb$^{-1}$ collected with the CMS detector in 2016. Spin-0 resonances with masses in a range between 650 GeV and 3 TeV are searched for. The results are presented in terms of an upper limit on the production cross section of such resonances.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png	Figure 1-a: Full acceptance times efficiency (including $\mathcal {BR}( {\mathrm {Z}} \to { {\mathrm {q}} {\overline {\mathrm {q}}} } )$) of the two signal categories for resonances with (a) $\Gamma /m =$ 0.014% and (b) $\Gamma /m =$ 5.6%. Points show the numbers extracted from the Monte Carlo simulation, curves show the fit of the values with a polynomial.
png	Figure 1-b: Full acceptance times efficiency (including $\mathcal {BR}( {\mathrm {Z}} \to { {\mathrm {q}} {\overline {\mathrm {q}}} } )$) of the two signal categories for resonances with (a) $\Gamma /m =$ 0.014% and (b) $\Gamma /m =$ 5.6%. Points show the numbers extracted from the Monte Carlo simulation, curves show the fit of the values with a polynomial.
png	Figure 2-a: $ {M_{\text {Z}\gamma }} $ invariant mass spectra for (a) anti-b-tagged and (b) b-tagged signal regions. The results of the fits to the two categories with the parametric background shape are shown. The difference between the yields measured in data and the estimates from the fit is divided by the statistical uncertainty of the measurement and reported in the lower panel.
png	Figure 2-b: $ {M_{\text {Z}\gamma }} $ invariant mass spectra for (a) anti-b-tagged and (b) b-tagged signal regions. The results of the fits to the two categories with the parametric background shape are shown. The difference between the yields measured in data and the estimates from the fit is divided by the statistical uncertainty of the measurement and reported in the lower panel.
png pdf	Figure 3-a: Observed and Expected limits on the narrow spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained in the (a) anti-b-tagged and (b) b-tagged categories.
png pdf	Figure 3-b: Observed and Expected limits on the narrow spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained in the (a) anti-b-tagged and (b) b-tagged categories.
png pdf	Figure 4-a: Observed and Expected limits on the broad spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained in the (a) anti-b-tagged and (b) b-tagged categories.
png pdf	Figure 4-b: Observed and Expected limits on the broad spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained in the (a) anti-b-tagged and (b) b-tagged categories.
png pdf	Figure 5-a: Observed and Expected limits on the production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained with the combination of the two categories for (a) narrow spin-0 resonance and (b) broad spin-0 resonance.
png pdf	Figure 5-b: Observed and Expected limits on the production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained with the combination of the two categories for (a) narrow spin-0 resonance and (b) broad spin-0 resonance.

Tables
png pdf	Table 1: Summary of the sources of uncertainties and their effects on the yield variation.

Summary

We have presented a search for narrow and broad resonances in the mass range from 650 GeV to 3 TeV, decaying to a Z boson and a photon, where Z boson further decays hadronically. The search is carried out with two exclusive categories of events, with or without a $\mathrm{ Z }\to\mathrm{ b \bar{b} }$ candidate, and the final result is obtained by combining the two categories. Information from jet substructure variables is used in order to enhance the sensitivity of the analysis to heavy-particle production. No significant excess over the Standard Model expectation is found. The results are presented in form of upper limits at a 95% confidence level on the production cross section of a new resonances. For a narrow resonance with a mass of 750 GeV an observed (expected) cross section limit is 42.8 (42.3) fb. At higher masses the sensitivity improves and reaches 3.4 (2.9) fb in the observed (expected) limits for a narrow resonance with a mass of 2 TeV, and 1.7 (1.2) fb at 3 TeV. For a broad resonance, the observed (expected) upper limits on the resonance production cross section are 79 (2.3) fb at 750 GeV, and 15.4 (10.5) fb at 3 TeV.

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