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| CMS-PAS-EXO-16-025 | ||
| Search for high-mass resonances in the $\mathrm{Z(q\overline{q})}\gamma$ final state at $ \sqrt{s} = $ 8 TeV | ||
| 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 8 TeV at the LHC corresponding to an integrated luminosity of 19.7 fb$^{-1}$ collected by the CMS detector. Spin-0 resonances with various widths and with masses in a range between 650 GeV and 2.5 TeV are probed. Since no signal is found, the results are presented in terms of an upper limit on the production cross section of such resonances. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PLB 772 (2017) 363. The superseded preliminary plots can be found here. |
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| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1-a:
Full acceptance times efficiency (including $\mathcal {B}( {\mathrm {Z}} \to { {\mathrm {q}} {\overline {\mathrm {q}}} } $)) of the two signal categories for resonances with different widths as a function of resonance mass. Points show the numbers extracted from the Monte Carlo simulation, curves show the fit of the values with a polynomial. |
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Figure 1-b:
Full acceptance times efficiency (including $\mathcal {B}( {\mathrm {Z}} \to { {\mathrm {q}} {\overline {\mathrm {q}}} } $)) of the two signal categories for resonances with different widths as a function of resonance mass. Points show the numbers extracted from the Monte Carlo simulation, curves show the fit of the values with a polynomial. |
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Figure 2-a:
Fits on $ {M_{\text {Z}\gamma }} $ invariant mass spectra in signal region for a) anti-b-tagged and b) b-tagged categories. No events have been found above 2.5 TeV . The results of the fits to the two categories with the parametric background shape are shown. The difference between the yield measured in data and the estimate from the fit is divided by the statistical uncertainty on the measurement and reported in the lower panel. |
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Figure 2-b:
Fits on $ {M_{\text {Z}\gamma }} $ invariant mass spectra in signal region for a) anti-b-tagged and b) b-tagged categories. No events have been found above 2.5 TeV . The results of the fits to the two categories with the parametric background shape are shown. The difference between the yield measured in data and the estimate from the fit is divided by the statistical uncertainty on the measurement and reported in the lower panel. |
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Figure 3-a:
Expected and observed limits on the narrow spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained for the a)anti-b-tagged and b)b-tagged categories. |
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Figure 3-b:
Expected and observed limits on the narrow spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained for the a)anti-b-tagged and b)b-tagged categories. |
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Figure 4-a:
Expected and observed limits on the wide spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained for the a)anti-b-tagged and b)b-tagged categories. |
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Figure 4-b:
Expected and observed limits on the wide spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained for the a)anti-b-tagged and b)b-tagged categories. |
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Figure 5-a:
Expected and observed limits on the a) narrow and b) wide spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $. |
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Figure 5-b:
Expected and observed limits on the a) narrow and b) wide spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $. |
| Tables | |
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Table 1:
Summary of the sources of uncertainties and their effects on the yield variation. |
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Table 2:
Expected limits, in fb, for two categories of the analysis, as well as the results from combined asymptotic limits, for a narrow resonance. |
| Summary |
| We have presented a search for a possible resonance in the mass range from 650 GeV to 2.5 TeV decaying into a Z boson and a photon, where the Z boson further decays to a pair of quarks, merged in a single jet. The search is based on the analysis of pp collision data collected at $ \sqrt{s} = $ 8 TeV and corresponding to an integrated luminosity of 19.7 fb$^{-1}$. The final results were obtained by combining the observations from searches in two exclusive categories of the events with or without a $\mathrm{ Z }\to\mathrm{ b \bar{b} }$ candidate. The observed data was found to be compatible with the standard model prediction. The final results are expressed in terms of expected upper limits at 95% CL on the production cross section of a new resonance. |
| Additional Figures | |
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Additional Figure 1:
Overlaid expected and observed limits on the narrow spin-0 resonance production cross section times branching fraction $\mathrm {X} \rightarrow \mathrm {Z}\gamma $ obtained with the hadronic $\mathrm {Z}({\rm q \bar{q} } )\gamma $ analysis in CMS-PAS-EXO-16-020 for 2015 data, CMS-PAS-EXO-16-025 for 2012 data, and CMS-PAS-EXO-16-035 for 2016 data. The scaling of upper limits from EXO-16-025 (8TeV) takes into account the different parton luminosities at different center of mass energies, which have been calculated with NNPDF2.3 parton distributions. The parametrization of parton luminosity ratio is identicle to the one used in CMS-PAS-EXO-16-021 (Combination of searches for high-mass resonances in $\mathrm {Z}({\rm l \bar{l} })\gamma $ final state at $\sqrt {s} =$ 8 TeV and $\sqrt {s} =$ 13 TeV). |
| References | ||||
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Compact Muon Solenoid LHC, CERN |
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