CMS-PAS-EXO-16-034

CMS-PAS-EXO-16-034
Search for high-mass resonances in $\mathrm{ Z\gamma \rightarrow e^+e^-\gamma/\mu^+\mu^-\gamma }$ final states in proton-proton collisions at $ \sqrt{s} = $ 13 TeV with 12.9 fb$^{-1}$
CMS Collaboration
August 2016

Abstract: A search for a heavy resonance decaying to $\mathrm{ Z\gamma }$, with the Z boson further decaying to a pair of electrons or muons is presented. The search makes use of 13 TeV proton-proton collision data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 12.9 fb$^{-1}$. The analysis estimates the background directly from data, through an unbinned likelihood fit. No significant excess over the background-only hypothesis is observed, therefore limits at 95% confidence level are set on the production cross section of particles with a mass between 300 GeV and 2 TeV, in the narrow width approximation.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1-a: ${m_{\mathrm{Z}\gamma }}$ invariant mass distribution for events with ${\mathrm{e^+e^-}\gamma }$ (a) and ${\mu ^+\mu ^-\gamma }$ (b) after full event selection. The data (black markers) are compared to the simulation(green color for the irreducible Z+$\gamma $ contribution, and yellow for Z+jets). The simulation is normalized to the expected yield for this luminosity.
png pdf	Figure 1-b: ${m_{\mathrm{Z}\gamma }}$ invariant mass distribution for events with ${\mathrm{e^+e^-}\gamma }$ (a) and ${\mu ^+\mu ^-\gamma }$ (b) after full event selection. The data (black markers) are compared to the simulation(green color for the irreducible Z+$\gamma $ contribution, and yellow for Z+jets). The simulation is normalized to the expected yield for this luminosity.
png pdf	Figure 2-a: Fits of the ${m_{\mathrm{Z}\gamma }}$ distribution in the data, for the ${\mathrm{e^+e^-}\gamma }$ channel (a) and the ${\mu ^+\mu ^-\gamma }$ channel (b). Data are shown as black markers, in bins of 20 GeV, and the fitted function is represented by a red line, with the 68% uncertainty band as gray shade.
png pdf	Figure 2-b: Fits of the ${m_{\mathrm{Z}\gamma }}$ distribution in the data, for the ${\mathrm{e^+e^-}\gamma }$ channel (a) and the ${\mu ^+\mu ^-\gamma }$ channel (b). Data are shown as black markers, in bins of 20 GeV, and the fitted function is represented by a red line, with the 68% uncertainty band as gray shade.
png pdf	Figure 3-a: Observed (solid) and expected (dashed) 95% C.L. exclusion limits on $\sigma (\mathrm{A \rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma} )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, separately for the ${\mathrm{e^+e^-}\gamma }$ (a) and ${\mu ^+\mu ^-\gamma }$ (b) channels.
png pdf	Figure 3-b: Observed (solid) and expected (dashed) 95% C.L. exclusion limits on $\sigma (\mathrm{A \rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma} )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, separately for the ${\mathrm{e^+e^-}\gamma }$ (a) and ${\mu ^+\mu ^-\gamma }$ (b) channels.
png pdf	Figure 4: Observed (solid) and expected (dashed) 95% C.L. exclusion limits on $\sigma (\mathrm{A \rightarrow Z\gamma } )$ as a function of signal mass, together with the 68%(green) and 95%(yellow) ranges of expectation in the background-only hypothesis. The range 300 $ < {m_{\mathrm{Z}\gamma }} < $ 2000 GeV is shown.

Summary

A search for heavy resonances decaying to $\mathrm{ \mathrm{Z}\gamma }$, with further decay $\mathrm{ \mathrm{Z} \rightarrow \ell^+\ell^-}$, with $\ell = \mathrm{e}$, $\mu$, has been presented. The search makes use of 12.9 fb$^{-1}$ 13 TeV proton-proton collision data collected in 2016 by the CMS experiment at the LHC. The search strategy measures the non-resonant background directly on data, and looks for localized excesses. No significant excess over the Standard Model expectation is found, and limits at 95% confidence level are set on the production cross section of narrow resonances with masses between 300 GeV and 2 TeV.

References
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