CMS-PAS-EXO-16-011

CMS-PAS-EXO-16-011
Search for dark matter produced in association with a Higgs boson decaying to two photons
CMS Collaboration
August 2016

Abstract: The results of a search for dark matter produced in association with a Higgs boson where the Higgs boson decays to two photons are presented. The analysis is based on the data collected in 2015 at a center-of-mass energy of 13 TeV in proton-proton collisions with the CMS detector at the LHC. A two-Higgs-doublet model is taken as the benchmark model. After the final selection, using a dataset of 2.3 fb$^{-1}$ of integrated luminosity, no significant evidence for dark matter particle production has been observed. For the benchmark model, limits on the cross section times branching ratio for dark matter production are placed at approximately 3 fb for the Z' mass range of 600 to 2500 GeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagram for the 2HDM DM-Higgs interaction.
png pdf	Figure 2: Distribution of the diphoton invariant mass of events passing all selection criteria expect the requirement on ${E_{\mathrm {T}}^{\text {miss}}}$ applied. The signal cross section times branching fraction is set to 1 fb. The total MC background is normalized to the integral of the data.
png pdf	Figure 3: Distribution of the missing transverse energy of the events passing all selection criteria including the requirement that ${m_{\gamma \gamma }}$ be within [120,130] GeV. The signal cross section times branching fraction is set to 1 fb. The total MC background is normalized to the integral of the data.
png	Figure 4: Fit to the diphoton spectra in the low-$ {E_{\mathrm {T}}^{\text {miss}}}$ control region in data used to evaluate $\alpha $. The fit function used is a power-law with one free parameter. The uncertainties on the background shapes associated with the statistical uncertainties of the fit are shown by the 1 and 2$\sigma $ bands.
png pdf	Figure 5: Expected and observed limits at 95% CL on the signal cross section. Also plotted is the theoretical cross section with the assumption that $g_Z =$ 0.8. Details on this model are listed in Section 3.1 and in Ref. [6].

Tables
png pdf	Table 1: Maximum allowable value of each variable used in barrel and endcap photon identification [22]. The ${p_{\mathrm {T}}}$ used in these formulas is expressed in GeV.
png pdf	Table 2: Signal acceptance times efficiency in the signal region.

Summary

A search for dark matter produced in association with a Higgs boson is presented. The analysis is based on 2.3 fb$^{-1}$ of pp collision collected by the CMS experiment in 2015 at $\sqrt{s} =$ 13 TeV. This analysis focuses on a 2HDM simplified model in which a DM-Higgs interaction occurs from the decay of a Z' into a pseudoscalar $\mathrm{A}^0$ and a Higgs boson. We study the case where the Higgs boson decays to two photons. After passing trigger requirements, events are selected if they contain two photon candidates passing kinematic requirements on the $p_{\mathrm{T}}/m_{\gamma\gamma}$ of the two photons, $E_{\mathrm{T}}^{\text{miss}}$ and $p_{\mathrm{T}\gamma\gamma}$ obtained with an optimization study on the benchmark model. A lepton veto is applied to reduce the electroweak background together with topological requirements to avoid events with highly energetic objects collinear with the $E_{\mathrm{T}}^{\text{miss}}$ for which the $E_{\mathrm{T}}^{\text{miss}}$ could simply arise from a misreconstruction of the jet itself. Data driven techniques are applied to estimate the non-resonant background contributions. With the optimized selection, limits on the signal cross section are calculated. The projected upper limits on the cross section are approximately 2 to 5 fb for the $m_{\mathrm{Z}'}$ range considered. Observed limits are consistent with the expectation at the one-sigma level.

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