CMS-PAS-SUS-23-008

CMS-PAS-SUS-23-008
Search for dark matter produced in association with a pair of bottom quarks in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
2 April 2024

Abstract: A search for dark matter (DM) particles produced in association with bottom quarks is presented. The analysis uses proton-proton collision data at a center-of-mass energy of $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The search is performed in the final state with large missing transverse momentum and a pair of jets originated from bottom quarks. No significant excess of data is observed with respect to the standard model expectation. Limits are set on the DM production cross section in the context of two Higgs doublet models with an additional light pseudoscalar (2HDM+a). This is the first search at the LHC to probe DM produced in association with two nonresonant b quarks in 2HDM+a. Sensitivity to the parameter space with tan$ \beta \leq $ 15 is achieved, capitalizing on the enhancement of couplings between pseudoscalars and bottom quarks with $ \tan \beta $.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagram for the $ \mathrm{b}\overline{\mathrm{b}}+p_{\mathrm{T}}^\text{miss} $ process in the 2HDM+a model.
png pdf	Figure 2: Distributions of the generator-level $ p_{\mathrm{T}}^\text{miss} $ for different illustrative lighter pseudoscalar masses $ m_{\textrm{a}} $.
png pdf	Figure 3: QCD background contribution in the QCD CRs (black and pink dots) in the 2b category in 2017. The exponential is fitted in the range $ \textrm{min}(\Delta\phi(\textrm{jet, }{\vec p}_{\mathrm{T}}^{\,\text{miss}})) < $ 0.3, checked to perform well in the range 0.3 $ < \textrm{min}(\Delta\phi(\textrm{jet, }{\vec p}_{\mathrm{T}}^{\,\text{miss}})) < $ 0.5, and extrapolated to the SRs for $ \textrm{min}(\Delta\phi(\textrm{jet, }{\vec p}_{\mathrm{T}}^{\,\text{miss}})) > $ 0.5.
png pdf	Figure 4: Observed and predicted $ p_{\mathrm{T}}^\text{miss} $ or recoil distributions in the 1b category, in the SR and CRs. The uncertainty band includes all sources of uncertainty, both systematic and statistical.
png pdf	Figure 5: Observed and predicted $ \cos\Theta^{*} $ distributions in the 2b category, in the SR and CRs. The uncertainty band includes all sources of uncertainty, both systematic and statistical.
png pdf	Figure 6: 95% CL upper limit on the signal strength modifyer of DM produced in association with a pair of b quarks for $ m_{\textrm{A}}= $ 600 GeV, $ \sin\theta= $ 0.7, $ m_{\chi}= $ 1 GeV, and $ \tan\beta= $ 35, for the combination of SR1 and SR2. The green and yellow bands show the $ \pm $ 1 and $ \pm $ 2 standard deviations from expected limits
png pdf	Figure 7: Left: 95% CL Upper limit on the signal strength in the $ m_{\textrm{a}}-\tan\beta $ plane. The shaded area above the curve is excluded. Right: Upper limit on the signal strength in the $ m_{\textrm{a}}-\sin\theta $ plane. The shaded area above the curve is excluded.
png pdf	Figure 7-a: Left: 95% CL Upper limit on the signal strength in the $ m_{\textrm{a}}-\tan\beta $ plane. The shaded area above the curve is excluded. Right: Upper limit on the signal strength in the $ m_{\textrm{a}}-\sin\theta $ plane. The shaded area above the curve is excluded.
png pdf	Figure 7-b: Left: 95% CL Upper limit on the signal strength in the $ m_{\textrm{a}}-\tan\beta $ plane. The shaded area above the curve is excluded. Right: Upper limit on the signal strength in the $ m_{\textrm{a}}-\sin\theta $ plane. The shaded area above the curve is excluded.

Tables
png pdf	Table 1: Preselection criteria applied to all the events entering the SRs and CRs.

Summary

A search for dark matter produced in association with a pair of bottom quarks is performed using data collected by the CMS detector in Run 2 and corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The analysis aims to capture the signal using two independent categories with different multiplicities of jets reconstructed as originating from a b quark. The results are interpreted in the framework of a simplified model, namely 2HDM+a. This search performs best in the high $ \tan\beta $ phase space, where the signal production cross section is enhanced. This provides a complementary search to constrain the 2HDM+a model parameter phase space in the region where other DM searches are less sensitive. The observed exclusion range on the DM particle mass is up to 260 GeV for $ \tan\beta= $ 35, $ \sin\theta= $ 0.7, and $ m_{\textrm{A}}= $ 600 GeV.

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