CMS-PAS-EXO-16-014

CMS-PAS-EXO-16-014
Search for dark matter and large extra dimensions in the $\gamma + E_{\mathrm{T}}^{\text{miss}}$ final state in pp collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
June 2016

Abstract: We present searches for dark matter pair-production and for graviton production predicted by the ADD large extra dimension model in a final state with a photon and missing transverse energy in pp collisions at $\sqrt{s}=$ 13 TeV. Data taken by the CMS experiment in 2015 corresponding to an integrated luminosity of 2.3 fb $^{-1}$ is analyzed. We find no deviation from the Standard Model prediction for this final state, and achieve an extension of the current limits on parameter space.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The photon ${E_{\mathrm {T}}}$ and ${E_{\mathrm {T}}}^{\text{miss}}$ distribution for the candidate sample, compared with estimated contributions from SM backgrounds and background uncertainty includes statistical and systematic error. The last bin includes the overflow. The bottom panel shows the ratio of data and SM background predictions, where the uncertainty includes both the statistical and systematic error.
png pdf	Figure 1-a: The photon ${E_{\mathrm {T}}}$ distribution for the candidate sample, compared with estimated contributions from SM backgrounds and background uncertainty includes statistical and systematic error. The last bin includes the overflow. The bottom panel shows the ratio of data and SM background predictions, where the uncertainty includes both the statistical and systematic error.
png pdf	Figure 1-b: The ${E_{\mathrm {T}}}^{\text{miss}}$ distribution for the candidate sample, compared with estimated contributions from SM backgrounds and background uncertainty includes statistical and systematic error. The last bin includes the overflow. The bottom panel shows the ratio of data and SM background predictions, where the uncertainty includes both the statistical and systematic error.
png pdf	Figure 2: 95% CL upper limits on $\mu = \sigma /\sigma _{Th}$ in the $m_{DM}$ - $M_{med}$ plane for vector and axial-vector mediator, assuming $g_{q}$ =0.25 and $g_{\chi }$ =1.The solid red and black curves are the expected and observed exclusion contours. The dotted black contours around the observed limit and the dotted red contours around the expected limit represent the one standard deviation theoretical uncertainties in the cross section and the combination of the statistical and experimental systematic uncertainties, respectively.
png pdf	Figure 2-a: 95% CL upper limits on $\mu = \sigma /\sigma _{Th}$ in the $m_{DM}$ - $M_{med}$ plane for a vector mediator, assuming $g_{q}$ =0.25 and $g_{\chi }$ =1.The solid red and black curves are the expected and observed exclusion contours. The dotted black contours around the observed limit and the dotted red contours around the expected limit represent the one standard deviation theoretical uncertainties in the cross section and the combination of the statistical and experimental systematic uncertainties, respectively.
png pdf	Figure 2-b: 95% CL upper limits on $\mu = \sigma /\sigma _{Th}$ in the $m_{DM}$ - $M_{med}$ plane for an axial-vector mediator, assuming $g_{q}$ =0.25 and $g_{\chi }$ =1.The solid red and black curves are the expected and observed exclusion contours. The dotted black contours around the observed limit and the dotted red contours around the expected limit represent the one standard deviation theoretical uncertainties in the cross section and the combination of the statistical and experimental systematic uncertainties, respectively.
png pdf	Figure 3: The 90% CL exclusion limits on the $\chi$ -nucleon scattering cross section in a simplified model of dark matter production involving a vector and axial-vector operator as a function of the dark matter mass $m_{\chi }$ .
png pdf	Figure 3-a: The 90% CL exclusion limits on the $\chi$ -nucleon scattering cross section in a simplified model of dark matter production involving a vector operator as a function of the dark matter mass $m_{\chi }$ .
png pdf	Figure 3-b: The 90% CL exclusion limits on the $\chi$ -nucleon scattering cross section in a simplified model of dark matter production involving an axial-vector operator as a function of the dark matter mass $m_{\chi }$ .
png pdf	Figure 4: (a) The 95% CL observed and expected lower limits on $\Lambda$ for a dimension-7 operator EFT model with a contact interaction of type $\gamma \gamma \chi \overline {\chi }$ as a function of dark matter mass $m_{\chi }$ .
png pdf	Figure 5: The 95% CL upper limits on the LO ADD cross sections as a function of $M_{D}$ for $n$ =3.
png pdf	Figure 6: Limits on $M_{D}$ as a function of $n$ , compared to LO results from similar searches at the Tevatron, LEP, and CMS Run 1.

Tables
png pdf	Table 1: Summary of estimated backgrounds and observed total number of candidates.
png pdf	Table 2: Summary of systematic unceratinties for different background sources.
png pdf	Table 3: The 95% CL observed(expected) limits on the cross section as a function of $M_{D}$ and $n$ .
png pdf	Table 4: 95% CL observed and expected limits on $M_{D}$ as a function of $n$ .

Summary

Proton-proton collision events containing a photon and missing transverse momentum have been investigated to search for new phenomena. In the

$\sqrt{s} =$ 13 TeV data set corresponding to 2.3 fb

$^{-1}$ of integrated luminosity, no deviations from the standard model predictions are observed. Upper limit of 10.7 fb on the cross section is set at the 95% confidence level for events with a monophoton final state with photon

$p_{\mathrm{T}} >$ 175 GeV and

$E_{\mathrm{T}}^{\text{miss}} >$ 170 GeV. Upper limits are obtained on dark matter production cross sections and effective Planck scale in the ADD large extra dimension models at 95% confidence level. For the simplified DM model considered, the search excludes mediator masses of up to 600 GeV for massless dark matter. For an effective field theory model with a photon-dark matter contact interaction, values for the suppression scale up to 542 GeV are excluded. For the large extra dimension models, an effective Planck scale of up to 2.35 TeV is excluded.

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