CMS-SUS-15-012

CMS-SUS-15-012 ; CERN-EP-2016-269
Search for supersymmetry in events with photons and missing transverse energy in pp collisions at 13 TeV
CMS Collaboration
20 November 2016
Phys. Lett. B 769 (2017) 391
Abstract: The results of a search for new physics in final states with photons and missing transverse energy are reported. The study is based on a sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV with the CMS detector in 2015, corresponding to an integrated luminosity of 2.3 fb$^{-1}$. Final states with two photons and significant missing transverse energy are used to search for supersymmetric particles in models of supersymmetry (SUSY) with general gauge-mediated (GGM) supersymmetry breaking. No excess is observed with respect to the standard model expectation, and the results are used to set limits on gluino pair production and squark pair production in the GGM SUSY framework. Gluino masses below 1.65 TeV and squark masses below 1.37 TeV are excluded at a 95% confidence level.
Links: e-print arXiv:1611.06604 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Diagrams showing the production of signal events in the collision of two protons with four momenta ${P}_{1}$ and ${P}_{2}$. In gluino $ \tilde{ \gamma } $ pair production in the T5gg simplified model (left ), the gluino decays to an antiquark $ \mathrm{ \bar{q} } $ , quark $\mathrm{ q } $, and neutralino $\tilde{\chi}^0_1$ . In squark $\tilde{\mathrm{q}}$ pair production in the T6gg simplified model (right ), the squark decays to a quark and a neutralino. In both cases, the neutralino subsequently decays to a photon $\gamma$ and a gravitino $\tilde{G}$ . In the diagram on the right, we do not distinguish between squarks and antisquarks.
png pdf	Figure 1-a: Diagrams showing the production of signal events in the collision of two protons with four momenta ${P}_{1}$ and ${P}_{2}$. In gluino $ \tilde{ \gamma } $ pair production in the T5gg simplified model (left ), the gluino decays to an antiquark $ \mathrm{ \bar{q} } $ , quark $\mathrm{ q } $, and neutralino $\tilde{\chi}^0_1$ . In squark $\tilde{\mathrm{q}}$ pair production in the T6gg simplified model (right ), the squark decays to a quark and a neutralino. In both cases, the neutralino subsequently decays to a photon $\gamma$ and a gravitino $\tilde{G}$ . In the diagram on the right, we do not distinguish between squarks and antisquarks.
png pdf	Figure 1-b: Diagrams showing the production of signal events in the collision of two protons with four momenta ${P}_{1}$ and ${P}_{2}$. In gluino $ \tilde{ \gamma } $ pair production in the T5gg simplified model (left ), the gluino decays to an antiquark $ \mathrm{ \bar{q} } $ , quark $\mathrm{ q } $, and neutralino $\tilde{\chi}^0_1$ . In squark $\tilde{\mathrm{q}}$ pair production in the T6gg simplified model (right ), the squark decays to a quark and a neutralino. In both cases, the neutralino subsequently decays to a photon $\gamma$ and a gravitino $\tilde{G}$ . In the diagram on the right, we do not distinguish between squarks and antisquarks.
png pdf	Figure 2: The $ {E_{\mathrm {T}}^{\text {miss}}} $ distributions of the candidate $\gamma \gamma $, reweighted ee, and reweighted ff samples in the $ {E_{\mathrm {T}}^{\text {miss}}} < $ 100 GeV sideband.
png pdf	Figure 3: Measured $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in comparison with the background prediction. The four bins with $ {E_{\mathrm {T}}^{\text {miss}}} \geq $ 100 GeV constitute the signal region, and the $ {E_{\mathrm {T}}^{\text {miss}}} < $ 100 GeV bins serve mainly to normalize the background. The systematic uncertainty on the background prediction and the ratio of the data to the prediction are also shown. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} \geq $ 140 GeV, but for normalization by bin width, the bin is taken to be from $140 \leq {E_{\mathrm {T}}^{\text {miss}}} < $ 300 GeV. The distributions for two signal model points are overlaid for comparison.
png pdf	Figure 4: The 95% CL upper limits on the gluino (left ) and squark (right ) pair production cross sections as a function of neutralino versus gluino (squark) mass. The contours show the observed and median expected exclusions assuming the NLO+NLL cross sections, with their one standard deviation uncertainties. The limit curves terminate at the centers of the bins used to sample the cross section.
png pdf	Figure 4-a: The 95% CL upper limits on the gluino (left ) and squark (right ) pair production cross sections as a function of neutralino versus gluino (squark) mass. The contours show the observed and median expected exclusions assuming the NLO+NLL cross sections, with their one standard deviation uncertainties. The limit curves terminate at the centers of the bins used to sample the cross section.
png pdf	Figure 4-b: The 95% CL upper limits on the gluino (left ) and squark (right ) pair production cross sections as a function of neutralino versus gluino (squark) mass. The contours show the observed and median expected exclusions assuming the NLO+NLL cross sections, with their one standard deviation uncertainties. The limit curves terminate at the centers of the bins used to sample the cross section.

Tables
png pdf	Table 1: Systematic uncertainties from the QCD background estimation.
png pdf	Table 2: Numbers of expected and observed events in the signal region. The last row shows the total number of expected and observed events in the inclusive bin $ {E_{\mathrm {T}}^{\text {miss}}} \geq $ 100 GeV. The uncertainties include all of the systematic uncertainties described in Section {sec:SystUncert}.

Summary

A search is performed for supersymmetry with general gauge mediation in proton-proton collisions yielding events with two photons and large missing transverse energy. The data were collected at a center-of-mass energy of 13 TeV with the CMS detector in 2015, and correspond to an integrated luminosity of 2.3 fb$^{-1}$. Using background estimation methods based on control samples in data, limits are determined on the gluino and squark pair production cross sections, and those limits are used together with NLO+NLL cross section calculations to constrain the masses of gluinos, squarks, and neutralinos in simplified SUSY models with gauge mediated symmetry breaking. Gluino masses below 1.65 TeV and squark masses below 1.37 TeV are excluded at a 95% confidence level, which represents an improvement of approximately 300 GeV with respect to previous analyses performed at a center-of-mass energy of 8 TeV.

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