CMS-PAS-SUS-17-009

CMS-PAS-SUS-17-009
Search for selectrons and smuons at $\sqrt{s}= $ 13 TeV
CMS Collaboration
December 2017

Abstract: A search for direct production of the supersymmetric partners of electrons and muons is presented in final states with two opposite-charge, same-flavor leptons (electrons and muons), little hadronic activity, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ of proton-proton collisions at $ \sqrt{s}= $ 13 TeV collected with the CMS detector at the LHC in 2016. The analysis uses the $M_\text{T2}$ variable which generalizes the transverse mass for systems with two invisible objects, and exhibits an endpoint for standard model backgrounds containing a W boson. The observed yields are consistent with the expectations from the standard model, and the results are interpreted in the context of simplified models of supersymmetry, resulting in observed (expected) limits at the 95% confidence level on the left-handed slepton mass of up to 400 (450) GeV and on the right-handed slepton mass of up to 290 (330) GeV for massless LSP, improving the existing limits by approximately 150 (200) GeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 790 (2019) 005. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Diagram for slepton pair production with direct decays into leptons and the lightest neutralino.
png pdf	Figure 2: Top: Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ [GeV], for SM background predictions (coloured histograms) and data (black points) for events in the signal region. Bottom : Ratio of data to SM prediction, with the filled band representing the total systematic uncertainty.
png pdf	Figure 3: Cross section upper limit and exclusion contours at 95% CL for the direct slepton production as a function of the $\tilde{\chi}^0_1$ and $\tilde{\ell}$ masses, assuming the production of both left- and right-handed sleptons of two flavors (top), or production of only left- (bottom left) or right-handed (bottom right) sleptons of two flavors. The region under the thick red dotted (black solid) line is excluded by the expected (observed) limit. The thin red dotted curves indicate the regions containing 95% of the distribution of limits expected under the background-only hypothesis. The thin solid black curves show the change in the observed limit due to variation of the signal cross sections within their theoretical uncertainties.
png pdf	Figure 3-a: Cross section upper limit and exclusion contours at 95% CL for the direct slepton production as a function of the $\tilde{\chi}^0_1$ and $\tilde{\ell}$ masses, assuming the production of both left- and right-handed sleptons of two flavors (top), or production of only left- (bottom left) or right-handed (bottom right) sleptons of two flavors. The region under the thick red dotted (black solid) line is excluded by the expected (observed) limit. The thin red dotted curves indicate the regions containing 95% of the distribution of limits expected under the background-only hypothesis. The thin solid black curves show the change in the observed limit due to variation of the signal cross sections within their theoretical uncertainties.
png pdf	Figure 3-b: Cross section upper limit and exclusion contours at 95% CL for the direct slepton production as a function of the $\tilde{\chi}^0_1$ and $\tilde{\ell}$ masses, assuming the production of both left- and right-handed sleptons of two flavors (top), or production of only left- (bottom left) or right-handed (bottom right) sleptons of two flavors. The region under the thick red dotted (black solid) line is excluded by the expected (observed) limit. The thin red dotted curves indicate the regions containing 95% of the distribution of limits expected under the background-only hypothesis. The thin solid black curves show the change in the observed limit due to variation of the signal cross sections within their theoretical uncertainties.
png pdf	Figure 3-c: Cross section upper limit and exclusion contours at 95% CL for the direct slepton production as a function of the $\tilde{\chi}^0_1$ and $\tilde{\ell}$ masses, assuming the production of both left- and right-handed sleptons of two flavors (top), or production of only left- (bottom left) or right-handed (bottom right) sleptons of two flavors. The region under the thick red dotted (black solid) line is excluded by the expected (observed) limit. The thin red dotted curves indicate the regions containing 95% of the distribution of limits expected under the background-only hypothesis. The thin solid black curves show the change in the observed limit due to variation of the signal cross sections within their theoretical uncertainties.

Tables
png pdf	Table 1: Summary of the slepton signal region selection.
png pdf	Table 2: The total predicted SM background processes and the observed number of same flavor events in data. The yields for several signal scenarios are provided as a reference. The uncertainties associated to the yields stem from statistical and systematic sources.
png pdf	Table 3: List of systematic uncertainties taken into account for the signal yields.

Summary

A search for direct slepton (selectron or smuon) production, in events with opposite-charge, same-flavor leptons, no jets and missing transverse momentum has been presented. The data used consist of a sample of pp collisions collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Observations are in agreement with SM expectation given statistical and systematic uncertainties. Exclusion limits are provided assuming right and left-handed, only left-handed and only right-handed sleptons production scenarios, of two flavors, and exclude slepton masses up to masses of 450, 400 and 280 GeV depending on the handedness assumed. Current results improve the previous 8 TeV exclusion limits by 150 GeV in slepton masses depending on the model.

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