Searches for Gauge Mediated Supersymmetry Breaking scenarios at CMS

In this proceedings, the latest results from the CMS collaboration on searches for Supersymmetry with Gauge Mediated Supersymmetry Breaking (GMSB) in final states with photons and leptons are presented using pp collision data from the 7 and 8 TeV LHC run. The experimental results are interpreted in terms of weak as well as strong production of SUSY particles, followed by cascade decays to a Gravitino as lightest supersymmetric particle.


Introduction
The CMS experiment [1] at the Large Hadron Collider (LHC) has accumulated data corresponding to an integrated luminosity of around 5 fb −1 in 2011 and around 20 fb −1 .The discovery of a Brout-Englert-Higgs (BEH) boson has moved the phase of hunting for the Standard Model (SM) BEH boson to evaluating the consistency of this new particle with the SM expectation.Beyond the SM, it is predicted that there should be super-partner particles corresponding to the SM model particles in order to explain the unification of the forces, the stability of the BEH boson mass and the dark matter candidate.The CMS experiment has pursued the searches for the super-partner particles.The gauge mediated supersymmetry breaking (GMSB) model has been motivated at low energy scale where the required breaking of supersymmetry can occur in hidden sector by a mean of couping to the visible sector through the SM gauge interactions [2].In GMSB model, the large flavor-changing neutral currents (FCNC) is suppressed so we can avoid the large FCNC.In this model, the lightest super-symmetry (SUSY) particle is gravitino (< around 1 keV) and the lightest neuralino becomes the nextto-lightest-superpartner (NLSP).Therefore, the final signature is determined by the nature of the NLSP.The neutralino (NLSP) is the mixture of binos, winos and higgsinos.The CMS experiment has performed the searches sensitive to the bino-or wino-like neutralino scenario scanning the parameters of squark and gluino mass.
The bino-like neutralino will decay dominantly into a gravitino LSP and photon while decaying into a gravitino and a Z boson is suppressed [3].If the NLSP is wino-like neutralino, the neutral wino would decay dominantly into a gravitino and a Z boson.Since the splitting the charged and neutral wino becomes small, the charged wino becomes co-NLSP which decays directly to a gravitino LSP and a W boson. a e-mail: Tae.Jeong.Kim@cern.chIn this proceedings, the results of GMSB searches by the time LHCP2013 conference with the fraction of collected data which is correspond to an integrated luminosity of up to 9.2 fb −1 at 8 TeV as well as 5 fb −1 at 7 TeV will be presented.The searches with photon final states has been updated with 8 TeV [5].The review of 7 TeV results will contain the Gamma-Jet Balancing (JGB) method [7], Stealth SUSY searches with low MET [8] and searches for the charged NLSP with tau final states [10].The interpretation of di-lepton final states analysis in the context of GMSB will be also briefly mentioned [11].

Physics objects
The physics objects are reconstructed through a particleflow reconstruction algorithm which combines information from all sub-detectors and reconstruct all particles [9].Photons are selected using the ECAL cluster shape to be consistent with that expected from a photon.The energy in HCAL behind the photon shower should not exceed 5 % of the ECAL energy.Photons should be isolated to suppress hadronic jets.Since these selections are similar to electron selection, the candidates are rejected if there are hit patterns in the pixel detector consistent with a track from an electron.Tau is identified with the Hadrons plus strips (HPS) algorithm combining charged hadrons and calorimeter information in strips to take into account π 0 [12].Particle-flow jets are reconstructed using anti-kt algorithm with R=0.5.E miss T is the opposite direction of vector sum of reconstructed particles.
One topology is to select two photons (or more) with 40 (25) GeV, at least one jet and MET > 50 GeV.The other topology is at least one photon with 80 GeV, at least two jets and MET > 100 GeV.Single-photon topology is sensitive to bino-like neutralino scenario while di-photon topology is sensitive to wino-like neutralino scenario.Datadriven method is used to estimate the background contributions which are mainly from the QCD process where jets can fake photons and the electroweak (EWK) process where electrons can fake photons.The QCD process was determined using the control samples that are kinematically similar to the candidate sample.The electroweak process estimation was based on the electron misidentification rate as photon which is estimated using Z candidate decaying to ee or eγ in the mass window around Z peak. Figure 1 shows E miss T distribution comparing data with QCD and EWK background contributions.The example signal expectations for di-photon and single-photon topologies are also shown.There is no excess observed in this distribution.The limits are calculated in six distinct bins above MET requirement.
The 95 % confidence level cross section upper limits in squark-gluino mass plane are shown in Fig. 2. For binolike neutralino scenario, mass for squark and gluino below around 1.1 TeV has been excluded in di-photon selection.For wino-like neutralino scenario, mass below 850 GeV has been excluded in single-photon selection.This is a significant improvement with respect to 7 TeV result [4].As expected, it was observed that bino-like neutralino scenario is less sensitive in single-photon while wino-like neutralino scenario is less sensitive in di-photon selection.

Jet-gamma balance method
Jet-Gamma Balancing (JGB) method is a complementary analysis to sideband method described in Section 3.1.The analysis was performed at 7 TeV with 4.7 fb −1 data [7].There is Jet-Z Balancing (JZB) analysis which is based on the balance between Z and jets [6].In this analysis, Z is replaced with photon.In the JGB method, the requirement of the jet p T is much harder than the relevant of other method 3.For event selection, at least one photon with p T > 80 GeV and |η| < 1.442 is required.There should be also at least 3 jets with p T > 100 GeV.HT > 460 GeV is also required.
JGB variable is basically the MET information with the sign.In the case of cascade decay like SUSY, JGB tends to go higher.If photons from primary vertex are kinematically balanced like in the SM, JGB will close to 0. Figure 3 shows the simulated JGB distributions for the signal and the SM backgrounds.We do not observe any excess in this distribution so the limit was set for winolike scenario.JGB method has been shown to be have more sensitivity for wino-like scenario in Fig. 4. Greendashed line indicates 7 TeV analysis result with sideband method.

Stealth SUSY
As the parameter space available for high E miss T SUSY has been reduced by recent LHC results, interest in low E miss T alternatives has increased.The simplest Stealth SUSY model introduces additional hidden sector SUSY particle (LHSP) at the week scale.The LHSP (singlino) decays to the SM partner (singlet) and LSP (gravitino).Near mass degeneracy requires the LSP to carry out the small momentum which represents low MET.This analysis was performed at 7 TeV with 5 fb −1 data [8].The S T is defined as a scalar sum of E miss T , the energy of all photons and the energy of all jets in the event.The background is estimated directly from data by taking the shape of S T with 2 jets or 3 jets requirement assuming that the shape is similar in the signal region where 4 or >=5 jets are required.The data are in good agreement with the background expectation.The number of events with S T greater than a threshold is

4.04fb CMS preliminary
Figure 2. 95 % confidence level upper limit cross section exclusion contours in gluino-squark mass space for bino-like neutralino for di-lepton event topology (upper) and for wino-like scenario for single-lepton event topology (lower).
counted.The squark mass is excluded below 1430 GeV for bino-like neutralino as shown in Fig. 5.

Lepton final states 4.1 tau final state
The τ is produced via chargino and neutralinos in cascade of decays of colored SUSY particles.In about two third of cases, τ-leptons decay into a hadronic system with one, three or five charged mesons that can be accompanied by neutral pions and a τ-neutrino while one third of cases, τ-leptons decay into lighter leptons plus neutrinos.Therefore, events with τ-leptons in the presence of a high multiplicity of jets is an interesting probe for new physics.The searches with tau final states has been performed at 7 TeV with data corresponding to 5 fb τ is the charged NLSP which decays to a τ and a gravitino ( χ0 2 → ττ → ττ G).It it important to understand the τ mis-identification rate as the main contribution comes from one or more jets being mis-identified as a τ.The mis-identification rate was estimated from data and found to be 1-2 %.Each background contribution estimation is based on a well defined control region in data.
Di-tau final state result is interpreted in the context of GMSB assuming 100% branching ratio to ττ. Figure 6 18014-p.3

fb
1 SD Expected ± Figure 5. Cross section limit at 95 % confidence level as a function of squark mass.We show the observed limit, median expected limit with ± standard deviation.The predicted cross section from Stealth SUSY for bin-like neutralino scenario is also shown together.shows the exclusion limits for the simplified GMSB scenario as a function of gluino mass.The mass below 860 GeV is excluded at 95 % CL in this analysis.

multi-lepton final state
Di-and four-lepton and final state analyses are sensitive to SUSY particles in electroweak production and has been final state with assuming that the ratio of Higgs expectation values tanβ = 2 and fixed squark and gluino mass equal to 1 TeV. Figure 7 shows the cross section upper limit at 95 % confidence level The neutralino mass below 370 GeV is excluded in this model.

Conclusions
The CMS experiment has pursued the searches for the super-partner particles in the context of GMSB model with data collected at 7 TeV in 2011 corresponding to an integrated luminosity of 5 fb −1 and up to 9.2 fb −1 at 8 TeV in 2012.The results by the time LHCP2013 conference has been presented.The gluino and squark mass are excluded below around 1.1 TeV for bino-like NLSP scenario and around 850 GeV for wino-like NLSP scenario.Searches with low E miss T or lepton final states have been explored also in the context of GMSB.SUSY in GMSB like other SUSY models at the LHC is excluded more if it is strongly produced.It has yet been explored that much for EWK production.Updating with full data with lepton+photons, sensitive to EWK production, is foreseen in near future.More searches for the higgsino-like neutralino are also expected in the future.

Figure 1 .
Figure 1.E miss T distributions comparing data and QCD background estimation together with EWK background estimation for single-photon selection (upper) and di-photon selection (lower).Two GGM benchmark points with masses (m q/m q/m χ0 1 ) are shown together as examples.

Figure 3 .Figure 4 .
Figure 3.The JGB distribution in MC simulation for five different signals and the most important SM backgrounds with at least one photon and at least 3 jets.

Figure 6 .
Figure6.95 % confidence level cross section upper limit as a function of gluino mass in the GMSB scenario.

Figure 7 .
Figure 7. Interpretations of the analyses with di-lepton and fourlepton final states in the context of GMSB model.The observed and cross section upper limit at 95 % confidence level are shown as a function of neutralino mass (µ).The mass below 370 GeV is excluded.