Weak Production SUSY Search In LHC Bai Yu IHEP, Beijing 2014-01-23 , @USTC

Outline Introduction to super symmetry(SUSY) SUSY at LHC Search in ATLAS 2-lepton(2L) Search 3-lepton (3L) Search 2-tau (hadronic decay) Search in CMS 3-lepton search 4-lepton search (in GMSB scenario) Summary

SUSY : A Brief Introduction Standard Model SUSY Partners An Maximum Extension to Poincare Symmetry A solution to the hierarchy problem Provide candidate to Dark Matter A clue of unification incorporate the gravity SM particles and their super partner

SUSY Breaking and Parameters Why SUSY is broken? NO SUSY PARTNER FOUND YET! MSSM-124 : Minimum SUSY extension to SM Most of parameter are from symmetry broken Not all the parameter space is physical Usually simplified for experment intepretation SUSY Breaking Mechanism: GMSB (gauge mediated) SUGRA (gravity mediated) AMSB (anomaly mediated) …. Gaugino Chargino: Mixed wino and charged higgsino , , Neutralino: Mixed bino and netrual , , , , R-Parity Conserved Process LSP : netrual massive susuy particle

SUSY Symmetry in TeV Scale “Naturalness ” requires SUSY breaking parameter not higher than a few TeV Need to probe in electro-weak scale We can do it here! Over 20/fb 8-TeV collision data collected in 2012

SUSY in Weak Production Might be the dominant SUSY production in LHC if gluino and squark are heavy Interaction Vertex : Process : Decay process determined by mass spectrum of gaugino and slepton Enssential to Analyis Strategy Final state : 2-3 leptons , large Missing transverse energy(MET), low jet activity

Electro-Weak SUSY Search in ATLAS Experiment with 2L(e/mu) Final States ATLAS-CONF-2013-049

Scenarios and Signal Regions 4 scenarios explored Slepton pair production Mass of gaugions(except LSP) set to 2.5 GeV, slepton at least 30 GeV hevier than LSP, varying between 90-370 GeV Chargino to slepton Mass set the mean of LSP and chargino mass. Chargino mass in 100-450 GeV Chargino to W Chargino mass at least 80 GeV greater than LSP mass, scan LSP mass from 0 GeV GMSB NLSP chargino 1 mass set to be 110 GeV, most sensitive signal grid

Background Estimation Main background Same flavor ZV, ttbar, WW Different flavor ttbar, WW Strategy Define control region for each signal region For each SR, Implementing simultaneous fit to these CR and SR(Standard method in ATLAS SUSY WG)

Results from the Simultaneous Fit SRWWa SRWWb SRWWc e+e- in SR mt2 90 μ+μ- in SR mt2 90 eμ in SR mt2 90 Data and MC agrees reasonably Fit results used as inputs for exclusion limit

Interpretation No discovery Right handed sleptonn pair Left handed sleptonn pair Mass degenerate No discovery Set exclusion limit for the first 2 scenario Set upper limit for the last 2 scenario

Electro-Weak SUSY Search in ATLAS Experiment with at Least 2 hadronically decaying taus in Final States ATLAS-CONF-2013-028

Scenarios and Signal Regions C1C1 production C1N2 production Direct stau production Simplified model Minimum particle contents necessary Parametrized directly in terms of the sparticle masses C1 and N2 are mass-degenerate stau and tau sneutrino are mass-degenerate SUSY particle other than stau/stau neutrino, C1, N1 and N2 are assumed to be heavy pMSSM model Squark and gluino are heavy tan β = 50(large) M1 = 50 GeV M2 and μ vary between 100-500 GeV Ligtest stau mass 95 GeV

Background Estimation in Tau Channel ABCD method Backgrounds Fake tau backgrounds QCD and W+jets, estimated by Data Driven Method Z+jets, top, diboson estimated from MC(Directly or ABCD-like MC driven method) Two orthogonal variables: tau-id and MT2 Extrapolate from CR-A to SR Validate in other regions Good agreement between data and MC Simultaneous fit applied for both QCD-CR and SR SR OS-mt2 SR OS-mt2 nobjet

Interpretation Exclusion limit for C1N2 production Exclusion limit for C1C1 production Exclusion limit for pMSSM No discovery. 95% CL exclusion limit was set For C1C1 production, chargino mass are excluded up to 350 GeV for light neutralino mass For C1N2 production, charigno mass are excluded up to 300 (330) GeVwith neutralino mass 50(100) GeV For pMSSM, region with high M2(corresponding to stau production) are excluded

On-going Work on tau Analysis Aming publishment in 2014 New SR definition 5 signal regions defined now, including SR for direct stau production New background estimation Use large statistic W+jets sample Define W control region, implemented in simultaneous fit Try to be approved in SUSY WG no later than end of February

Electro-Weak SUSY Search in ATLAS Experiment with 3L(e/mu) Final States ATLAS-CONF-2013-035

Scenarios and Signal Regions Same C1 and N2 decay brach ratio for each flavor Slepton and lepton sneutrino mass degenerate, set as mean value of C1 mass and N1 mass Slepton and sneutrino assumed to be very heavy Branch ratio decay to higgs set to be 0 SR Definition

Background Estimation Reducible Backgrounds ttbar, Z+jets, W+jets, single top Include fake leptons, Estimated by Matrix Method Irreducible Backgrounds WZ, tri-boson, ttW/Z Control region for background WZ selected, simultaneous fit applied to both WZ-CR and SR

Interpretation Decay via sleptons Decay via gauge bosons Null results, exclusion limit set with context of simplified model C1N2 decay With assumption C1N2 decay via slepton, the C1 and N2 mass have been rejected up to 600 GeV for large mass difference with C1 With assumption C1N2 decay via gauge boson, , the C1 and N2 mass have been rejected up to 315 GeV for large mass difference with C1

Electro-Weak SUSY Search in CMS Experiment with 2L Final States

Scenarios and Analysis Strategy OS 2-lepton search (non-resonant), slepton pair production or chargino decay slepton SS 2-lepton search: One of the 3 lepton from C1N2 elude from detection OS Analysis strategy : fit the data with template SS Analysis strategy : directly from MC (with rejection to OSSF lepton pair) Flavor Democratic : C1 and N2 decay to different flavor slepton with same BR, τ-enriched : C1 decay to tau, N2 decay democratically τ -dominant : both C1 and N2 decay to tau

Result of Template Fit in OS Analysis Opposite flavor channel Same flavor channel Extrapolation from Low to High Region

Results of Background Estimation in SS Analysis Reasonable agreement between data and MC in MET distribution Results with/without 3rd lepton rejection listed, interpretation only use that with 3rd lepton veto

Interpretation-1, Flavor Dem

Intepretation-2, tau-enriched and tau dominant

Electro-Weak SUSY Search in CMS Experiment with 3L Final States Scenario much the same as that in ATLAS

Interpretation of 3L Analysis WZ + MET C1 pair production Slepton pair production

Summary EWK SUSY limit in ATLAS EWK SUSY Limit in CMS All the study give null results, exclusion or upper limit set in parameter space Need to continue probing with high energy

Thank you!