Adrien Renaud (LAL-Orsay IN2P3/CNRS and Université Paris-Sud) for the Atlas collaboration. Search for supersymmetry via resonant final states with the ATLAS detector HEP2012 – Valparaiso, Chile January 6, 2012 PRL (arXiv: ) EPJC (arXiv: ) EPJCL (arXiv: )

2 Overview 1) Introduction 2) RPV tau sneutrino search in the eμ final state 3) Scalar gluon search in the four jets final state 4) Conclusion

3 Susy via Resonances ?? MSSM: - particles with L or B numbers - renormalizable terms violate L or B Potential disaster: - much too fast proton decay R P conservation: - P R = (-1) 2S (-1) 3(B-L) - forbids L and B violating terms - P R = +1 (-1) for SM (SUSY) particles - LSP stable, in all cascade decays, DM No resonances --> look for an excess in SM tail

4 Susy via Resonances ?? Beyond MSSM with R P conservation: Extended supersymmetry: -- minimal ? new pheno ? flavor-violation ? dirac gauginos ? … -- new particles with P R = +1 --> resonances in R P conserved susy ! R P violated susy: -- B and L conservation ? neutrino masses and mixing ? … -- some of the couplings have to be small --> stable proton --> Scalar-gluon search --> R P V tau sneutrino search

5 Introduction to RPV Sneutrino search Search for RPV sneutrino with lepton number violation decay: - eμ clean signature with low SM background - previous limit from low energy tau branching ratio: λ’ 311 < 0.11 and λ 312 < 0.07 for M slepton = M squark = 100 GeV λ’ 311 ≠ 0 and λ 312 ≠ 0

6 Event Selection Using L=1.07 fb -1 : 2011 data Single lepton (e, μ) trigger (100±1%) Electron: -- p T > 25 GeV -- |η| < 1.37 or 1.42 < |η| < isolated in EM calorimeter -- shower shape requirements Muon: -- p T > 25 GeV -- |η| < reconstructed in ID and MS -- isolated in the ID - Exactly one muon and one electron with opposite-sign charge - No requirements on #jets and E T miss Signal generated with HERWIG + JIMMY + NLO k-factor

7 Highest invariant mass (662 GeV) eμ event

8 Backgrounds Physics backgrounds (real leptons) -- Z/γ * ->tau,tau top pair single top WW, WZ, ZZ -- Estimated using MC corrected for data/MC differences Instrumental background (lepton faked by photon or jet) -- W/Z+γ estimated using MC -- SM multijet and W/Z+jets estimated using data-driven matrix method: 1) Define loose and tight lepton definitions 2) Apply on all events to get N TT,N TL,N LT,N LL 3) Determine efficiency (r) and fake rate (f) for a lepton that has passed the loose definition to also pass the tight definition 4) Solve the 4*4 matrix:

9 Data / Background Kolmogorov-Smirnov test probability: 56% Data consistent with absence of new physics Final observable:

10 Limits 95% CL: GeV TeV 95% CL: TeV for λ′ 311 = 0.10 and λ 312 = TeV for λ′ 311 = 0.11 and λ 312 = 0.07 Bayesian method (uniform prior for signal cross section ) : Best limits for: - M sneutrino > 270 GeV

11 Introduction to scalar-gluon search Non minimal realisations of SUSY: Extended SUSY: hybrid N=1/N=2 Extended R-Parity: MRSSM Sgluon = Scalar color-octet with SM-like P R Production: Decay: Wojciech Pair production Single production A 4-jets final state: Diff cross section from PL.B672,2009 implemented as external process to PYTHIA

12 Analysis strategy 4 jets p T > 0.55 * M sgluon ΔR jj < 1.6 | Cos(θ*)| < 0.5 |M1–M2|/(M1+M2) < Look for an excess in the (M1+M2)/2 distribution. Combinatory:Event selection: Using L=34 pb -1 : 2010 data Multijet trigger: 4 jets p T > 55 GeV --> Low threshold = low mass ~same amount recorded in 2011 for this threshold Scalar production at rest suppressed by factor β -- > “ Slightly Boosted ” regime Minimize : | ΔR ij – 1 | + |ΔR kl - 1| Where ijkl are the 4 leading jets

13 Multijet Event

14 DATA-driven BGR estimation ABCD method: N A = N B * N C / N D Take shape of final observable in region B via a fit: JHEP09(2011)074 Only Simulation Background Background estimation Signal Background + Signal |M1–M2|/(M1+M2) |Cos(θ*)| CD B A %

15 ABCD results (1/2) Prediction within 1-2 sigma stat Reasonably good fit Good agreement A/B Agreement between data and background prediction:

16 ABCD results (2/2) Systematic uncertainties

17 Limits Profile likelihood ratio and CL S approach : Likelihood is the Product of : -- Poisson for each bin (shape analysis) -- Gaussian for each systematic uncertainty Contamination in ABCD method. Correlations between systematic. Excluded 95% CL : GeV GeV 95% CL: Sgluon : GeV (except 5 GeV around 140 GeV) L = 34 pb -1 :

18 Conclusion Search for tau sneutrino decaying to eμ: -- limits for sneutrino mass vs coupling in R P V (0.1 – 2. TeV) Search for pair-produced sgluon decaying to four-jets: -- limits for low mass colored scalar (100 – 200 GeV) Other interpretations already available (LFV Z’, hypercolor). More to come with higher Luminosity, Energy, refined analysis Already 3 published papers Funny link between 2 analysis: - slightly modified analysis to search for R P V stops ! q q Λ’’ 313

19 Spare

20 The ATLAS detector

21 Jet reconstruction Jets : -- Anti-k t R= EM+JES calibration -- p T > 20 GeV && |η| < 2.8 JER JES

22 RPV sneutrino search E T miss not used in the analysis to make the search more generic

23 Other interpretations Z′ gauge bosons with lepton flavor violating (LFV) interactions --> Same analysis as for stau sneutrino Hypercolor model: Hyperpion, scalar color octet --> Same as analysis as sgluon

24 Data / MC (1/2) ALPGEN+HERWIG+JIMMY SM-multijet production after p T cut (4 jets p T >55 GeV -> M=100GeV) 1) 4 jets p T > 0.55 * M sgluon --> sliding cut 2) ΔR(jj) < 1.6

25 Data/MC (2/2) After p T cut and ΔR cuts After all cuts but cos(θ*) - Reasonably good description - Ratio compatible with 1 even without JES uncertainty - large MC stat uncertainty 3) |M1–M2|/(M1+M2) < ) |Cos(θ*)| < 0.5

26 Data / Background Good agreement with SM prediction