T. Kono (ATLAS) - Latest Results on Searches for Dark Matter Candidates with the ATLAS Detector at the LHC
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T. Kono (ATLAS) - Latest Results on Searches for Dark Matter Candidates with the ATLAS Detector at the LHC

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The SEENET-MTP Workshop JW2011 ...

The SEENET-MTP Workshop JW2011
Scientific and Human Legacy of Julius Wess
27-28 August 2011, Donji Milanovac, Serbia

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  • 1. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 1 LATEST RESULTS ON SEARCHES FOR DARK MATTER CANDIDATES WITH THE ATLAS EXPERIMENT AT THE LHC Takanori Kono (University of Hamburg/DESY) BW2011 Workshop, Serbia 28.08 – 01.09, 2011
  • 2. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 2Outline• Standard model and supersymmetry• LHC and ATLAS• SUSY searches in ATLAS • 0-lepton + missing transverse energy (w/wo b-tag) • 1-lepton/2-lepton + missing transverse energy • 2 photon + missing transverse energy • Long-lived particle search • Medium-lived particles with displaced vertex R-parity violating • eμ resonance scenarios• Conclusion
  • 3. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 3 Standard Model of particle physics• Standard Model (SM) is a beautiful theory which describes nature with great precision• Quarks, leptons and force-carrying particles• Electroweak symmetry breaking (EMSB) is essential to describe observed particle masses and interactions • Masses of W/Z bosons • Coupling between W/Z and fermions • Higgs field drives EWSBUnanswered questions in SM• 3 generation structure• Particle mass hierarchy and mixing• Matter-antimatter asymmetry• Stability of the Higgs mass• What is dark matter? (evidence from cosmology)
  • 4. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 4Extensions of the SM• Many extensions to the SM have been proposed • Fourth generation • New symmetry • Extra-dimensional models • …..• Supersymmetry (SUSY) • SUSY provides an elegant solution to the hierarchy problem by introducing a super-partner to every SM particle (fermion – boson) • Provides a natural dark matter candidate • Unification of gauge couplings• If SUSY is accessible, new particles are expected to be produced copiously at the LHC • Production of gluinos and squarks and their decays
  • 5. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 5 Supersymmetry (SUSY)• SUSY • Introduces a superpartner to each SM particle which differs ½ in spin • SUSY must be a broken symmetry • Different symmetry breaking mechanism leads to different phenomenologies• Minimal Supersymmetric SM (MSSM) • Minimal extension of the SM • 124 free parameters• mSUGRA (5 parameters) m0 : common scalar mass at the GUTscale m1/ 2 : common fermion mass at the GUTscale A0 : trilinear coupling Most experimental results are tan  : sign of SUSY Higgs potential parameter interpreted in the context of sign  : sign of SUSY Higgs potential parameter mSUGRA
  • 6. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 6 Large Hadron Collider (LHC)2011 running• Proton-proton collision at the center- of-mass energy of 7 TeV• 50 ns bunch spacing• Peak luminosity : 2.37×1033 cm-2s-1• Delivered luminosity : >2.5 fb1• Average pileup: ~8 collisions/bunch • 2 general-purpose experiments (ATLAS, CMS) • Experiments dedicated for specific physics (ALICE, LHCb, TOTEM, LHCf)
  • 7. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 7 ATLAS experiment Calorimeter • Large acceptance and hermiticity • LAr : EM calorimeter • Tile: Fe/Scintillator tile • High granularity readout and excellent resolutionInner Detector• Pixel (pixel detector)• SCT (silicon strip detector)• TRT (transition radiation tracker)Muon spectrometer Magnet system• MDT, CSC : precise momentum measurement • 2 T solenoid• RPC, TGC : trigger chambers • 0.5 T toroid
  • 8. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 8 Physics at the LHCσ (proton-proton) Total inelastic pp collision  Minimum bias events QCD jet production including heavy flavors W/Z boson production top pair production Higgs, SUSY and other new physics searches With >2 fb-1 of data we are already probing this region
  • 9. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 9 Searches for SUSY at the LHCCharacteristic SUSY production and decay• In R-parity is conserved, SUSY particles are produced in pairs and the lightest SUSY particle (LSP) becomes stable • R=(-1)3(B-L)+2s • No direct observation of SUSY particles, but only SM particles are reconstructed directly • No mass peaks • LSP escapes the detector undetected producing a missing transverse energy (ETmiss) • Evidence of SUSY is done by establishing an excess of events in some region of phase space • Crucial to understand the contribution from SM processes
  • 10. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 10 Overview of SUSY searches in ATLASChannel Signature Integrated lumi.0-leptons+jets+ETmiss ≥2-4 jets, large ETmiss, meff 1.04 fb-11-leptons+jets+ETmiss ≥3 jets, e or μ, large ETmiss, meff 1.04 fb-12-leptons+ETmiss Exactly 2 leptons, large ETmiss 1.04 fb-10-leptons+bjets+ETmiss ≥3 jets, large ETmiss, meff 0.83 fb-1Diphoton+ETmiss γγ+ETmiss+X 1.07 fb-1Long-lived particle Slowly moving particle 37 pb-1eμ resonance eμ+X 0.87 fb-1Medium-lived particle μ+displaced vertex 35 pb-1 n• Interpretation of search results in the context of meff   pT  ET i miss • mSUGRA/CMSSM model i 1 • M0, M1/2, A0, tanβ, sgn(μ) • Simplified model
  • 11. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 11 L=1.04 fb-1 ETmiss + jets + 0-lepton channelFive signal regions are definedto maximize sensitivities forvarious production mechanisms ~~ ~    ~ q q  q10 q10 ~~ ~   ~ g q  qq10 q10 ~~ ~   ~ g g  qq 0 qq 0 1 1Background sourcesW+jets Leptons reconstructed as jetsZ/γ+jets γ/leptons as jets, Z+jetsνν+jetsTop Hadronic tau decay All background estimationsQCD Mis-measurement of jets or ν from heavy are data-driven flavor decay
  • 12. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 12 L=1.04 fb-1 Entries / 100 GeV Search in 0-lepton : Results Entries / 150 GeV Entries / 100 GeV 105 Data 2011 ( s = 7 TeV) 105 Data 2011 ( s = 7 TeV) Data 2011 ( s = 7 TeV) 105 ∫ L dt ~ 1.04 fb -1 SM Total QCD multijet W+jets 104 ∫ L dt ~ 1.04 fb -1 SM Total QCD multijet W+jets 104 ∫ L dt ~ 1.04 fb -1 SM Total QCD multijet W+jets Three Jet Channel Z+jets Four Jet Channel Z+jets Four Jet High Mass Z+jets 104 Channel tt and single top tt and single top 103 tt and single top SM + SU(660,240,0,10) 103 SM + SU(660,240,0,10) SM + SU(660,240,0,10) 103 ATLAS Preliminary ATLAS Preliminary 102 ATLAS Preliminary 102 102 10 10 10 1 1 1 10-1 DATA / MC DATA / MC 2.50 500 1000 1500 2000 2500 3000 2.50 500 1000 1500 2000 2500 3000 DATA / MC 2 2.50 500 1000 1500 2000 2500 3000 2 1.5 2 1.5 1 1.5 1 0.5 1 0.5 0 0.5 0 -0.5 0 -0.5 0 500 1000 1500 2000 2500 3000 -0.5 0 500 1000 1500 2000 2500 3000 0 500 1000 1500 2000 2500 3000 meff [GeV] meff [GeV] meff [GeV] ≥2 jets ≥3 jets ≥4 jets ≥4 jets ≥4 jets meff>500 GeV meff>1000 GeV high massTotal 62.3±4.3±9.2 55.0±3.8±7.3 984±39±145 33.4±2.9±6.3 13.2±1.9±2.6expectedData 58 59 1118 40 18Limit on 22 (fb) 25 (fb) 429 (fb) 27 (fb) 17 (fb)fiducial crosssection No excess was observed
  • 13. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 13 ETmiss + jets + 0-lepton : InterpretationPhenomenological MSSM (squark-gluino) grids mSUGRA/CMSSM, A0=0, tanβ=10, μ>0• Masses from 100 GeV to 2 TeV, m(χ01)=0• Limits unchanged if LSP mass raised to 200 GeV Squark-gluino-neutralino model (m = 0 GeV) MSUGRA/CMSSM: tanβ = 10, A = 0, μ>0 LSP 0 2000 squark mass [GeV] m1/2 [GeV] ATLAS Preliminary ATLAS Preliminary 0 lepton 2011 combined 0 lepton 2011 combined L int = 1.04 fb -1, s=7 TeV CLs observed 95% C.L. limit LEP2 ∼ 1 ± CLs observed 95% C.L. limit χ CLs median expected limit 1750 600 ~, ~, tanβ=3, μ <0, 2.1 fb-1 CLs median expected limit D0 g q exp. limit 68%, 99% CL CDF ~,~, tanβ=5, μ <0, 2 fb-1 gq Reference point exp. limit 68%, 99% CL Theoretically excluded 2010 data PCL 95% C.L. limit 1500 2010 data PCL 95% C.L. limit int 500 L = 1.04 fb-1, s=7 TeV ~ (140 q 1250 ~ (1200) g Tevatron, Run I 0) σSUSY = 0.01 pb CDF, Run II D0, Run II 1000 400 ~ (1000) g ~ (10 q σSUSY = 0.1 pb 750 00) 300 σSUSY = 1 pb ~ (800) g 500 ~ (6 q σSUSY = 10 pb 00 200 ~ (600) g ) 250 LEP2 ~ q 0 0 250 500 750 1000 1250 1500 1750 2000 500 1000 1500 2000 2500 3000 3500 gluino mass [GeV] m0 [GeV] Exclude at 95 % C.L. Exclude at 95 % C.L. mg  800 GeV, mq  850 GeV ~ ~ if mg  mq , masses 980 GeV ~ ~ if mg  mq , masses 1075 GeV ~ ~
  • 14. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 14 ETmiss + bjets + 0-lepton L=0.83 fb-1 • Analysis similar to jets+ channel but requires at least one b-jet • Sensitive to 3rd generation squarks in R-parity conserving scenarios • Define 4 signal regions to maximize sensitivity 1 b-tag 105 Events/ 50 GeV ATLAS Preliminary 0-lepton,3 jets3J-A 3J-B 3J-C 3J-D >= 1 bjet 104 ∫ -1 L dt = 0.83 fb , s = 7 TeV Data 2011 SM Total top production 3 10 W production Z production QCD production ~ 700 GeV, ~ 380 GeV 102≥1 b-tag ≥1 b-tag ≥2 b-tag ≥2 b-tag g b 10meff>500 GeV meff>700 GeV meff>500 GeV meff>700 GeV 1 10-1 data / MC 2.5 Pheonomenological MSSM 2 1.5 1 0.5 mg  mb  m 0 ~ ~ ~ 00 200 400 600 800 1000 1200 1400 meff [GeV] 1 1 ~ ~ ~ ~ g  b1b, b1  b10 (100 %) 105 2 b-tag Events/ 50 GeV ATLAS Preliminary 0-lepton,3 jets >= 2 bjets 104 ∫ L dt = 0.83 fb ,-1 s = 7 TeV Data 2011 m 0  60 GeV SM Total top production 103 W production ~ Z production QCD production 1 102 ~ 700 GeV, ~ 380 GeV g b General simplified model 10 1 • Squarks assumed to be heavy 10-1 • Gluino-gluino pair production data / MC 2.5 2 1.5 ~ ~ g  bb10 (3 - body decay) 1 0.5 00 200 400 600 800 1000 1200 1400 meff [GeV]
  • 15. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 15 ETmiss + bjets : Results L=0.83 fb-1 Signal region 3J-A 3J-B 3J-C 3J-D Total expected 356+103-92 70+24-22 79+28-25 13+5.6-5.2 Data 361 63 76 12 σ (pb) 95 % C.L. 0.288 0.061 0.078 0.017 upper limitPhenomenological MSSM Simplified model (gluinobbχ01) 1000 ~-~ + ~ -~ production, ~ → b+∼0 g g b1 b1 b1 χ 1 ∫ L dt = 0.83 fb , -1 s=7 TeV ~-~ production, ~→ 2b+∼0, m(~) >> m(~) gg g χ q 1 g ∫ L dt = 0.83 fb , -1 s=7 TeV mb [GeV] mχ0 [GeV] Maximum cross section [pb](CLs) CLs observed limit ATLAS Preliminary CLs expected limit 800 Observed 95% CL s limit 900 68% and 99% C.L. 107.7 102 CLs expected limits 1 1 700 ~ 0 lepton, 3 jets ∼ ATLAS (35 pb-1) Expected CLs limit 90.6 38.4 b-jet analyses 800 87.9 20.5 13.7 ∼0 ~ m(χ ) = 60 GeV, m( 1,2)>>m(~) 600 q g ATLAS Preliminary 93.4 30.5 10.0 6.6 1 en 10 700 dd 82.4 19.0 14.0 6.3 3.8 ~~ CDF b1b1 2.65 fb-1 500 0 lepton, 3 jets rbi ∼ fo 0 60.0 13.1 8.3 7.1 1.2 1.6 b-jet analyses b+χ 1 600 ~~ ~ →2 80.6 19.0 4.5 4.7 2.2 0.9 1.1 D0 b1b1 5.2 fb-1 400 g 52.6 8.1 4.4 4.1 3.4 2.0 0.7 0.8 1 e n 500 ~ CDF ~~, → b1b 2.5 fb-1 gg idd 114.7 20.7 5.1 2.2 2.1 1.0 0.5 0.6 0.6 rb 300 ~ b fo 68.2 26.0 21.0 3.5 1.3 1.0 0.7 0.3 0.4 0.5 400 ~g→b 275.0 34.4 11.8 6.3 1.7 1.0 0.7 0.4 0.3 0.3 0.5 10-1 200 136.9 97.5 17.0 5.2 2.6 1.0 0.4 0.3 0.2 0.2 0.3 0.4 Reference point 89.5 31.8 8.9 3.4 1.2 0.7 0.4 0.2 0.2 0.2 0.3 0.4 300 100 79.9 19.9 6.5 1.5 0.8 0.6 0.4 0.2 0.2 0.2 0.2 0.4 102.0 15.2 2.9 1.5 0.7 0.4 0.3 0.2 0.2 0.2 0.2 0.4 10-2 200 0 100 200 300 400 500 600 700 800 900 1000 200 300 400 500 600 700 800 mg [GeV] ~ mg [GeV] ~Gluino masses below 720 GeV excluded Gluino masses between 200-660 GeVfor sbottom masses below 600 GeV excluded up to LSP mass of 160 GeV
  • 16. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 16 ETmiss + jets + 1-lepton L=1.04 fb-1 107 Events / 10 GeV ATLAS Preliminary Data 2011 ( s=7 TeV) Data under/over flow = 0/0 Standard ModelEvent selection 106 ∫L dt = 1.04 fb -1 multijets (data estimate) W+jets Z+jets 105 Electron Channel tt• 1 lepton (electron or muon) 104 single top Dibosons MSUGRA m 0=500 m1/2=330 • electron pT>25 GeV or muon pT>20 GeV miss Δφ(ET ,jet )>0.2 103 1,2,3 • Veto second lepton if 102 • electron pT>20 GeV or 10 1 • muon pT>10 GeV 10-1• 3 jets (>60, >25, >25 GeV) Data / SM 2• ∆φ(jet, ETmiss)> 0.2 for all jets 1 0• ETmiss >125 GeV, ETmiss >0.25*Meff 0 100 200 300 400 500 600 Emiss [GeV] T• Meff>500 GeV Events / 10 GeV ATLAS Preliminary Data 2011 ( s=7 TeV) Data under/over flow = 0/1 106 Standard Model 105 ∫L dt = 1.04 fb -1 multijets (data estimate) W+jets4 signal regions Z+jets Muon Channel tt single top 104 Dibosons• Loose 3 jets MSUGRA m 0=500 m1/2=330 miss Δφ(E ,jet )>0.2 103 T 1,2,3• Tight 3 jets 102• Loose 4 jets 10 1• Tight 4 jets 10-1 Data / SM 2Main background: W+jets 1 0 0 100 200 300 400 500 600 Emiss [GeV] T
  • 17. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 17 ETmiss + 1-lepton : Interpretation L=1.04 fb-1 MSUGRA/CMSSM: tanβ = 10, A = 0, μ>0 0 500 m1/2 [GeV]mSUGRA ATLAS int L = 1.04 fb-1, s=7 TeV Observed CLS 95% CL 450 Preliminary 1 lepton, combination Expected CLS• Gluino mass<875 GeV excluded 400 ~ q (900 GeV) ~ g (900 GeV) Expected CLS ± 1σ ∼ ± LEP2 χ 1 350 ~ ~ g (800 GeV) D0 ~, ~, tanβ=3, μ<0, 2.1 fb-1 g q q (700 GeV)Simplified model 300 CDF ~, ~, tanβ=5, μ<0, 2 fb-1 g q• LSP masses below 200 GeV are 250 ~ q (500 GeV) ~ g (600 GeV) excluded for gluino mass below 200 ~ g (500 GeV) ~ q (400 GeV) 150 600 GeV (for x>1/2) ~ g (400 GeV)    200 400 600 800 1000 1200 1400 x  m   m 0 / mq  m 0 ~ ~ ~ ~ m0 [GeV] 1 1 1 800 mLSP [GeV] Cross Section Excluded at 95% CL [pb] 1-Step Decay, x=1/2 ATLAS Preliminary ∼∼ ~~→qqqqWWχ0χ0 bRPV MSUGRA: tanβ = 10, A = 0, μ>0 700 gg 1 1 102 0 500 m1/2 [GeV] Combination ATLAS int L = 1.04 fb-1, s=7 TeV Observed CLS 95% CL 600 Lint = 1.04 fb-1, s=7 TeV Preliminary 1 muon, ≥ 4 jets, tight SR Expected CLS 450 Expected CLS ± 1σ Observed 95% CL 500 Expected ~ q (900 GeV) 10 400 Expected ±1σ 400 ~ g (900 GeV) 350 300 ~ 1 q (700 GeV) 200 300 ~ g (700 GeV) cτ = 3 mm cτ = 7 mm 100 250 cτ = 15 mm 10-1 100 150 200 250 300 350 400 450 500 550 600 0 m0 [GeV] 300 400 500 600 700 800 mgluino [GeV]Constraints on Bilinear R-parity violating model
  • 18. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 18 ETmiss + 2-lepton• Several leptons may be produced in the cascade decay of SUSY particles• 2-lepton channel is sensitive to the pair production of weak gauginos ~ ~ ~ ~ ~ ~ ~ ~ 1  20 , 1 10 , 1 1 ,  20  20 ~ ~ (a)  i0  l   j 1 lepton on one leg ~ ~ (b)    l  0 i j ~ ~ (c)  i0  l  l   0 j 2 leptons on one leg ~ ~ (d)    l  l    (identical flavor, i j opposite-sign pair) Search for ETmiss+2-leptons events with • Same-sign leptons (SS) • Opposite-sign leptons (OS) • Opposite-sign, identical flavor (OS, identical flavor)
  • 19. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 19 ETmiss + 2-lepton L=1.04 fb-1 SS OS pT  25, 20 GeV eEvents / 20 GeV Entries / 10 GeV ∫L dt ~ 1.04 fb ATLAS Preliminary ∫L dt ~ 1.04 fb -1 Data 2011 ( s = 7 TeV) 104 -1 Data overflow: 1590 di-lepton [SS] Data 2011 ( s = 7 TeV) 10 6 di-lepton [OS] SM Background Data overflow: 30 SM Background Fake leptons Z+jets Fake Leptons 5 Drell-Yan 10  3 ATLAS Preliminary pT  20, 10 GeV 10 Z+jets tt Dibosons Drell-Yan 104 Single top 2 Diboson 10 3 10 10 102 10 1 1 -1 10 10-1 20 3 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 Data/MC Data/MC 1.5 2 1 1 0 0.5 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 Mll [GeV] Mll[GeV]Events / 20 GeV Entries / 10 GeV ∫L dt ~ 1.04 fb ATLAS Preliminary ∫L dt ~ 1.04 fb -1 Data 2011 ( s = 7 TeV) 104 -1 di-lepton [SS] Data 2011 ( s = 7 TeV) 10 6 di-lepton [OS] SM Background Data overflow: 0 Data overflow: 0 SM Background Fake leptons Z+jets Fake Leptons 5 Drell-Yan 3 10 10 Z+jets tt ATLAS Preliminary Dibosons Drell-Yan 104 Single top 2 Diboson 10 3 10 10 102 10 1 1 -1 -1 10 10 30 50 100 150 200 250 30 50 100 150 200 250 300 350 400 450 500 Data/MC Data/MC 2 2 1 1 0 0 0 50 100 150 200 250 0 50 100 150 200 250 300 350 400 450 500 Emiss [GeV] T Emiss[GeV] T
  • 20. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 20 2-lepton channel results SS, OSSignal regions (SR)• SS SR1 : ETmiss>100 GeV• SS SR2 : ETmiss>80 GeV, jet pT>50,50 GeV• OS SR1 : ETmiss>250 GeV• OS SR2 : ETmiss>220 GeV, jet pT>80,40,40 GeV• OS SR3 : ETmiss>100 GeV, jet pT>100,70,70,70 GeV Limits on A×ε×σ
  • 21. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 21 Flavor subtraction, OS 240 Events / 20 GeV Events / 20 GeV ATLAS Preliminary Data 2011 ( s = 7 TeV) SF ATLAS Preliminary Data 2011 ( s = 7 TeV) SF 250 220 Data 2011 ( s = 7 TeV) DF Data 2011 ( s = 7 TeV) DF 200 SM Background SF SM Background DF 200 180 SM Background SF SM Background DF Observed value of S Fake leptons (SF) Z+jets (SF) 160 140 Fake leptons (SF) Z+jets (SF) Sobs=-3.1 150 Drell-Yan (SF) Drell-Yan (SF) tt (SF) 120 tt (SF) Diboson (SF) 100 Diboson (SF) 100 single top (SF) 80 single top (SF) With pseudo-experiments ∫ L dt ~ 1.04 fb ∫ L dt ~ 1.04 fb 60 Ss<4.9 (95 % CL) -1 -1 50 40 20 0 0Data/MC SF Data/MC SF 2 2 3 ×10 Experiments 20 1 1 ATLAS Preliminary S=0.4±4.6 18 0 0 0 50 100 150 200 250 300 >300 0 50 100 150 200 250 300 >300 16 Mll [GeV] Mll [GeV] 14 12 10       8 N     Ne      6 Ne e S   4    1  1   e 2 1  1    2 1  1   e 1     2 0 -20 -15 -10 -5 0 5 10 15 20 Spseudo-obs electron, muon trigger efficiency ratio of electron and muon reconstruction efficiencies and acceptances
  • 22. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 22 L=1.07 fb-1 Diphoton + ETmiss Events / 5 GeV 104 Data 2011 ( s = 7 TeV) • In gauge-mediated SUSY breaking QCD 103 W→eν +jets, W →eν +γ , t t →eν +X Z→ν ν +γ γ , W→lν +γ γ (GMSB) models, the LSP is the gravitino GGM m~ / mχ = 800 / 400 GeV g ∼ 102 ~ SPS8 Λ = 140 TeV   G 0 1 UED 1/R = 1200 GeV 10 ATLAS Preliminary ∫ Ldt = 1.07 fb -1 • Signature: 2γ + ETmiss +X 1 10-1• Generalized model of gauge- 10-2 0 50 100 150 200 250 300 350 400 450 500 mediated SUSY breaking (GGM) ET miss [GeV] with a bino-like lightest neutralino GGM: bino-like neutralino, tanβ = 2, cτNLSP < 0.1 mm 1200 (95 % C.L.) mg [GeV] ATLAS Expected CL s Limit 1100 • σ<0.02 – 0.04 pb ATLAS Observed CL s Limit ~ 1000 ± 1σ • m(gluino)>776 GeV 900 ATLAS Observed CL s Limit (36 pb-1)• Universal Extra Dimension (UED) 800 (95 % C.L.) 700 ∫ Ldt = 1.07 fb-1 • σ<0.015 – 0.027 pb s = 7 TeV 600 • 1/R>1224 GeV on the UED 500 ~ NLSP g ATLAS Preliminary compactification radius 400 200 400 600 800 1000 1200 m∼ [GeV] χ
  • 23. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 23 Massive long-lived particle (LLP) search• SUSY particles produced at the LHC may have a long lifetime • The particle can travel >10 meters • This may happen when the mass difference between the LSP is very small• Long-lived slepton • For example, stau as the NLSP • Behaves like a heavy muon in the detector• Long-lived squarks/gluinos • Hadronizes with normal quarks or gluons  R-hadrons Measured β from real muons Search strategy • Look for a slowly traveling particle reaching the muon spectrometer • Measure the velocity (β)  m=p/(βγ) • Timing resolution : 1-2 ns with the Tile calorimeter, 3-4 ns with the muon spectrometers
  • 24. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 24LLP search resultsReconstructed mass distributions for• slepton search• R-hadron searchConsistent with BG expectation
  • 25. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 25 R-parity violating SUSY
  • 26. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 26 Heavy long-/medium-lived particles L=33 pb-1• Heavy stable particles are predicted in a number of theories including SUSY • Models with stau as the LSP • R-hadron (long-lived gluinos or squarks after hadronization) • SUGRA with R-parity violationR-parity violating interaction Event selection • Muon pT>45 GeV (also used for the trigger) • Displaced vertex (DV) using tracks with d0>2 mm • DV fit quality : χ2<5 • Fiducial region of the pixel detector • |zDV|<300 mm, |rDV|<180 mm • Distance from the primary vertex > 4 mm • Ntrk,DV≥4 • mDV>10 GeV • Veto vertices in high density material regions
  • 27. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 27 Results on medium-lived particle search 50 Vertex mass [GeV]• No signal observed 45 Signal Region• Set limit on the cross section 40 35 • σ・acceptance・ε<0.09 pb @ 95 % C.L. 30 ATLAS preliminary for m(squark)=150 GeV and 100 % 25 ∫Ldt = 33 pb -1 branching ratio 20 15 10 5 0 2 4 6 8 10 12 14 16 18 20 Number of tracks in vertex Distributions of mDV and Ntrk Cross-section x B.F. [pb] 102 ATLAS 103 preliminaryVertices / bin Number of vertices data 2010 data 2010 102 QCD MC W,Z MC ATLAS preliminary 102 QCD MC W,Z MC 10 ∫Ldt = 33 pb -1 ttbar MC ∫ Ldt = 33 pb -1 ttbar MC 10 10 1 ATLAS preliminary 700 GeV ~, 494 GeV ∼ 0 q χ 1 1 1 ∫ Ldt = 33 pb -1 10-1 700 GeV ~, 108 GeV ∼ q χ 0 1 1.5 TeV ~, 494 GeV ∼ 0 q χ 1 150 GeV ~, 108 GeV ∼ 0 10-1 10-1 -2 q χ 10 1 0 1 2 3 4 5 6 7 8 9 10 2 4 6 8 10 12 Vertex mass [GeV] Number of tracks in vertex 1 10 102 103 cτ [mm]
  • 28. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 28 Search for e-μ resonance• Look for particles decaying into opposite-sign different flavor lepton • R-parity violating SUSY • Extra Z’ gauge boson with lepton flavor violation• High mass e-μ pair: clear signal with small SM contribution 1 Lagrangian term : ijk Li L j Ek  ijk Li Q j Dk  2 L / Q : lepton/quark SU(2) double superfield E / D : charged lepton/down - type quark singlet
  • 29. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 29 Limits from e-μ resonance search L=0.87 fb-1 ATLAS Preliminary ’ Theory λ 311 = 0.10, λ 312 = 0.05 (a) ’ Theory λ 311 = 0.01, λ 312 = 0.01 s = 7 TeV 95% CL σ × BR(eμ)[fb] 104 Observed Limit ∫ Ldt = 0.87 fb -1 Expected Limit Expected Limit ±1 σ Expected Limit ±2 σ 3 10 ATLAS 2010 limit 102 10 1 100 200 300 400 500 600 700 800 900 1000 m∼ [GeV] ν τ λ311Limit on the cross section * BR ’ (b) ATLAS Preliminary   pp      BR    e  ~ ~ 10-1 ∫ Ldt = 0.87 fb -1 10-2 λ312 = 0.07σ≤130 fb for mντ=100 GeV λ312 = 0.05 λ312 = 0.01 λ312 = 0.07(ATLAS 2010 data) ≤11 fb for mντ=1 TeV 10-3 100 200 300 400 500 600 λ312 = 0.07(D0@Tevatron) 700 800 900 1000 m∼ [GeV] ν τ
  • 30. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 30Summary of ATLAS SUSY limits
  • 31. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 31Conclusion• LHC is operating wonderfully • Already L>2 fb-1 collected by ATLAS• ATLAS is exploring new physics in the TeV scale • Good understanding of the detector and reconstruction to estimate the contribution from SM processes • Latest results use ~1 fb-1 of data• No excess was observed over SM expectation so far • Gluino/squark masses are excluded up to ~1 TeV for certain SUSY mass hierarchies • More data will be collected in 2011/2012. Searches in higher mass region and also in wider SUSY parameter space • Possibly go to higher energy (14 TeV) after 2013• All results are accessible at • https://twiki.cern.ch/twiki/bin/view/AtlasPublic • https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicRe sults
  • 32. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 32 Backup slides
  • 33. 28.08.2011 - 01.09.2011 BW2011 Workshop, Serbia 33Summary of ATLAS limits (exotics)