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Searches for Supersymmetry and Other New Physics at ATLAS

Dive into the latest findings on Supersymmetry and beyond at the ATLAS experiment. Analyzing limits, models, and implications of the newly discovered boson. Stay updated on SUSY searches and new particle physics phenomena.

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Searches for Supersymmetry and Other New Physics at ATLAS

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  1. Searches for Supersymmetry and Other New Physics at ATLAS Cigdem Issever University of Oxford Johns Hopkins 36th Workshop 16.10 -19.10.2012 Florence Z event with 25 vertices C. Issever, University of Oxford

  2. Comment to Search Result Selection in this Talk “What is the impact of the newly discovered boson on searches at the LHC?” Results not shown at ICHEP 8 TeV Results C. Issever, University of Oxford

  3. Supersymmetry • “Standard” SUSY (mSUGRA) limits are beyond 1 TeV • Now focusing on more general models • Minimal requirements for a weak-scale SUSY: • i.e. how to avoid fine-tuning? 1. 2. 3. 4. LLP L. Hall (LBL Workshop, 21-Oct11) C. Issever, University of Oxford

  4. SUSY: 1st and 2nd generation squarks / gluinos Trigger Pileup QCD Meff ATLAS-CONF-2012-109 2 – 6 jets • “Standard” SUSY search: 0-lepton + jets + Missing ET • highest branching ratios in • Main backgrounds: • leptonic W+jets/ttbar+jets, Zvv+jets, Multijets 8 TeV data! 12 Signal regions split in Tight (t) and Medium/Loose (l, m) C. Issever, University of Oxford

  5. Meff for 5 jets D5j tight Meff [GeV] C. Issever, University of Oxford

  6. Limits on MSUGRA/CMSSM C4jt D5jt E6jt Very Constrained Model (105 parameters → 5) C. Issever, University of Oxford

  7. Limits on Phenomenological MSSM (only strong production of gluinos and first- and second-generation squarks, with direct decays to jets and neutralinos ) C4jt B3jt A2jt 3 sparticles: gluino, squark 1rst,2nd gene., LSP For m(squarks)=m(gluinos), exclude below 1.5 TeV C. Issever, University of Oxford

  8. Event with two τh’s, two jets and large MET pT(jet)=466 GeV pT(jet)=131 GeV pT(τ)=129 GeV pT(τ)=22 GeV MET = 452 GeV C. Issever, University of Oxford

  9. Search for SUSY in ≥1τh+MET+Jets most stringent test of GMSB in large part of parameter space • minimal gauge-mediated supersymmetry-breaking • Limits set on SUSY breaking scale Λ and tan β 2τ Sensitive to m(gluino) up to 1.3 TeV C. Issever, University of Oxford

  10. 3rd Generation Squarks • Small fine-tuning →m(stop) ~ m(top) • Look stop and sbottom: → Direct production → Through gluino decays C. Issever, University of Oxford

  11. Direct Sbottom Production ATLAS-CONF-2012-106 • 2 b-jets + Missing ET • Use “contransverse mass”: Sensitive to m(sbottom) < 500 GeV (as the direct stop) C. Issever, University of Oxford

  12. Direct Stop C. Issever, University of Oxford

  13. Direct Stop M.-H. Genest C. Issever, University of Oxford

  14. Direct Stop • Final results at √s=7 TeV, 5 fb-1 m(stop)<m(top) m(stop)>m(top) C. Issever, University of Oxford

  15. Gluino mediated Stop Production 1207.4686,ATLAS-CONF-2012-104/105/108 • New results at √s=8 TeV, 5.8 fb-1 • 4 top in the final state • Most sensitive ttbar-killer signatures: • 3 b-jets, • 2 leptons Same Sign, • 0 lepton+6-9 jets • 3lepton+jets+MET to be (a bit more) sensitive near the diagonal C. Issever, University of Oxford

  16. Direct Gauginos (1) 1208.2884 • Final results at √s=7 TeV, 5 fb-1 for direct charginos production • Consider in leptonic decays • 2 leptons [e,mu] + MET + jet veto Sensitive also to direct slepton production (beyond LEP!) C. Issever, University of Oxford

  17. Direct Gauginos (2) 1208.3144 • Final results at √s=7 TeV, 5 fb-1 for associated production • Consider in leptonic decays • 3 lept. [e,mu] + MET+ Z-veto/Z-request and/or mT(l,v)>90 GeV C. Issever, University of Oxford

  18. R-Parity Violating SUSY in ≥ 4 leptons Small MET (m1/2,tanβ)-slice of MSUGRA/ CMSSM 1210.4457 New Simplified MSSM charged wino masses up to 540 GeV excluded m1/2 up to 820 GeV are excluded for 10 < tan β < 40 C. Issever, University of Oxford

  19. RPV & Long-Lived particles • Three main mechanism: • R-Parity violation: • τ ~ to λ2λ’2λ’’2 → Displaced vertex if λ2λ’2λ’’2 < 10-7 • Mass degeneration • Low π emitted, kinked track or R-Hadrons • Weak coupling to Gravitino (Cgrav>>1) in GMSB • Stable sleptons Stable MetaStable C. Issever, University of Oxford

  20. RPV Displaced Vertex Search • Assume RPV with λ’2ij≠0 • heavy particle decay • multi-track vertex that contains a high pT muon btw O(mm) and O(10cm) from IP • dedicated tracking ATLAS-CONF-2012-113 expected bkg < 0.06 events, 0 observed C. Issever, University of Oxford

  21. SUSY Conclusions • No hints of SUSY … but search in every corner • 34 papers completed at √s=7 TeV with L= 1 - 2 - 4.7 fb-1 ! • Strong push on naturalness dedicated searches for L=2-4.7 fb-1 • Direct sbottom & stop • Gluino mediated stop/sbottom • Direct Gauginos [Also sensitive to direct slepton !] • New Long-Lived Particles, RPV & Beyond MSSM • 8 TeV programme well advanced • 4 new results with L=5.8fb-1 for inclusive searches • More to come in future…. C. Issever, University of Oxford

  22. SUSY Conclusions • ATLAS bites into weak scale SUSY between 100 GeV and 1 TeV Inclusive Natural SUSY LLP RPV C. Issever, University of Oxford All publications: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults

  23. Exotics Searches • Heavy resonances • Dileptons • Dijets • Ttbar • 4th gen quarks and vector-like quarks • Dark matter and extra dimension • Displaced Muonic Lepton Jets from Light Higgs C. Issever, University of Oxford

  24. Highest Dimuon Invariant Mass Event; 8 TeV pT=289 GeV minv = 1258 GeV pT=274 GeV C. Issever, University of Oxford

  25. Heavy Resonances Search: 8 TeV Dileptons ATLAS-CONF-2012-129 • Models: • Randall-Sundrum ED → Kaluza-Klein graviton • GUT-inspired theories, Little Higgs → heavy gauge boson(s) • Technicolor → narrow technihadrons • Leptons reaching pT ~ 1 TeV NEW C. Issever, University of Oxford

  26. Heavy Resonances Search: 8 TeV Dileptons ATLAS-CONF-2012-129 • No deviation from SM found → set limits 8 TeV 7 TeV m(SSM Z') > 2.49 TeV at 95% CL C. Issever, University of Oxford

  27. Dijet Event Display with minv = 3.62 TeV C. Issever, University of Oxford

  28. Heavy Resonance Search: 8 TeV Dijets • Strong gravity, excited quarks, contact interaction • Look for resonance above phenomenological fit of data: Probing quark structure ~ 4 TeV ATLAS-CONF-2012-088 C. Issever, University of Oxford

  29. Heavy Resonance Search: 8 TeV Dijets Gaussian resonance limits: mean mass, mG, and 3 σG Excited quark limit: m > 3.66 TeV at 95% CL C. Issever, University of Oxford

  30. Search for Heavy Resonance: Dijet Angular Models and Limits: Quark contact interaction (quark compositeness) Λ>7.6 TeV (7.7 TeV) Quantum Blackholes MD>4.1 TeV (4.2 TeV) n=6 arXiv:1210.1718 NEW C. Issever, University of Oxford

  31. Boosted Top Event Candidate with mttbar=2.5 TeV C. Issever, University of Oxford

  32. Heavy Resonances Search: Ttbar ATLAS-CONF-2012-136 NEW • Lepton+jets channel • Models: e.g. bulk-RS (esp. KK gluons) and Leptophobic Z’ • Large Branching Ratio to top-antitop • Taking full advantage of boosted techniques • Combining resolved and boosted reconstructions C. Issever, University of Oxford

  33. Heavy Resonances Search: Ttbar • Event Selection S. Fleischmann, Top2012 C. Issever, University of Oxford

  34. Heavy Resonances Search: Ttbar • Improve efficiency at high t-tbar mass with: • Lepton “mini-isolation”: • cone shrinks at high momentum • Trigger: • use Fat Jet trigger (anti-kt jet R=1.0, pT>240 GeV) • Better efficiency than lepton trigger at high mass • Combine resolved and boosted selection: • If event is reconstructed by both methods, use the boosted one (better mass resolution) C. Issever, University of Oxford

  35. Heavy Resonances Search: Ttbar Boosted selection C. Issever, University of Oxford

  36. Heavy Resonances Search: Ttbar • mtt̄ resolved + boosted in e+jets and μ+jets C. Issever, University of Oxford

  37. Heavy Resonances Search: Ttbar m(Z’) > 1.7 TeV @95% CL Γ/m(Z’) = 1.2% m(gKK) > 1.9 TeV @95% CL Γ/m(gKK) = 15% C. Issever, University of Oxford

  38. 4th Generation and Heavy Quarks C. Issever, University of Oxford

  39. 4th Generation and Heavy Quarks • 4th generation would significantly enhance Higgs production cross section • (almost) excluded by observed Higgs cross-section • t't' → WbWb (100%): just like t-tbar but heavier • b’b’ →WtWt (100%): just like ttbar but messier • Beyond 4th generation: Vector-Like Quarks in Composite Higgs theories • More diverse phenomenology • T': Decays to Wb, Zt, Ht • B': Decays to Wt, Zb, Hb • Loose constraints on CKM4 → decays to light quarks possible! C. Issever, University of Oxford

  40. Search for Heavy Quarks • Up-type heavy quark: t't' → WbWb • l + MET + 4 jets (l=e,μ) + b-tagging • Reconstruct boosted had. W decays m(t')>656GeV at 95% CL (exp. 638GeV) Vector-Like Quark interpretation: setting limits on branching ratios to Wb, tH, tZ C. Issever, University of Oxford

  41. Vector-like Quarks Coupling to Light Generations ATLAS-CONF-2012-137 • Mixing to first generations is not excluded • Benchmark model: degenerate VLQ doublets (U2/3 ,Y2/3 ,D-1/3 ,X5/3 ) • Single Production • e and μ channel NEW m(D-1/3)>1120GeV, m(X5/3)>1420GeV, m(U2/3)>1080GeV (not shown) C. Issever, University of Oxford

  42. Exotic Same-Sign Dilepton Signatures: b', T5/3 2 isolated same-sign leptons (e or μ) MET > 40 GeV ≥2 jets (≥1 b-tagged jet) large overall transverse momentum HT > 550 GeV NEW ATLAS-CONF-2012-130 4 events observed expected background of 5.6±1.7 C. Issever, University of Oxford

  43. Exotic Same-Sign Dilepton Signatures: b', T5/3 ATLAS-CONF-2012-130 m(b’/T5/3)> 0.67 (0.64) TeV at 95% confidence level, when produced in pairs C. Issever, University of Oxford

  44. Inclusive Same-Sign Dilepton Search 1210.4538 NEW • Model independent approach • Limit presented in terms of fiducial cross-section limit • σfidis (almost) model-independent • Can turn σfid into σtotal with generator-level information only • Caveat: not exactly model-independent → must be conservative 95% CL upper limit on yield (given Nobs and Nbkg) Reconstruction and Selection efficiency Within acceptance C. Issever, University of Oxford

  45. Inclusive Same-Sign Dilepton Search 1210.4538 • Particle-level definition of acceptance: • upper limits between 1.7 fb and 64 fb depending on the dilepton mass and flavour combination. • Used to set limits on doubly charged Higgs • submitted EPJC NEW C. Issever, University of Oxford

  46. Doubly Charged Higgs Limits M(H++/--) > 409 GeV C. Issever, University of Oxford

  47. Mono Jet Event Display C. Issever, University of Oxford

  48. Search for Dark Matter and Extra Dimensions arXiv:1209.4625 arXiv:1210.4491v1 Mono jet Mono photon Analyses are not optimized for benchmark models C. Issever, University of Oxford

  49. Mono jet & Mono Photon Limits on Extra Dimensions Mono jet Mono photon C. Issever, University of Oxford

  50. Limits on Dark Matter (DM) • Effective theory with only 2 parameters • M* : characterize interaction strength of the interactions with SM particles • mχ: mass of dark matter candidate • Pair production of DM: • Events with MET,recoiling against additional hadronic radiation Effective interactions coupling DM to SM quarks or gluons C. Issever, University of Oxford

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