Searching for Supersymmetry with the ATLAS Detector at the LHC for the ATLAS Collaboration CIPANP 2012 St. Petersburg, FL May 29 – June 2, 2012 Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz

CIPANP 2012: Searches for SUSY with ATLAS2 Bruce Schumm SUSY States SUSY posits a complete set of mirror states with S SUSY = |S SM – ½| Stabilize Higgs mass for GUTs Can provide reasonable dark-matter candidate Minimum of two Higgs doublets

CIPANP 2012: Searches for SUSY with ATLAS3 Bruce Schumm To avoid lepton/baryon number violation can require that “SUSYness” is conserved, i.e., preserves a multiplicative “parity” quantum number R such that R SM = +1; R SUSY = -1 If you can’t get rid of SUSYness, then the lightest super-symmetric particle (LSP) must be stable  dark matter, missing energy LSP is typically a “neutralino” (dark matter must be neutral); admixture of, known as “  1 0 ”, whose identity is not that relevant to phenomenology R Parity

CIPANP 2012: Searches for SUSY with ATLAS4 Bruce Schumm But we know that SUSY is broken… SUGRA: Local supersymmetry broken by supergravity interactions Phenomenology: LEP (usually  1 0 ) carries missing energy. GMSB: Explicit couplings to intermediate-scale (M EW <  < M GUT ) “messenger” gauge interactions mediate SUSY breaking. Phenomenology: Gravitino ( ) LSP; NLSP is  1 0 or. Content of  1 0 germane. AMSB: Higher-dimensional SUSY breaking communicated to 3+1 dimensions via “Weyl anomaly”. Phenomenology: LSP tends to be, with  1 +,  1 0 nearly degenerate. SUSY Breaking

CIPANP 2012: Searches for SUSY with ATLAS5 Bruce Schumm Classes of Models GUT unification: few parameters mSUGRA/CMSSM mGMSB e.g. mSUGRA: m 0 : GUT scale common scalar mass m ½ : GUT scale common gaugino mass tan  :Ratio of Higgs doublet VEVs A 0 :Common trilinear coupling Sgn(  ):Higgs mass term Minimal ModelsGeneral Models e.g. General Gauge Mediation (GGM)

CIPANP 2012: Searches for SUSY with ATLAS6 Bruce Schumm Strong vs. Electroweak Production SUSY Breaking Scale  (TeV)  probe high mass scale  steep mass dependence (~M -8 )  beam energy vs. luminosity  lower backgrounds; “scale chasing”  probe intermediate mass scales  higher backgrounds  benefit from high  L. dt mGMSB EW Strong STRONG COUPLING ELECTROWEAK COUPLING However: if colored states are decoupled, EW production will dominate Dedicated EW prod. analyses Pure-EW simplified models (new!) 5 fb -1 reach  s = 7 TeV

CIPANP 2012: Searches for SUSY with ATLAS7 Bruce Schumm The ATLAS Data Set A total of 4.7 fb -1 deemed to be adequate for SUSY analyses

CIPANP 2012: Searches for SUSY with ATLAS8 Bruce Schumm The ATLAS Detector Non-prompt tracks Photon conversions

CIPANP 2012: Searches for SUSY with ATLAS9 Bruce Schumm Synopsis of ATLAS SUSY Searches ATLAS public results: 18 signatures analyzed with 1 fb -1 or greater Interpretation (some signatures have more than one!) Minimal models: 4 mSUGRA, 1 mGMSB Simplified: 8 mSUGRA-like, 4 GMSB-like, 1 AMSB-like  Of these, three are EW production Six R-parity-violating or non-contextual  Generic scalar top exchange (lepton flavor violation)  pMSSM (19-parameter R-parity-conserving SUSY model)  SO(10) GUTS  e-  resonance  R hadrons  “BC1” R-parity-violating mSUGRA (no missing energy) Acceptance, efficiency, CLs confidence level for each analysis to be found at

CIPANP 2012: Searches for SUSY with ATLAS10 Bruce Schumm Basic signature: No leptons, several jets, E T miss Signature: E T miss + several jets (0 leptons) One of several “standard” signatures Six sub-channels (based on # jets) For each point in m 0, m 1/2 plane, choose channel that provides best a-priori sensitivity In this constrained model, exclude m gluino < ~850 GeV m squark < ~1400 GeV LSP (  0 ) undetectable  missing transverse energy E T miss 5 fb -1 ATLAS-CONF

CIPANP 2012: Searches for SUSY with ATLAS11 Bruce Schumm Lepton + jets + E T miss Simplified Model Same analysis “recast” in terms of a simplified model: Two generations of squarks Gluino octet Massless neutralino (generic) Everything else decoupled Colored sparticle limits similar to those of more constrained mSUGRA interpretion : M gluino > 940 GeV M squark > 1380 GeV In this case simplified model captures the generic dynamics of the more constrained model 5 fb -1 ATLAS-CONF

CIPANP 2012: Searches for SUSY with ATLAS12 Bruce Schumm mSUGRA processes often produce many jets e.g. Exploit with multi-jet analysis (6-9 jets) Jet trigger (no E T miss )  sensitive to low E T miss 5 fb -1 mSUGRA: M gluino < 850 GeV for large m 0 Simplified model only M gluino < 880 GeV for M  0 < 100 GeV ATLAS-CONF

CIPANP 2012: Searches for SUSY with ATLAS13 Bruce Schumm Additional discriminating variable: lepton-E T miss transverse mass New “soft-lepton” signal region for cascades with nearly-degenerate steps 1 Lepton + Jets + E T miss New Backgrounds estimate: N jet distributions of ttbar, W+jets control regions times signal-region transfer functions Fit for allowed signal assuming poisson probability of control-region projections When exploring specific model, use signal m eff distribution as additional constraint 5 fb -1 ATLAS-CONF

CIPANP 2012: Searches for SUSY with ATLAS14 Bruce Schumm “One-step” simplified model: production with 1 Lepton + Jets + E T miss Captures region of degeneracy 5 fb -1 3/4 jet channels soft lepton channel M gluino > 900 GeV for M  0 < 200 GeV mSUGRA/CMSSM: M squark, M gluino < 1200 GeV (for M squark = M gluino ) ATLAS-CONF

CIPANP 2012: Searches for SUSY with ATLAS15 Bruce Schumm GGM (General GMSB): Diphoton Search GGM and the Diphoton+E T miss Analysis Everything decoupled except Gluino octet Bino-like NLSP; B(  0   G) ~ 1  Require two photons, E T miss > 125 GeV Observe: 5 events Expect: 4.1  0.6 (syst.) events M gluino > 805 GeV for 50 < M  0 < M gluino 1 fb -1 Phys Lett. B 710 (2012), 519

CIPANP 2012: Searches for SUSY with ATLAS16 Bruce Schumm EW Production Few-hundred GeV gauginos, decoupled colored sparticles “natural”.  Multi-lepton signals  E T miss from and  1 0  Simplified model, only gauginos and sleptons light 3-Lepton (e,  ) + E T miss Search  Require one opposite-sign, same flavor pair (  0  l + l - )  E T miss > 50 GeV  Observe 127; expect 98  13  Limits reach GeV 2 fb -1 See Brokk Toggerson’s talk Saturday!! arXiv:

CIPANP 2012: Searches for SUSY with ATLAS17 Bruce Schumm In Search Of: Light 3 rd Generation Maximal mixing for 3 rd generation: naturally lightest sfermions See next talk by Katerina Pajchel !! Look for leptons, E T miss, b-tagged jets Stop generally more difficult than sbottom (softer jets)  Gluino mass limits can be compromised if stop dominates decay chain Scalar Bottom Gluino-mediated production Direct sbottom production 2 fb -1 arXiv:

CIPANP 2012: Searches for SUSY with ATLAS18 Bruce Schumm Light Stop 2 fb -1 Stop-mediated gluino decay  Softer gluino mass limits M gluino > 750 GeV for lower  1 0 mass Gluino-mediated stop production production with M gluino > 650 GeV; M stop > M gluino - M top Direct search (dilepton) imminent arXiv: arXiv:

CIPANP 2012: Searches for SUSY with ATLAS19 Bruce Schumm Disappearing Tracks!!! (+ E T miss ) AMSB: Chargino/Neutralino naturally quasi-degenerate  Long-lived states  Asymmetric decay  Disappearing tracks  TRT is critical component Disappearing track  few TRT hits Exclude 0.2 <   + < 90 ns for M  + < 90 GeV 5 fb -1 arXiv:

CIPANP 2012: Searches for SUSY with ATLAS20 Bruce Schumm NEW Lepton Flavor Violation in the e  Continuum R-Parity Violating (RPV) SUSY has terms in Lagrangian of form  RPV stop exchange  Search continuum (rather than for resonances)  1 e, 1 , opposite charge  0 jets, M eμ > 100 GeV, Δφ eμ > 3.0, E T miss < 25 GeV Observe: 39 events Expected: 44  6 events 2 fb -1 arXiv:

CIPANP 2012: Searches for SUSY with ATLAS21 Bruce Schumm Stau LSP: 4 Leptons “BC1” model mSUGRA + RPV while:  Preserving proton stability  Unstable stau LSP  Strong pair production 4 Lepton Analysis   4 isolated leptons  Moderate E T miss > 50 GeV Observed: 0 events Expected: 0.7  0.8 events For most favorable region, gluino mass limits approach 1.8 TeV 2 fb -1 M stau = 200 GeV M g = 1400 GeV ATLAS-CONF

CIPANP 2012: Searches for SUSY with ATLAS22 Bruce Schumm Compendium of ATLAS SUSY Search Limits

CIPANP 2012: Searches for SUSY with ATLAS23 Bruce Schumm Wrap-Up  Vibrant and expanding program of SUSY searches  No discoveries claimed  At 5 fb -1, colored sparticle limits above 1 TeV for some contexts  Non-colored partner limits in GeV range  Increased consideration of “simplified” models (especially EW)  Many analyses have yet to update to 5 fb -1 Speculation about 2012 reach (assume 20 fb -1 at  s = 8 TeV)  ~10% gain from increased  s   colored  M -8  ~10% gain from statistics (background-limited) Somewhat better for EW production (not on PDF tails) Ingenuity, “scale-chasing”  Guesstimate: ~25% increase in sensitive range (e.g GeV limits increase to 1250 GeV if SUSY doesn’t exist at that scale)

CIPANP 2012: Searches for SUSY with ATLAS24 Bruce Schumm Back-Up

CIPANP 2012: Searches for SUSY with ATLAS25 Bruce Schumm E T miss :Transverse momentum imbalance  LSP escapes detection (RP conserving SUSY) M eff, H T, etc: Transverse energy scale  Strong production can reach high mass scales  “Scale chasing”  X : Minimum  separation between E T miss vector and any object of type X.  LSP produced in intermediate-to-high mass decay  Separation between LSP and decay sibling  Jet backgrounds tend to have small separation (combinatoric) Heavy Flavor: “Natural” preference for 3 rd generation  b jets,  jets Favorite Discriminating Variables

CIPANP 2012: Searches for SUSY with ATLAS26 Bruce Schumm Maximal mixing for 3 rd generation: naturally lightest squark. Scalar Bottom Searches: bjets + E T miss (+ lepton)  2 bjets  E T miss > 130 GeV   jet > 0.4 Then look for kinematic endpoint via “contransverse mass”, defined as E T miss > 130 GeV Sbottom/gluino simplified plane:  Gluon-mediated production  Direct production  In all cases  Mass limits: GeV range 2 fb -1 Direct sbottom Gluino-mediated sbottom 0 LEPTON 1 LEPTON, 1 b jet

CIPANP 2012: Searches for SUSY with ATLAS27 Bruce Schumm Stop-mediated gluino decay  Lepton + bjet + E T miss (SR1-D, SR1-E from previous slide) Lepton signs need not be correlated  2 same-sign leptons, 4 jets, E T miss > 150 GeV Softer gluino mass limits: M gluino < 750 GeV for any  0 mass SUSY with Light(est) Scalar Top: Part I SUSY processes involving stop more challenging (softer jets) 2 fb -1

CIPANP 2012: Searches for SUSY with ATLAS28 Bruce Schumm Gluon-mediated Stop production production followed by As above: 2 same-sign leptons, 4 jets, ETmiss > 150 GeV; also > (100 GeV) 2 M gluino > 650 GeV; M stop > M gluino - M top SUSY with Light(est) Stop: Part II Direct Stop production GMSB: NLSP decay provides additional handle: Light higgsino  B(  1 0  ZG) ~ 1  Two jets, one b-tagged  Reconstructed Z  l + l -  E T miss > 50 (80) GeV for Signal Region A (B) Stop limits in the ~ 300 GeV range. 2 fb -1

CIPANP 2012: Searches for SUSY with ATLAS29 Bruce Schumm Stau LSP/NLSP Tau jets MET 2 fb 2 taus jets MET 2 fb Dilepton jet MET 1 fb 4 leptons + mET 2 fb (BC1) 2  + jets + E T miss Analysis  Exactly two hadronic   Two jets; (E T 1, E T 2 ) > (130,30) GeV  E T miss > 130 GeV  M eff > 700 GeV Efficiency 0.2 – 3%; lowest in non-stau NLSP region of course. Observed: 3 Expected: Probe strong scales  1000 GeV Similarly, 3 rd generation sleptons are naturally light mGMSB: Multiple messenger fields, high tan   NLSP Strong production  Busy decay chain 2 fb -1 M gluino = 1000 GeV M gluino = 600 GeV

CIPANP 2012: Searches for SUSY with ATLAS30 Bruce Schumm mGMSB “SPS8” trajectory has single free parameter  EW production (  +  0,  +  - ) Bino NLSP  Two photons; ETmiss > 125GeV Observed: 5 events Expected: 4.1  0.6  1.6   > 145 TeV at 95% CL 145 TeV UL on  implies M  10 > 205 GeV M  1+ > 390 GeV M gluino > 1170 GeV Although gluino scale is artificial… Two photons; E T miss > 125 GeV 1 fb -1

CIPANP 2012: Searches for SUSY with ATLAS31 Bruce Schumm Late-Breaking: Dilepton Light Stop Search  Two leptons  At least one jet  E T miss Include if approved!!

CIPANP 2012: Searches for SUSY with ATLAS32 Bruce Schumm Simplified Models D. Shih, J. Ruderman arXiv: Simplified/Pheno Models focus on small set of parameters “Pheno” models maintain basic flavor of underlying minimal model e.g. General Gauge Mediation (GGM) Bino NLSP from mGMSB Gluino octet only other light states All other states decoupled Yield general constraints on, e.g., gluino mass under assumption of bino/gravitino NLSP/LSP Also, non-contextual (ad- hoc) searches: light stop, generic resonances, etc.

CIPANP 2012: Searches for SUSY with ATLAS33 Bruce Schumm Back-Up