SUSY searches @ LHC Alan Barr University of Oxford A perspective UK HEP Forum 8th September 2011

Motivational arguments… 8 Sept 2011 Alan Barr, University of Oxford

Motivational arguments… 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford What sort of searches? Lepton(s) [taus] Proton Jet(s) [b-jets] Photon(s) Proton Invisible(s) Signature driven. “Measure what you can measure.” (Some signatures arguably better motivated…) 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford What sort of searches? Strongly interacting particles produced  Decay to WIMP candidate… [ Lepton(s) ] Proton Jet(s) Proton Invisible(s) 8 Sept 2011 Alan Barr, University of Oxford

A discovery could have come (very) early… 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Jets + pTmiss June 2010 Pileup 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford ICHEP, July 2010 ATLAS and CMS show “commissioning” & “early search” plots Plenary speakers talk about first top quarks… 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford interpretation paper… ATLAS was “already surpassing Tevatron’s reach” for compressed SUSY 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford ATLAS July/Aug 2010 Early SUSY searches with Etmiss and b-jets 08/2010 7 0.3 ATLAS-CONF-2010-079 Background to long-lived stopped particle searches 07/2010 0.07 ATLAS-CONF-2010-071 Early SUSY searches with >=1 isolated leptons, jets and Etmiss ATLAS-CONF-2010-066 Early SUSY searches with jets and Etmiss ATLAS-CONF-2010-065 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford CMS: first 2010 paper Use jets only – not pTmiss 8 Sept 2011 Alan Barr, University of Oxford

First papers from ATLAS Lepton + jets + pTmiss Jets + pTmiss 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford And limits from ATLAS… PRL 106 (2011) 131802 PLB 701 (2011) 186 8 Sept 2011 Alan Barr, University of Oxford

Observations on first papers Data-driven background techniques PTmiss resolutions & tails from data State of the art Monte Carlos: Alpgen, Herwig++, … In-situ measurements of: non-collision backgrounds pTmiss smearing Use of new variables: (mT2, T, …) as well as old favourites (meff, hT, …) Full statistical analysis Limits in mSUGRA/CMSSM and for simplified models Fiducial  to allow reinterpretation 8 Sept 2011 Alan Barr, University of Oxford

Observations on first measurements Experiments performed much better than (I) expected 8 Sept 2011 Alan Barr, University of Oxford

Observations on first measurements Experiments performed much better than (I) expected Monte Carlo generators performed much better than (I) expected 8 Sept 2011 Alan Barr, University of Oxford

Observations on first measurements Experiments performed much better than (I) expected Monte Carlo generators performed much better than (I) expected Writing papers with thousands of co-authors is both extremely helpful and mind-blowingly frustrating(!) 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Summer 2011 (Much) more luminosity: Improved BG determination (control region stats) Improved signal reach New channels become tractable Efficient update/development of existing analyses Branch out in new directions 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Bruneliere: Implications of LHC physics https://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=141983 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Bruneliere: Implications of LHC physics https://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=141983 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Paper imminent 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford 8 Sept 2011 Alan Barr, University of Oxford

Recent highlights: 3rd generation ATLAS-CONF-2011-098 Recent highlights: 3rd generation 8 Sept 2011 Alan Barr, University of Oxford

Recent highlights: 3rd generation ATLAS-CONF-2011-130

Lepton + (B-)jets + ptmiss https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-130/ 8 Sept 2011 Alan Barr, University of Oxford

Recent highlights: CMS mT2 PAS-SUS-11-005 8 Sept 2011 Alan Barr, University of Oxford

Recent highlights: ATLAS multijets https://indico.fnal.gov/contributionDisplay.py?contribId=395&sessionId=11&confId=3563 SUSY 2011 conference 8 Sept 2011 Alan Barr, University of Oxford

ATLAS Multijets - results Paper imminent… 8 Sept 2011 Alan Barr, University of Oxford

UK groups are centrally involved… Particularly: Liverpool: susy with b-jets, photons Oxford: pile-up, large jet multiplicities Sheffield: jet smearing & QCD BGs Cambridge: dilepton, VB + jets Imperial: alpha T, early searches Sussex: multi-lepton searches 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Where next – short term? ~10 x factor in lumi at 7 TeV Limited improvement in existing channels/models Getting systematics limited Can improve BG determinations but getting tougher… Raising cuts slightly will increase reach slightly. Many more channels/interpretations open up: Compressed models Lower cross-section models EW production 3rd generation – Stops and Taus Large lepton multiplicities Z + ptmiss Higgs + ptmiss? Kinks, stubs, exotics… 8 Sept 2011 Alan Barr, University of Oxford

The game starts again at 14 TeV Where next longer term? The game starts again at 14 TeV 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Multi-lepton SUSY Multi-lepton SUSY ≥ 3 leptons (electron or muon) Expect: Observe no events Charginos and neutralino cascade decays ≥ 3 leptons (electron or muon) pT > {20, 20, 20(e) or 10 (mu)} GeV ≥ 2 jets with pT > 50 GeV and |η| < 2.5 ETmiss > 50 GeV mll (ossf) Z mass veto (within 5 GeV of mZ) mll (ossf) photon veto (< 20 GeV) Top dominates after Z veto Also phenomenological limits: see… https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-039/ 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Dilepton SUSY Di-lepton SUSY 1) Opposite sign and same sign 2) Charge asymmetry analysis Two papers in the pipeline 8 Sept 2011 Alan Barr, University of Oxford

Stable charged particle search R-hadrons Two independent detector subsystems dE/dx: pixels (Time over threshold) β: tile (ToF resolution ≈ns) The 2-dimensional distribution of mass estimates as reconstructed in the tile calorimeter and pixel detector. Data and signal predictions for a gluino R-hadron of mass 500 GeV are displayed. The distributions are shown following the selection dE/dx > 1.8 MeV g^{-1} cm^{2} (pixel), beta < 1 (tile) and pT > 50 GeV. Cross-section limits at 95% CL as a function of sparticle mass. Since some candidate events are observed for the mass windows used for the 100 GeV mass hypotheses, the mass points between 100 and 200 GeV are connected with a dotted line. This indicates that fluctuations in the excluded cross-section will occur. The mass limits quoted in the text are inferred by comparing the cross-section limits with the model predictions. Systematic uncertainties from the choice of PDF and the choice of renormalisation and factorisation scales are represented as a band in the cross-section curves. Previous mass limits are indicated by shaded vertical lines for sbottom (ALEPH), stop (CDF) and gluino  95% confidence limits: Stable gluino > 586 GeV Stable stop > 309 GeV Stable sbottom 294 GeV 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Electroweak symmetry breaking Hierarchy problem? WIMPs? What is the physics at the TeV-scale? 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Analysis of the 2010 data 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford Other searches? Lepton(s) [taus] Proton Jet(s) [b-jets] Photon(s) Proton Invisible(s) Signature driven. “Measure what you can measure.” (Some signatures arguably better motivated…) 8 Sept 2011 Alan Barr, University of Oxford

Example Supersymmetry search Mass (GeV) “Typical” SUSY spectrum Assume R-parity Look for: Jets from squark & gluino decays Leptons from gaugino & slepton decays Missing energy from (stable) LSPs 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford 8 Sept 2011 Alan Barr, University of Oxford

Alan Barr, University of Oxford ATLAS-CONF-2011-130 all the squarks are heavier than the gluino, which decays exclusively (via virtual stop) into three-body final states ( t + tbar + LSP) 8 Sept 2011 Alan Barr, University of Oxford