SUSY searches LHC A perspective Alan Barr University
SUSY searches @ LHC A perspective Alan Barr University of Oxford UK HEP Forum 8 th September
Motivational arguments… 8 Sept 2011 Alan Barr, University of Oxford 2
Motivational arguments… 8 Sept 2011 Alan Barr, University of Oxford 3
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 4
What sort of searches? Strongly interacting particles produced Decay to WIMP candidate… [ Lepton(s) ] Proton Jet(s) Proton 8 Sept 2011 Invisible(s) Alan Barr, University of Oxford 5
A discovery could have come (very) early… 8 Sept 2011 Alan Barr, University of Oxford 6
Jets + p. Tmiss June 2010 Pileup 8 Sept 2011 Alan Barr, University of Oxford 7
ICHEP, July 2010 ATLAS and CMS show “commissioning” & “early search” plots 8 Sept 2011 Alan Barr, University of Oxford Plenary speakers talk about first top quarks… 8
70 nb-1 interpretation paper… ATLAS was “already surpassing Tevatron’s reach” for compressed SUSY 8 Sept 2011 Alan Barr, University of Oxford 9
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 7 0. 07 ATLAS-CONF 2010 -071 Early SUSY searches with >=1 isolated leptons, jets and Etmiss 07/2010 7 0. 07 ATLAS-CONF 2010 -066 Early SUSY searches with jets and Etmiss 07/2010 7 0. 07 ATLAS-CONF 2010 -065 8 Sept 2011 Alan Barr, University of Oxford 10
CMS: first 2010 paper Use jets only – not p. Tmiss 8 Sept 2011 Alan Barr, University of Oxford 11
First papers from ATLAS Lepton + jets + p. Tmiss Jets + p. Tmiss 8 Sept 2011 Alan Barr, University of Oxford 12
And limits from ATLAS… PRL 106 (2011) 131802 8 Sept 2011 PLB 701 (2011) 186 Alan Barr, University of Oxford 13
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 – p. Tmiss smearing – Use of new variables: (m. T 2, T, …) as well as old favourites (meff, h. T, …) • Full statistical analysis • Limits in m. SUGRA/CMSSM and for simplified models • Fiducial to allow reinterpretation 8 Sept 2011 Alan Barr, University of Oxford 14
Observations on first measurements • Experiments performed much better than (I) expected 8 Sept 2011 Alan Barr, University of Oxford 15
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 16
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 mindblowingly frustrating(!) 8 Sept 2011 Alan Barr, University of Oxford 17
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 18
Bruneliere: Implications of LHC physics Alan Barr, University of Oxford https: //indico. cern. ch/conference. Other. Views. py? view=standard&conf. Id=141983 8 Sept 2011 19
Bruneliere: Implications of LHC physics Alan Barr, University of Oxford https: //indico. cern. ch/conference. Other. Views. py? view=standard&conf. Id=141983 8 Sept 2011 20
8 Sept 2011 Alan Barr, University of Oxford 21
8 Sept 2011 Alan Barr, University of Oxford 22
Paper imminent 8 Sept 2011 Alan Barr, University of Oxford 23
8 Sept 2011 Alan Barr, University of Oxford 24
8 Sept 2011 Alan Barr, University of Oxford 25
ATLAS-CONF-2011 -098 Recent highlights: 3 rd generation 8 Sept 2011 Alan Barr, University of Oxford 26
ATLAS-CONF-2011 -130 Recent highlights: 3 rd generation 27
Lepton + (B-)jets + ptmiss https: //atlas. web. cern. ch/Atlas/GROUPS/PHYS ICS/CONFNOTES/ATLAS-CONF-2011 -130/ 8 Sept 2011 Alan Barr, University of Oxford 28
Recent highlights: CMS m. T 2 PAS-SUS-11 -005 8 Sept 2011 Alan Barr, University of Oxford 29
Recent highlights: ATLAS multijets 8 Sept 2011 https: //indico. fnal. gov/contribution. Display. py? contrib. Id=395&session. Id=11&conf. Id=3563 SUSY 2011 conference Alan Barr, University of Oxford 30
ATLAS Multijets - results Paper imminent… 8 Sept 2011 Alan Barr, University of Oxford 31
UK groups are centrally involved… 8 Sept 2011 Alan Barr, University of Oxford 32
Where next – short term? • ~10 x factor in lumi at 7 Te. V • 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: – – – – 8 Sept 2011 Compressed models Lower cross-section models EW production 3 rd generation – Stops and Taus Large lepton multiplicities Z + ptmiss Higgs + ptmiss? Kinks, stubs, exotics… Alan Barr, University of Oxford 33
Where next longer term? The game starts again at 14 Te. V 8 Sept 2011 Alan Barr, University of Oxford 34
Multi-lepton SUSY ≥ 3 leptons (electron or muon) Expect: Observe no events 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 35
Di-lepton SUSY Dilepton SUSY Two papers in the pipeline 8 Sept 2011 1) Opposite sign and same sign 2) Charge asymmetry analysis Alan Barr, University of Oxford 36
R-hadrons Stable charged particle search Two independent detector subsystems d. E/dx: pixels (Time over threshold) β: tile (To. F resolution ≈ns) 8 Sept 2011 95% confidence limits: Stable gluino > 586 Ge. V Stable stop > 309 Ge. V Stable sbottom 294 Ge. V Alan Barr, University of Oxford 37
Electroweak symmetry breaking Hierarchy problem? WIMPs? What is the physics at the Te. V-scale? 8 Sept 2011 Alan Barr, University of Oxford 38
Analysis of the 2010 data 8 Sept 2011 Alan Barr, University of Oxford 39
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 40
Example Supersymmetry search Mass (Ge. V) “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 41
8 Sept 2011 Alan Barr, University of Oxford 42
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 43
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