ATLAS Alan Barr University of Oxford Kings College London 23 rd March 2011 23032011 Alan Barr University of Oxford 2 Electroweak symmetry breaking ID: 543517
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Slide1
New physics
@
ATLAS
Alan
Barr
University
of Oxford
Kings College London 23
rd
March 2011Slide2
23/03/2011
Alan Barr, University of Oxford
2
Electroweak symmetry breaking
Hierarchy problem?What is the physics at the
TeV-scale?WIMPs?Slide3
23/03/2011
Alan Barr, University of Oxford
3
22 July
ICHEPEnd of 2010 runSlide4
Parton-
parton luminosity
23/03/2011Alan Barr, University of Oxford4Slide5
23/03/2011
Alan Barr, University of Oxford
5Slide6
SUSY & BSM strategy
Precision reliable hermetic detectorBasic kinematicsUnderstand detector and SMLook at final states with:23/03/2011
Alan Barr, University of Oxford6
Proton
Proton
Lepton(s)
Jet(s)Invisible(s)Photon(s)Examples givenSlide7
Basic
kinematics23/03/2011
Alan Barr, University of Oxford7
Transverse mass
mT =
Transverse momenta, pTScalar sums of transverse momenta: HT, meff = HT + ETmiss Missing transverse momentum, ETmiss “Stransverse” mass (generalisation of mT to 2 parent
particles)Azimuthal angle differences ΔφPseudorapidity, η = - ln tan θ/2Slide8
1-lepton + Jets +
E
Tmiss8
1-lepton SUSY1 electron or
muon pT>20 GeV3 jets p
T > {60, 30, 30} GeVETmiss > 125 GeVETmiss > 0.25 * meffmT > 100 GeVmeff > 500 GeVSelection based heavily on pre data-takingMC studies e.g. arXiv:0901.0512First ATLAS SUSY paper
arXiv:1102.2357 accepted by PRLLepton reduces QCD BGExpect leptons in SUSY cascade decaysSlide9
Control regions – some examples
23/03/2011Alan Barr, University of Oxford9
Multiple
redundant control regions
QCD background separatelySystematics include (not only)
JES, JER, lumi, lepton efficiency, CR stats, extrapolation, …Top C/R distinguished from W+jets using b-tagging1-lepton SUSYGreat care with BG for all analyses presentedSlide10
1-lepton results
23/03/2011Alan Barr, University of Oxford10
1-lepton SUSY
Likelihood ratio as a function of signal strength
Toy MCs for p-valuesProfile likelihood for nuisance parameters (conservative systematics)Fully simulated backgrounds, signal pointsIncludes systematic uncertainties on signal strengthSlide11
SUSY: Jets
+ ETmiss23/03/2011Alan Barr, University of Oxford
110-lepton SUSY
Squark
decays
Gluino
decaysConceptually simple search for squarks and gluinosSeveral overlapping signal regions:ArXiV:1102.5290Slide12
Robust background determinations
23/03/2011Alan Barr, University of Oxford12
2-4 measurement methods per backgroundExamples:Reversal of cuts & kinematic control regionsFully data-driven inc.
jet transfer functionsTau re-decay, smearZ νν from:Z
ee, Z μμW e
ν, W μν 0-lepton SUSYSlide13
23/03/2011
Alan Barr, University of Oxford13
0-lepton SUSY
Exclude non-SM effective cross sections (
σ x BR x Acc x Eff):A: 1.3
pb B: 0.35 pb C: 1.1 pb D: 0.11 pbSquark, Gluino interpretationshttps://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/susy-0lepton_01/Slide14
Multi-lepton SUSY
23/03/2011Alan Barr, University of Oxford14
Multi-lepton SUSY
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-039/Also phenomenological limits: see…
Expect:
Observe no eventsTop dominates after Z veto≥ 3 leptons (electron or muon)Slide15
SUSY with b-jets
23/03/2011
Alan Barr, University of Oxford15
SUSY with b jetsDone for both
1-lepton, 0-lepton channelsPaper in the pipeline…Sensitive to Stop,
Sbottom, GluinoproductionTop background dominates after b-jet requirementData-driven QCD background determinationSlide16
Stable charged particle search
23/03/2011Alan Barr, University of Oxford16
95%
confidence limits:Stable gluino > 586 GeV
Stable stop > 309 GeV Stable sbottom 294 GeV
R-hadronsTwo independent detector subsystemsdE/dx: pixels (Time over threshold)β: tile (ToF resolution ≈ns)Slide17
W’ searches
23/03/2011Alan Barr, University of Oxford17
ElectronsMuons
arxiv:1103.1391
Electron
pT > 25 GeV, |η| < 1.37 or 1.52 < |η| < 2.40Muon pT > 25 GeV, |η| < 1.05ETmiss > 25 GeVM(W’SSM) > 1.49 TeVSlide18
Z’ searches…
23/03/2011
Alan Barr, University of Oxford18
Electrons
Muons
M(Z’
SSM) > 1.05 TeVSlide19
Dijet inv. mass,
angular distributions23/03/2011Alan Barr, University of Oxford19
http://arxiv.org/abs/1103.3864
Compositeness scale,
Λ
> 9.6 TeVSlide20
Diphoton
resonances23/03/2011Alan Barr, University of Oxford
20https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-044/Slide21
Diphoton +
ETmiss23/03/2011Alan Barr, University of Oxford
21
Interpret in context of Universal Extra Dimensions
ΛR = 20Slide22
Fourth generation Q search
Di-leptonic channel23/03/2011Alan Barr, University of Oxford
22
Approximate mass reconstruction on varying
Δη
, ΔφExcludes m(Q) < 270 GeV (@95% CL) Slide23
Preliminary c
onclusions
Excellent operation of LHC and ATLAS
Commissioned physics objects:Jets, e, mu, ETmiss , photons, b-jets, (tau)
Wide variety of such final states studiedAlso exotics… R-hadrons, multi-charged particles, stopped gluinos…Many limits well beyond previous colliders
23/03/2011Slide24
Extras
A few little23/03/2011Alan Barr, University of Oxford
24Slide25
Papers and CONF notes 1/3:
SUSY papers and notes
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults
23/03/2011
Alan Barr, University of Oxford
25Slide26
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults
23/03/2011
Alan Barr, University of Oxford
26
Papers and CONF notes 2/3:Exotics papersSlide27
Papers and CONF
notes 3/3Exotics Conf notes23/03/2011Alan Barr, University of Oxford
27
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResultsSlide28
23/03/2011
Alan Barr, University of Oxford28
0-lepton SUSY
Missing transverse momentumSlide29
m
eff distributions23/03/2011Alan Barr, University of Oxford
29
0-lepton SUSY
Cuts shown on mass-sensitive variable in final selectionSlide30
BG example: E
Tmiss tails23/03/2011Alan Barr, University of Oxford
300-lepton SUSY
One example of very, very, very many background studiesSlide31
23/03/2011
Alan Barr, University of Oxford31
1-lepton SUSYSlide32
1-lepton + Jets + E
Tmiss23/03/2011Alan Barr, University of Oxford
32
arXiv:1102.2357
1-lepton SUSYSlide33
1-lepton results
23/03/2011Alan Barr, University of Oxford33
1-lepton SUSYSlide34
Profile likelihood
Hatted quantities maximise likelihoodDouble hatted quantities maximise L for given value of ss and s-hat constrained to be non-negativeLikelihood ratio is the test statistic used to calculate the p-value 23/03/2011
Alan Barr, University of Oxford34Slide35
Kinematic distributions
23/03/2011Alan Barr, University of Oxford35
1-lepton SUSY
Electron channel
Muon
channelSlide36
Di-photon +
ETmissS23/03/2011
Alan Barr, University of Oxford36
arxiv:1012.4272Slide37
Jets, Electrons,
Muons, ETmissCharginos 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| < 2.5E
Tmiss > 50 GeVmll (ossf) Z mass veto (within 5 GeV of mZ
)mll (ossf) photon veto (< 20 GeV)23/03/2011Alan Barr, University of Oxford37Multi-lepton SUSY
SM:Observe no eventsTop dominates after Z vetoSlide38
38
SM: H→γγMass range: 110 GeV
- 140 GeVData-driven estimation of all background components γγ, γj, jj
Inclusiveonly discriminant diphoton inv. mass
Sensitivity close to the current Tevatron limits.
ATLAS-CONF-2011-025Slide39
39
Z →ττ
mu + had
e + had
e + mu
ATLAS-CONF-2011-010
ATLAS-CONF-2011-045 Slide40
Stable massive particle search
Two independent detector subsystemsdE/dx: pixels(Time over threshold)β: tile (
ToF resolution ≈ns)ETmiss > 40 GeV (trigger)pT > 50
GeV23/03/2011Alan Barr, University of Oxford
40
http://arxiv.org/abs/1103.1984R-hadronsSlide41
0-lepton results
Alan Barr, University of Oxford41
0-lepton SUSY
Conservative systematics
Jet energy scale (~7%)Luminosity (11%)Control region statisticsLepton vetoDifferent MCb-jet fractionMC statisticsHigher orders… more …Slide42
Dilepton SUSY
23/03/2011Alan Barr, University of Oxford42
Di-lepton SUSY