ATLAS Alan Barr University of Oxford Freiburg 11 th May 2011 British press report the turn on of the LHC ID: 577245
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Slide1
New physics
@
ATLAS
Alan
Barr
University
of Oxford
Freiburg 11
th
May 2011Slide2
British press report
the turn on of the LHC…December 2008:Slide3
23/03/2011
Alan Barr, University of Oxford3
Did you hear about the ATLAS di-photon distribution?
April 2011:Slide4
This talk
Why
a
Large Hadron Collider?Accelerator and detector status100 years of discovery in 10 monthsThe energy-frontier measurements
SupersymmetryExoticsProspects for the future (inc. Higgs)
11/05/2011Alan Barr, University of Oxford4Slide5
23/03/2011
Alan Barr, University of Oxford
5
Electroweak symmetry breaking
Hierarchy problem?Physics at the TeV-scale?
WIMPs?Slide6
6
CMS
LHCb
ATLAS
ALICE
Proton - Proton
Controlled environment
CM energy = 7 TeV (
14
)~ 109 collision / second~ decade of operationSlide7
Semiconductor Tracker @ Oxford
11/05/2011Alan Barr, University of Oxford7Slide8
23/03/2011
Alan Barr, University of Oxford
8
UPDATE MESlide9
23/03/2011
Alan Barr, University of Oxford
9
22 July
ICHEP
2010 to same vertical scale
35 pb-1Slide10
Parton-
parton luminosity23/03/2011Alan Barr, University of Oxford
10
Event rate at the unitary limit as a function of CM energy Exciting!Slide11
11Slide12
Top candidate event
12
12
p
T
(μ)= 48 GeV
pT(e)=23 GeVETmiss=77 GeV, HT=196 GeVpT
(b-tagged jet) = 57 GeVSecondary vertex:
-- distance from primary: 3.8 mm -- 3 tracks pT
> 1 GeV -- mass=1.56
GeV
p
T
(tracks) > 1 GeVSlide13
23/03/2011
Alan Barr, University of Oxford13
Top quark
σ
WW
Inelastic cross-section
J/Ψ suppression in Pb-PbInteresting things I won’t discuss…Slide14
23/03/2011
Alan Barr, University of Oxford14
Measurement of the WW cross section in sqrt(s) = 7
TeV pp collisions with ATLAS Inspire record
, Plots Submitted to PRL (27 April 2011)
Measurement of the differential cross-sections of inclusive, prompt and non-prompt J/psi production in proton-proton collisions at √s = 7 TeV Inspire record, Plots Submitted to Nuclear Physics B (15 April 2011) Measurement of the Inelastic Proton-Proton Cross-Section at √s=7 TeV with the ATLAS Detector Inspire record, Plots
Submitted to Nature Comm (2 April 2011) Measurement of the Muon Charge Asymmetry from W Bosons Produced in pp Collisions at sqrt(s) = 7 TeV with the ATLAS detector Inspire record, Plots submitted to PLB (15 Mar 2011) Measurements of underlying event properties using neutral and charged particles in p-p collisions at 900
GeV and 7 TeV with the ATLAS detector at the LHC
Inspire record, Plots submitted to EPJC (9 Mar 2011)
Measurement of Dijet Azimuthal Decorrelations in pp Collisions at √s=7 TeV
Inspire record
,
Plots
Phys. Rev. Lett. 106, 172002 (2011)
(14 Feb 2011)
Luminosity Determination in
pp
Collisions at √(s)=7
TeV
Using the ATLAS Detector at the LHC
Inspire record
,
Plots
EPJC 71 (2011) , 1630
(11 Jan 2011)
Study of Jet Shapes in Inclusive Jet Production in pp Collisions at √s = 7 TeV using the ATLAS Detector
Inspire record
,
Plots
Phys. Rev. D 83, 052003 (2011)
(30 Dec 2010)
Measurement of the centrality dependence of J/Psi yields and observation of Z production in lead-lead collisions with the ATLAS detector at the LHC
Inspire record
,
Plots
Phys Lett. B697 (2011) 294-312
(24 Dec 2010)
Measurement of the production cross section for W-bosons in association with jets in pp collisions at √s = 7 TeV with the ATLAS detector
Inspire record
,
Plots
Phys.
Lett
. B698 (2011) 325-345
(23 Dec 2010)
Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC
Inspire record
,
Plots
accepted by New J Phys (submitted 22 Dec 2010)
Measurement of the inclusive isolated prompt photon cross section in pp collisions at √s = 7 TeV with the ATLAS detector
Inspire record
,
Plots
Phys. Rev. D 83, 052005 (2011)
(20 Dec 2010)
Measurement of the top quark-pair production cross section with ATLAS in
pp
collisions at √s=7
TeV
Inspire record
,
Plots
EPJC 71 (2011) 1577
(8 Dec 2010)
Measurement of underlying event characteristics using charged particles in pp collisions at √s = 900 GeV and 7 TeV with the ATLAS detector
Inspire record
,
Plots
accepted by Phys Rev D (submitted 3 Dec 2010)
Measurement of the W ->
lnu
and Z/gamma* ->
ll
production cross sections in proton-proton collisions at √s = 7
TeV
with the ATLAS detector
Inspire record
,
Plots
JHEP 12 (2010) 060
(11 Oct 2010)
Measurement of inclusive jet and
dijet
cross sections in proton-proton collisions at 7
TeV
centre-of-mass energy with the ATLAS detector
Inspire record
,
Plots
,
Data points
EPJC 71 (2011) 1-59 (30 Sep 2010)
See: https://twiki.cern.ch/twiki/bin/view/AtlasPublic
‘Standard Model’ papers
Lots of other very interesting
things
not
covered ...Slide15
SUSY & BSM strategy
Precision reliable hermetic detectorBasic kinematicsUnderstand detector and SMLook at final states with:23/03/2011
Alan Barr, University of Oxford15
Proton
Proton
Lepton(s)
Jet(s)Invisible(s)Photon(s)Examples givenSlide16
23/03/2011
Alan Barr, University of Oxford16
Why
Supersymmetry?
+SUSY
Log
10
(
μ
/ GeV)
1/
α
Lots of interesting physics at ~ 1 TeV
top
Δ
m
2
(h)
Λ
2
cutoff
higgs
higgs
stop?
higgs
higgs
λ
λ
λ
λSlide17
Basic kinematics
23/03/2011
Alan Barr, University of Oxford17
Transverse mass
mT = Transverse momenta, p
TScalar sums of transverse momenta: HT, meff = HT + ETmiss Missing transverse momentum, ETmiss “Stransverse” mass mT2(generalisation of m
T to 2 parent particles)Azimuthal angle differences ΔφPseudorapidity, η = - ln tan θ/2Slide18
11/05/2011
Alan Barr, University of Oxford
18
Final
statesReferenceLepton + Jets + ETmiss
Phys. Rev. Lett. 106, 131802 (2011)Jets + ETmiss arXiv:1102.5290 (submitted to PLB)≥ 3 leptons + jets + ETmissATLAS-CONF-2011-039
≥ 1 b-jet + jets (± leptons) + ETmiss arXiv:1103.4344 (submitted to PLB)Identical flavours.................Either sign combination.......arXiv:1103.6208arXiv:1103.6214Statistical combination(0-lep + 1-lep)
ATLAS-CONF-2011-064
1-lepton SUSY0-lepton SUSY
Multi-lepton SUSY
SUSY with b jets
Di-lepton SUSY
For all public papers see:
https
://
twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults
1-lepton SUSY
0-lepton SUSYSlide19
1-lepton + Jets +
E
Tmiss19
1-lepton SUSY1 electron or muon
pT>20 GeV3 jets pT
> {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 paperarXiv:1102.2357 accepted
by PRLLepton reduces QCD BGExpect leptons in SUSY cascade decaysSlide20
Control regions – some examples
23/03/2011Alan Barr, University of Oxford20
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 presentedSlide21
1-lepton results
23/03/2011Alan Barr, University of Oxford21
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 strengthSlide22
SUSY: Jets
+ ETmiss23/03/2011Alan Barr, University of Oxford
220-lepton SUSY
Squark
decays
Gluino decays more jetsConceptually simple search for squarks and gluinosSeveral overlapping signal regions:Four overlapping signal regionsSlide23
Robust background determinations
23/03/2011Alan Barr, University of Oxford23
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 eν
, W μν 0-lepton SUSY
Only a couple of very many data-driven checks/BG determinationsSlide24
23/03/2011
Alan Barr, University of Oxford24
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 interpretationsAuxiliary plots (Acc x Eff) allow reinterpretation in a variety of modelsSlide25
Multi-lepton SUSY
23/03/2011Alan Barr, University of Oxford25
Multi-lepton SUSY
Expect:
Observe
no eventsTop dominates after Z veto≥ 3 leptons (electron or muon)Charginos and neutralino cascade decaysSlide26
SUSY with b-jets
23/03/2011
Alan Barr, University of Oxford26
SUSY with b jetsDone for both
1-lepton, 0-lepton channelsSensitive to Stop, Sbottom, Gluinoproduction
Top background dominates after b-jet requirementData-driven QCD background determinationSlide27
Dilepton
SUSY23/03/2011Alan Barr, University of Oxford27
Di-lepton SUSY
Two papers:
1) Opposite sign and same sign 2) Charge asymmetry analysis
Majorana nature of gluinos, neutralino same sign dilepton eventsLepton number carried by sleptons flavour correlationsSlide28
Stable charged particle search
23/03/2011Alan Barr, University of Oxford28
95%
confidence limits:Stable gluino > 586 GeVStable stop > 309
GeV Stable sbottom 294 GeV
R-hadronsTwo independent detector subsystems:dE/dx: pixels (Time over threshold)β: tile (ToF resolution ~ns)Slide29
Combined exclusion
11/05/2011Alan Barr, University of Oxford29
1-lepton SUSY
0-lepton SUSY
Statistical combination fromproduct of likelihoodsSlide30
Wider interpretation...
23/03/2011
Alan Barr, University of Oxford30
http://arxiv.org/abs/1103.0969Allanach, Khoo, Lester, Williams
Cassel, Ghilencea, Kraml, Lessa, Ross
http://arxiv.org/abs/1101.4664Points sampled from fits to global dataGlobal CMSSM fits Regions with low fine tuning
ATLAS 0/1 lepton
CMS
α
T
Excluded by ATLAS
0-lepton searchSlide31
A race through some
exotic signatures…Not only Supersymmetry...11/05/2011
Alan Barr, University of Oxford31Slide32
W’ searches
23/03/2011Alan Barr, University of Oxford32
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 TeVSlide33
Z’ searches…
23/03/2011
Alan Barr, University of Oxford33
Electrons
Muons
M(Z’
SSM) > 1.05 TeVSlide34
Dijet inv. mass, angular distributions
23/03/2011Alan Barr, University of Oxford34
http://arxiv.org/abs/1103.3864
Compositeness scale,
Λ
> 9.6 TeVSlide35
Diphoton
resonances23/03/2011Alan Barr, University of Oxford35
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-044/
Limits on
RS graviton: 545 GeV (920 GeV
), for k/MPl = 0.02 (0.1)Slide36
Diphoton +
ETmiss23/03/2011Alan Barr, University of Oxford
36
Interpret in context of Universal Extra Dimensions
Vary size of extra dimension with constant ΛR = 20Slide37
Fourth generation Q search
Di-leptonic channel23/03/2011Alan Barr, University of Oxford
37
Approximate mass reconstruction on varying
Δη
, ΔφExcludes m(Q) < 270 GeV (@95% CL) Slide38
(e,mu
) resonance searchLimits on RPV sneutrino e muLimits on flavour violating Z’
23/03/2011Alan Barr, University of Oxford38
Paper in the pipelineSlide39
Story so far
Excellent operation of LHC and ATLAS
Commissioned physics objects:
Jets, e, mu, ETmiss , photons, b-jets, (tau)
Monte Carlo doing very wellData-driven backgrounds provenWide variety of final states studiedAlso exotics… R-hadrons, multi-charged particles, stopped gluinos…Many limits well beyond previous colliders23/03/2011Slide40
Higgs -> WW
23/03/2011Alan Barr, University of Oxford40Slide41
41
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-2011-025Slide42
Physics prospects: Higgs
23/03/2011Alan Barr, University of Oxford42Slide43
Current h
ττ23/03/2011Alan Barr, University of Oxford
43https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-024/Slide44
Exploring new worlds...
Launch is complete11/05/2011Alan Barr, University of Oxford
44Slide45
Extras
A few little23/03/2011
Alan Barr, University of Oxford45Slide46
Exotics conf notes
23/03/2011Alan Barr, University of Oxford46
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResultsSlide47
23/03/2011
Alan Barr, University of Oxford47
0-lepton SUSY
Missing transverse momentumSlide48
m
eff distributions23/03/2011Alan Barr, University of Oxford48
0-lepton SUSY
Cuts shown on mass-sensitive variable in final selectionSlide49
BG example: E
Tmiss tails23/03/2011Alan Barr, University of Oxford
490-lepton SUSY
One example of very, very, very many background studiesSlide50
23/03/2011
Alan Barr, University of Oxford50
1-lepton SUSYSlide51
1-lepton results
23/03/2011Alan Barr, University of Oxford51
1-lepton SUSYSlide52
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 Oxford52Slide53
Kinematic distributions
23/03/2011Alan Barr, University of Oxford53
1-lepton SUSY
Electron channel
Muon
channelSlide54
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| < 2.5ET
miss > 50 GeVmll (ossf) Z mass veto (within 5 GeV of mZ)m
ll (ossf) photon veto (< 20 GeV)23/03/2011Alan Barr, University of Oxford54Multi-lepton SUSY
SM:Observe no eventsTop dominates after Z vetoSlide55
55
Z →ττ
mu + had
e + had
e + mu
ATLAS-CONF-2011-010
ATLAS-CONF-2011-045 Slide56
Stable massive particle search
Two independent detector subsystemsdE/dx: pixels(Time over threshold)β: tile (ToF
resolution ≈ns)ETmiss > 40 GeV (trigger)pT > 50 GeV
23/03/2011Alan Barr, University of Oxford56
http://arxiv.org/abs/1103.1984
R-hadronsSlide57
0-lepton results
Alan Barr, University of Oxford57
0-lepton SUSY
Conservative systematics
Jet energy scale (~7%)Luminosity (11%)Control region statisticsLepton vetoDifferent MCb-jet fractionMC statisticsHigher orders… more …