hunting the invisible at the lhc alan barr
TRANSCRIPT
Hunting the invisible at the LHC
Alan Barr
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults
Alan Barr
Motivation
The usual blah blah? Dark Matter … Naturalness of the Higgs boson mass… Electroweak unification… Radiative electroweak symmetry breaking…
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Alan Barr
Motivation – as a pragmatist
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Lots of effort to build it: let’s make good use of it…
Alan Barr
1 pb
1 fb
Integrated luminosity: 2 fb-1 (Mid 2012) 5 fb-1 (All of 2011)
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Alan Barr
Missing momentum… invisibles
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Alan Barr
Missing momentum (ETmiss)
signatures: challenges in 2011 Instantaneous luminosity:
3.65×1033 cm−2s−1
Trigger: ETmiss-only trigger:
threshold up to 180 GeV Others available
Pile-up: up to Calorimeter response
(in-time and out-of-time) Jet and ET
miss resolution
Particle ID Data collectedInt. Lumi: ~5 fb-1
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Alan Barr
Pile-up: track ↔ jet association
A spectacular 9-jet + ETmiss event
All nine jets associated to same primary vertex(even in presence of many other vertices)
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Alan Barr
Uncertainties?
Standard Model backgrounds
Instrumental backgrounds
Expected Signal?
Alan Barr
Momentum imbalance…
Mismeasurement? Cosmics? Noise? Beam halo?
Neutrinos?WIMPs?
PATHOLOGIES
PHYSICS
Alan Barr
JETS + MISSING MOMENTUM
From collisions
Jets
PTmiss
Jets
Alan Barr
JETS
From collisions
Jets:Had. CalorimeterE.M. CalorimeterTracks from vertexIn-time
b,c quark jets can decayto neutrinos
Alan Barr
JETS + MISSING MOMENTUM
Measurements
Jets: cut
Reduce:Had. CalorimeterE.M. CalorimeterTracks from vertex
Measure remainderat small
Alan Barr
JETS + MISSING MOMENTUM
From cosmics
Reduce by: (a) requiring tracks with jets(b) look for muon hits
Measure remainder: (a) no beam(b) timing
Alan Barr
JETS + MISSING MOMENTUM
From beam halo
Reduce by requiring tracks with jetsMeasure remainder with single beam / timing
Alan Barr
JETS + MISSING MOMENTUM
Calorimeter noise
Reduce by requiring tracks with jets
Measure remainder (a) no beam(b) timing
Alan Barr
Neutrinos
Z ( ) + jets
W ( l) + jets
(+ jets)
Alan Barr
Analysis philosophy Dedicated analysis for different final states State of the art Monte Carlo Validated GEANT-4 detector simulation* Multiple redundant control regions (CR) Multiple cross-checks & validation regions
(VR) Appropriate kinematic & ID variables Uncertainties based on measurements
wherever possible Signal systematics in limits
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* We have some fast-sim for signal
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Try to make it simple…
Lots of different final states…
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Jets: anti kT, R=0.4, emhad calibration
ETMiss: Missing transverse momentum
-ve sum pT of: jets, leptons, unclustered ET
Tau: 1- or 3- prong hadronicpT > 20 GeV
B-tagged jets: secondary vertex fitter Typically at point: (εB~60%, εlight<1%)
Leptons (either e or µ), isolatedTrigger requires: (e > 25, µ > 20), soft lep down to (7,6) GeV
Photon: isolated
? Disappearing track LEGEND
Alan Barr
ATLAS SUSY review: missing momentum
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ArXiv:1111.41161fb-1ATLAS-CONF-2011-096
ATLAS-CONF-2012-036
2 fb-1
ATLAS-CONF-2012-003
arXiv:1112.3832
arXiv:1203.5763
ATLAS-CONF-2012-023ATLAS-CONF-2012-001
ATLAS-CONF-2012-005
ATLAS-CONF-2012-002
2 fb-1
ATLAS-CONF-2012-037ATLAS-CONF-2012-033 ATLAS-CONF-2012-041
5 fb-1ATLAS-CONF-2012-034
?
Alan Barr [ 21 ]
ATLAS-CONF-2012-037ATLAS-CONF-2012-033 ATLAS-CONF-2012-041
5fb-1
ATLAS-CONF-2012-034
? Full 2011 dataset
Alan Barr
ATLAS-CONF-2012-033
No leptons,≥(2-6) jets + ET
miss
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Squarks, Gluinos
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Alan Barr Page 23
ATLAS-CONF-2012-033
Squarks Gluinos/cascadesSmall Δm
Different mass scalesTotal of 11 signal regions
Alan Barr Page 24
ATLAS-CONF-2012-033
Control regions for each significant BGMultijet BG determined from data-driven smearing methodSmaller backgrounds, e.g. diboson: MC only
Alan Barr
meff (incl.): scalar sum of ET of all jets and ET
miss
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ATLAS-CONF-2012-033
MC scaled by ~0.75 (based on control regions)Band shows JES, JER, MC stats
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ATLAS-CONF-2012-033
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Simplified gluino-squark-neutralino model
ATLAS-CONF-2012-033
MSUGRA/CMSSM
Non-disjoint SRs: exclusion based on best expected significance
Alan Barr
ATLAS-CONF-2012-037
No leptons≥(6-9) jets + ET
miss
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Gluinos cascadesGluinos 4 x tops
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Alan Barr Page 29
ATLAS-CONF-2012-037
Final variable quantifies significance of Etmiss
Multi-jets dominated control regions Subtract (subdominant) “leptonic” backgroundsQCD background is reliably predicted (~20%)Tested in further control regions and
cross-checked with jet-smearing method
QCD background: stochastic term HT
Independent of jet multiplicity
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ATLAS-CONF-2012-037
Top validation region
SR: 7j80
SR: 9j55
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ATLAS-CONF-2012-037
Most discrepant 7j80 p-value 0.07
Alan Barr Page 32
Simplified gluino/top model
ATLAS-CONF-2012-037
ATLAS-CONF-2012-003
arXiv:1203.5763
Alan Barr
ATLAS-CONF-2012-037
ATLAS-CONF-2012-033
ATLAS-CONF-2012-041
Gluino mass > ~850 GeVMSUGRA/CMSSM interpretation
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5 fb-1
Alan Barr
NOTHING SO FAR…
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Alan Barr
…AND TO KNOWLEDGE, SELF-CONTROL; AND TO SELF-CONTROL, PERSEVERANCE…
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Forecast of fraction of “interesting” points “discovered”
1105.1024Allanach, AJB, Dafinca, Gwenlan
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Tough points…. 1105.1024
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1105.1024Tough points….
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1105.1024Tough points….
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1105.1024Tough points….
Alan Barr [ 40 ]
arXiv:1203.5763
ATLAS-CONF-2012-023ATLAS-CONF-2012-001
ATLAS-CONF-2012-005
ATLAS-CONF-2012-002
2 fb-1
ATLAS-CONF-2012-036
2 fb-1
ATLAS-CONF-2012-003
ArXiv:1111.41161 fb-1
ATLAS-CONF-2011-096
ArXiv:1112.3832
ATLAS-CONF-2012-037ATLAS-CONF-2012-033 ATLAS-CONF-2012-041
5 fb-1ATLAS-CONF-2012-034
?
Alan Barr [ 41 ]
arXiv:1203.5763
ATLAS-CONF-2012-023ATLAS-CONF-2012-001
ATLAS-CONF-2012-005
2 fb-1
EW gauginos, staus
ATLAS-CONF-2012-002
Alan Barr [ 42 ]
ATLAS-CONF-2012-023
Three-lepton + ETmiss
Direct EW gaugino
Alan Barr
Three-lepton + ETmiss
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Z depleted(+b jet veto)
Z enriched(within 10 GeVof mZ)
pT (µ) > 20,10,10 GeVpT (e) > 25,10,10 GeVET
miss > 50 GeV
Searches for direct gaugino productionChargino + neutralino 3 leptons + 2 LSPOSSF pair(s) allowed (mll > 20)
ATLAS-CONF-2012-023
Alan Barr
3-lepton + Etmiss - gauginos
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ATLAS-CONF-2012-023
Chargino-1
LSPVia slepton
Alan Barr [ 45 ]
ATLAS-CONF-2012-001
ATLAS-CONF-2012-035
Direct gauginos
L-violating RPV
4 lepton + ETmiss
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L-violating RPV
LSPλ121
gut ~ 0.032
ATLAS-CONF-2012-001
ATLAS-CONF-2012-035
Alan Barr
ATLAS-CONF-2012-036
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arXiv:1111.4116
2 fb-1
1 fb-1
ATLAS-CONF-2012-003
ATLAS-CONF-2011-096
arXiv:1112.3832
Alan Barr [ 48 ]
arXiv:1112.3832
Direct sbottom
2 jets only(veto on third jet)
Alan Barr
Direct sbottom
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ArXiv:1112.3832
(Pure MC predictions in parentheses)
2 jets only – veto on third jet
Alan Barr
Direct Sbottom
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ArXiv:1112.3832
2 jets only – veto on third jet
Alan Barr
SUSY / invisibles: summary Analysis of 2011 data still in flow
Several analyses with full 5 fb-1, more on the way Lower limits* of:
squark ~ 1400 GeV gluino ~ 900 GeV sbottom ~ 400 GeV [stop ~ 300 GeV]**
[gauginos ~ 200-300 GeV]**
Also: taus, photons, monojets, disappearing tracks, … + ET
miss
Preparations for 2012, 8 TeV in full swing
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* indicative & for particular scenarios
Direct productionParticular decays
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2012 data taking
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Further motivation: the future…
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~1 TeV ?
Multi-TeV ?
LH-LHC?HE-LHC?
Alan Barr
A luminosity upgrade: additional reach…
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Perhaps measuring properties…
Alan Barr
EXTRAS
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Alan Barr Page 56
ATLAS-CONF-2012-041
1-lepton + jets + ETmiss
Strong chargino neutralino
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Chargino cascade decays etc: One-lepton
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Small Δm
ATLAS-CONF-2012-041
Alan Barr
1-lepton: background determination
Control regions split by jet multiplicity (up to 9 jets)
Nuisance parameters fitted
B-tagging kTfact (Alpgen)
Normalisations Over-constrained system
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Control & validationregions
ATLAS-CONF-2012-041
Alan Barr
Control regions – jet multiplicity
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ATLAS-CONF-2012-041
Alan Barr
1-lepton results
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Fit allows different backgrounds to adjust, based on CR(Also relative fraction of different multiplicities in Alpgen)
ATLAS-CONF-2012-041
Alan Barr
Significantly improved
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ATLAS-CONF-2012-041
3j, 4j signal regions statistically combined (first time)Shape of meff used when making exclusion (6 bins 4001600 GeV)
Alan Barr
Simplified model limits
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Near-degenerate region: gain factor of 20-30 from soft lepton
Soft lepton analysisHard lepton analyses
ATLAS-CONF-2012-041
Alan Barr [ 63 ]
ATLAS-CONF-2012-041
1-lepton channel: improvement in limit using soft lepton
Alan Barr
Multijet control regions
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ATLAS-CONF-2012-033
Alan Barr
Three-lepton + ETmiss
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ATLAS-CONF-2012-023
Limits in pMSSM space (Wino Bino decays)
M1 = 100
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Top pair with extra ETMiss
Limit interpreted in terms of fermionic top partner
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Phys. Rev. Lett. 108 (2012) 041805
Alan Barr
t + tbar + ETmiss
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Phys. Rev. Lett. 108 (2012) 041805
Not yet sensitive to stop production
Alan Barr
ATLAS-CONF-2011-096
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Alan Barr [ 69 ]
ATLAS-CONF-2012-036
Direct Stop pair Hino LSP + Z
b-jet, same flavour, opposite sign leptonsmll ~ mZ
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1 pair production
1 t +
Etmiss > 50 GeV
80 GeV
SR2
SR1
Decays via sbottom, h also included
ATLAS-CONF-2012-036
Alan Barr
Disappearing track
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ATLAS-CONF-2012-034
?
Light winos, AMSB
Finally…
Alan Barr
Disappearing tracks
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ATLAS-CONF-2012-034
?
Chargino mass=90.2GeV
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https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults
Good reading…
Alan Barr
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/
ExoticsPublicResults
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ATLAS-CONF-2011-096
Monojet
Found elsewhere…
Alan Barr Page 77
ATLAS-CONF-2012-005
≥1 tau or ≥2 taus + Jet(s) + ETmiss
GMSB, stau NLSP
ATLAS-CONF-2012-002
Alan Barr
Final states with taus
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Same trigmEff > 600 GeVmT(1) > 110 GeV
ATLAS-CONF-2012-002
Expect: 5.3 ±1.3(stat)±2.2(sys)Observe: 3
ε(1p) ~ 30% ε(j) ~ 0.5%ε(3p) ~ 50% ε(j) ~ 3%
ATLAS-CONF-2012-005
Jet (130) + ETmiss (130) trig.
mEff > 700 GeVmT(1) + mT(1) > 80 GeV
Alan Barr Page 79
ATLAS-CONF-2011-156
1fb-1
ATLAS-CONF-2011-156
ATLAS-CONF-2012-002
ATLAS-CONF-2012-005
2 fb-1
Alan Barr [ 80 ]
ATLAS-CONF-2012-003
b-jet(s) (+ 1 lepton) + jet(s) + ET
missGluinoSbottom/Stop
Alan Barr [ 81 ]
ATLAS-CONF-2012-003
B jet(s) (+ 1 lepton) + jet(s) + ET
miss
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0-lepton≥2 b-tags
1-electron≥1 b-tag
ATLAS-CONF-2012-003
Alan Barr [ 83 ]
(MC yields in parentheses)
1-lepton
0-lepton
ATLAS-CONF-2012-003
Alan Barr [ 84 ]
Virtual sbottom Real sbottom
ATLAS-CONF-2012-003