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

Alan Barr [ 18 ]

Try to make it simple…

Lots of different final states…

Alan Barr Page 19

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

Alan Barr Page 26

ATLAS-CONF-2012-033

Alan Barr Page 27

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

Alan Barr Page 30

ATLAS-CONF-2012-037

Top validation region

SR: 7j80

SR: 9j55

Alan Barr Page 31

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

Alan Barr [Page 36

Tough points…. 1105.1024

Alan Barr [Page 37

1105.1024Tough points….

Alan Barr [Page 38

1105.1024Tough points….

Alan Barr [Page 39

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

[ 44 ]

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

Alan Barr [ 46 ]

L-violating RPV

LSPλ121

gut ~ 0.032

ATLAS-CONF-2012-001

ATLAS-CONF-2012-035

Alan Barr

ATLAS-CONF-2012-036

Page 47

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

Alan Barr

2012 data taking

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Alan Barr

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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Alan Barr

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

Alan Barr

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

Page 68

Alan Barr [ 69 ]

ATLAS-CONF-2012-036

Direct Stop pair Hino LSP + Z

b-jet, same flavour, opposite sign leptonsmll ~ mZ

Alan Barr [ 70 ]

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

[ 71 ]

ATLAS-CONF-2012-034

?

Light winos, AMSB

Finally…

Alan Barr

Disappearing tracks

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ATLAS-CONF-2012-034

?

Chargino mass=90.2GeV

Alan Barr Page 73

https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults

Good reading…

Alan Barr

https://twiki.cern.ch/twiki/bin/view/AtlasPublic/

ExoticsPublicResults

Page 74

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

Alan Barr [ 82 ]

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