Hunting the invisible at the LHC

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…

[

Alan Barr

Motivation – as a pragmatist

[

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)

Alan Barr

Missing momentum… invisibles

[

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 collected

Int. Lumi: ~5 fb-1

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)

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


MeasurementsJets: cut

Reduce:Had. CalorimeterE.M. CalorimeterTracks from vertex

Measure remainderat small

Alan Barr


From cosmics

Reduce by: (a) requiring tracks with jets(b) look for muon hits

Measure remainder: (a) no beam(b) timing

Alan Barr


From beam halo

Reduce by requiring tracks with jetsMeasure remainder with single beam / timing

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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

[ 17 ]

* We have some fast-sim for signal

Alan Barr [ 18 ]

Try to make it simple…

Lots of different final states…

Alan Barr

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

[ 20 ]

ArXiv:1111.41161fb-1ATLAS-CONF-2011-096

ATLAS-CONF-2012-036

2 fb-1

ATLAS-CONF-2012-003

arXiv:1112.3832arXiv: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 ]


5fb-1ATLAS-CONF-2012-034

? Full 2011 dataset

Alan Barr

ATLAS-CONF-2012-033

No leptons,≥(2-6) jets + ET

miss

Squarks, Gluinos

Page 22

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ATLAS-CONF-2012-033

Squarks Gluinos/cascadesSmall Δm

Different mass scalesTotal of 11 signal regions

Alan Barr

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

ATLAS-CONF-2012-033

MC scaled by ~0.75 (based on control regions)Band shows JES, JER, MC stats

Alan Barr

ATLAS-CONF-2012-033

Alan Barr

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

Gluinos cascadesGluinos 4 x tops

Page 28

Alan Barr

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

ATLAS-CONF-2012-037

Top validation region

SR: 7j80

SR: 9j55

Alan Barr

ATLAS-CONF-2012-037

Most discrepant 7j80 p-value 0.07

Alan Barr

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

5 fb-1

Alan Barr

NOTHING SO FAR…

[

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 [

Tough points…. 1105.1024

Alan Barr [

1105.1024Tough points….

Alan Barr [ 40 ]

arXiv:1203.5763


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


5 fb-1ATLAS-CONF-2012-034

?

Alan Barr [ 41 ]

arXiv:1203.5763


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


[ 43 ]

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 ]


Direct gauginos

L-violating RPV

4 lepton + ETmiss

Alan Barr [ 46 ]

L-violating RPV

LSPλ121

gut ~ 0.032


Alan Barr

ATLAS-CONF-2012-036

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

[ 49 ]

ArXiv:1112.3832

(Pure MC predictions in parentheses)

2 jets only – veto on third jet

Alan Barr

Direct Sbottom

[ 50 ]

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

[ 51 ]

* indicative & for particular scenarios

Direct productionParticular decays

Alan Barr

2012 data taking

[

Alan Barr

Further motivation: the future…

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~1 TeV ?

Multi-TeV ?

LH-LHC?HE-LHC?

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A luminosity upgrade: additional reach…

Perhaps measuring properties…

Alan Barr

EXTRAS

[ 55 ]

Alan Barr

ATLAS-CONF-2012-041

1-lepton + jets + ETmiss

Strong chargino neutralino

Page 56

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Chargino cascade decays etc: One-lepton

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

Control & validationregions

ATLAS-CONF-2012-041

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Control regions – jet multiplicity

[ 59 ]

ATLAS-CONF-2012-041

Alan Barr

1-lepton results

[ 60 ]

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

[ 61 ]

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

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

[ 64 ]

ATLAS-CONF-2012-033

Alan Barr


[ 65 ]

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

Phys. Rev. Lett. 108 (2012) 041805

http://prl.aps.org/abstract/PRL/v108/i4/e041805



Alan Barr

t + tbar + ETmiss

[ 67 ]

Phys. Rev. Lett. 108 (2012) 041805

Not yet sensitive to stop production




Alan Barr

ATLAS-CONF-2011-096

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

[ 72 ]

ATLAS-CONF-2012-034

?

Chargino mass=90.2GeV

Alan Barr

https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResultsGood reading…






Alan Barr

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

ExoticsPublicResults

ATLAS-CONF-2011-096

Monojet

Found elsewhere…

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



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

Page 78

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

Hunting the invisible at the LHC

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