SUSY Discovery at 10TeV? SUSY working group meeting 21 st May 2008 Claire Gwenlan, UCL.

SUSY Discovery at 10TeV?SUSY Discovery at 10TeV?

SUSY working group meetingSUSY working group meeting

2121stst May 2008 May 2008

Claire Gwenlan, UCLClaire Gwenlan, UCL

IntroductionIntroduction10 TeV run coming soon (2-3 months? 100 pb10 TeV run coming soon (2-3 months? 100 pb-1-1 possible?) possible?)

Studies show that, if SUSY is relatively light, it could be discovered Studies show that, if SUSY is relatively light, it could be discovered

very early at the LHC (based on 14 TeV Monte Carlo)very early at the LHC (based on 14 TeV Monte Carlo)

22

EG: 0-lepton + 2-Jet + MET inclusive SUSY search (CSC5)

so what about at 10 TeV – could we hope to see something?

Currently no MC… BUT can re-weight existing 14 TeV samplesCurrently no MC… BUT can re-weight existing 14 TeV samples hadronic cross section given by:hadronic cross section given by:

For a particular kinematic configuration For a particular kinematic configuration

with s, t, u, should just need to change the with s, t, u, should just need to change the

probability that incoming partons *had* probability that incoming partons *had*

that configuration i.e. just a PDF re-weightthat configuration i.e. just a PDF re-weight

PDFs PDFs from 14TeV from 14TeV 10TeV 10TeV

' 2 ' 21, 2

2 21 2

PDF x Q ,flav1 ×PDF x ,Q ,flav2Weight=

PDF x ,Q ,flav1 ×PDF x ,Q ,flav2

' 2 ' 21, 2

2 21 2

PDF x Q ,flav1 ×PDF x ,Q ,flav2Weight=

PDF x ,Q ,flav1 ×PDF x ,Q ,flav2

proton PDFs

Plot from James Stirling: DIS08 ^ ^ ^ ^ ^̂

xi : x of parton i at 14TeV; x i’: x of parton i at 10TeV

Re-weight MC to 10 TeV using:Re-weight MC to 10 TeV using:

33

1

0

ˆ 2 2 2 21 2 1 1 2 2 1 2 s

flav

= dx dx PDF(x ,Q ,flav ) × PDF(x ,Q ,flav ) × σ p ,p ,α (Q ),Q

hard subprocess cross section

Check of MethodCheck of Method

Good agreement between re-weighted and 10 TeV samples (bkgs also checked)Good agreement between re-weighted and 10 TeV samples (bkgs also checked)

EG:EG: sample of SU3 SUSY events generated in ATLFAST sample of SU3 SUSY events generated in ATLFAST

Effective MassEffective Mass

example weights (all < 1)example weights (all < 1)

44

PDF weightsPDF weights

pTJet,1,2 >150,100

GeV

Meff = pTJet,1 + pT

Jet,2 + MET [GeV]

Good agreement between re-weighted and 10 TeV samples (bkgs also checked)Good agreement between re-weighted and 10 TeV samples (bkgs also checked) method rather general method rather general can re-weight to any CM energy < 14 TeV can re-weight to any CM energy < 14 TeV

Check of MethodCheck of Method

Good agreement between re-weighted and 10 TeV samples (bkgs also checked)Good agreement between re-weighted and 10 TeV samples (bkgs also checked)

EG:EG: sample of SU3 SUSY events generated in ATLFAST sample of SU3 SUSY events generated in ATLFAST

Effective MassEffective Mass

example weights (all < 1)example weights (all < 1)

55

PDF weightsPDF weights

pTJet,1,2 >150,100

GeV

Meff = pTJet,1 + pT

Jet,2 + MET [GeV]

Good agreement between re-weighted and 10 TeV samples (bkgs also checked)Good agreement between re-weighted and 10 TeV samples (bkgs also checked) method rather general method rather general can re-weight to any CM energy < 14 TeV can re-weight to any CM energy < 14 TeV

Cut No.Cut No. 22Jet + MET Analysis CutsJet + MET Analysis Cuts

00 J70_XE70 triggerJ70_XE70 trigger

11 ppTTJet,1Jet,1 > 150 GeV > 150 GeV


33 MET > max(100,0.3*MMET > max(100,0.3*Meffeff))

44 |phi(Jet1,2)-phi(MET)| > 0.2|phi(Jet1,2)-phi(MET)| > 0.2

55 no isolated leptonno isolated lepton

SUSY analysisSUSY analysis

“Generic search for R-parity conserving SUSY in the inclusive 2-Jet + MET+0-lepton channel”

Effective Mass: Meff = ∑ pTJet,i + MET [sum runs over two highest-pT jets]

66

EG: CSC5-style, inclusive 2- and 3-Jet analyses (full details in note)EG: CSC5-style, inclusive 2- and 3-Jet analyses (full details in note) results shown in main part of talk are for the 2-Jet case (3-Jet results in backups)results shown in main part of talk are for the 2-Jet case (3-Jet results in backups)

no optimisation of cuts for 10 TeV – i.e. just a simple repeat of CSC5 analysis

Results: SU3 vs. SM bkgResults: SU3 vs. SM bkg

Integrated L = 100 pbIntegrated L = 100 pb-1-1

BEFOREBEFORE reweighting reweighting

EG: CSC5 2EG: CSC5 2Jet + MET + Jet + MET + 00lepton SUSY analysis:lepton SUSY analysis:

77NOTE: all MC predictions shown at LO (i.e. no k-factors applied)

Results: SU3 vs. SM bkgResults: SU3 vs. SM bkg


BEFOREBEFORE reweighting reweighting

AFTERAFTER reweighting reweighting

14 TeV 14 TeV 10 TeV: 10 TeV: SU3 signal reduced by ~ 2.9SU3 signal reduced by ~ 2.9 SM bkg reduced by ~ 2.3SM bkg reduced by ~ 2.3 - QCD reduced by ~ 2.4- QCD reduced by ~ 2.4 - tt reduced by ~ 2.6- tt reduced by ~ 2.6 - W/Z reduced by ~ 2- W/Z reduced by ~ 2 - diboson reduced by ~ 1.9- diboson reduced by ~ 1.9

88


NOTE: all MC predictions shown at LO (i.e. no k-factors applied)


Comparison of some Comparison of some other SUSY benchmark other SUSY benchmark points (SUX)points (SUX)

all are mSUGRA, but cover all are mSUGRA, but cover quite a wide range of quite a wide range of phenomenologies phenomenologies

SU1SU1 coannihilation regioncoannihilation region

SU2SU2 focus point regionfocus point region

SU3SU3 bulk regionbulk region

SU4SU4 low mass pointlow mass point

SU6SU6 funnel regionfunnel region

SU8.1SU8.1 coannihilation regioncoannihilation region

Results: Results: other mSUGRA pointsother mSUGRA points

99


Statistical Significance (S/√B)Statistical Significance (S/√B)

14 TeV14 TeV 10 TeV10 TeV

SU1SU1 2323 1212

SU2SU2 < 1< 1 < 1< 1

SU3SU3 3939 2222

SU4SU4 106106 6767

SU6SU6 1616 88

SU8SU8 2424 1212

Statistical SignificancesStatistical Significances

100 pb100 pb-1-1

Numbers are maximum Numbers are maximum significances (taken above significances (taken above some Msome Meffeff threshold) threshold)

1010

Discovery SignificancesDiscovery Significances

100 pb100 pb-1-1

Discovery Significance (ZDiscovery Significance (Znn) *) *

14 TeV14 TeV 10 TeV10 TeV

SU1SU1 9.19.1 5.95.9

SU2SU2 <1<1 <1<1

SU3SU3 11.211.2 8.38.3

SU4SU4 12.512.5 12.512.5

SU6SU6 7.57.5 4.84.8

SU8SU8 9.79.7 6.26.2

* Zn is a measure of the significance (as

used in CSC5) which tries to take into

account systematic uncertainties on the

bkg measurements. Numbers in the table

are calculated assuming 50% uncertainty

on QCD and 20% on all other bkgs –

these are not the “right” numbers –

dedicated bkg studies needed for those!

1111

Numbers are maximum Numbers are maximum significances (taken above significances (taken above some Msome Meffeff threshold) threshold)

(don’t take too much notice of the (don’t take too much notice of the actual values – it’s just to get a actual values – it’s just to get a (very) rough feeling)(very) rough feeling)

SummarySummaryIs there potential for discovery with small amounts of 10 TeV data?Is there potential for discovery with small amounts of 10 TeV data?

YES – there does at least seem to be potential!YES – there does at least seem to be potential!

A 5x increase in centre-of-mass energy compared to previous A 5x increase in centre-of-mass energy compared to previous experiments is still experiments is still a lota lot !!! – and the discovery of light SUSY may not !!! – and the discovery of light SUSY may not need much data (it doesn’t take much to give large S/need much data (it doesn’t take much to give large S/B values for the B values for the models considered here)models considered here)

BUT that data still needs to be understoodBUT that data still needs to be understood

This was really just a quick look for fun – to see if anything is even This was really just a quick look for fun – to see if anything is even potentially feasible! It looks like it could be, but the limiting factor will of potentially feasible! It looks like it could be, but the limiting factor will of course be how well we can course be how well we can determine and understanddetermine and understand the the backgrounds with the small amount of data we expect.backgrounds with the small amount of data we expect.

1212

Bonus Extra – method could be useful to allow studies to proceed before 10 TeV Bonus Extra – method could be useful to allow studies to proceed before 10 TeV MC available? Or as an alternative for samples that will not be re-generated?MC available? Or as an alternative for samples that will not be re-generated?

BackUpsBackUps


Results: Results: other mSUGRA pointsother mSUGRA points

1414

Cut Cut 3-Jet Analysis Cuts3-Jet Analysis Cuts

00 J70_XE70 triggerJ70_XE70 trigger



33 MET>max(100,0.25*MMET>max(100,0.25*Meffeff))

44 |phi(Jet1,2,3)-phi(MET)| > |phi(Jet1,2,3)-phi(MET)| > 0.20.2

55 no isolated leptonno isolated lepton


mSUGRA PointsmSUGRA Points

m0m0 m1/2m1/2 A0A0 tantan RegionRegion

SU1SU1 7070 350350 00 1010 > 0> 0 CoannihilationCoannihilation

SU2SU2 35503550 300300 00 1010 > 0> 0 Focus pointFocus point

SU3SU3 100100 300300 -300-300 66 > 0> 0 BulkBulk

SU4SU4 200200 160160 -400-400 1010 > 0> 0 Low massLow mass

SU6SU6 320320 375375 00 5050 > 0> 0 FunnelFunnel

SU8.1SU8.1 210210 360360 00 4040 > 0> 0 CoannihilationCoannihilation

More details on the mSUGRA points consideredMore details on the mSUGRA points considered

1515

MC Bkg SamplesMC Bkg SamplesSampleSample CSC IDCSC ID (pb)(pb) NN

T1T1 005200005200 450450 600 K600 K

TTbarTTbar 005204005204 383383 100 K100 K

J4METJ4MET 008090008090 916.40916.40 70K70K

J5METJ5MET 008091008091 655.655. 85K85K

J6METJ6MET 008092008092 67.4267.42 35K35K

J7METJ7MET 008093008093 5.35.3 4K4K

J8METJ8MET 008094008094 2.21x102.21x10-2-2 4K4K

WWWW 005985005985 24.524.5 50K50K

WZWZ 005986005986 2.12.1 50K50K

ZZZZ 005987005987 7.87.8 50K50K

ZeeZee 008194008194 46.246.2 5K5K

ZmumuZmumu 008195008195 9.609.60 5K5K

ZtautauZtautau 008191008191 4.504.50 5K5K

ZnunuZnunu 008190008190 41.3341.33 35K35K

WenuWenu 008270008270 49.0549.05 50K50K

WmunuWmunu 008271008271 28.6428.64 50K50K

WtaunuWtaunu 008272008272 55.9155.91 50K50K1616

some other example checks some other example checks all show good agreement all show good agreement (within statistical limitations)(within statistical limitations)

Method: Some Bkg ChecksMethod: Some Bkg Checks

CSCID: 008270CSCID: 008270CSCID: 008190CSCID: 008190

CSCID: 005985CSCID: 005985CSCID: 008094CSCID: 008094

Some Bkg Weight ExamplesSome Bkg Weight Examples

T1T1 WenuWenu

ZnunuZnunu

WWWWZeeZee SU3SU3

Weights for all processed events i.e. no cuts imposed

J5METJ5MET

J8METJ8MET

SU4SU4

Sensitivity to choice of QSensitivity to choice of Q22

2 2 2F LSP LSP2 2 2

2F 2 2 2

2F

2st'u'• default : ; t' = t-m , u'=u-m

s +t' +u'2stu

(1): s +t +u

(2): s

s, t, u are the usual Mandelstam variables

Re-weighting technique not very sensitive to choice of factorisation scale

Meff = pTJet,1 + pT

Jet,2 + MET [GeV]

EG. EG. Re-weighting to Other Re-weighting to Other s Valuess Values

Meff = pTJet,1 + pT

Jet,2 + MET [GeV]

Should be able to re-weight to any CM energy < 14 TeVShould be able to re-weight to any CM energy < 14 TeV but *not* to higher beam energies, since some regions of phase space but *not* to higher beam energies, since some regions of phase space

accessible at higher accessible at higher s, will not be populated in the 14 TeV Monte Carlos, will not be populated in the 14 TeV Monte Carlo

5 TeV5 TeV

7 TeV7 TeV

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“Commissioning to 10 TeV should be fast, no quench being anticipated, giving us confidence that the experiments will be recording data at record high energies by the summer.

In 1989, it was only a matter of weeks before LEP produced its first profound result – a measurement of the number of light neutrino families. In this respect at least, history will not be repeating itself. The LHC is a discovery machine, and the discoveries it is chasing will require a little more patience.”

Robert Aymar, on the 10TeV run

SUSY Discovery at 10TeV? SUSY working group meeting 21 st May 2008 Claire Gwenlan, UCL.

Documents

tev slide

tev method

jet results

tev su19

jet case

tev reweight mc

jet analyses

jet analysis cuts