Discovery Potential in Jets + MET at 10 TeV ? ATLAS Monojets/Dijets Meeting 20 th May 2008 Claire Gwenlan.

Discovery Potential in Discovery Potential in

Jets + MET at 10 TeV ?Jets + MET at 10 TeV ?

ATLAS Monojets/Dijets MeetingATLAS Monojets/Dijets Meeting

2020thth May 2008 May 2008

Claire GwenlanClaire Gwenlan

IntroductionIntroduction

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

Studies at 14 TeV show that some new discoveries could be made Studies at 14 TeV show that some new discoveries could be made very early at the LHC (eg. light SUSY (UED)? Black Holes? TeV-very early at the LHC (eg. light SUSY (UED)? Black Holes? TeV-scale resonances?)scale resonances?)

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

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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

As a case study, I have used a search for As a case study, I have used a search for SUSY in the SUSY in the dijets+METdijets+MET channel channel (based on CSC note work)(based on CSC note work)

Currently no MC… BUT can re-weight existing 14TeV samplesCurrently no MC… BUT can re-weight existing 14TeV 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:

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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 Reweight MethodCheck of Reweight Method

Good agreement between reweighted and 10 TeV samples (bkgs also checked)Good agreement between reweighted and 10 TeV samples (bkgs also checked)

EG:EG: sample of SUSY signal (SU3) events generated in ATLFAST sample of SUSY signal (SU3) events generated in ATLFAST

pTJet,1,2 >150,100

GeV

Meff = pTJet,1 + pT

Jet,2 + MET

Effective Mass

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

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PDF weight

SUSY search in SUSY search in 22Jet + MET final stateJet + MET final state analysis strategy based on SUSY CSC5 – full details found in note)analysis strategy based on SUSY CSC5 – full details found in note)

Cut No.Cut No. 2-Jet+MET Analysis Cuts2-Jet+MET Analysis Cuts

00 J70_XE70 triggerJ70_XE70 trigger

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

22 ppTTJet,2Jet,2 > 100 GeV > 100 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

Case Study: 2Case Study: 2Jets + METJets + MET

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

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

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

BEFOREBEFORE reweighting reweighting

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Case Study: 2Case Study: 2Jet + MET Jet + MET

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

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

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

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Case Study: 2Case Study: 2Jet + MET Jet + MET

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

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

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

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Case Study: 2Case Study: 2Jet + MET Jet + MET

numbers are maximum significances (taken above some Mnumbers are maximum significances (taken above some Meffeff threshold) threshold)

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

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

Some Example NumbersSome Example Numbers100 pb100 pb-1-1

99

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. The numbers in the table above are calculated assuming 50% uncertainty on QCD and

20% on all other bkgs – these are not necessarily the “right” numbers – dedicated bkg studies needed for those!

SummarySummary

Is 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 seem to be potential!YES – there does 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 a lot !!! – this case study has focussed on SUSY experiments is still a lot !!! – this case study has focussed on SUSY discovery in Jets+MET– and this may not need much data (i.e. it discovery in Jets+MET– and this may not need much data (i.e. it doesn’t take much to give large S/doesn’t take much to give large S/B values for the models B values for the models considered here!)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 for potentially feasible! It looks like it could be, but the limiting factor for Jets+MET searches will of course be how well we can Jets+MET searches will of course be how well we can determine determine and understandand understand the bkgs with the small amount of data we expect the bkgs with the small amount of data we expect

1010

BackUpsBackUps

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Method: Method: other example checksother example checks a few other example checks a few other example checks (currently low statistics, except for J8MET)(currently low statistics, except for J8MET) good good agreementagreement

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

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

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

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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 50K50K1414