Searching for New Physics at the LHC using Dijets

Searching for New Physics Searching for New Physics at the LHC using Dijetsat the LHC using Dijets

Marco CARDACIMarco CARDACI

Universiteit Antwerpen Universiteit Antwerpen

on behalf of the CMS and ATLAS on behalf of the CMS and ATLAS collaborationscollaborations

Les Rencontres de Moriond, QCD, 2008Les Rencontres de Moriond, QCD, 2008La Thuile, Valle d’Aosta, March 8-15La Thuile, Valle d’Aosta, March 8-15

OutlineOutline

IntroductionIntroduction

CMS searchesCMS searches

ATLAS searchesATLAS searches

ConclusionsConclusions

Marco CARDACI,10/03/08, La ThuileMarco CARDACI,10/03/08, La Thuile

Short introductionShort introduction

CMS & ATLAS use:CMS & ATLAS use:

AA= +1 destructive interference sign; g= +1 destructive interference sign; g22 = 4 = 4

XX

q, q, gq, q, g

q, q, gq, q, g

q, q, gq, q, g

q, q, gq, q, gDijet ResonanceDijet Resonance

s - channels - channel

Contact InteractionContact Interaction

qq

qq qq

qq

Signals are Dijet Resonances and Contact Interactions Signals are Dijet Resonances and Contact Interactions

LLqqqqqqqq = A (g = A (g22/2/2LLLL) q) qLLqqLLqqLLqqLL

Quark compositeness (scale Quark compositeness (scale ):): √√s s Narrow resonant states of excited fermions on Narrow resonant states of excited fermions on

shellshell

√√ss Effective 4 fermions Contact Interaction: Effective 4 fermions Contact Interaction:

Resonances:Resonances: Technicolor Technicolor Color Octect Color Octect

TechnirhoTechnirho Grand Unified Theory Grand Unified Theory W’ & Z’ W’ & Z’ Superstrings & GUTSuperstrings & GUT E E66 diquarks diquarks Compositeness Compositeness Excited quarks Excited quarks Extra Dimensions Extra Dimensions RS Gravitons RS Gravitons Extra Color Extra Color Colorons & Axigluons Colorons & Axigluons

Marco CARDACI,10/03/08, La ThuileMarco CARDACI,10/03/08, La Thuile 33

MotivationsMotivations CMS Physics Technical Design Report (PTDR) CMS Physics Technical Design Report (PTDR)

is the CMS baseline plan for dijet analysisis the CMS baseline plan for dijet analysis

Complementary to the PTDR sensitivity estimatesComplementary to the PTDR sensitivity estimates Focus on 10 pbFocus on 10 pb-1-1 , 100 pb , 100 pb-1-1 & 1OOO pb & 1OOO pb-1 -1 luminositiesluminosities

Explores how we do analysis, find optimalExplores how we do analysis, find optimal cuts cuts

XX

q, q, gq, q, g

q, q, gq, q, g

q, q, gq, q, g

q, q, gq, q, gDijet ResonanceDijet Resonance

s - channels - channel

Dijet Angular DistributionsDijet Angular Distributions

Starting pointStarting point

mainly t - channelmainly t - channel

QCDQCDq, q, gq, q, g

q, q, gq, q, g

q, q, gq, q, g

q, q, gq, q, g


Analysis strategiesAnalysis strategies

MET / MET / EETT for QCD Dijet and cut for QCD Dijet and cut

Use jets in the Barrel which are sensitive to New PhysicsUse jets in the Barrel which are sensitive to New Physics Cut on MET/Cut on MET/EETT to reject catastrophic noise/beam halo/cosmics to reject catastrophic noise/beam halo/cosmics

raysrays Inclusive Jet Rate vs Jet pInclusive Jet Rate vs Jet pTT: Contact Interactions: Contact Interactions

Large rate compared to QCDLarge rate compared to QCD

Dijet Rate vs Dijet Mass: ResonancesDijet Rate vs Dijet Mass: Resonances SimpleSimple bump hunting in Dijet Spectra bump hunting in Dijet Spectra

Dijet Ratio = Dijet Ratio = N (|N (||<0.7) / N (0.7<||<0.7) / N (0.7<||<1.3 ): both searches|<1.3 ): both searches Simple measure of angular distribution vs dijet massSimple measure of angular distribution vs dijet mass

|||<1.3|<1.3

|||<1|<1

Jet Response vs Jet Response vs relative to Barrel relative to Barrel

CMS PreliminaryCMS Preliminary


Inclusive Jet pInclusive Jet pT T and Contact and Contact

InteractionsInteractions Contact Interactions create large rate at high pContact Interactions create large rate at high pT T and immediate discovery and immediate discovery

possiblepossible Error dominated by Jet Energy Scale (Error dominated by Jet Energy Scale (10%) in early running (10 pb10%) in early running (10 pb-1-1))

EE 10% not as big an effect as 10% not as big an effect as ++= 3 TeV for p= 3 TeV for pTT>1 TeV>1 TeV PDF “errors” and statistical errors (10 pbPDF “errors” and statistical errors (10 pb-1-1) smaller than E scale error) smaller than E scale error

With 10 pbWith 10 pb-1-1 we can see new physics beyond Tevatron exclusion of we can see new physics beyond Tevatron exclusion of + + up to up to 2.7 TeV2.7 TeV

Rate of QCD and Contact InteractionsRate of QCD and Contact Interactions Sensitivity with 10 pbSensitivity with 10 pb-1-1

Sys Sys Err.Err.

PDF PDF Err.Err.


Dijet Resonances in Rate vs Dijet Dijet Resonances in Rate vs Dijet MassMass

Measure rate vs Corrected Dijet Mass and look for resonancesMeasure rate vs Corrected Dijet Mass and look for resonances Use a smooth parameterized fit or QCD prediction to model backgroundUse a smooth parameterized fit or QCD prediction to model background

Strongly produced resonances can be seenStrongly produced resonances can be seen Convincing signal for a 2 TeV excited quark in 100 pbConvincing signal for a 2 TeV excited quark in 100 pb-1-1

evatron excluded up to 0.87 TeVevatron excluded up to 0.87 TeV

QCD BackgoundQCD Backgound Resonances with 100 pbResonances with 100 pb-1-1


Resonances: Resonances: cut & mass resolution cut & mass resolution QCD cross section rises dramaticallyQCD cross section rises dramatically

with |with || cut due to t-channel pole| cut due to t-channel pole

Z’ signal only gradually increases Z’ signal only gradually increases with |with || cut | cut optimal value at low | optimal value at low |||

Optimal cut is at |Optimal cut is at || < 1.3 | < 1.3 for a 2 TeV dijet resonancefor a 2 TeV dijet resonance

Optimization uses Pythia Z’ angular Optimization uses Pythia Z’ angular distribution for the resonancedistribution for the resonance

cut and cross sectioncut and cross section

ResolutionResolution

Gaussian core of resolution Gaussian core of resolution for for |||<1 and ||<1 and ||<1.3 is similar|<1.3 is similar

Resolution for Corrected JetsResolution for Corrected Jets 9% at 0.7 TeV 9% at 0.7 TeV 4.5% at 5 TeV4.5% at 5 TeV

cut and sensitivitycut and sensitivity

pp00+p+p11/M/MCorrected CaloJets

GenJets

Natural Width


Dijet Ratio from QCD & Contact Dijet Ratio from QCD & Contact InteractionsInteractions

Dijet Ratio = N(|Dijet Ratio = N(||<0.7) / N(0.7<||<0.7) / N(0.7<||<1.3):|<1.3): Number of events in which each leading jet has Number of events in which each leading jet has |||<0.7|<0.7

divided by the number ofevents in which each leading jet has 0.7<divided by the number ofevents in which each leading jet has 0.7<|||<1.3|<1.3 Dijet Ratio is a simple measure of the dijet angular distribution vs Dijet MassDijet Ratio is a simple measure of the dijet angular distribution vs Dijet Mass Numerator is sensitive to New Physics, denominator is dominated by QCDNumerator is sensitive to New Physics, denominator is dominated by QCD QCD background has flat dijet ratio = 0.5 up to Dijet Mass = 6 TeVQCD background has flat dijet ratio = 0.5 up to Dijet Mass = 6 TeV Contact interactions increase the Dijet Ratio at high massContact interactions increase the Dijet Ratio at high mass CMS can discover CMS can discover ++= 4, 7 & 10 TeV with 10, 100 & 1000 pb= 4, 7 & 10 TeV with 10, 100 & 1000 pb -1-1

33

55

10

++ (TeV) (TeV)

QCD

Dijet RatioDijet Ratio

Jet 1Jet 1

Jet 2Jet 2

NumeratorNumeratorSensitiveSensitiveto New to New PhysicsPhysics

|cos |cos **| ~ 0| ~ 0

DenominatorDenominatorDominated Dominated

by QCDby QCD|cos |cos *| ~ 0.7,*| ~ 0.7,

usuallyusually

Jet 1Jet 1

Jet 2Jet 2 Jet 2 (rare)Jet 2 (rare)oror

= -1.3 - 0.7 0.7 1.3= -1.3 - 0.7 0.7 1.3

zz

zz


Dijet Resonances with Dijet RatioDijet Resonances with Dijet RatioDijet Ratio vs MassDijet Ratio vs Mass

Dijet Ratio for Spin ½, 1, 2Dijet Ratio for Spin ½, 1, 2

Spin ½ (q*), spin 1 (Z’), and spin 2 (RS Spin ½ (q*), spin 1 (Z’), and spin 2 (RS Graviton)Graviton)resonances are more isotropic resonances are more isotropic than QCD in dN / dcosthan QCD in dN / dcos**

Resonances Dijet Ratio larger than for QCD Resonances Dijet Ratio larger than for QCD because numerator mainly low cos because numerator mainly low cos *and*anddenominator mainly high cos denominator mainly high cos **

Dijet Ratio from signal + QCD Dijet Ratio from signal + QCD compared to statistical errors for QCDcompared to statistical errors for QCD

Resonances normalized with q* Resonances normalized with q* cross section for |cross section for ||<1.3 to see effect of |<1.3 to see effect of spinspin

Convincing signal for 2 TeV strongConvincing signal for 2 TeV strongresonance in 100 pbresonance in 100 pb-1-1 regardless of spin regardless of spin

Technique for discovery, confirmation Technique for discovery, confirmation and eventually spin measurementand eventually spin measurement


Analysis strategiesAnalysis strategies Inclusive Jet Rate vs Jet pInclusive Jet Rate vs Jet pTT

To characterize the excess of high pTo characterize the excess of high pTT events:events:

R(R() = ( N(E) = ( N(ETT > E > ETT00 )/N(E )/N(ETT < E < ETT

00) ) |) ) |

To quantify the distance: To quantify the distance:

RRdistdist = (R( = (R() – R(SM)) / √ ) – R(SM)) / √ 22R(R()) + + 22

R(SM)R(SM)

EETT00 11001100 GeV to optimize R GeV to optimize Rdistdist

Dijet angular distributionDijet angular distribution

= e= e| | 11 - - 22 | |

RR(() = ) = (( N( N(OO )/N( )/N(OO) ) )) | |

Sensitivity: Sensitivity: R R11 = (R = (R(() – R) – R(SM)) / √ (SM)) / √ 22RR(()) + + 22

RR(SM)(SM)

00 2.82.8 to optimize R to optimize R11

1010 TeV TeV

33 TeVTeV

4040 TeV TeV

2020 TeVTeV

55 TeV TeV L=20fL=20fbb-1-1

ATLAS ATLAS PreliminaryPreliminary

EETT (GeV) (GeV)

EETT00

RRdistdist optimization optimization


L=30fbL=30fb-1-1

(TeV)(TeV)

33 55 1010 2020 4040

LL 4.3 pb4.3 pb--

11

15 pb15 pb-1-1 1.4 fb1.4 fb--

11

19 fb19 fb--

11

234 fb234 fb-1-1

Integrated Luminosities to achieve RIntegrated Luminosities to achieve Rdistdist = 3 = 3

RRdistdist values for L = 300 fb values for L = 300 fb-1-1

(TeV)(TeV)

33 55 1010 2020 4040

RRdistdist 797944

427427 4444 1212 3.3.44

QCDQCD

QCD +1,2,3%QCD +1,2,3%

QCD -1,2,3%QCD -1,2,3%

15 TeV15 TeV

33 TeV TeV

55 TeV TeV

2200 TeV TeV1010 TeV TeV

L=L=330 0 fbfb-1-1

ATLAS PreliminaryATLAS Preliminary

1% uncertainty in Energy Scale is 1% uncertainty in Energy Scale is enough to hide enough to hide = 20 TeV = 20 TeV

InIncclulussivivee jjetet production production Inclusive leading Dijet pInclusive leading Dijet pTT spectra (QCD+CI) spectra (QCD+CI) Fractional Difference from QCDFractional Difference from QCD

=3, 5, 10 TeV might be =3, 5, 10 TeV might be ruled out or verified ruled out or verified withwith first first tens of pbtens of pb-1-1 of good of good datadata

No systematics is included (PDF, No systematics is included (PDF, calorimeter non linearity, …), therefore calorimeter non linearity, …), therefore the required L will be larger, in case of the required L will be larger, in case of = 40 TeV the discovery is still unclear = 40 TeV the discovery is still unclear

Marco CARDACI,10/03/08, La ThuileMarco CARDACI,10/03/08, La Thuile1414

PDF uncertainties studiesPDF uncertainties studies

CTEQ6M PDFs based on NLO CTEQ6M PDFs based on NLO calculations fitted to DIScalculations fitted to DIS

20 parametric global fit,20 parametric global fit, 40 error PDFs (+ one central value) 40 error PDFs (+ one central value)

used to obtain right-hand plotused to obtain right-hand plot

PDF uncertainty studies PDF uncertainty studies done done with with Pythia 6.326, pPythia 6.326, pTT > 1 TeV > 1 TeV

centrcentralal

PDF errorPDF error

=10 =10 TeV TeV L=30 fbL=30 fb--

11

ATLAS ATLAS PreliminaryPreliminary

CTEQ6M errors

CTEQ6M central

10 10 TeVTeV

10 fb10 fb-1-1

RRdistdistNN

CTEQ6M errors

10 10 TeVTeV100 100 fbfb-1-1

RRdistdistNN

CTEQ6M central

Systematic error due to PDF uncertainties in this case Systematic error due to PDF uncertainties in this case PDFPDF(R(Rdistdist)= 1.40)= 1.40To be compared with to RTo be compared with to Rdistdist((=40TeV, 300 fb=40TeV, 300 fb-1-1) = 3.40) = 3.40

Fractional Difference + PDF errorFractional Difference + PDF error


Dijet angular Dijet angular distributiondistribution

ppTT > 350 GeV > 350 GeV

Mjj > 4 TeVMjj > 4 TeV

20 fb20 fb-1-1

2020 TeV TeV

33 TeVTeV55 TeV TeV

4040 TeV TeV

1010 TeVTeV

ppTT > 350 > 350 GeVGeV

RR11

(Te(TeV)V)

R1R1350350 R1R110001000

33 646646 100100

55 172172 7171

1010 1616 1010

2020 2.32.3 0.70.7

4040 0.650.65 <0.1<0.1 Inclusive leading Dijet angular distributionInclusive leading Dijet angular distribution

ppTT cut optimization cut optimizationDijet mass cut optimizationDijet mass cut optimization

RR11 optimization optimization

ppTT > 350 GeV increase > 350 GeV increase the sensitivitythe sensitivity

Dijet invariant mass cut Dijet invariant mass cut optimized for each optimized for each


Discovery Discovery limitslimits

RR11 from Pythia (2 partons with highest p from Pythia (2 partons with highest pTT), ), = 10 TeV, m = 10 TeV, mjjjj = 4 TeV, p = 4 TeV, pTT > 1 TeV > 1 TeV Systematic error due to PDF uncertainties in this case Systematic error due to PDF uncertainties in this case

PDFPDF(R(R11)= 0.88, which is comparable to R)= 0.88, which is comparable to R11((=40TeV, 30 fb=40TeV, 30 fb-1-1) = 0.80) = 0.80 Preliminary to say RPreliminary to say R11 is less sensitive than R is less sensitive than Rdistdist

(TeV)(TeV)

33 55 1010 2020 4040

L (fbL (fb--

11))< 1 < 1 pbpb-1-1

6 pb6 pb-1-1 0.7 fb0.7 fb-1-1 34 fb34 fb-1-1 426 fb426 fb--

11

Integrated luminosities to achieve RIntegrated luminosities to achieve R11 = 3 = 3

RR11 values for L = 300 fb values for L = 300 fb-1-1

(TeV)(TeV)

33 55 1010 2020 4040

RR11 25002500 666655

6262 8.98.9 2.52.5

CTEQ6M errors

CTEQ5L

CTEQ6M central

10 10 TeVTeV

10 fb10 fb-1-1

RR11

CTEQ5L

RR11

CTEQ6M errors

CTEQ6M central

10 10 TeVTeV100 100 fbfb-1-1

Also in this case no systematics are included Also in this case no systematics are included (PDF, calorimeter non linearity, …)(PDF, calorimeter non linearity, …) = 40 TeV the discovery is unclear = 40 TeV the discovery is unclear


CoConclusionsnclusions

Inclusive jet pInclusive jet pTT analysis gives a convincing signal for a Contact analysis gives a convincing signal for a Contact InteractionInteractionscale scale ++ = 3 TeV in 10 pb = 3 TeV in 10 pb-1-1

Rate vs. Dijet mass gives a convincing signal for a 2 TeV q* with 100 pbRate vs. Dijet mass gives a convincing signal for a 2 TeV q* with 100 pb --

11

Dijet Ratio can discover Dijet Ratio can discover ++ 4, 7 and 10 TeV for 10 pb 4, 7 and 10 TeV for 10 pb-1-1, 100 pb, 100 pb-1-1, and , and 1 fb1 fb-1-1

Dijet Ratio can discover or confirm a dijet resonance,Dijet Ratio can discover or confirm a dijet resonance,and eventually measure its spinand eventually measure its spin

Early limits: Early limits: ++ 3, 5,10 TeV might be discovered or rulled out 3, 5,10 TeV might be discovered or rulled outwith first with first tens of pbtens of pb-1-1 of good data of good data

++ 20 20 TeV TeV still should be visible with larger integrated luminositystill should be visible with larger integrated luminosity Discovering Discovering ++ 40 40 TeV TeV still unclear still unclear Systematic errors studies in progressSystematic errors studies in progress


Dijet group in CMS:Dijet group in CMS:A. Bhatti, B. Bollen, M. C., F. A. Bhatti, B. Bollen, M. C., F.

Chlebana,Chlebana,S. Esen, R. Harris, K. Kousouris, M. Jha, S. Esen, R. Harris, K. Kousouris, M. Jha,

D. Mason and M. ZielinskiD. Mason and M. Zielinski

ATLAS:ATLAS:

S. Ferrag, S. Ferrag, LL.. Přibyl Přibyl

Thanks toThanks to

BACKUP SLIDES BACKUP SLIDES

Resonances propertiesResonances properties

(qg (qg q q**)) dN/d cos dN/d cos** 1 + cos 1 + cos**

(QCD)(QCD) dN/d cos dN/d cos** 1/(1 1/(1 –– cos cos**))22

(qq, gg (qq, gg A or C; qq A or C; qq Z’, q Z’, q11qq22 W’ )W’ )

dN/d cosdN/d cos** 1 + cos 1 + cos22**

Spin Spin ½½

Spin Spin 11

Spin Spin 22

(qq (qq G G gg, gg gg, gg G G qq) qq)dN/d cosdN/d cos** 1 1 – cos– cos44**

(qq (qq G G qq) qq) dN/d cos dN/d cos** 1 – 3 cos 1 – 3 cos22** + 4 cos + 4 cos44**

(gg (gg G G gg) gg) dN/d cos dN/d cos** 1 + 6 cos 1 + 6 cos22** + cos + cos44**

2121

CDF current limitsCDF current limits

Observed mass exclusion Observed mass exclusion range (GeV)range (GeV)

Model Model descriptiondescription

260 – 870260 – 870 Excited quarkExcited quark

260 – 1110260 – 1110 Color-octet Color-octet technirhotechnirho

260 – 1250260 – 1250 Axigluon or Axigluon or ColoronColoron

290 – 630290 – 630 E6 diquark E6 diquark

280 – 840280 – 840 W'W'

320 – 740320 – 740 Z'Z'

Mass exclusionMass exclusion

Limits on production of new particles decaying into dijetsLimits on production of new particles decaying into dijets

Preliminary results just releasedPreliminary results just released Best limits on dijet resonancesBest limits on dijet resonances Thanks to Ken HatakeyamaThanks to Ken Hatakeyama

2222

Preliminary Results Just ReleasedPreliminary Results Just Released Best limits on dijet resonancesBest limits on dijet resonances Thanks to Ken Hatakeyama !Thanks to Ken Hatakeyama !

ResonanResonancece

Excluded Excluded (GeV)(GeV)

ResonanResonancece

Excluded Excluded (GeV)(GeV)

A or CA or C 260 - 1250260 - 1250 DD 290 - 630290 - 630

T8T8 260 - 1110260 - 1110 W ’W ’ 280 - 840280 - 840

q*q* 260 - 870 260 - 870 Z ’Z ’ 320 - 740320 - 740

CDF Dijet Resonance Search in CDF Dijet Resonance Search in Run IIRun II

2323

Model descriptionModel description

Excited quark (f=f'=fs=1) Excited quark (f=f'=fs=1)

Color-octet technirho [top-color-assisted-technicolor (TC2) Color-octet technirho [top-color-assisted-technicolor (TC2) couplings, M'couplings, M'88=0, M(pi=0, M(pi2222

88)=5M()=5M()/6, M(pi)/6, M(pi222211)=M(pi)=M(pi2222

88)/2, )/2, MM88=5M(=5M()/6] )/6]

Axigluon and flavor-universal coloron (mixing of two Axigluon and flavor-universal coloron (mixing of two SU(3)'s, cot(SU(3)'s, cot())1) 1)

E6 diquark E6 diquark

W' (SM couplings)W' (SM couplings)

Z' (SM couplings)Z' (SM couplings)

Model detailsModel details

2424

Detectors characteristicsDetectors characteristics

2525

DetectorsDetectors

2626

Particle detection in CMSParticle detection in CMS

2727

Dijet eventDijet event

5.022 R

CalorimeterCalorimeterSimulationSimulation

hhff

EETT

0011

-1-1

Jet 1Jet 1 Jet 2Jet 2

Dijet Mass = 900 Dijet Mass = 900 GeVGeV 2

212

21 )()( ppEEm

CMS Barrel & Endcap CMS Barrel & Endcap CalorimetersCalorimeters

protonproton

=-1=-1

protonproton

Jet 1Jet 1

Jet 2Jet 2

=1=1

ff

TransverseTransverse

=0=0

qq

Dijets are easy to findDijets are easy to find Two jets with highest pTwo jets with highest pTT

in the calorimeterin the calorimeter A jet is the sum of calorimeterA jet is the sum of calorimeter

energy in a cone of radiusenergy in a cone of radius

2828

Jet Reconstruction & Correction Jet Reconstruction & Correction in CMSin CMS

Barrel jets have uniform response Barrel jets have uniform response & sensitive to new physics& sensitive to new physics

Jet response changes smoothlyJet response changes smoothly and slowly up to | jet and slowly up to | jet | = 1.3 | = 1.3

CaloTowers with | CaloTowers with | | < 1.3 are in | < 1.3 are in barrelbarrel with uniform construction. with uniform construction.

CaloTowers with 1.3< | CaloTowers with 1.3< | | < 1.5 | < 1.5 are in barrel / endcap transition are in barrel / endcap transition regionregion

Some of our analyses use | jet Some of our analyses use | jet | < | < 1.3, 1.3, others still use | jet others still use | jet | < 1 | < 1

All are migrating to | jet All are migrating to | jet | < 1.3 | < 1.3 which is optimal for dijet resonanceswhich is optimal for dijet resonances

Measure relative response vs. jet Measure relative response vs. jet in data with dijet balance in data with dijet balance

Data will tell us what is Data will tell us what is the region of response we can trustthe region of response we can trust

Barrel JetBarrel Jet(|(||<1.3)|<1.3)

Probe Probe JetJet

(any (any ))

Dijet BalanceDijet Balance

|||<1.3|<1.3

|||<1|<1

Jet response vs Jet response vs relative to | relative to | | < 1.3| < 1.3

CMS PreliminaryCMS Preliminary

= 1.3= 1.3

HBHBHEHE

Hcal towers and Hcal towers and cuts cuts

Transition RegionTransition Region

= 1= 1

Standard jet reconstructionStandard jet reconstruction Cone algorithm R=0.5Cone algorithm R=0.5

Midpoint & iterative cone Midpoint & iterative cone indistinguishable at high pindistinguishable at high pTT

Standard jet kinematicsStandard jet kinematics Jet E = Jet E = EEii, Jet p=, Jet p=ppii

= tan= tan-1-1(p(pyy/p/pxx)) EETT = E sin = E sin, p, pTT==√√ppxx

22+p+pyy22

Standard MC jet correctionsStandard MC jet corrections Scales Jet (E,pScales Jet (E,pxx,p,pyy,p,pzz) by) by

~~1.5 at E1.5 at ETT = 70 GeV = 70 GeV ~~1.1 at E1.1 at ETT = 3 TeV = 3 TeV for jets in barrel region for jets in barrel region

Dijet is two leading jets.Dijet is two leading jets. m=m= √ √(E(E11+E+E22))22 –(p –(p11+p+p22))22

2929

Inclusive Jet pInclusive Jet pTT Inclusive jet pInclusive jet pTT is a QCD measurement that is sensitive to new physics is a QCD measurement that is sensitive to new physics

Counts all jets inside a pCounts all jets inside a pTT bin and bin and interval, and divides by bin width and luminosity interval, and divides by bin width and luminosity

Corrected CaloJets agree reasonably well with GenJetsCorrected CaloJets agree reasonably well with GenJets CaloJets jets before corrections shifted to lower ECaloJets jets before corrections shifted to lower ETT than GenJets than GenJets Ratio between corrected CaloJets and GenJets is “resolution smearing”: small at high Ratio between corrected CaloJets and GenJets is “resolution smearing”: small at high

ppTT

Simple correction for resolution smearing in real data is to divide rate by this Simple correction for resolution smearing in real data is to divide rate by this ratioratio

Resolution SmearingResolution SmearingInclusive Jet Cross SectionInclusive Jet Cross Section

3030

Trigger and LuminosityTrigger and Luminosity Collision rate at LHC is expected to be 40 MHzCollision rate at LHC is expected to be 40 MHz

40 million events every second40 million events every second CMS cannot read out and save that manyCMS cannot read out and save that many

Trigger chooses which events to saveTrigger chooses which events to save

Two levels of trigger are used to reduce rate in stepsTwo levels of trigger are used to reduce rate in steps Level 1 (L1) reduces rate by a factor of 400 Level 1 (L1) reduces rate by a factor of 400 High Level Trigger (HLT) reduces rate by a factor of 700High Level Trigger (HLT) reduces rate by a factor of 700

Trigger tables are intended for specific luminositiesTrigger tables are intended for specific luminosities We’ve specificied a jet trigger table for three We’ve specificied a jet trigger table for three

luminositiesluminosities L = L = 10103232 cm cm-2-2 s s-1-1. Integrated luminosity . Integrated luminosity 100 pb 100 pb-1-1

LHC schedule projects this after LHC schedule projects this after 1 months running1 months running L = L = 10103333 cm cm-2-2 s s-1-1. Integrated luminosity . Integrated luminosity 1 fb 1 fb-1-1

LHC schedule projects these after LHC schedule projects these after 1 year of 1 year of runningrunning

L = L = 10103434 cm cm-2-2 s s-1-1. Integrated luminosity . Integrated luminosity 10 fb 10 fb-1-1

One months running at design luminosityOne months running at design luminosity

4 x 107 Hz

1 x 105 Hz

1.5 x 102 Hz

Event Selection

CMS Detector

L1 Trigger

HLT Trigger

Saved for Analysis

3131

PathPathL1L1 HLTHLT ANAANA

EETT

(GeV(GeV))

Pre-Pre-

scalescaleRateRate

(Hz)(Hz)EETT

(GeV(GeV))

RateRate

(Hz)(Hz)

Dijet Dijet MassMass

(GeV)(GeV)

LowLow 2525 20002000 146146 6060 2.82.8

MedMed 6060 4040 9797 120120 2.42.4 330330

HighHigh 140140 11 4444 250250 2.82.8 670670

SupeSuperr

450450 11 1414 600600 2.82.8 18001800

L = 10L = 103232

100 pb100 pb-1-1

UltraUltra 270270 11 1919 400400 2.62.6 11301130

L = 10L = 103333

1 fb1 fb-1-1

Add New Threshold (Ultra) - Increase Prescales by 10Add New Threshold (Ultra) - Increase Prescales by 10

Mass values Mass values are efficient are efficient for each for each trigger, trigger, measured measured with prior with prior trigger trigger

L = 10L = 103434

10 fb10 fb-1-1

Add New Threshold (Super) - Increase Prescales by 10Add New Threshold (Super) - Increase Prescales by 10

CMS jet trigger saves all high ECMS jet trigger saves all high ETT jets & pre-scales the lower E jets & pre-scales the lower ETT jets jets

As luminosity As luminosity increases increases new trigger new trigger paths are paths are addedadded

Each with Each with new new unprescaled unprescaled threshold.threshold.

CMS Jet Trigger Table and Dijet Mass CMS Jet Trigger Table and Dijet Mass AnalysisAnalysis

3232

Dijet Ratio and Systematic Dijet Ratio and Systematic UncertaintiesUncertainties

Systematics (red) Systematics (red) are smallare small

They cancel in They cancel in the ratiothe ratio

Relative Energy Relative Energy

ScaleScale Energy scale in Energy scale in

center vs edge center vs edge of barrel in of barrel in

Estimate Estimate +/- +/- 0.5 %0.5 % is is achievable in achievable in barrelbarrel

Determined with Determined with dijet balancedijet balance

Parton Parton DistributionsDistributions

We’ve used We’ve used CTEQ6.1 CTEQ6.1 uncertaintiesuncertainties

P T D R

3333

Resonances produced by the Resonances produced by the valence quarks of each protonvalence quarks of each proton

Large cross section from higher Large cross section from higher probability of quarks in the initial probability of quarks in the initial state at high x state at high x

E6 diquarks (ud E6 diquarks (ud D D ud) can be ud) can be discovered up to 3.7 TeV for 1 fbdiscovered up to 3.7 TeV for 1 fb-1-1

Resonances produced by color forceResonances produced by color force Large cross sections from strong Large cross sections from strong

forceforce With just 1 fbWith just 1 fb-1-1 CMS can discover CMS can discover

Excited Quarks up to 3.4 TeVExcited Quarks up to 3.4 TeV Axigluons or Colorons up to 3.3 TeVAxigluons or Colorons up to 3.3 TeV Color Octet Technirhos up to 2.2 TeVColor Octet Technirhos up to 2.2 TeV

Discoveries possible with only 100 Discoveries possible with only 100 pbpb-1-1

Large discovery potential with 10 fbLarge discovery potential with 10 fb-1-1

Mass (TeV)

E6 Diquark

Excited Quark

Axigluonor Coloron

Color OctetTechnirho

CMS100 pb-1

CMS1 fb-1

CMS10 fb-1

5 Sensitivity to Dijet Resonances

0 1 2 3 4 5

P T D R

Rate: Discovery Sensitivity to Rate: Discovery Sensitivity to ModelsModels

3434

Rate: Exclusion Sensitivity to Rate: Exclusion Sensitivity to ModelsModels

E6 Diquark

Excited Quark

Axigluonor Coloron

Color OctetTechnirho

W ’

R S Graviton

Z ’

Tevatron Exclusion (Dijets)

CMS100 pb-1

CMS1 fb-1

CMS10 fb-1

Mass (TeV)

95% CL Sensitivity to Dijet Resonances

0 1 2 3 4 5 6

Resonances produced via Resonances produced via color interaction or valence color interaction or valence quarksquarks

Wide exclusion possibility Wide exclusion possibility connecting up with many connecting up with many exclusions at Tevatronexclusions at Tevatron

CMS can extend to lower CMS can extend to lower mass to fill gapsmass to fill gaps

Resonances produced weakly Resonances produced weakly are harderare harder

But CMS has some sensitivity But CMS has some sensitivity to each model with sufficient to each model with sufficient luminosityluminosity

Z’ is particularly hardZ’ is particularly hard Weak coupling and requires Weak coupling and requires

an anti-quark in the proton at an anti-quark in the proton at high xhigh x

P T D R

3535

Discovery and Exclusion Discovery and Exclusion sensitivity to CIsensitivity to CI

Excluded ScaleExcluded Scale Discovered ScaleDiscovered Scale

10 pb10 pb-1-1 100 pb100 pb--

11

1 fb1 fb-1-1 10 pb10 pb-1-1 100 pb100 pb--

11

1 fb1 fb-1-1

(TeV)(TeV) < 5.3< 5.3 < 8.3< 8.3 < 12.5< 12.5 < 4.1< 4.1 < 6.8< 6.8 < 9.9< 9.9

Excluded ScaleExcluded Scale Discovered ScaleDiscovered Scale

10 pb10 pb-1-1 100 pb100 pb--

11

1 fb1 fb-1-1 10 pb10 pb-1-1 100 pb100 pb--

11

1 fb1 fb-1-1

(TeV)(TeV) < 3.8< 3.8 < 6.8< 6.8 < 12.2< 12.2 < 2.8< 2.8 < 4.9< 4.9 < 9.1< 9.1

Before |Before | cut optimization cut optimization

After |After | cut optimization cut optimization

Senstivity to contact interactions with 10 pb-1, 100 pb-1, and 1 fb-1 Estimates include statistical uncertainties only

3636

InIncclulussivivee jjetets – calorimeter s – calorimeter nonlinearitynonlinearity

What effect a calorimeter nonlinearity will make?What effect a calorimeter nonlinearity will make? To parametrize nonlinearity of ATLAS hadronic calorimeter (simple method):To parametrize nonlinearity of ATLAS hadronic calorimeter (simple method):

)ln)1/(1(

1.)(

TTT EbhecEmeasE

e/h - noncompensation, b – nonlinearity e/h - noncompensation, b – nonlinearity (smaller values achievable by e.g. weighting method)(smaller values achievable by e.g. weighting method)

c makes nonlin. and lin. spectra equal at 500 GeVc makes nonlin. and lin. spectra equal at 500 GeV

=10 TeV=10 TeV

b = 0.045, 2% @ 2TeVb = 0.045, 2% @ 2TeV

pT (GeV)pT (GeV)

QCDQCD

3737

Documents

Searching for New Physics at the LHC using Dijets