Tracey Berry UK SUSY/Exotics Meeting 1 st March 2007 1 Gravitons Tracey Berry Royal Holloway A first look into at ATLAS

Tracey Berry UK SUSY/Exotics Meeting1st March 2007

1

Gravitons

Tracey Berry

Royal Holloway

A first look into

at ATLAS


2

10-2

10-4

10–6

10-8Tevatron 700 GeV GKK

Signature: Narrow, high-mass resonance states in dilepton/dijet/diboson channels

Dilepton channelH

andall undrum ModelRandall, Sundrum, Phys Rev Lett 83 (99)

1 highly curved/warped extra dimension (ED)

Gravity localised in the ED

ED

SM

Dilepton Channel

l-Z/

l+

l-

l+

l-

l+

l-

Diphoton Channel


3

10-2

10-4

10–6



700 GeV KK Graviton at the Tevatron

k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from

top to bottom

Mll (GeV)

Mll (GeV)

Davoudiasl, Hewett, Rizzo hep-ph0006041

1000 3000 5000

10.50.10.050.01

KK excitations can be excited individually on

resonance

1500 GeV GKK and subsequent tower states

K/MPl

LHC

Dilepton channelH

andall undrum Model

d/dM (pb/GeV)

10-2

10-4

10-6

10-8

10-10

Model parameters:• Gravity Scale:

1st graviton excitation mass: m1

= m1Mpl/kx1, & mn=kxnekrc(J1(xn)=0) • Coupling constant: c= k/MPl

1 = m1 x12 (k/Mpl)2

width

positionResonance

= Mple-kRc

k = curvature, R = compactification radius

Randall, Sundrum, Phys Rev Lett 83 (99)


4

Allenach et al, hep-ph0006114

RS1 Discovery Limit

Allenach et al, hep-ph0211205*


k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from

top to bottom

Mll (GeV)

400 600 800 1000

Mll (GeV) 1000 3000 5000

10.50.10.050.01


resonance


K/MPl

LHC

At the LHC only the 1st excitations are likely to be seen at the LHC, since the other modes are suppressed by the falling parton distribution functions.Allenach et al, JHEP 9 19 (2000), JHEP 0212 39 (2002)

d/dM (pb/GeV)

10-2

10-4

10-6

10-8

10-10

Davoudiasl, Hewett, Rizzo hep-ph0006041

• Best channels to search in are G(1)e+e- and G(1) due to the energy and angular resolutions of the LHC detectors

• G(1)e+e- best chance of discovery due to relatively small bkdg, from Drell-Yan*


5

Present RS Constraints

D0 performed combined ee+ (diem search)

• c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale)

• Theoretically preferred <10TeV assures no new hierarchy appears between mEW and

Present Experimental LimitsTheoretical Constraints

CDF performed ee & search, then combine


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MG=1.5 TeV100 fb-1

HERWIG Main Bkdg: Drell-Yan Model-independent analysis

RS model with k/MPl=0.01 as a reference (pessimisitc scenario) Fast Simulation

Sensitive at 5 up to 2080 GeV

RS1 Discovery Limit

Di-electron

*Reach goes up to 3.5 TeV for c=0.1 for a 20% measurement of the coupling.

Allenach et al, hep-ph0211205*

100 fb-1


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CMS RS Discovery Limits

GG11GG11μμ++μμ--

GG11ee++ee--

c>0.1 disfavoured as bulk curvature becomes to large (larger than the 5-dim Planck scale)

Theoretically preferred <10TeV

LHC completely covers the region of interest


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RS1 Model Determination

Allanach et al, hep-ph 0006114

Note: acceptance at large pseudo-rapidities is essential for spin discrimination (1.5<|eta|<2.5)

e+e-

LHC

MC = 1.5 TeV

MG=1.5 TeV 100 fb-1

Stacked histograms

How could a RS G resonance be distinguished from a Z’ resonance?Potentially using Spin information:G has spin 2: ppGee has 2 components: ggGee & qqGee: each with different angular distributions:

Spin-2 could be determined (spin-1 ruled out) with 90% C.L. up to MG = 1720 GeV with 100 fb-1


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RS Gravitons Datasets

MC Dataset• 3400 G and 10200 Gee Events: • Generated with Mass = 1000 GeV k/Mpl=0.1• Code version 11.0.42 and reconstructed with FullSim

• Limited reconstruction information available. - can't trace mother/daughter - so just use the highest 2 Et e/photons in the event for now to lookat distributions.

More detailed investigations to follow in future….

Thanks to Barry King at Liverpool for generating the samples and producing ntuples.


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ee Invariant Mass

Generator level invariant mass: first two e+/- with opposite charge and with E>100 GeV

Reconstructed mass:highest energy 2 Et’s in the eventwhich pass the selection criteria

101905323

No +/- requirement here


11

Reconstructed e/Selection Criteria Electron:Has a TrackIsEMel==0Pt > 5.0|Eta|<2.5E/P>0.5WeightRatio>0.6NBel + NPixel>0NHitsel = NBel + NPixel + ElecNSCTHits[i-1] + ElecNTRTHits[i-1]> 5

Photon:isEMphot==0Etphot>5.0|Eta|<2.5Charge photon==0


12

Reconstructed e variables

5323

For G=1000 GeV

Interested in reconstructing e+/- with E above 200 GeV

And up to ~1.5-2 TeV

GeV

GeVGeV

GeV


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5323

LHC

In G rest-frame

MG=1 TeVFor MG=1 TeV

Graviton production is mainly gg initiated

e+e-


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e+e- ~ uniformly

distributed in phi


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Gee Distributions

peaks atimplies e’s back-to-back

Expect the ee to be back-to-back in the G rest frame


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Reconstructed mass:highest energy 2 e’s in the event which pass the selection criteria

Charge ReconstructionWhen more generator information available will match generated and reconstructed electrons

5.1%94.9%


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Most events have 1 or 2 “good” reconstructed electrons

Gee Events


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G

Reconstructed mass:highest Et 2 ’s in the event which pass the selection criteria


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Future Plans

Look at new samples which have more generator level information available.

Look into reconstruction efficiencyInvestigate e/ selection criteria

Look into backgrounds


20

BACKUP….


21

10-2

10-4

10–6




k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from

top to bottom

Mll (GeV)

400 600 800 1000

Mll (GeV)Davoudiasl, Hewett, Rizzo

hep-ph0006041

1000 3000 5000

10.50.10.050.01


resonance


K/MPl

LHC

Dilepton channelH

Model parameters:• Gravity Scale:

1st graviton excitation mass: m1

= m1Mpl/kx1, & mn=kxnekrc(J1(xn)=0) • Coupling constant: c= k/MPl

1 = m1 x12 (k/Mpl)2

width

positionResonance

= Mple-kRc

Experimental Signature for Model

jetjet,,,eeGgg,qq KK

k = curvature, R = compactification radius

d/dM (pb/GeV)

10-2

10-4

10-6

10-8

10-10

1 extra warped dimension


22

RS1 Discovery Limit

• Two muons/electrons in the final state

• Bckg: Drell-Yan/ZZ/WW/ZW/ttbar

• PYTHIA/CTEQ6L

• LO + K=1.30 both for signal and DY

• Full (GEANT-4) and fast simulation/reco

• Viable L1 + HLT(rigger) cuts

• Theoretical uncert.

• Misalignment, trigger and off-line reco inefficiency, pile-up

Di-lepton statesGG11μμ++μμ--

GG11ee++ee--

c=0.1100 fb-1

c=0.01100 fb-1 Solid lines = 5

discoveryDashed = 1 uncert. on L

I. Belotelov et al. CMS NOTE 2006/104CMS PTDR 2006

B. Clerbaux et al. CMS NOTE 2006/083CMS PTDR 2006


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• Two photons in the final state

• Bckg: prompt di-photons, QCD hadronic jets and gamma+jet events, Drell-Yan e+e-

• PYTHIA/CTEQ5L

• LO for signal, LO + K-factors for bckg.

• Fast simulation/reco + a few points with full GEANT-4 MC

• Viable L1 + HLT(rigger) cuts

• Theoretical uncert.

• Preselection inefficiency

Di-photon states

GG11

RS1 Discovery Limit

c=0.1

• Bckg: QCD hadronic jets• L1 + HLT(rigger) cuts

Di-jet states

5 Discovered Mass: 0.7-0.8 TeV/c2

K. Gumus et al. CMS NOTE 2006/070CMS PTDR 2006

M.-C. Lemaire et al. CMS NOTE 2006/051CMS PTDR 2006


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Also the size (R) of the ED could also be estimated from mass and cross-section measurements.

RS1 Model Parameters

Allenach et al, JHEP 9 19 (2000), JHEP 0212 39 (2002)

A resonance could be seen in many other channels: , , jj, bbbar, ttbar, WW, ZZ, hence allowing to check universality of its couplings:

Relative precision achievable (in %) for measurements of .B in each channel for fixed points in the MG, plane. Points with errors above 100% are not shown.


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Extra Dimensions: Motivations

if warp factor kRc ~11-12

Planck TeV brane

Randall, Sundrum, Phys Rev Lett 83 (99)

MEW (1 TeV) << MPlanck (1019 GeV)?

1 highly curved EDGravity localised in the ED

Some of these models can be/have been experimentally tested at high energy colliders

= Mple-kRc

~ TeV

Documents

Tracey Berry UK SUSY/Exotics Meeting 1 st March 2007 1 Gravitons Tracey Berry Royal Holloway A first look into at ATLAS