Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Gravitons
Tracey Berry
Royal Holloway
A first look into
at ATLAS
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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10-2
10-4
10–6
10-8Tevatron 700 GeV GKK
Signature: Narrow, high-mass resonance states in dilepton/dijet/diboson channels
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)
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Allenach et al, hep-ph0006114
RS1 Discovery Limit
Allenach et al, hep-ph0211205*
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)
400 600 800 1000
Mll (GeV) 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
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*
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Allenach et al, hep-ph0006114
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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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.
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Reconstructed e variables
5323
LHC
In G rest-frame
MG=1 TeVFor MG=1 TeV
Graviton production is mainly gg initiated
e+e-
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Reconstructed e variables
e+e- ~ uniformly
distributed in phi
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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%
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Most events have 1 or 2 “good” reconstructed electrons
Gee Events
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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G
Reconstructed mass:highest Et 2 ’s in the event which pass the selection criteria
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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BACKUP….
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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10-2
10-4
10–6
10-8Tevatron 700 GeV GKK
Signature: Narrow, high-mass resonance states in dilepton/dijet/diboson channels
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)
400 600 800 1000
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
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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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Allenach et al, hep-ph0211205
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.
Tracey Berry UK SUSY/Exotics Meeting1st March 2007
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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