Tracey Pratt DIS 2002, Poland April 02
•CDF Detector
•Drell-Yan Signatures and New Physics
•Run I Limits and Run II reaches
•First Run II Data
•Near Future
A Search for New Physics in the High Mass Dilepton spectrum at CDF
Tracey Pratt, Oxford UniversityRepresenting the CDF collaboration
Tracey Pratt DIS 2002, Poland April 02
CDF at Fermilab
CDF CDF
D0
Tevatron
Main Injector
pp collisions
Tracey Pratt DIS 2002, Poland April 02
CDF Run I and Run II overview
Run I ran from 1992 until 95
In total 110pb-1 of data was collected
Centre of mass energy 1.8 TeV
Since the shutdown in 1996, the Tevatron and CDF have undergone major upgrades
Run II started in spring 2001
Centre of mass energy 2 TeV
Tracey Pratt DIS 2002, Poland April 02
CDF detector – what’s new?Muon System
COT
Plug Calorimeter
Time-of-Flight
Central Calorimeters
Solenoid
Silicon Tracker
New
Partially New
Old
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Cosmic Ray event in CDF
-6 4 2 0 2 4300 200 100 0
2
0
Et
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Z candidate
46.3 GeV
44.8 GeV
Invariant Mass 90.0 GeV
Tracey Pratt DIS 2002, Poland April 02
Drell-Yan (DY)
Low background at high dilepton invariant massDistinctive signatures:
•two oppositely charged leptons produced •have a high transverse momentum •are isolated•originate from a single interaction point
qq */ Z l+l-
p p
l+ l-
*/ Z
q q
Tracey Pratt DIS 2002, Poland April 02
New Physics Searches with Dileptons
New Gauge Bosons (Z')
Extra Dimensions
Quark-lepton Compositeness
Technicolor (T,T)
Looking for deviations to the Standard Model at high invariant mass
Tracey Pratt DIS 2002, Poland April 02
Run I Drell-Yan (DY)
•AFB smaller than SM
• AFB dips beyond 200 GeV/c2
X 88/89 CDF dileptons (ee+ 4pb-1)
o 92-95 CDF dimuons (107.4pb-1)
Invariant Mass in GeV/c2
0 100 200 300 400
101
100
10-1
10-2
10-3
10-4
Z and
only
d2/dMdy
CDF Collaboration, F.Abe et al., Phys. Rev. D 59, 052001 (1999)
Tracey Pratt DIS 2002, Poland April 02
Run 1 Z' limitsset limits for Z' ll, in both dielectron and dimuon channels
CDF Run I (110pb-1), for MZ > 600 GeV/c2 (Z ).BR(Z ->ll) is 40 fb.
which excludes MZ with Standard Model coupling < 690 GeV/c2
(Phys. Rev. Lett.79: 2192-2197, 1997))
Tracey Pratt DIS 2002, Poland April 02
Extrapolating from Run I, with 2 fb-1, if no candidates events in the high mass region are found, then predicted Z' mass reach could be extended to
1000 GeV/c2 with s =2.0 TeV
1200
1000
800
600
400
200
0
Integrated Luminosity (fb-1)
95 % CL Mass Reach (GeV/c2)
W'e (1.8TeV)
Z'll (2.0 TeV)
W' dijet (1.8TeV)
Z' dijet (1.8TeV)
10-2 10-1 1 10 102
Searches for New Gauge Bosons at Fermilab
Run II Reaches
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ADD modelIn which the fundamental Planck scale (MPl) can brought down to the TeV range, by allowing for a large compactified dimensions at the TeV scale.The SM fields are confined to a 3-D braneMassless gravitons propagate in the full 4+n dimensional space G
RS modelMPl is determined by the higher-dimensional curvature rather than the size of the extra dimension. There is one additional dimension.Gravity can be localised near a brane. Kaluza-Klein states can be produced separately on resonance,and produce potentially observable spin 2 resonances.The cleanest signal for graviton resonance production is either an excess in Drell-Yan,or in the dijet channel.L.Randall and R.Sundrum, Phys. Rev. Lett. 83,3370 (1999), Phys. Rev. Lett. 83,4690 (1999)
G
Gravitons can be detected by 1) Graviton Emission - gravitons radiate into the bulk appearing as missing energy2) Graviton Exchange - deviations in the cross-section from SM predictionN. Arkani-Hamed et el., Phys. Lett. B 429, 263 (1998), I. Antoniadis et al., Phys Lett. B 436, 257 (1998)
Extra Dimensions
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Extra DimensionsGraviton Exchange - modifies the rate and angular distribution of high-mass Drell-Yan events
Gg
g
l-
l+
Gq
q
l-
l+
+
+
• The SM exchange of a or Z boson interferes with the exchange of a graviton
• There is also a gluon-gluon initiated graviton exchange process which has no SM analogue.
/Z0 l-
l+
q
q
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ADD model and RS model limits
SM predictionQuantum Gravity Model for Ms valuesCDF results for dimuon samples
Effective Planck Scale lower limit (95% C.L.)0.9-1.5 TeV Run I1.3-2.5 TeV Run IIa, 1.7-3.5 TeV LHCRange corresponds to number of extra dimensions n=7-2. (hep-ph/9904234, hep-ph/9909218)
Compactification scales R-1 (TeV) 0.9 Run 1 at 95% C.L., 1.2 Run II, 6.7 LHC(hep-ph/9905311)
Run I
Mll (GeV)
RS model
10 -2
10 -4
10 –6
10 -8
200 400 600 800 1000 1200
d/dM (pb/GeV) 1
0.70.50.30.20.1
700 GeV KK graviton K/MPl
Mll (GeV)
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CompositenessQuark-lepton contact interaction was searched for in Run I in the dimuon and dielectron channels, by looking for an excess of dileptons compared to the Drell-Yan prediction.
Run Ib dielectron data set the limits on the compositeness scale to - > 3.8 TeV and + > 2.6 TeV.
In Run II we expect to be able to explore up to limits of approximately 5 TeV.
(Where +/- corresponds to the constructive / destructive interference with the dominant up-quark contribution to the cross-section.)
(Phys. Rev. Lett.79: 2198-2203, 1997))
Tracey Pratt DIS 2002, Poland April 02
TechnicolourIntegrated plots of dielectron mass distributions of D0 120 pb-1data and expected background
No signal above background found. T and T with masses < 225 GeV/c2 are ruled out for M( T) and M(T) < MW
B(
T
T e
+e- )*
(pb
)
100 200 300 400 500Mass (GeV)
1
10-1
10-295 % C.L. theoretical limits for T T e+e-
MT = 100 GeV
M, - M = 60 GeV
M, - M = 100 GeV
D0 Run I data
CC-CC
CC-EC
• Run I Data Background
100 200 300 400Minimum Mee (GeV)
Num
ber
of E
vent
s
103
102
101
1
103
102
101
1
*,Z*q
q
l-
l+T0,T
0
Tracey Pratt DIS 2002, Poland April 02
Run IIRun II started in spring 2001
CDF Upgrade improvements for Drell-Yan measurements•Dielectron channel New plug calorimeter •Dimuon channel Increased muon chamber coverage Better background rejection using Time-of-Flight detector to remove cosmic rays
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Time-Of-Flight (ToF) Detector in CDF
216 scintillator bars located just outside the COT
Expected time resolution is 100 ps.
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ToF Cosmic-Ray Rejection
~ 2L/c for CR dimuons ~ 0 for interaction ee and
Removal of the cosmic ray background is important for high mass dimuon sample
Above plots are from uncalibrated ToF. Calibration work is in progress.
Move Cosmic Rays with a cut requiring Tupper – Tlower > -5 ns
Cosmic Ray
Sample
Z ee
Tupper – Tlower
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Run II Drell-Yan spectrumDielectron Dimuon
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Future Plans
It is hoped that approximately 50-70 pb-1 data will be collected by Summer 2002
And 150 pb-1 by end of 2002.
We hope to find new physics or set new limits using the dilepton channels.
Tracey Pratt DIS 2002, Poland April 02
The End !