High mass bump searches in DrellYan spectrum at CDF

1
High mass bump searches in Drell-Yan spectrum
at CDF
By Tracey Pratt

• CDF Detector
• Drell-Yan Signatures for New Physics
• Present Limits and Run II reaches
• First Run II Data
• Future Plans

April 02
Supervisor Todd Huffman, Oxford
University Advisor Kaori Maeshima,
FNAL Presented work by Tracey Pratt, Oxford and
Koji Ikado, Waseda University
2
CDF at Fermilab
CDF
CDF
Main Injector
Tevatron
D0
3
CDF Run I and Run II overview
Run I consisted of Run 1a (88/89) and Run 2b
(92-95) 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 June
2001 Centre of mass energy 2 TeV
4
CDF Detector - whats new
Barrel Muon Chamber
Silicon Microstrip Tracker
Old Partially New New
Muon System
Time-of-Flight
Central Calorimeter
Plug Calorimeter
Solenoid
5
Drell-Yan (DY)

• The Drell-Yan process probes the parton
  distribution
• functions (pdfs) of the protons at the scale Q2
  M?/ Z2

• Low background at high dilepton invariant mass
• Distinctive signatures
• two oppositely charged leptons produced
• have a high transverse momentum
• are isolated
• originate from a single interaction point

• For ?/Z production ? ? ?q fq q(x1)q(x2)

6
New Physics Searches with DY
Looking for deviations to the Standard Model at
high invariant mass

• New Gauge Bosons (Z')
• Extra Dimensions
• Quark-lepton Compositeness
• Technicolor (?T , ? T )

7
Run I Drell-Yan (DY)

• AFB smaller than SM
• AFB dips beyond 200 GeV/c2

X 88/89 CDF Run 1 dileptons (ee?? 4pb-1) o
92-95 CDF Run 1 dimuons (107.4pb-1)
8
Run 1 Z' limits
set limits for Z'? ll, with 110pb-1, in both
dielectron and dimuon channels
CDF Run I (110pb-1), for MZ? gt 600 GeV/c2 ?(Z?
).BR(Z? -gtll) is 40 fb. which excludes MZ? with
Standard Model coupling lt 690 GeV/c2 (Phys.
Rev. Lett.79 2192-2197, 1997))
9
Run II Extrapolated limits
Extrapolating from Run I, with 2 fb-1, the
predicted Z' mass reach could be extended to 900
GeV/c2 with ?s 1.8 TeV assuming Standard Model
couplings and to about 1000 GeV/c2 with ?s 2.0
TeV
10
Extra Dimensions
ADD model references

• New parameters
• String Scale Ms MPl(4n)
• A Factor ? (? 1)

RS model L.Randall and R.Sundrum,
Phys. Rev. Lett. 83,3370 (1999), Phys. Rev. Lett.
83,4690 (1999)
Graviton Exchange - modifies the rate and angular
distribution of high-mass Drell-Yan events
11
ADD model and RS model limits
700 GeV KK graviton
Run I
Compactification scales R-1 (TeV) ? 0.9 Run 1 at
95 C.L., 1.2 Run II, 6.7 LHC (one large
extra dimension) (hep-ph/9905311)
Effective Planck Scale lower limit (95
C.L.) 0.9-1.5 TeV Run I 1.3-2.5 TeV Run IIa,
1.7-3.5 TeV LHC Range corresponds to number of
extra dimensions n7-2. (hep-ph/9909218)
12
Compositeness
Compositeness Quark-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 ?- gt 3.8 TeV and ? gt 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))
13
Run II
Run II officially began on March 1st 2001 Started
taking physics quality data from June 2001

• CDF Upgrade improvements for Drell-Yan
  measurements
• Dielectron channel
• New plug calorimeter
• Dimuon channel
• Increased muon chamber coverage
• Improved Dimuon Background Rejection in run II

14
Time-Of-Flight (ToF) Detector in CDF
216 scintillator bars located just outside the
COT Expected time resolution is ? 100 ps.
15
ToF Cosmic-Ray Rejection
For high mass dimuon sample the dominant
background at high invariant mass is from cosmic
rays
Tupper Tlower
2L/c for CR dimuons
0 for interaction dimuons as for dielectrons
Above plots are from uncalibrated ToF.
Calibration work is in progress. Expected time
resolution is ? 100 ps.
16
Run II data
Run II officially began on March 1st 2001 Started
taking physics quality data from June 2001
Z???
Z?ee
17
Total Luminosity So Far
2 week shutdown in June to install 2 new
stochastic cooling tanks in the pbar accumulator,
aim is to give us higher luminosity and a smaller
transverse pbar beam size
18
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.
19
The END
Thats All Folks!
20
Run 1 limits on Z' production
21
CDF Run II Detector
? 1.0
? 1.5
? 2.0
? 3.0
ToF
Silicon Tracker Fiber Tracker Drift Chamber
Scintillator EM Cal. Hadronic Cal.
Solenoid Coil Toroid Steel Shielding
Key
22
CDF Upgrades for Run II
New Silicon tracking System SVX II 5 layers,
96cm, r-phi and r-z ISL 2 additional
layers, covers eta lt 2 L00 (Addition
of stereo capability to SVX, 3D Vertex and 2
more acceptance) New central drift chamber (And
strengthened COT stereo capabilities, maintain
Run 1 track eff and resolution) Improved and
integrated tracking system New deadtimeless
Trigger (track trigger moved to Level 1 and use
Silicon info at L2) Improved Calorimeter
resolution, efficiency and coverage New Plug
calorimeter, out to ? 2. Extra Muon
coverage Luminosity monitor Electronics Higher
center of mass energy Addition of a ToF detector
23
ADD model
ADD model Effective Planck Scale lower limit
0.9-1.5 TeV Run I (at 95 C.L.) 1.3-2.5 TeV Run
IIa and 1.7-3.5 TeV LHC Range corresponds to
number of extra dimensions n7-2. (hep-ph/9909218)
24
Extra Dimensions
RS model
Tevatron 700 GeV KK graviton
K/MPl
RS model Compactification scales R-1 (TeV) ?
0.9 Run 1 at 95 C.L., 1.2 Run II,
6.7 LHC (one large extra dimension)
(hep-ph/9905311)