Searches at the Run II Tevatron Collider
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Transcript of Searches at the Run II Tevatron Collider
1 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Searches at the Run II Searches at the Run II Tevatron ColliderTevatron Collider
Leslie Groeron behalf of the DØ and CDF
Collaborations
Columbia University, New York
Conference on the Intersections of Particle and Nuclear Physics
New York City, NY May 22, 2003
2 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Searching for New Phenomena at the Searching for New Phenomena at the TevatronTevatron
• Many different forms– Observation of the last unseen particle predicted by
SM • Higgs
– Discovery of particles not in the SM• SUSY, Leptoquarks
– Identification of new gauge interactions• W’/Z’, Technicolor
– Unexpected complexities beyond the SM • Compositeness
– Fundamental changes to modern physics • Extra dimensions
• Common theme - look for experimental signatures that could exhibit deviations from expectations– Prefer to set model independent limits
Outline• Tevatron Run II• CDF+DØ Detectors • Preliminary Results
– Higgs– New Physics
• Run II future prospects
• Conclusions
3 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Tevatron Run II pp ColliderTevatron Run II pp Collider
’92-96 Run I 125 pb-1
top quark discovery ’96-’00 Accelerator and
Detector upgrades Main Injector and Recycler
rings Increased luminosity and
energy 2001-2005 Run IIa 2 fb-1
Upgrade Silicon and Trigger 2006 Run IIb 9-15 fb-1
--
Main Injector+ recycler
Tevatron
DØCDF
Chicago
Booster
p source
circumference: 6.2 km
• 1.8 TeV 1.96 TeV
– e.g. tt increase ~ 30%
• 6 p x 6 pbar 36 p x 36 pbar• Bunch spacing 3.5s 0.396s
Run II Delivered LuminosityTotal ~ 240 pb-1
Best week: ~7 pb-1
L = 4.5 x 1031 cm-2s-1
4 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
CDF & DØ Run II DetectorsCDF & DØ Run II Detectors
• Major upgrades to both detectors– New inner tracking chambers and silicon detectors– Extensions and improvements to muon systems and triggering– Complete replacement of trigger and DAQ elements for higher
rate• DØ: SMT, CFT, 2T superconducting
solenoid, preshowers, forward muon
DØ
CDF
• CDF: SVX, ISL, COT, TOF, plug calorimeters, intermediate muon
5 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Hunting for the Higgs at the TevatronHunting for the Higgs at the Tevatron
• Production cross section and decays are all calculable within the SM
• Inclusive Higgs cross section ~ 1pb– gg fusion ~0.7 pb (MH = 120 GeV)
(very large background)– Associated production with W/Z
WH ~ 0.16 pb ZH ~ 0.1 pb– leptonic decays of W/Z help give
the needed background rejection• At higher masses, can use inclusive
production plus WW decays
• Decay channels
– For MH < 135 GeV, H bb
– For MH > 135 GeV, HWW
H bb H WW
g
g
Hb
b
t
Associated production
q
q
W
Hb
b
*W
0Z
q
qH
b
b
*Z
Gluon fusion
b-tagging and Mbb resolution & scale
are critical for a light Higgs !
H bb H WW
LEP 95% CLMH>114.4 GeV/c2
6 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
W/Z + Jets in Leptonic ChannelsW/Z + Jets in Leptonic Channels
• First step towards W(→lv )/Z(ll) + H(bb) measurement
• Major background: W/Z + di-jets• W+jets
– Isolated high pT lepton (e or ) with large missing ET
– Jets pT > 20 GeV in || < 2.5
Zll channelDi-jet
Invariant Mass Mjj
L = 35 pb-1
Wl channelDi-jet
Invariant Mass Mjj
L = 35 pb-1Dominated byJet energy scale systematic uncertainty
36 events ~340 events
• Z+jets– 2 high pT lepton (ee or
) with mass consistent with Z
– Jets pT > 20 GeV in || < 2.5
Improvements• b-tags• Jet and mET
resolutions• Optimize
analyses
7 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
HiggsHiggsW*W/W*W/ final states final states• HW*Wl+l- (search for dilepton + mET)• h (search for high pT isolated diphotons)• A lot of interest in these channels as could be
greatly enhanced by new couplings:– 4th generation– Fermiophobic or Topcolor Higgs
• Physics backgrounds: Z/*, WW, tt, W/Z+jets, QCD• Use spin correlations to suppress background
contributions in leptonic mode()• Derive .Br limits assuming BR = 1 HW*Wl+l-
h
8 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
CDF Searches for H++CDF Searches for H++
• LR Symmetry breaking: SU(2)L x SU(2)L x U(1)B-L SU(2)L x U(1)L
• Higgs fields are a left-right doublet (½,½,0) and 2 triplets:• SUSY models suggest low mass doubly-charged Higgs
H++ Properties and Selection:• Pair (*/Z exchange) or singly (WW fusion) produced in pp
collisions• Same sign leptons decay mode provide strong experimental
signature• Inclusive electron trigger used (915.3 pb-1)• Two central same-sign
electrons required• MH 10% dielectron
mass windows explored
• Acceptance 20-35%• 0 events observed• Bckd: 0.60.5
9 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Limits on new Neutral Gauge Limits on new Neutral Gauge Bosons Z’Bosons Z’
DØ Run II Preliminary
L = 50.0 pb-1
DØ ee channel
Run I: MZ’ > 670 GeV
CDF e + combined
Run II(ee): MZ’ > 650 GeV/c2
Run II(): MZ’ > 455 GeV/c2
Run I (ee): MZ’ > 690 GeV /c2
L = 72 pb-1
• Neutral Gauge Bosons Z’– Assume SM couplings
• Searches in both ee and channels
• No excess observed in e or channels
• Bckds: DY, QCD misid electrons, WW, WZ, tt
10 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Mgraviton Lum Hewett
TeV pb- 1 GRW n=2 n=7
di- EM 50 1.12 1.16 0.89 1
di- muon 30 0.79 0.68 0.63 0.71
Run I (EM) 110 1.2 1.37 0.97 1.1
HLZ
Searches for Large Extra DimensionSearches for Large Extra Dimension
DØ Run II Preliminary
• Assume SM particles are confined to a 3D-brane
• Gravity propagates in the extra dimensions
• Signature is an excess of high mass dilepton and diphoton events from virtual KK graviton diagrams
• Angular distribution asymmetries arise from inteference terms
• DØ searches in diEM and dimuon– Invariant mass– Cos * (* = scattering
angle in rest frame)
di-EM
11 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
e+e+ combined combined
R-S Extra Dimension SearchesR-S Extra Dimension Searches
• Excited graviton in 5 dimensions
• Kaluza-Klein Modes lead to observable spin-2 resonancesG
• Free parameters: mass MG and coupling k/MPL
Dielecton: MG’ > 535 GeV/c2
Dimuon: MG’ > 370 GeV/c2
• Look for high mass excess in Drell-Yan dilepton events
• CDF searches in ee and channels
12 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
• Gravity Mediated SUSY• LSP is a light (<< 1 keV) gravitino,
phenomenology driven by nature of the NLSP (0)
• Signatures include 2 and missing ET
• DØ search
– Require two photons with pT > 20 GeV, apply quality and topological cuts
– 0 events observed– QCD fake background
determined from data (1.6 0.4)• Derive limits in Snowmass model • 95% CL on : 51 TeV gives
equivalent limit on Snowmass model gives M(0) > 66 GeV
• Run I limit: > 75 GeV
New Physics Searches in Diphoton New Physics Searches in Diphoton ChannelsChannels
ET
DØ Run II Preliminary
EETT//
L = 50.0 pb-1
Theory = "Snowmass“ slope:M = 2N
5 = 1
tan = 15, > 0
M0 > 66 GeV/c2
DØ Run II Preliminary
GG~~~0
1
13 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Limits on New Physics in the eLimits on New Physics in the e+X +X channelchannel
Cross-section Limit as a function of missing ET
• Very low backgrounds → pursue analysis in a model-independent way
• Require e,pT > 15 GeV, estimate fake rates from data, physics backgrounds from simulation
• 13 events, 9.6 2.7 exp. background(Z, QCD+W+jets, WWe, tt)L = 33.0 pb-1
A* new physics(e.g. acceptance for WW→e ~ 17%)
• At low MET physics backgrounds dominate, at high MET instrumental effects
• Complementary search in jets + MET• Sensitivity at the 0.1 pb level already
14 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Search in Trileptons: eel + XSearch in Trileptons: eel + X
• Typical selection efficiency for SUGRA 2-4%
• Sensitivity still about factor 7 away from extending excluded area in parameter space
• working on improving efficiency, adding channels
• Start from dielectron sample: understand trigger, reconstruction, simulation• Also verify determination of QCD fake background (from data)• Main backgrounds: Zee, and We)
.Br(3 leptons) < 3.5 pb (95% C.L.)Backgrounds Data
313210 GeV < M(ee) < 70 GeV 721
123
3
0
pT(e1) > 15 GeV, pT(e2) > 10 GeV 3216 ± 43.2660.2 ± 19.1
MT > 15 GeV 96.4 ± 8.1Add. Isolated Track, pT > 5 GeV 3.2 ± 2.3Missing ET > 15 GeV 0.0 ± 2.0
L = 42.0 pb-1
~~~~ 01
021 leepp
15 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
New: CDF Search for Excited Electrons New: CDF Search for Excited Electrons e*e*
• pp e* + e e + e (U. Baur PRD42, 3, 1990)
• Compositeness scale • Reconstruct M(e) in ee events• Bckds: Z, Z+jet, Multijet, W+jets• No events observed in 72 pb-1
• New Limit on e* mass is 785 GeV (=Me*)
• Previous limit from H1 was 223 GeV
16 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Searches in heavy flavor: tau Searches in heavy flavor: tau leptonsleptons
• Measurements of tau leptons important for tests of the SM and in the Higgs and SUSY sectors – Large backgrounds from jets– Multivariate techniques useful
• Both experiments have established a Z eh signal
• CDF has measured .B(W h)
Ntracks
L = 50 pb-1
OS-SScollinear approximation
14 9 data, 13 4 expected
• DØ also seen Z h using NN techniques
CDF Z
.BR(W) = 2.62 0.07stat 0.21sys 0.16lum nb .BR(Wl) = 2.69 0.1 nb (NNLO)
L = 70 pb-1
CDF Run II Preliminary
DØ Zeh
17 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Search for LeptoQuarksSearch for LeptoQuarks
• Extended gauge sectors and composite modelsLQ
• Directly couple leptons and quarks
• LQ lq or q, =BR(LQlq)
• Search for dilepton + jets and reconstruct LQ mass- or -
• Search for mET and dijets
• Limits depend on coupling
• Assume =1 or 0 for limits
LQ
LQLQ
LQ
L = 40.0 pb-1
MLQ2 > 157 GeV/c2
Run I >200 GeV
MLQ1 > 230 GeV/c2
Run I > 220 GeV/c2
60 < MLQ > 107 GeV/c2
DØ LQ2
CDF LQq
42 events, bckd: 4311
0 events, bckd: 3.43
18 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
- Inclusive jet sample
- 2 highest ET jets, ||<2
-
Search for Resonances in DijetsSearch for Resonances in Dijets
• Test QCD and sensitive to high mass resonances• Both experiments have measured dijet cross-section in Run II
– Agreement so far with SM expectations
• No significant excess beyond the Standard Model
- Fit mass spectrum with simple background parameterization
- Search for bumps comparable with the mass resolution
• Derive mass limits on the BR for various exotic particles
19 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
To set limits useTo set limits usestable stopstable stop
modelmodel
CHACHArged rged MMassive stable assive stable PParticlesarticles
TOF• Long lived particles escape without
decaying• Look like isolated slow-moving high-pT
muon• Use TOF and look for t(TOF) –t
(interaction)• Derive limit on production• Interpret 95% CL limits in stable stop
model– M(isolated stop) > 107 GeV/c2
– M(non-isolated stop) > 96 GeV/c2
• Limits independent of details of SUSY• Previous limits from ALEPH: M > 95 GeV
20 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
ConclusionsConclusions
Run II is well underway• We have commissioned all the detectors and have initial physics
results
– Cross-sections: W/Z, b-quarks, jets, B-lifetimes, rediscovered top
– New phenomena and Higgs searches are underway!
– Many results already competitive with Run I
• Excellent performance of new tracking systems
• CDF L2 Silicon displaced Vertex Trigger a great success
• DØ Silicon Track Trigger online by this summer
• Fully exploiting the luminosity delivered by the Tevatron
– New Physics results this summer (LP03, etc) + publications
– Sensitive at the 0.1 pb and 1 TeV scale in many channels
• Joint working group re-evaluating the Tevatron Higgs reach
• CoM Energy (~ x1.3-2), luminosity (~ x20-50), better detectors and analysis techniques (~ x2?) ~ x100 increase in sensitivity for some channels
The Tevatron will be the place for high-pT for the next few years
21 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
BackupsBackups
22 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
CDFII DetectorCDFII Detector
Retained from Run ISolenoid (1.4 Tesla)Central calorimetersCentral muon detectors
New in Run IITracking system
Silicon vertex detector (SVXII)Intermediate silicon layersCentral outer tracker (COT)
End plug calorimeterIntermediate muon detectorsTime of flight systemFront-end electronicsTrigger systemDAQ system
COT
0
.5
1.0
1.5
2.0
0 .5 1.0 1.5 2.0 2.5 3.0
END WALL
HADRON
CAL.
30
300
SOLENOID
= 1.0
= 2.0n
EN
D P
LUG
EM
CA
LOR
IMETER
EN
D P
LUG
HA
DR
ON
CA
LOR
IMETER
= 3.0n
n
m
m
Inner Silicon Intermediate Silicon
Time of Flight
23 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
DØ Inner Tracking VolumeDØ Inner Tracking Volume
(2T)
24 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
• The Higgs discovery potential for Run II was evaluated(hep-ph/0010338) using a parameterized fast detector simulation
• Discovery at 3-5 can be made
– Combine all channels, data from both D0 and CDF
– Improve understanding of signal and background processes
• b-tagging, resolution of Mbb
• Advanced analysis techniques are vital• Largest luminosity required to discover Higgs• Reevaluation of the expectations with real detector simulations and
Run II experience underway at the moment
Tevatron Higgs Working Group Tevatron Higgs Working Group
LE
P e
xcl
ud
eda
t 95
% C
.L.
Fermilab Run II Higgs Workshop
25 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
114 GeV 200 GeV
Searching for the HiggsSearching for the Higgs
• Focus has been on experiments at the LEP e+e–
collider at CERN (European Laboratory for Particle Physics) – Fits of electroweak data from precision
measurements of parameters of the W and Z bosons, combined with Fermilab’s top quark mass measurements, set an upper limit of mH ~ 200 GeV
– direct searches for Higgs production exclude mH < 114.4 GeV/c2
– Much of the favored region already excluded
• Fermilab Tevatron Run II has an exciting window of opportunity before LHC turn on
26 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Tevatron Luminosity Goals: 2003Tevatron Luminosity Goals: 2003
• Base– 200 pb-1 for FY03– 10 pb-1/week by year end
• Stretch– 320 pb-1 for FY03– 15 pb-1/week by year
end• FY02
– 80 pb-1 for the year– 6.7 pb-1 best week
best
luminosity 1 year ago
highest luminosity
to date
FY03 stretch goals
max. antiproton stackrate (E10/ hr) 10.2 13.1 18
max. antiproton stacksize (E10/ hr) 100 149 200
pbar xfer eff. .44 .66 .80
pbars/ bunch at low beta (E9) 8.7 25.1 31.0
protons/ bunch at low beta (E9) 126 205 240
peak luminosity (E31 cm-2sec-1) 1.18 4.06 6.6
27 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Tevatron Luminosity ScenariosTevatron Luminosity Scenarios
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Fiscal Year End
Ru
n I
I In
teg
rate
d L
um
ino
sity
(p
b-1
)
10/02 Projection Stretch 10/02 Projection Base
End of Run IIbDetector upgrades complete
Limit of Run I Silicon
Earliest date forLHC physics
28 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
ExpectedExpectedbb mass resolutionsbb mass resolutions
• Directly influences signal significance• Requires b-jet specific energy corrections (semi-leptonic,
fragmentation)• Z bb will be a calibration signal for b-jet energy corrections• To improve mass resolution, combine tracks with calorimeter
cells for jet energy measurementCDF observation in Run I Z bb
Higgs simulation for 2 x 15fb-1 (2 expt’s)
Higgs
Jet energy corrections
Z
mH = 120 GeV
29 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
SUSY Higgs Production at the TevatronSUSY Higgs Production at the Tevatron
• bb(h/H/A) couplings are enhanced at large tan (= ratio of v.e.v’s) ~ 1 pb for tan = 30 and mh = 130 GeV
bb(h/A) 4b
oneexpt
CDF Run 1 analysis (4 jets, 3 b-tags)
sensitive to tan > 60
Preliminary
increasingluminosity
30 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
+ jet sample
b-tagging b-tagging
• b-tagging explores IP significance method• Lepton from semileptonic decay of b is very useful
Positive IP
Negative IP
• Impact Parameter > 0 track crosses jet axis after primary vertex
Jet
Jet
track
track
Resolution
b enhancedInteraction point
Interaction point
• Impact Parameter < 0 track crosses jet axis before primary vertex
Significance = IP/IP
31 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
B-taggingB-tagging
• B-tagging is crucial for light Higgs search to reject light-quark content
• Estimated efficiency and fake rates from impact parameter resolution– b-tag efficiency ~60%– c-quark mistag rate ~15-20%– Light quarks (u,d,s) mistag rate ~few %
• Ongoing improvement in alignment and track-finding efficiency
High-pTrel muon sample
MC
32 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
SUSY search Run I (120 pb-1) Run II
Jets +mET (new) --------- x < 4.2 pb (4.1 pb-1)
mET >70 GeV
e +mETA x <0.1 pb (33 pb-1)
mET >45 GeV
lll+mET (Run I)
eel+mET (Run II)
x BR< 0.3 pb
M(0)60 GeVmET >10-15 GeV
x BR< 2.2 pb (42 pb-1)
M(0)=62 GeVmET >15 GeV
Analysis Run I (120 pb-1) Run II
SUSY 2 + mET M(0) > 75 GeV M(0) > 66 (40 pb-1)
1st LQ 2 e + 2 jets MLQ > 225 GeV MLQ > 179 (43 pb-1)
2nd LQ 2 + 2 jets MLQ > 200 GeV MLQ > 157 (30 pb-1)
LED 2em MS> 1.1 TeV MS> 1.0 (50 pb-1)
LED 2 (new) -------MS> 0.71 (30 pb-1)
DØ Search ScorecardDØ Search Scorecard
33 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Run IIa ProspectsRun IIa Prospects
• Towards the next few years:
Sample
W’lZ’ll
WV (W’l, V=W,,Z)
ZV (Z’ll, V=W,,Z)
tt (mass sample, 1 b-tag)
Run I
77k10k903020
Run IIa
2300k202k1800500800
Event yields per experiment (2 fb-1)
MW~40 MeVMt ~ 3 GeV
DØ / CDF
Run 2aPredicti
on
34 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003
Run IIB UpgradesRun IIB Upgrades
• Both detectors were designed to withstand ~2-4 fb-1 with an average of ~2-3 interactions per crossing– Integrated luminosity limited by radiation
damage to silicon tracker– Instantaneous luminosity limited by trigger
rejection• Tevatron goals for Run IIb are to accumulate
5-15 fb-1 with an average of ~5 interactions per crossing, necessitating – Replacement of silicon trackers
• Similar design for both and common SVX4 chip
– Replacement and upgrades to few key trigger and DAQ components for high-pT physics program
• Run 2 to continue in 2006 following ~7 month shutdown
• All critical elements have been prototyped, sensor procurement has begun
CDF
DØ
CDF
The “Luminosity The “Luminosity Lift”Lift”
New physics panoramas open up each time we take the “Luminosity Lift”