Meenakshi Narain, ICHEP2002, 7/29/2002
Results from the Results from the DzeroDzero Experiment at the Experiment at the TevatronTevatron
Meenakshi NarainBoston University
Representing the Dzero Collaboration
XXXI International Conference on High Energy Physics (ICHEP2002), Amsterdam, The Netherlands
Meenakshi Narain, ICHEP2002, 7/29/2002
DDØØ in in RunIIRunII
• Center of Mass Energy = 1.96 TeV• Expect 2 fb-1 by end of 2004 (RunIIa),
15 fb-1 by 2008 (RunIIb)• Goals
– Comprehensive study of top quark properties– Precise measurements of mtop, mW, AFB
– Search for new phenomena (SUSY, technicolor,…)– Search for the Higgs boson– QCD (proton structure, quark compositeness)– B-physics (Bs mixing)
• DØ’s strength is high-pT physics• Requires
– Measurement of leptons (e, µ), jets, missing pT
– Flavor tagging of jets
Meenakshi Narain, ICHEP2002, 7/29/2002
Main Injector& Recycler
Tevatron
Chicago↓
p source
Booster
p
p CDF
DØDØ
DØ
• pp collisions• Ecom = 1.96 TeV• 396 ns bunch spacing• Run II peak luminosity
now: 2.1×1031 cm-2s-1
goal: 8.6×1031 cm-2s-1
• pp collisions• Ecom = 1.96 TeV• 396 ns bunch spacing• Run II peak luminosity
now: 2.1×1031 cm-2s-1
goal: 8.6×1031 cm-2s-1
FermilabFermilab
Meenakshi Narain, ICHEP2002, 7/29/2002
D0 D0 RunIIRunII DetectorDetector
Meenakshi Narain, ICHEP2002, 7/29/2002
Tracking SystemTracking System
SuperconductingSolenoid
Scintillating Fiber Tracker
Silicon Microstrip Tracker
Meenakshi Narain, ICHEP2002, 7/29/2002
CalorimeterCalorimeter
DØ
D0 LIQUID ARGON CALORIMETER
1m
CENTRAL CALORIMETER
END CALORIMETER
Outer Hadronic(Coarse)
Middle Hadronic(Fine & Coarse)
Inner Hadronic(Fine & Coarse)
Electromagnetic
Coarse Hadronic
Fine Hadronic
ElectromagneticNew preamps, signal shaping
Meenakshi Narain, ICHEP2002, 7/29/2002
Muon SystemMuon System
Muon Trigger Counters
DØ Detector in Collision Hall, January 2001
Meenakshi Narain, ICHEP2002, 7/29/2002
Detector PerformanceDetector Performance
• Silicon Tracker
p-side pulse-height (ADC)n-
side
pul
se-h
eigh
t (AD
C)
p-side pulse-height (ADC)
Silicon cluster charge
noise < 2 ADC counts1 mip ~25 ADC counts⇒ S/N ~ 12
Charge correlation between p and n-side of a silicon detector
Hit efficiencies >97%
Meenakshi Narain, ICHEP2002, 7/29/2002
pT GeV
track
x
width = 36 µmσ(beam) = 30 µm
σ = 20 µm
width = 36 µmσ(beam) = 30 µm
σ = 20 µm
Impact parameter
Detector PerformanceDetector Performance y
• Impact Parameter Resolution
Survey-only alignment constants
significant improvement expected from alignment with data in near future
Meenakshi Narain, ICHEP2002, 7/29/2002
Detector PerformanceDetector Performance
• Fiber Tracker
light yield vs pseudorapidity η
Hit efficiency ¼ 98%
Ks0! π+π-
All tracking detectors working as expected
Z→ee candidateMass 89.9GeV/c2
Meenakshi Narain, ICHEP2002, 7/29/2002
Detector PerformanceDetector Performance
0 10 20 30 40 50 60 70 80 90 100
10-1
1
10
Missing Transverse Energy, GeV
J/ψ and ψ’• Muons
• Electrons
E/P0 0.5 1 1.5 2 2.5 3
Eve
nts
/ 0.
05
0
50
100
150
200
250Chi2 / ndf = 0.5317 / 4
156.4 ±p0 = 105.6
490.4 ±p1 = -411.3
459.2 ±p2 = 530.6
141.7 ±p3 = -192.2
26.31 ±N = 147.6
0.01741 ±Mean = 1.031
0.02659 ±Sigma = 0.165
DØ Run 2 Preliminary
candidate eventsν e→W
>20 GeVmissT>20 GeV, Eel
TP
E/P Chi2 / ndf = 0.5317 / 4
156.4 ±p0 = 105.6
490.4 ±p1 = -411.3
459.2 ±p2 = 530.6
141.7 ±p3 = -192.2
26.31 ±N = 147.6
0.01741 ±Mean = 1.031
0.02659 ±Sigma = 0.165
W! eν
Z→µµ
DØ Run 2 Preliminary
• Missing ET
Detector performanceconsistent with expectations!
Di-photon Data
Multijet data
Meenakshi Narain, ICHEP2002, 7/29/2002
IdentyfyingIdentyfying bb--quarksquarks• Signed impact parameter
jet
trackImpact parameter > 0(secondary decay vertex)
IP
jet
trackImpact parameter < 0(resolution)
IP
Reconstruct secondary vertexAlso use semileptonic decays
-15 -10 -5 0 5 10 151
10
102
103
104
Significance = dca/σ
~Resolution
-15 -10 -5 0 5 10 15
1
10
102
10
Significance = dca/σ
µ+jet sampleenhanced b-jet content
dijet sample
Meenakshi Narain, ICHEP2002, 7/29/2002
RunIIRunII Data and First Physics ResultsData and First Physics Results
• Delivered luminosity about 50 pb-1
• Mostly used to commission detector– Now complete
• First results from about 10 pb-1 of physics quality data– New center of mass energy → measure cross sections
– Exploit our High pT Physics capabilities at the energy frontier
• See also talks in parallel sessions – include results from both RunI and RunII
Meenakshi Narain, ICHEP2002, 7/29/2002
DzeroDzero talks during the parallel sessionstalks during the parallel sessions
• Jet measurement with the KT method (Ursula Bassler) • Minireview on Low Scale Gravity and ED at HERA/LEP/Tevatron
(Gregorio Bernardi )• Photon and Jet Physics at DØ (Marek Zielinski)• Search for SUSY at the Tevatron (Vishnu Zutshi)• W boson mass and width measurements (Sarah Eno)• Top physics at the Tevatron (Ia Iasvilli)• The DØ tracking system for Run II (George Ginther) • The DØ detector for Run II (Levan Babukhadia)
• +… a few more talks by CDF speakers which include DzeroRunII results.
Meenakshi Narain, ICHEP2002, 7/29/2002
BB--Mesons Mesons
) [GeV]+,K-µ,+µM(5 5.1 5.2 5.3 5.4 5.5 5.6 5.7
0
2
4
6
8
10
0.021 GeV±Mean = 5.277 0.014 GeV±Sigma = 0.057
D0 Run 2 PreliminaryB+(-)! J/ψ K+(-)
20 30 40 50 60 70 80 90 1010-4
10-3
10-2
10-1
1
Run 2 Preliminary D
MC
R = 0.5 Cone Jets
| < 0.6jetη|
> 4 GeV/cµTp
| < 0.8µη|
) < 0.7µR(jet, δ
EJet [GeV]T
d[n
b/10
GeV
]d/
σE
T
DØ Run 2 Preliminaryµ+jet Production Cross SectionDataMC Pythia
Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
mµE
ven
ts/5
0
1
10
102
103
Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
mµE
ven
ts/5
0
1
10
102
103
Data
Background from sidebands
ψBackground + prompt J/
B lifetime signal
Signal+background
D0 Run II Preliminary
+ X)ψ J/→Average B lifetime (B
DataBackground from sidebandsBackgrounds from prompt J/ψB-lifetime signalSignal + background
Average B Lifetime (B! J/ψ+X)
details
Rapid
ityJ/
00.2
0.40.6
0.81
1.21.4
1.61.8
2
Cross Section, arbitrary scale
1
Cross
Sectio
n per
unit o
f rapid
ity
Dzero
Run2
PREL
IMINA
RY
)>5Ge
V/cψ
pT(J/
)>8Ge
V/cψ
pT(J/
Cross
Sectio
n per
unit o
f rapid
ity
J/ψ production cross section asa function of pseudo rapidity
pT >
5 GeV
8 GeV
10102ψJ/η: 0.2 1.6ψJ/
Meenakshi Narain, ICHEP2002, 7/29/2002
eta
3.7
0.0
-3.7
-1.2
1.2
phi
0.0
2PI
ET Ge
55
Bins: 1097Mean: 0.405Rms: 2.88Min: 0.00188Max: 52.4
E_t: 0.0062phi_t: 160deg
Run 131957 Event 4781549 Wed Nov 14 17:33:47 2001Jets Physics Jets Physics • At √s=1.96 TeV, cross section 2x
larger compared to 1.8 TeV (Run I) for jets with pT > 400 GeV
2-jet event• ET
jet1~230 GeV
• ETjet2~190 GeV
[GeV]Tp50 100 150 200 250 300 350 400
[nb/
GeV
]ηd
Tpa
rtial
ly c
orre
cted
dN
/Ldp
10-4
10-3
10-2
10-1
1
10
Cone algorithm, R = 0.7
| < 0.4η |
| < 0.7η 0.4 < |
DØ preliminary
Inclusive jet pT spectrum
[GeV]jjM200 300 400 500 600 700
[nb/
GeV
]2η
d1η
d jjpa
rtia
lly c
orre
cted
dN
/LdM
10-4
10-3
10-2
10-1
Cone algorithm, R = 0.7
| < 0.41,2η |
| < 0.71,2η 0.4 < |
DØ preliminary
Dijet mass spectrum
• Only statistical errors• Preliminary jet energy scale• Not fully corrected
(for unsmearing, efficiencies)• In the works:
– expanded η range, Improved energy scale…
Luminosity5.8 pb-1
Meenakshi Narain, ICHEP2002, 7/29/2002
W and Z boson productionW and Z boson production
Di-Electron Mass (GeV)0 20 40 60 80 100 120
Eve
nts
/ 2
GeV
0
20
40
60
80
100
Number of Entries: 604
Peak Mass: 90.8 +- 0.2 GeV
Width: 3.6 +- 0.2 GeV
D0 Run II Preliminary
W(! eν) event characteristics
25 30 35 40 45 50 55 60 65 70 75
0
100
200
300
400
500
600
0 10 20 30 40 50 60
0
100
200
300
400
500
600
700
800
25 30 35 40 45 50 55 60 65 70 75
0
100
200
300
400
500
600
30 40 50 60 70 80 90 100 110 120
0
100
200
300
400
500
ET
/GeV
T/GeVM
DO Run2 Preliminary
ET
/GeV
pT/GeV
a)
c)
b)
d)
Red dots: DataYellow filled histogram: MC
missing ET
electron ET
MTW pT
Z!ee
Distributions modeled well by MC
Invariant mass (GeV)
Meenakshi Narain, ICHEP2002, 7/29/2002
W and Z Boson production cross sectionW and Z Boson production cross section
• Data Sample:– Luminosity ¼ 7.5 pb-1
– 9205 W candidates– 328 Z candidates
• Cross section measurements:
10 2
10 3
1Center of Mass Energy (TeV)
σ W, Z
× B
(pb)
DØ Run2 Preliminary
Center of Mass Energy (TeV)Center of Mass Energy (TeV)
pp_ → W+X → lν+X
pp_ → Z+X → ll+X
DØ(e) Run2DØ(e)CDF(e) CDF(µ)UA1 UA2
DØ(µ)
DØ Run 2 Preliminary
theory
theory
Meenakshi Narain, ICHEP2002, 7/29/2002
W and Z Boson production cross sectionW and Z Boson production cross section
• Ratio of cross sections
• W boson width
– Using σ(W)/σ(Z) from theory and B(Z! ee) from LEP
– In good agreement with world averageΓW = 2.135§0.069 GeV
First results at 1.96 TeV
Meenakshi Narain, ICHEP2002, 7/29/2002
W/Z boson + W/Z boson + multijetmultijet eventsevents
2GeV/c20 40 60 80 100 120
0
2
4
6
8
10
12
14e+jets data
multijet background
DØ Run 2 PreliminaryW + >= 2 jets njets≥0 1 2 3 4 5
Eve
nts
10-1
1
10
102
103
|<2jetη |
>15 GeVjetTE
>20 GeVjetTE
>25 GeVjetTE
DØ Run 2 Preliminary
stat. errors. only
W! eν+jets
JetsN0 2 4 6
Eve
nts
1
10
102
Events with
Jets N≥no. of Jets
candidates-µ +µ →0Z
DØ Run II Preliminary• Jet multiplicity distributions
W+≥ 2jetsTransverse massspectrum
•Top Physics:W+≥3jets, Z+≥2jets
•Higgs Physics: W/Z +≥ 2jets
•Need excellent b-jet identification•Secondary vertex recons.•Soft leptons in jets
Z!µ+µ-
Meenakshi Narain, ICHEP2002, 7/29/2002
H H !! WW WW • Why H ! WW at low luminosities?
– 4th fermion family enhances SM Higgs cross sections by a factor of ¼ 8.5 for Higgs mass between 100-200 GeV
– Fermiophobic Higgs: B(H! WW) >98% for mH ≥ 100 GeV
• Search for ee+ET events• Understand Backgrounds for SM Higgs Search
Require good e+e-
luminosity8.8 pb-1Azimuthal opening angle
between the leptons
Observed events in our data and estimated backgrounds are in good agreement.
Develop tools necessary for analysisOf larger data sets.
Meenakshi Narain, ICHEP2002, 7/29/2002
eta
4.7
0
-4.7
1 2
3
-1 -2
-3
phi180
0
360
ET(GeV)
10
Run 152415 Event 603157 Wed Jun 19 07:23:52 2002
An eeµ candidate
XGG
ZWgauginospp
++→
+→→~~
,, 01
01
γγ
χχγ
Search for Phenomena beyond the SMSearch for Phenomena beyond the SM• Many Analyses in progress:
– Likesign dielectrons– Jets+Missing Et
– Tri-lepton signatures• One of cleanest signatures of SUSY
chargino+neutralino production via W*• GMSB SUSY
⇒inclusive search for γγET + X– Limit:
– Sensitivity is still too low to exclude SUSY pointsCLpb %[email protected]<σ
Meenakshi Narain, ICHEP2002, 7/29/2002
LeptoquarksLeptoquarks• particles with properties of both quarks and
leptons; restore symmetry between the two• Signature: eejj events
Data : 18 eventsBackground : 15.3 ± 5.3 eventsLQ (m = 100 GeV) : 15.4 ± 2.0 eventsLQ (m = 140 GeV) : 3.1 ± 0.3 events
MLQ > 113 GeV/c2
at 95% CL, for β=1
β2×C
ross
Sec
tion
[pb]
Consistent with our Run I result6 candidates after removing Z
8.8 pb-1
Meenakshi Narain, ICHEP2002, 7/29/2002
Extra DimensionsExtra Dimensions
• Search for large extra spatial dimensions via virtual graviton effects
• e+e-, γγ and µ+µ- events
• Run2 Preliminary Limit:– Ms(GRW) > 0.92 TeV (ee,γγ)
• DØ Run I limits:– Ms(GRW) > 1.2 TeV
Meenakshi Narain, ICHEP2002, 7/29/2002
Future ProspectsFuture Prospects
• Continue to Search for New Physics– SUSY, strong dynamics, others…
• Rich program of B-physics • Measure W/Z Properties (AFB, W mass to 30 MeV)• Comprehensive study of Top quark Properties (2fb-1)
– Cross section(7%), Mass (2 GeV) – spin correlations, charge, top-gauge boson couplings
• Precision measurements of Top quark and W Boson mass ⇒ constrain the Higgs Boson
• Direct Searches for the Higgs Boson – Run IIa: MH & 115 GeV– Run IIb: MH & 180 GeV or see signal
• With 15 fb-1
– δmt ¼ 1 GeV, δmW ¼ 15 MeV, δAFB ¼ 2 £ 10-4
Meenakshi Narain, ICHEP2002, 7/29/2002
• current central values• δ∆α(5)
had(MZ2) = 10-4, δMW = 20 MeV, δmt = 1 GeV
• could lead to inconsistency within SM framework
¼ 2008summer 2002Grünewald, Heintz, Narain, Schmitt, hep-ph/0111217
0
2
4
6
10020 400
mH GeV
∆χ2
Excluded Preliminary
∆αhad =∆α(5)
0.02761+÷∠ 0.00036
0.02747+÷∠ 0.00012
Without NuTeV
theory uncertainty
?
Can we exclude the SM?Can we exclude the SM?
Meenakshi Narain, ICHEP2002, 7/29/2002
Thanks to my collaborators…Thanks to my collaborators…
33 US, 40 non USInstitutions:
Collaborators:334 from US 312 from non US institutions
Meenakshi Narain, ICHEP2002, 7/29/2002
ConclusionConclusion• First physics results at 1.96 TeV
– W and Z production cross sections– First generation LQ limits, Limit on Large Extra Dimensions– Lay foundation towards measurement of:
• B lifetime, b-quark cross sections, jet cross sections• Many High pT analyses in progress awaiting more luminosity
• Enormous progress made over the last year – detector performance optimization– developing analysis tools
• Improvements in store:– optimization of event reconstructionand selection procedures – Triggers and DAQ performance,– calibration, and alignment of the detectors
• Looking forward to collecting large integrated luminosity !
Meenakshi Narain, ICHEP2002, 7/29/2002
OutlookOutlook
• We are curious to see where it leads…
H?Prof. Peter Higgs
Meenakshi Narain, ICHEP2002, 7/29/2002
Status detailsStatus detailsAll subdetectors operational & reading out
All electronics, fronts ends, trigger & DAQ hardware installedRemaining: tuning up of the trigger/DAQ system2.5 106 int./sec396 nsec 5-10kHz 1000Hz 50HzDesign:
Level 2Level 1 Level 3 tapeNow: ~200Hz
2.5 106 int./sec396 nsec 50Hz~100Hz
Changed to new modern L3/DAQ system this year (done)
Commissioning and tuning up this systemVERY COMPLEX and high bandwidth systemExpect full rate by middle of fall of 2002
Large effort
Data taking continuesNo loss of physics at current luminosities
Meenakshi Narain, ICHEP2002, 7/29/2002
Backup SlidesBackup Slides
• Insert backup slides after this page
Meenakshi Narain, ICHEP2002, 7/29/2002
The Most Massive Candidate eventThe Most Massive Candidate event
M(diEM) = 377 GeV; cosθ* = 0.77; MET = 12.6 GeV;
EM2EM1
ET = 106.2 GeVη = -2.10ϕ = 2.19No track match
ET = 120.3 GeVη = 0.10ϕ = 5.27No track match
Meenakshi Narain, ICHEP2002, 7/29/2002
LuminosityLuminosity
Total Run 2 luminosity delivered & used A snapshot: July 1 to July
6, 2002
Meenakshi Narain, ICHEP2002, 7/29/2002
BB--Mesons Mesons
) [GeV]+,K-µ,+µM(5 5.1 5.2 5.3 5.4 5.5 5.6 5.7
0
2
4
6
8
10
0.021 GeV±Mean = 5.277 0.014 GeV±Sigma = 0.057
D0 Run 2 PreliminaryB+(-)! J/ψ K+(-)
20 30 40 50 60 70 80 90 10010-4
10-3
10-2
10-1
1
Run 2 Preliminary Data
MC
R = 0.5 Cone Jets
| < 0.6jetη|
> 4 GeV/cµTp
| < 0.8µη|
) < 0.7µR(jet, δ
EJet [GeV]T
d[n
b/10
GeV
]d/
σE
T
DØ Run 2 Preliminaryb-quark Production Cross SectionDataMC Pythia
Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
mµE
ven
ts/5
0
1
10
102
103
Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
mµE
ven
ts/5
0
1
10
102
103
Data
Background from sidebands
ψBackground + prompt J/
B lifetime signal
Signal+background
D0 Run II Preliminary
+ X)ψ J/→Average B lifetime (B
DataBackground from sidebandsBackgrounds from prompt J/ψB-lifetime signalSignal + background
Average B Lifetime (B! J/ψ+X)
Also have measured J/ψ cross sections out to pseudorapitidy of 1.6
Meenakshi Narain, ICHEP2002, 7/29/2002
BB--quark Production Cross Section quark Production Cross Section
0 0.5 1 1.5 2 32.5 30
100
200
300
400
500
600
700
800
900
TRelP of (GeV)
Mu
on
s/0.
1 G
eV
µ
DØ Run 2 Preliminary
µ→Pythia b
Fit
Run 2 data,20 < E < 25 GeV T
jet
Pythia
µ→Pythia c
µ→/Kπ
20 30 40 50 60 70 80 90 1010-4
10-3
10-2
10-1
1
Run 2 Preliminary D
MC
R = 0.5 Cone Jets
| < 0.6jetη|
> 4 GeV/cµTp
| < 0.8µη|
) < 0.7µR(jet, δ
EJet [GeV]T
d[n
b/1
0 G
eV
]d/
σE
T
yDataMC
PythiaP jet
p trel
Pµ
back
fit b component
µ+jet Cross Section
Meenakshi Narain, ICHEP2002, 7/29/2002
BB--Mesons Mesons
) [GeV]+,K-µ,+µM(5 5.1 5.2 5.3 5.4 5.5 5.6 5.7
0
2
4
6
8
10
0.021 GeV±Mean = 5.277 0.014 GeV±Sigma = 0.057
D0 Run 2 PreliminaryB+(-)! J/ψ K+(-)
Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
mµE
ven
ts/5
0
1
10
102
103
Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
mµE
ven
ts/5
0
1
10
102
103
Data
Background from sidebands
ψBackground + prompt J/
B lifetime signal
Signal+background
D0 Run II Preliminary
+ X)ψ J/→Average B lifetime (B
DataBackground from sidebandsBackgrounds from prompt J/ψB-lifetime signalSignal + background
Average B Lifetime (B! J/ψ+X)
20 30 40 50 60 70 80 90 1010-4
10-3
10-2
10-1
1
Run 2 Preliminary D
MC
R = 0.5 Cone Jets
| < 0.6jetη|
> 4 GeV/cµTp
| < 0.8µη|
) < 0.7µR(jet, δ
EJet [GeV]T
d[n
b/10
GeV
]d/
σE
T
DØ Run 2 Preliminaryb-quark Production Cross SectionDataMC Pythia
Meenakshi Narain, ICHEP2002, 7/29/2002
IdentyfyingIdentyfying bb--quarksquarks• Signed impact parameter µ+jet data sample
muon pTrel > 1.5 GeV wrt jet
enhanced b-jet contentjet
jet
track
track
Impact parameter < 0(resolution)
Impact parameter > 0(secondary decay vertex)
IP
IP
Reconstruct secondary vertexAlso use semileptonic decays
Meenakshi Narain, ICHEP2002, 7/29/2002
W/Z boson + W/Z boson + multijetmultijet eventsevents
2GeV/c20 40 60 80 100 120
0
2
4
6
8
10
12
14e+jets data
multijet background
DØ Run 2 PreliminaryW + >= 2 jetsJetsN
0 2 4 6e+jets inclusive jet multiplicity
0.5 1 1.5 2 2.5 3 3.5 4 4.5
W+≥ 2jetsTransverse massspectrum
•Top Physics: W+≥3jets, Z+≥2jets•Higgs Physics: W/Z +≥ 2jets
•Need excellent b-jet identification•Secondary vertex recons.•Soft leptons in jets
Eve
nts
1
10
102
Events with
Jets N≥no. of Jets
candidates-µ +µ →0Z
DØ Run II Preliminary
Nu
mb
er o
f ev
ents
10
102
e+jets data
multijet background
DØ Run 2 Preliminary• Jet multiplicity distributions
DataBackground
W! eν+jets
Z!µ+µ-