Latest result of DZero@Tevatron 韩韩 韩韩韩韩韩韩韩韩
Jan 05, 2016
Latest result of DZero@Tevatron
韩良中国科学技术大学
Main Injector & Recycler
TevatronBooster
p p
DØDØ
p source
Batavia, Illinois Chicago
Tevatron P-Pbar @ 1.96TeV 2x1032 cm-2s-1
CDF+DØ
Tevatron : Fermilab Proton-Antiproton Collider
2007/08/05 2L.HAN@2007威海
DØ International Collaboration
• 19 countries• 80 institutions• 650+ physicists
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The D0 Detector
Silicon Micro-vertex Tracker (SMT) - up to ||<3.0 - IP resolution ~ 10m
Central Fiber Tracker (CFT) - up to ||<1.6 - 10% at pT>40GeV
LAr+Ur EM-CAL, - e, up to |3.0
LAr+Cu HD-CAL - jet/met, up to |4.0
Muon in 1.8T Toroid - up to ||<2
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• Run 2a– Finished 03/2006– Inst. lumi up to
~1.5x1032 cm-2s-1
– Delivered ~1.6 fb-1
• Run IIb– Started 06/2006– Inst. lumi up to
~3x1032 cm-2s-1
– Delivered 3 fb-1
Run II Integrated Luminosity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
Apr-02
Jul-02
Oct-02
Jan-03
Apr-03
Jul-03
Oct-03
Jan-04
Apr-04
Jul-04
Oct-04
Jan-05
Apr-05
Jul-05
Oct-05
Jan-06
Apr-06
Jul-06
Oct-06
Jan-07
Apr-07
Jul-07
Delivered
Recorded
19 April 2002 - 3 J une 2007
2.55
3.00
Lum
inos
ity (/
fb)
Run 2bRun 2a
Accelerator and detector performance
L.HAN@2007威海
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B physics
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B production at the Tevatron
• bb cross section orders of magnitude larger than at B-factories (4S) or Z• σ(e+e- → Z → bb) = 7nb
• σ(e+e- → Υ(4S) → bb) = 1nb
• (B+, pT 6 GeV, |y|<1@Tevatron)~4 mb
• all kinds of b hadrons produced: – Bd, Bs, Bc, B**, b, b, …
• However:– Overwhelming QCD, b-hadrons hidden in 103 larger background
• crucial for B physics program:– good vertexing & tracking– muon system w/ good coverage
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1)1(2
11)1(
)(2
11
23
2242
32
AiA
AiA
iA
VVV
VVV
VVV
tbtstd
cbcscd
ubusud
tdV
0dB0sB
0dB0sB
b
sd , b
sd ,tcu ,,tcu ,, W
W
*tdV *
tsV
tsV tdV
0dB0sB
0dB0sB
b
sd , b
sd ,
tcu ,,
tcu ,,
W W
*tdV *
tsV
tsV
Vtd determination : CP violation Unitarity in SM
(0,0) (0,1)
(,)
*
ubud
*tbtd
VV
VVarg
*cbcd
*tbtd
VV
VV
*
tbtd
*cbcd
VV
VVarg
*
cbcd
*ubud
VV
VVarg
*cbcd
*ubud
VV
VV
(0,0) (0,1)
(,)
*
ubud
*tbtd
VV
VVarg
*cbcd
*tbtd
VV
VV
*
tbtd
*cbcd
VV
VVarg
*
cbcd
*ubud
VV
VVarg
*cbcd
*ubud
VV
VV
Bd oscillation frequency 2*
d tb tdm V V QCD
Bs oscillation frequency 2*
s tb tsm V V QCD
2
s ts
d td
m V
m V
Measurement of Δms contributes to better determination of Vtd
Bs Oscillation
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/ exp(- ) / 2 [1 cos( )] 0OSC NOSsP t m t
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KKBB ss 00
sDMost Clean mode BsνμDs(φπ)
The sign of Bs flavor at decay Transverse length LT(Bs) Transverse momentum PT(Bs) ~ PT(Dsμ)
Bs candidate (invi. mass/IP of tracks from , Ds) at reco-side:
μ+
π -
K+ K-
D-
S
μ(e) B
ν
00ss BB
XReconstructed Side
Opposite-side flavor tag (OST)
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μD±X7,422±281
μDsX26,710±560
Likelihood ration optimization on S/√B
Improvement on reco-side Bs candidate
Discriminator : Helicity angle (Ds,K1)Ds IsolationpT(K1K2)m(Ds)2 of Ds Vertex Fitm(K1K2 or K1)
Dataset:
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Initial Flavor Tagging
( )T
T
p qQ
p
6.0
||
6.0||
p
qpQSV
μ+
π -
K+K-
φD-
S
ν
00ss BB
37o
B
X tagging side
μ-
Flavor discriminate variables: - muon jet charge - SV charge - event charge
( )Tev
T
p qQ
p
Uncorrelated hadronization of two b-quark in PPbar interaction
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Likelihood ration from data (B+)
Single tagging variable
Δmworld-average = 0.507 ± 0.004 ps-1
Calibrate with Bd
d>0bInitial
d<0bInitial
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OSTμ sample @ D0 (~1 fb-1)
26,710±560
OST with tagging efficiency ~20%
7,422±281
1,519±96
5,601±102
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e.g. associated
μ+
π -
K+K-
φD-
S
μ(e) B
ν
X
PV
LT(BS)
00ss BB
PT(μDS)
2
s
s
s DT
DTT
BM
ppLmx
Transverse Proper Decay Length
Visible Proper Decay Length (VPDL)
Kxct MBs
K factor for missing particles Proper Decay L
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Asymmetry Amplitude Fitting Approach cos /nos osc
snos osc
N NAsymmetry D Δm Kx c
N NA
ms>14.8ps-1@ 95% CL, deviation of 2.5 from A=0 at 19ps-1
/ exp( ) 1 cos / / 2s s
nos oscs s
B B
K Kxp D Δm Kx c
cA
c
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Log Likelihood Scan Approach
Systematic:• Resolution• K-factor variation• Br (BsDsX) • VPDL model
-- 17<ms<21 ps-1@90% CL assuming Gaussian error most probable value of 19 ps-1
-- CDF result as 17.33±0.42±0.07ps-1
PDFs:• Proper Decay L• Dilution• Mass
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μ+
π -
K+K-
φ
D-S
BS
μ+
Tagging muon
Y, cm
X, cm
Oscillated BS candidate
• Two same sign muons are detected w/ tagging legη=1.4
• MKK=1.019 GeV, MKKπ=1.94 GeV
• PT(μBs)=3.4 GeV; PT(μtag)=3.5 GeV
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CKM fit without new D0 result CKM fit with new D0 result
-- First direct double sided precise measurement on the Bs oscillation frequency
ms< 21 ps-1 @ 90% CL
-- Impact on the CKM Unitarity Triangle
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b discovery @ CDF
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Heavy Baryon spectrum
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Be able to observe:
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,
1) 4 track decay of b 2) Determine background of data/PYTHIA
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3) Signal region observation:
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b discovery @ D0
J/
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MeV 1.117.6068)(
MeV 8.80.5840)(
MeV .92.5824)(
MeV 1.87.5805)(
*
b
b
b
b
M
M
M
M
E. Jenkins, PRD 55 , R10-R12, (1997)
Signal feature
-- Mass hierarchy M(Λb)< M(b-) < M(b),
with CDF result as 5.624 < M(b) < 5.8
Ξ-b→J/ψ + Ξ-
-- 3 vertexes + 4 particles fully reconstructed
-- PV lifetime: b ~ 0.1cm, - ~ 5cm, ~ 5cm
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(syst) (stat) 0.09 0.28)/()(
) /()( 0.09 0.08 -
JBRbf
JBRbf
bb
bb
1.90.4-4.415.2
bN
0.015 0.0115.774)( bM
-- Cascade B baryon discovery:
-- Production ratio :
with signal significance
~ 5
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31
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1.3fb-1
2fb-1
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Top studies
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Production cross section
Heavy resonance decay
W helicity
Anomalous coupling
CP violationSpin
Charge
Width
Mass
Production kinematics
Polarization
Rare decays
Branching ratiosCKM :|Vtb|
Top Quark Production at Tevatron
~85% ~15%• QCD pair production
NLO = 6.7 pb (for mTop= 175 GeV)
First observed at Tevatron in 1995
EWK single-top production s-channel: NLO = 0.9 pb
t-channel: NLO = 2.0 pb
(Both for mTop= 175 GeV)
First evidence in Dec. 2006 s-channel t-channel
Other: ???X 0 t t , t t H
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• Lepton + Jets: Relatively clean with manageable backgrounds
• Dilepton: Cleanest but lowest statistics
• All Hadronic: Large branching fraction but formidable backgrounds
Br(tWb) ~ 100%
Top quark pair production xsection
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pb1.00.58.2 ±±
• Important indirect test of many top quark properties
NLO calculation: 6.8 pb with ~13% uncertainty
HT>250 GeVMissing ET>30 GeV
≥1 tight tag
Lepton + Jets Dilepton
pb6.8 1.01.29.01.1
+
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Cross section measurement
SM prediction @2TeV PPbar
NNLO ~ 6.8 ± 0.8 pb
CDF D0
• Similar experimental and theoretical uncertainty• Working on Tevatron combination
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Top mass measurement
-- Affect W boson mass at NLO -- Decide Higgs mass with W
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e-channel
3 ( ) 3 ( ) ( , ) ( ) ( ) ( )
3 6 3 4 2 1 1 1 18 17 1e T W e W t te b b e jj E x y m e m m m
• #28 in 835pb-1 with high pT unlike signed e/ + 2 jets (wo b-tagging)
• underconstrained for mt
• Hypothesized mt 4 solutions with assigned weight
P/Pbar pdf Probability
b combination resolution
maximize for the estimator of mt
per eventpeak mass
(missing information eg ISR/FSR shift)
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• M.C. templates: signal tt(13 templates in 140-230GeV) + WW(ll) + Z(tt) etc
• binned maximum likelihood fit
Peak mass
Measure jets, not partons -- Calibrate the energy scale -- Associating jet with correct parton -- Extra jets add confusion
What a theorist sees: What an experimentalist sees:
-- In-situ calibration using hadronic W decays-- Sophisticated analysis methods: matrix element, kinematic fit, etc.
Lepton + 4Jets Channel
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• Event select in 370pb-1: high pT 1l + 4j, MET>20GeV, kinematic constrianed fit
• Combined fit for 0,1,2 b-tagged jets, then event weighted for 24 possible j/ solutions
• Full kinematic information + weighted solution Likelihood
where -- ftop, fraction of signal events in sample
-- JES, jet energy calibration in situ Wqq, to reduce dominant systematic by fitting mt and JES simultaneously
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(Fit JES with maximum likelihood)
170.9±2.2(stat+JES)±1.4(syst)GeV/c2 170.5±2.4(stat+JES)±1.2(syst)GeV/c2
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-- Full Run2a large statistic sample :
Latest Tevatron Combination
170.9 ± 1.1(stat) ± 1.5(syst) GeV/c2
Run I result:4.3 GeV
uncertainty
Latest Run II result:
1.8 GeV uncertainty
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-- Exceed original Run2 expectations due to in-situ jet energy scale calibration, namely statistic works on systematic
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First measurement on single top
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-- SM : direct access to |Vtb|
-- Sensitive to NSM :
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-- Event selection
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-- Signal v.s. background :
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-- Smaller cross section -- High pT lepton + MET + 2jets(>1tag) -- Large complicated background -- Multiple analysis techniques:
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First evidence for single top production
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Single top prospects – Tevatron vs LHC
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WZ Electroweak physics
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W and Z boson production @ Tevatron
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W Mass measurement @ CDF
Isolated high pT leptons + MET :
WGRAD
RESBOS
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-- 6 fits on MC template : electron + muon, MT, lepton pT and MET
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Di-boson Production & TGC
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W production @ D0
• TGC(WW) will distort CM between W boson and incoming quark
0.9fb-1,e+
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production @ D0
• TGC(ZZ, Z) will lead to excess of high energy photon
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WZ production @ D0
• TGC(WWZ) will lead to excess of triple-lepton +MET selection
SM NLO WZ=3.68 +/- 0.34pb
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ZZ production @ D0• SM NLO ZZ~1.6pb
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Hunt Standard Model Higgs
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LEP Direct searchesmH>114 GeV @95%CL
mH<153GeV @95%CL(<189 GeV if LEP2 limit incl.)
Consistency bounds on Higgs Mass
GeVmH362680
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excluded
Product@Tevatron and Decay
Search strategy: -- MH < 135 GeV: Hbb in WH/ZH associated production (gHbb overwhelmed by QCD)
-- MH > 135 GeV: ggHWW*llvv
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High-mass Search in HWW*lvlv
e+RW+L
W- e-L
nR
Sensitive to quark generation
• Understanding on dominate background
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Low mass search
u
d
W*+
W+
H0
b
b
l+
l
H
lb
b
WH associated:
W(e,) sample >=2 jets >=1 b-tag
ZH associated:
1) Z(ee,) sample >=2 jets >=1 b-tag2) 2 b-tag + MET
j1j2
ET
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CDF + D0 combination
-- Approaching sensitivity to SM Higgs -- With peak performance of Tevatron+CDF+D0, will limit or see Higgs before LHC
2007/08/05 L.HAN@2007威海 79
MSSM Higgs search
2007/08/05 L.HAN@2007威海 80
Yukawa couplings in MSSM
down type couplings to CP-odd A will be enhance by large tan
MA
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A@ CDF&D0
CDF Run IIa 1fb-1
tan
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Abb@ D0
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Backup
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Measurement Best result
Charge[1] Rule out +4/3e @ 94% C. L.
(D0)
Lifetime [2] c < 53 m @ 95% C. L.
(CDF)
heavy t’ [3] Exclude [196-207] GeV @ 95% C. L.
(CDF)
resonance Mx [4] >725 GeV @ 95% C. L.
(CDF)
>680 GeV @ 95% C. L.(D0)
W helicity fR [5] 0.08±0.08±0.06
<0.24@95%CL(D0)
[5] SM V-A couplings test
Longitudinal
f0 ~ 0.70
Right-handed
f R~ 0
Left-handed
fL ~ 0.30
[1] pT weighted track in jet
[2] the lepton impact parameter of W from top
No deviation from SM observed
X ?
[4] new tt resonance in exotic
[3] 4th generation of heavy quarks
Other top quark property measurement
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Impact and prospectsProspect for RunII (CDF+D0)
Δmtop < 1.5 GeV/c2
with 2 fb-1
Run I+II
mW = 80.425 ± 0.038 GeV (LEP2)mtop = 172.7 ± 2.3 GeV (DØ+CDF)
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Combined CDF+D0
mt =172.5±2.3GeV