Document

CDFの最新結果
武内勇司 (筑波大)
for CDF collaboration
特定領域「フレーバー物理の新展開」研究2011
鹿の湯ホテル
Jul. 2nd, 2011
Contents
•CDF/Tevatron status
•Top physics
–ttbar spin correlation (武政＠若手セッション)
•B physics (三宅)
•Higgs search （永井）
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Tevatron Run II
Chicago
CDF
D0
TEVATRON
MAIN INJECTOR
Tevatron
Proton-antiproton collisions at √s = 1.96 TeV
Shutdown on Sep. 30, 2011
Final dataset: ~10 fb-1 expected for physics
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The CDF II Detector
Silicon vertex detector (1+5+2 layers)
Central drift chamber (8 super layers)
1.4T solenoid
Good particle identification (K,p)
Central/Wall/Plug calorimeters
Scintillator+drift chamber muon detectors
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Tevatron Status
Peak luminosity
12.6×1032 cm-2 s-1(ATLAS)
4.14×1032 cm-2 s-1
Weekly integrated luminosity
84 pb-1/week
~1fb-1/month(ATLAS)
Annual integrated luminosity
2.5 fb-1 (US FY 2010)
FY10
FY08
FY11
FY09
FY07
FY06
FY05
FY04
FY03
FY02
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Integrated Luminosity
Delivered 11.3fb-1, Recorded 9.3fb-1
ATLAS x tt ratio
ATLAS
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Physics Programs at Tevatron
SM process
WZ,ZZ, Single-Top, ...
Top quark physics
Precise measurement
W mass, ...
Heavy flavor phyics
(bb)100s
Higgs search
Search for new physics
jets
HF
New
Physics?
W
Z
single
top
Higgs
Wg Zg
WW tt
WZ
ZZ
7TeV pp
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Top quark physics at CDF
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Heaviest elementary particle
play a special role in EWSB?
provides new test ground on Standard Model
Direct access to bare quark
Top quark decays before hadronization
Decays as a naked quark
Information on spin polarization and momentum at its
production is directly transferred to decay products
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Dominant process
at Tevatron
10%~20%
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Dilepton
• 2 lepton
• 2 b-jet
• MET
Lepton+Jet
• 1 lepton
• 4 jet(2 b-jet)
• MET
All Hadronic
• 6 jet(2 b-jet)
Categorize ttbar events into 3 decay types according to W decay mode
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343 cand./5.1fb-1
727 cand./4.3fb-1(4j, w/btag)
~105 bkg.
S/N~2.3
~126 bkg.
S/N~4.8
105 cand./35pb-1
~21.6 bkg.
S/N~3.7
ATLAS
402 cand./35pb-1
~93 bkg.
S/N~3.3
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Consistent with prediction
Better uncertainty than theoretical
uncertainties!
All channel, w/, w/o b-tag are consistent
Consistent with Br(t→Wb)~100%
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Top mass
Mt=1.09 GeV/c2 (0.63%)
Mt<1GeV/c2 can be
reachable
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Top charge (Qt=2/3 vs 4/3)
l+jet channel
l-b paring kinematics: Ppairing=83%
Jet charge kinematics: PJQ=61%
P-value for SM: 0.134
P-value for XM: 0.00014
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down-type
top spin polarization vector
in top rest flame
top quark decays before losing polarization
V-A coupling
flight direction of down-type fermion from W carries
100% spin information of parent top quark
can “see” top quark spin at its production
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Information on Wtb Vertex
Really W boson?
Really V-A?
b
t
b
t
Long
Left
0.8
In SM
sum (SM)
0.6
longitudinal
0.4
0.2
0
-1
left-handed
right-handed
-0.5
0
0.5
1
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Consistent with tWb vertex
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Backward
Forward
NLO prediction: Interference between LO and NLO
2
+
Also presence of new physics could make asymmetry
2
V
+
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RunII 5.3fb-1 l+jets results(1)
yt(=yt-ytbar)
Background subtracted, then unfolded back to parton level.
Attbar = 0.1580.074
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RunII 5.3fb-1 l+jets results(2)
Look at parton-level asymmetry as functions of yt and Mttbar
Attbar(yt >1.0) = 0.611  0.210  0.147
Attbar(Mttbar >450GeV) = 0.475  0.101  0.049
To be compared to Apred(Mttbar >450GeV) = 0.088  0.013
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RunII 5.1fb-1 dilepton results(1)
0jet
1jet
Inherit Afb of parent ttbar
0jet and 1jet events can be used as control sample to validate bkg
shapes
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RunII 5.1fb-1 dilepton results(2)
Subtracting background
Apply corrections for acceptance and dilution due to reconstruction
Attbar = 0.42  0.15(stat)  0.05(stat)
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F-B asymmetry at other experiments
Background subtracted asym.
Attbar = 8 4(stat)  1(syst) %
To be compared: APred=1+2-1 %
In pp collision
quark from valence, anti-quark from
sea: quark tends to larger x
Afb>0 |t|-|tbar| has positive asym.
AC=0.060  0.134(stat)  0.026(syst)
They claim same sensitivity as
Tevatron with 1/fb!
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ここまでのSummary
Tevatron は今年の9月までの運転
CDFのfull dataset は，約10/fbになる見込み
Top quark properties are consistent with SM so far
Except for forward-backward asymmetry at top pair production
Top quark properties are being measured more and more precisely, not to
overlook any hint of new physics.
Uncertainty in top mass measurement: < 1 GeV/c2
Uncertainty in pair production cross-section measurement is now better than
theoretical uncertainties
Top quark 対生成の機構は,Tevatron とLHCで異なる
Cross-section やforward-backward asymmetry, Mtt 共鳴, ttbar spin correlation な
どは，対生成の機構に依存
 Tevatron の解析もまだまだ重要
引き続きCDFのBの物理（三宅），Higgs探索(永井)のトークをお楽しみください
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