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CDF 実験の最新結果
Yuji Takeuchi (Tsukuba)for CDF collaborations
日本物理学会 第 64 回年次大会Mar. 28th, 2009
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CDFD0
Chicago
TEVATRON
MAIN INJECTOR
Tevatron Run IIStill at the Energy Frontier
Tevatron:• The world's highest-energy particle collider• Proton-antiproton collisions at √s = 1.96 TeV• Tevatron is performing really well:
Reach 6 fb-1 and 7~8 fb-1 expected by the end of 2009.
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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,)• Central/Wall/Plug calorimeters• Scintillator + drift chamber muon detectors
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CDF Collaboration
~700 physicists from
12 nations and 61 institutionsMcGill Univ.Univ. of Toronto
Argonne National Lab.Baylor Univ.Brandeis Univ.UC DavisUC Los AngelesUC San DiegoUC Santa BarbaraCarnegie Mellon Univ.Univ. of ChicagoDuke Univ.FermilabUniv. of FloridaHarvard Univ.Univ. of IllinoisThe Johns Hopkins Univ.LBNLMITMichigan State Univ.Univ. of MichiganUniv. of New MexicoNorthwestern Univ.The Ohio State Univ.Univ. of PennsylvaniaUniv. of PittsburghPurdue Univ.Univ. of RochesterRockefeller Univ.Rutgers Univ.Texas A&M Univ.Tufts Univ.Wayne State Univ.Univ. of WisconsinYale Univ.
JINR, DubnaITEP, Moscow
Univ. Karlsruhe
Univ. of Geneva
Glasgow Univ.Univ. of LiverpoolUniv. of OxfordUniv. College London
Univ. of Bologna, INFNFrascati, INFNUniv. di Padova, INFNPisa, INFNUniv. di Roma, INFNINFN-TriesteUniv. di Udine
IFAE, BarcelonaCIEMAT, MadridUniv. of Cantabria
LPNHE, Paris
KHCL
KEKOkayama Univ.Osaka City Univ.Univ. of TsukubaWaseda Univ.
Academia Sinica
USA Canada
Russia
Germany
Switzerland
UK
Italy
Spain
France
Korea
Japan
Taiwan
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• Continually establishing new records! – Peak luminosity
~3.5×1032 cm-2 s-1
– Weekly integrated luminosity78 pb-1/week
– Annual integrated luminosity1.8 fb-1 (US FY 2008)
– Average pbar accumulation rate
• 21×1010 pbar/ hour
• Very stable operation– Maximizing integrated
luminosity– ~12 weeks shutdown in 2009
summer
Tevatron Status
FY02FY03
FY04FY05
FY06FY07
FY08
FY09
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Integrated Luminosity• Integrated luminosities for each FY
– Extrapolation for FY2009: ~2 fb-1
• Data taking efficiency– Typically ~85%
FY08
FY09
7
FY09 start
9.32 fb-1
7.78 fb-1
Highest Int. Lum
Lowest Int. Lum
FY10 start
time since FY04
Inte
grat
ed lu
min
osity
(fb
-1)
FY08 start
~ 1.8 fb-1 delivered in FY08
FY2010• Fermilab plans to run (Budget approved)
and CDF/DØ are ready
• Another ~2.5 fb-1 , total ≳9 fb-1
FY2009• Run continues
~2 fb-1, total ~7 fb-1
Shutdown : ~12 weeks from June
Tevatron Prospects
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9
0
8
jets
HF
WZ
W Z
WW tt WZ
singletop
ZZ
Higgs
NewPhysics?
Physics Programs at Tevatron
• New SM process– WZ,ZZ, Single-Top, ...
• Top quark physics• Precise measurement
– W mass, ...
• Heavy flavor phyics (bb)50s
• Higgs search• Search for new physics
– First exploration of TeV scale
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Top Quark Physics
Single top については二つあとの中村氏(筑波)のトーク
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Top Pair production
Dominant process
10%~20%
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Top Pair Signature
Dilepton• 2 lepton• 2 bjet• MET
All Hadronic• 6jet(2bjet)
Lepton+Jet• 1lepton• 4jet(2bjet)• MET
-1-1QCD
11 MeV) (200 ~ << GeV 1.5
Top quark decays as a bare quark Information on spin polarization and momentum is directly
transferred to decay products
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Top Pair Production Cross-section
• Now better than theoretical uncertainties• Luminosity is dominant source of uncertainty
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new(ttbar)/(Z) in lepton + jet
channel
• The total uncertainty is decreased by 10% by taking the ratio of the top pair to the Z cross sections
+
• Event selection– High PT lepton 3jet, MET
• NN technique– Trained to separate
ttbar from W+jets bkg
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updateTop Quark Mass
Goal before Run-II started : 3 GeV/c2 with 2 fb-1
0.9% precision!
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Two Breakthroughs in Top Mass Measurements
Matrix Element Method• Use information on
leptons and jets maximally
in-situ Wjj JES calib.• JES (jet energy scale) calibration
using di-jet invariant mass from W• Incorporate JES into likelihood
function– L(Mt)→L(Mt,JES)
– Turn JES systematics into statistics Reduced with statistics of top events
Observables
Matrix element with a given top mass gives p.d.f. of observables
Likelihood function of top mass for a given set of observables
M jj→ MW
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update
Top Mass Measurement in Lepton + Jet channel
World Best. Better than 1%
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update
Measurement of dσ/dMtt in Lepton + Jet channel
Response matrix
κ/MPl > 0.16 (95% CL)
Unfolding
Reconstructed Mtt
Unfolded dist.
True Mtt vs Recons. Mtt
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Forward-Backward Asymmetry in ttbar production
PositiveAsymmetry
NegativeAsymmetry
LO: Afb=0NLO: Afb=(5 1.5)%
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update
Forward-Backward Asymmetry in ttbar production
unfolding
~2 away from NLO prediction~2.8 away from null asymmetry
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B Physics
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newY(4140) in B+ → J/ψφK+
• B→J/ψφK is OZI suppressed
Yield =145
m = 1046.3 2.9 (stat) MeV/c2
Width = 11.7 +8.3-5.0 (stat) MeV
Mass = 4143.0 2.9 (stat) 1.2 (syst) MeV/c2 (adding J/ψ mass)
Width = 11.7 +8.3-5.0 (stat) 3.7(syst) MeV
JPC=??+ tentatively name it as Y(4140)
Significance: 3.8σ
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SM Higgs Search
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Low mass Higgs region:m
H<135 GeV/c2
H → bb dominant decay. Search for associated W/Z production.
High mass Higgs region:m
H>135 GeV/c2
H → WW dominant decay. Gluon fusion production search (gg → H).
Higgs cross-section and BR
24
updateH WW l+ l-
• 2 opposite sign leptons + MET• WW from spin 0 higgs
– leptons tend to same direction– ∆φll is best discriminant
• Neural network technique– ∆φll, ∆Rll, HT, ...
25
updateH WW, WH WWW*
• Also search for same sign leptons for WH WWW* ll X – WH→WWW (2.7fb-1): Next talk ( 大阪市大 脇坂氏 )
• Combine OS+0j, OS+1j, OS+2j, and SS+1j• 95% CL Limit/SM: 1.33 (1.45 expected)@ MH=165 GeV/c2
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b
b
l
W* H
W
WHlbb
• Neutral network (NN) technique
– Limit: < 5.2 x SM @MH=115GeV/c2
• Matrix element (ME) + Boosted decision tree (BDT) technique
– Limit: < 5.24 x SM @MH=115GeV/c2
Bkg: W+bb, W+cc, W+qq, ttbar, ...
NN, 1 b-tag
永井氏(筑波)
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updateWHlbb (Combined)Updated on Nov 7, 2008• Combined result of NN and ME+BDT• Improved by 15%
• 95% CL Limit/SM: 5.6 (4.8 expected) @MH=115 GeV/c2
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bb
/l
W*/Z* H
W/Z
Other Low Mass Higgs Searches
bb
l
Z* H
Z
l
• 2lepton+2b-jets• Limit/SM: 7.1
@MH=115 GeV/c2
• MET + 2b jets• Limit/SM: 5.6
@MH=115 GeV/c2
had+had+ lep+2 jetslep+2 jets• Limit/SM: 25
@MH=115 GeV/c2
寄田氏(早稲田)
29
CDF Combined Results
WHlbb
WHWWW
Updated on Mar 5, 2009
• 95% CL Limit/SM: 3.64 (3.22 expected) @ MH=115 GeV/c2
• 95% CL Limit/SM: 1.46 (1.61 expected) @ MH=165 GeV/c2
ZHllbb
HWW
VHbbMET
Hττ
update
30
Higgs Exclusion @ Tevatron
CDF+DZero combination Updated on Mar 5, 2009update
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Projections
• CDF+DZero projections assuming they perform the same (2xCDF)• Possible improvements: (1.5~1.6x sensitivity)
– Acceptance, Analysis method, jet/MET resolutions, ...• Good possibility to see 3 evidence to a Higgs of 165 GeV/c2
– Doesn’t take data already analyzed into account.• Good possibility to see 2 excess to low mass higgs or to exclude
at 95% CL if there is no higgs and with improvements.
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Constraining the Higgs boson mass
33
Summary
• Tevatron is operating well. Better than ever!• CDF is ready to run FY2010. ∫Ldt > 9 fb-1 is expected.
• CDF is still providing constantly update results as well as new topics.– Top, Bottom, EWK, QCD, Higgs search, BSM search, ...
• CDF+DØ: Higgs exclusion: 160-170GeV/c2 (95%CL)– Indirect measurement:
• このあと CDF 実験のトークを引き続きお楽しみください.– Wh→WWW : 脇坂氏(大阪市大)– Single top search: 中村氏 ( 筑波大 )
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Backup
35
Higgs Projections (low mass)
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Higgs Projections (High mass)
37
S/B
52/48
Var1 > x1 Var1 ≤ x1
Var2 > x2 Var2 ≤ x2
S/B
4/37
S/B
48/11
S/B
2/10
S/B
46/1
What is a Boosted Decision Tree ?
• Weight Wi for each event(= 1 to start)• Purity: P=∑Ws/(∑Ws+ ∑Wb)• Split until minimal #event reached or limit
of purity reachedif P>Pmin “signal leaf”if P<Pmin “background leaf”
• Boosting– if a signal event is on a bkg leaf or if a bkg
event is on a signal leaf weight modified
• Then training re-performed with the new weights
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SM Higgs cross-section
Summer 2008