cdf での top flavor の物理
DESCRIPTION
CDF での Top Flavor の物理. 戸村 友宣 ( 筑波大学 ). Introduction. Top quark is the heaviest known fundamental particle. Is this large mass related to electroweak symmetry breaking? Relationship between m t , m W , and m H Top quark has very short lifetime Decay before hadronization - PowerPoint PPT PresentationTRANSCRIPT
2008/02/22 20特定領域「フレーバーの物理の新展開」研究会08
1
CDF
CDF での Top Flavor の物理
戸村 友宣( 筑波大学 )
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 2
CDF
Introduction Top quark is the heaviest
known fundamental particle. Is this large mass related to
electroweak symmetry breaking? Relationship between
mt, mW, and mH
Top quark has very short lifetime
Decay before hadronization Momentum and spin are
transferred to decay products
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 3
CDF
Tevatron Run II Proton-Antiproton Collider
with CM energy of 1.96 TeV Peak luminosity: 2.91032
cm-2s-1
Delivered luminosity: > 3.5 fb-1
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CDF
CDF II Detector
General Purpose solenoidal detector Efficiency: ~85% Recorded >2.9 fb-1
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CDF
Top Pair Production
Top pair production through strong interaction
~85%
~15%
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CDFTop Pair Production Cross Section
Measured using many different techniques
Good agreement Between measurements Between data and theory
LA bkgobs NN
ttpp
pb 7.6)GeV 175@( topMttppdilepton l+jets all hadronic
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CDFForward Backward Asymmetry
Forward-backward asymmetry arises from interference between LO and higher order diagrams
syst04.0stat07.017.0fb A syst04.0stat13.024.0fb A
(NLO Theory: Afb = 0.04±0.01) (NLO Theory: Afb = 0.04—0.07)
Lab (ppbar-rest) frame
ttbar (parton) rest frame1.9 fb-1
frame lab
framerest parton
fb
fb
A
A
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CDFttbar Production Mechanism
@95%CL38.0
07.015.007.0
ttpp
ttgg
Measure fraction of gg vs. qq top production
SM prediction: ~85% qq, ~15% gg Large theoretical uncertainty (~10%)
Two complementary approaches NN with production and decay kinematics Track multiplicity distributions
Combine two methods: ~6% improvement
1 fb-1
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 9
CDFttbar Differential Cross Section
Measure d/dMtt and test consistency with SM
Spectrum is sensitive to many BSM resonances (Z′, coloron, etc.)
ttbar invariant mass is reconstructed for l+jets events
Subtract background and correct the distribution using a regularized unfolding technique
Data is consistent with SM p-value = 0.45
1.9 fb-1
iMi
ii
tt
i
tt
NN
dM
d
LA
bkg
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 10
CDF
Search for Massive Gluon Search for heavy gluon-like
particle, Gttbar(color-octet model, etc.)
3 parameters Mass(M), Width(), coupling()
Event-by-event ttbar invariant mass reconstruction for l+jets with a Matrix Element technique (DLM)
Data is consistent with SM (<1.7) within 400M800, 0.05/M0.5
Set upper/lower limit for massive gluon coupling
Coloron model (=1, /M0.2) is excluded in the range, /M0.5 and M800
q Qg +
q QGgs gs qgs Qgs
SM interfere MG
1.9 fb-1
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CDF
Top Quark Mass Many techniques were deployed for
top mass measurements Tevatron combination calculated 1 year
ago
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CDFNew Mass Measurements (1)
Template Method Reconstruct top mass event-by-event and generate templates Use dijet mass from W daughters for in-situ jet energy calibration
Combined for dilepton and l+jets
all-hadronic
2top GeV syst6.1JESstat7.30.177 cM
2
2top
GeV 0.29.171GeV syst0.1
JESstat7.19.171
cc
M
Apply NN event-selection to improve S/B
1.9 fb-1
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CDFNew Mass Measurement (2)
Matrix Element Method Calculate event-probability from the kinematics of decay
products using Matrix Element dilepton
lepton+jets
2top GeV syst2.1stat8.17.172 cM 2
top GeV syst9.2stat7.22.171 cM
Apply NN event-selection to optimize S/B
Cut lower tail of log-likelihood distribution
1.9 fb-1
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 14
CDF
Top Quark Width
Measure width of top quark directly using template method
Use 1-tag and 2-tag l+jets data
Calculate upper limit using Feldman-Cousin prescription
GeV 0.175CL @95% GeV 7.12
t
tM
1 fb-1
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 15
CDF
Top Quark Charge Measure the charge of “top” quark
SM top charge: +2/3 XM top charge: −4/3
D. Chang et. al. Phys. Rev. D59 (1999) 091503
tW+b or tW−b Charge of W (lepton charge) Pairing between W and b Flavor of b-jet
Use dilepton and l+jets data
Measured f+=0.87p-value=0.31
Exclude XM @87% CL
1.5 fb-1
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 16
CDF
W Helicity V−A character of the top decay
makes the helicity of W onlyF0=0.70, F−=0.30, F+=0.00(longitudinal, left-handed, right-handed)
syst05.0stat10.015.0
syst07.0stat21.038.00
F
F 0 and GeV175for
syst069.0stat084.0637.02
0
Fcm
F
t
l
l+
W+
b*
cos Method Matrix Element Technique
syst06.0stat10.066.00 F
syst03.0stat05.001.0
F
F
1.9 fb-1
If F+ fixed to 0:
If F0 fixed to 0.7:
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CDFSearch for FCNC Decay tZq
Top FCNC is extremely rare In SM, BR(tZq)=O(10-14) BSM, up to O(10-4)
Calculate 2 for FCNC top decay
1.9 fb-1
CL %95@
%7.3BR Zqt
2
rec,
2
rec,
2
PDG,rec,2
Zqt
tZqt
Wbt
tWbt
W
WW mmmmmm
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CDF
Single Top Production Single top production through
weak interaction single top |Vtb|2
Sensitive to: 4-th generation H +
W′ FCNC Etc.
Background for WHlbbs-channelNLO = 0.88±0.07 pb
t-channelNLO = 1.98±0.21 pb
?
W,H+
Z
ct
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CDF
Evidence for Single Top Multivariate Likelihood Function
7 input variables (kinematics, kinematic solver and ANN b-tag outputs)
Matrix Element Technique Ratio of event probability
densities for signal and bkg
pb0.12.13.1pb,1.1
4.11.1 ts
pb1.13.17.2ts
2.7 significance (2.9 expected)
pb9.00.19.1pb,8.0
0.11.1 ts
pb1.12.10.3ts
3.1 significance (3.0 expected)
1.5 fb-1
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CDFDirect Measurement of |Vtb|
CKM Matrix Element |Vtb| Describes strength of Wtb vertex single top |Vtb|2
Assumes |Vtb|2+|Vtb|2<<|Vtb|2
Measured with Matrix Element Technique
Theory uncertainty arises from the cross-section dependence on
Top quark mass Factorization and
renormalization scales PDFs and s
(Z. Sullivan, Phys. Rev. D70 (2004) 114012)
theory07.0experiment18.002.1 tbV
1.5 fb-1
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 21
CDF
Search for W′ Resonance Search for resonance in tb channel using
MWJJ Many theories include new gauge boson
Extensions to the SM (GUT) Extra Dimensions (Kaluza-Klein)
Use massive W boson with SM-like couplings
Z. Sullivan, arXiv:hep-ph/0207290 Large branching fraction to tb
R
R
MMcM
MMcM
WW
WW
2
2
GeV825
GeV800@95%CL
1.9 fb-1
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 22
CDF
Summary CDF entered era of precision top measurements.
Mass and cross section No longer stat. dominant. Need revisit syst. Uncertainty.
New measurements for the properties of top quark.
Some of them are measurable only at Tevatron. Many improvements in analysis techniques. Top is a good probe for new physics. Good agreement with Standard Model, so far. New results will be coming!
CDF/Tevatron combination for top mass,including recent 2 /fb results.
Single top: 4~5 sigma w/ >2 /fb
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CDF
Backups
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CDFBackground Table @1.9 fb-
1
Dilepton Lepton+Jets
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CDFExample of Syst. Err. for Mtop
Combined Template Method for dilepton and lepton+jets
2
2top
GeV 0.29.171GeV syst0.1
JESstat7.19.171
cc
M
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CDF
b-jet Flavor Tagging
Jet Charge
Performance
xTT
xTT
pp
Qpp
jettrack
trackjettrackJetQ
Dil=87%, P=61%, D2=0.10
L+J: =98%, P=61%, D2=0.13
(x=0.5)
Jet axis
b tagged
Soft
PTrel
Away Jet
b tagged
SSOS
OSP
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CDF
W Helicity
2008/02/22 2008特定領域「フレーバーの物理の新展開」研究会 28
CDFForward-Backward Asymmetry
Interference between LO and NLO diagrams
ttqq
gttqq