余佳穎醫師 崇倫中醫診所 - Timing-life余佳穎醫師 崇倫中醫診所院長 2015‐09‐13文化中心中醫 生講座中醫養生講座 1
Shin-Shan Yu ( 余欣珊 ) Fermi National Accelerator Laboratory
description
Transcript of Shin-Shan Yu ( 余欣珊 ) Fermi National Accelerator Laboratory
Measurement of the Ratio B(b c)/B(b c)
&& Search for Anomalous
Production of Diphoton + e/at CDF
Shin-Shan Yu (余欣珊 )
Fermi National Accelerator Laboratory
Academia Sinica HEP Seminar, January, 2007
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DATA SAMPLE FOR THE ANALYSES
Lambdab relative BRSep 2003 shutdown
Diphoton + e/muMar 2006 shutdown
Measurement of the Ratio B(b c)/B(b c)
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OUTLINE
Why b
CDF Detector, Trigger
b Relative Branching Fractions
budb
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BIG PICTURE : WHY b BARYON?
u d b
Heavy Quark Effective Theory (HQET) simplifies the extraction of CKM elements
Assuming mb >> QCD Corrections expressed in the power
of 1/mb and s(mb) Spin-independent interaction
between light quarks and b quark
Spin of light degrees of freedom = 0, the corrections are simpler than those of b-mesons.
%45.0 )(
% 6.6)(
theorycb
theorycb
B
B
q
ud
0s
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HOW B(b c)/B(b c) ?
Four charged tracks in the final state
Data come from the same trigger, most systematics cancel.
Control samples: similar decays in the B meson system
Relative BR is the yield ratio corrected for the efficiency, e.g:
cbcb
cbcb
N
N
cb
cb
)(
)(
BB
)(
)(0
0
DB
DB
BB
)(
)(*0
*0
DB
DB
BB
and
But since we can not reconstruct neutrinos, several backgrounds can fake our semileptonic signals in the data ….
cbcb
cbc
N
NN XB
cb
cb
)(
)(
)( bgmix
BB
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CDF DETECTOR & TRIGGERSilicon Tracker
|| < 2vertex ~ 30 m
Central Outer Tracker (COT)96 layers drift chamber, up to ||~1
PT /PT~ 0.15% PT
Central Muon Chamber4 layers drift chamber outside the calorimeter|| < 0.6
Two Displaced-track Trigger pT > 2 GeV/c, 120 m ≤ d0 ≤ 1 mm,
Lxy > 200 m, pT > 5.5 GeV/c 150 M events analyzed for this measurement
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FORMULA REMINDER
cbcb
cbc
N
NN XB
cb
cb
)(
)(
)( bgmix
BB
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ANALYSIS REQUIREMENTS
2 out of 4 tracks matched to trigger tracks (two displaced-track trigger)
Muon 120 m ≤ d0 ≤ 1 mm
Pt(4 trks) > 6 GeV/c
Pt(Lc) > 5 GeV/c
Pt(, ) > 2 GeV/c
Pt(proton) > 2 GeV/c
Chi2 of secondary vertex fit < 15
Chi2 of tertiary vertex fit < 14
c of Lb candidate > 250 m
cof Lc candidate > -70 m
3.7 < M(Lc) < 5.64 GeV/c2
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SIGNAL SAMPLE b cX c p+ K- + Inclusive Semileptonic Signal
NDF=36.6/42Prob=70.7%
Inclusive b hadron -> X decays reconstructed as c
Hadronic SignalBackground shapes come from MC
Combinatorial and b-> other c hadron semileptonic decays
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FORMULA REMINDER
cbcb
cbc
N
NN XB
cb
cb
)(
)(
)( bgmix
BB
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MC AND DATA COMPARISON We used MC to obtain relative efficiencies of signals and backgrounds. Compare MC and background subtracted signal distribution in the data. Tune our MC if MC and data disagree, e.g: PT(b)
PT(b) [GeV/c]
BEFORE AFTER
PT(b) [GeV/c]
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FORMULA REMINDER
cbcb
cbc
N
NN XB
cb
cb
)(
)(
)( bgmix
BB
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SOURCES OF SEMILEPTONIC BACKGROUND
Feed-down/Feed-in from single b-hadron decays
Single b-hadron -> …. -> c additional particles e.g:
c
cb
)2593(
Hadrons mis-identified as muons
Real Lambdac and real muon from the decay of two heavy-flavor hadrons
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FEED-DOWN/IN FROM SINGLE B-HADRON Reduced by the M(c) cut
Normalize the amount of background to the measured hadronic signal
hadronichadronic
feedfeed
hadronic
feed
B
Bi
N
N
BR from PDG or estimated from theory and CDF preliminary measurements
Reconstruct as many backgrounds as possible
PDG BR(b -> c X)=9.2%constrain
BR of the other backgrounds
~10% contribution
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?
MIS-IDENTIFIED MUONSp, K, fake muons
cand muon d0 cuts suppress prompt fakes
Our fakes mostly come from b decays
Weight “c+TRKfail” events with the Pfake
~3% contribution
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c FROM TWO HEAVY-FLAVOR HADRONSCharm and from different b- or charmed hadrons
Suppressed due to the cand PT() cuts
Rely on Pythia MC
Most sensitive to hard gluon splitting
~0.2% contributionAssign 100% uncertainties
c+
p+
p+
c+
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SEMILEPTONIC SAMPLE FRACTION
4.3%
15.0%
79.8%
0.9%3.2%
9.8%
86.8%
0.2%
Signal
Feed-in/down
Fake mu
Two different heavy-flavor hadrons
4.9%
40.0% 53.9%
1.2%
Xc XD XD *
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CONSISTENCY CHECK
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UNCERTAINTY SUMMARY fractional uncertainty (%)
Measured BR +3.5 -10.5 8.2 2.3
Estimated BR 2.5 9.2 6.2
CDF Internal
Mass fitting 3.2 4.1 < 0.1
Muon fake 0.9 0.7 0.4
Pt spectrum +1.4-2.5 3.2 2.2
CDF material 1.1 1.7 1.3
scaling 0.4 0.5 0.4
0.2 2.2 1.3
b,c polarizations 1.9 -- --
c Dalitz 0.4 -- --
b lifetime 1.1 -- --
b decay model 2.9 -- --
6.0 6.1 3.4
Statistical 15.0 10.2 13.0
ccbb ,
)
)0
0
DB
DB
B(B(
)
)*0
*0
DB
DB
B(B(
)
)
cb
cb
B(B(
Feed-in/down background and hadronic signal branching fractions
MC modeling of production, decay, efficiency and acceptance
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CONTROL SAMPLE RESULT
(UBR) 0.9(BR) 0.8(syst) 0.6(stat) 0.18.9)
)0
0
DB
DB
B(B(
Consistent with the 2004 world average 7.8 1.0 at the 1level New world average ratio 8.3 0.9
(UBR) 1.1 (BR) 0.4 (syst) 0.6 (stat) 3.27.17)
)*0
*0
DB
DB
B(B(
Consistent with the 2004 world average 19.7 1.7 at the 0.7 level New world average ratio 19.1 1.4
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SIGNAL SAMPLE RESULT
Experimental uncertainties dominated by data sample size
(UBR) 0.5 (BR) 2.1-
0.7 )(2.1 (stat) 0.30.20
)
)
systcb
cb
B(B(
Unexpected and additionalphysics results
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FIRST OBSERVATION of NEW b DECAYSEstimated BR of the reconstructed background based on the first observation
c++
CDF Run II Preliminary 360 pb-1
CDF Run II Preliminary 360 pb-1
c(2593)
c(2625)
CDF Run II Preliminary 360 pb-1
Xcb 0
c0
Xcb
Xcb *
c++,+,0
c(2625)c(2593)
or *
ccc
cc
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084.0236.0)10(
)10(
0
TB
T
P
Pb
I Run CDF
BR) ( 22.0)( 11.0 (stat) 08.082.0)(
)(
)/ 6(
)/ 6( II Run CDF 0
0
ccb
TB
T systDBcGeVP
cGeVPb
BB
CROSS-SECTION RATIO AND B(b c
% )( 08.0
06.0)(stat 19.041.0)(
pTsystcb B
)( 11.0
19.0)(stat 20.056.0
) 6(
) 6(
GeV/c
GeV/c
0
pTsystP
P
TB
Tb
Consistent with the prediction 0.45% (Phys. Lett. B586, 337)
???
Make use of previous CDF measurements
b PT spectrum using fully reconstructed decay was not available for CDF I
Correct the CDF I cross-section ratio using measured PT spectrum
Acceptance correction
Different PT thresholds affect the ratio 10 GeV/c vs. 6 GeV/c
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AND b PT SPECTRA FROM DATA
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WHAT DO WE KNOW ABOUT b NOW?
c l c
20.0 3.7c(2593) +
l seenc(2625)
+l seenc
++ l
seenc
0 l
seen
(4.1 2.0) x 10-
3
Siganature-based Search for Anomalous Production of
Diphoton + e/ at CDF
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MOTIVATION
✔CDF Run I “ee+MET” event: 86 pb-1
✔Dominant SM: WW 810-7 events✔Total: ~10-6 events
✔Personal✔Use calorimeters✔Learn high-pt physics
Phys. Rev. D59, 092002 (1999) by Toback, et al
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RUN II PHOTON ANALYSES
Diphoton + X X = e, , , , met, b-jet, jet
Expand photon analysis to a more systematic search Do not optimize cuts based on any model Only compare kinematic distributions and number of events Look for excess above background prediction Not a blind analysis
Lepton + photon + X X = met, e, , met + b jet
Other model-dependent photon analyses RS graviton to diphoton search more …
+X signaturesSUSY: +MET+X
b`b`bbl*l*ll,
q*q*qqNew dynamics
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A RUN II e EVENT
Is it from SM? Fakes from jets or electrons ? Or new physics?
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ANALYSIS OVERVIEW
Require two central photons and lepton objects
photons || < 1.0
muons || < 1.0
electrons || < 2.0
Specific detector requirements for each lepton type
Data sample ~ 1.1 fb-1 collected with diphoton trigger
2 EM clusters with Et > 12 GeV
isolation, E_had/E_em, shower profile requirements
Compare prediction with observation by applying several levels of loose and tight photon requirements
Includes a wire chamber at showermax
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ANALYSIS REQUIREMENTS
cuts Tight cuts Loose cuts
Photon ET >13 GeV
Showermax fiduciality |XCES|<21.0 cm; 9.0 cm<|ZCES|<230.0 cm
Average CES 2 <20
Had/Em <0.055+0.00045*ET <0.125
Calorimeter Energy Isolation <2.0+0.02(ET-20) or
<0.1*ET if ET<20.0 GeV
<3.0+0.02(ET-20) or
<0.15*ET if ET<20.0 GeV
Track Pt Isolation <2.0+0.005*ET <5.0
Tracks point to photon candidate
0,1
Track Pt if there’s one track pointing
<1.0+0.005*ET <0.25*ET
2nd Showermax cluster (wire or strip)
<0.14*ET if ET<18 GeV
<2.4+0.01*ET if ET>18 GeV
No cut
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DIPHOTON + e/FROM SM AND FAKESW Z : Madgraph MC, weighted with data/MC ID scale factor, luminostiry, trigger efficiency, K factor to correct LO to NLO cross-section
Fake leptons + real photons: apply lepton fake rates to the events with 2 photon candidate + fakeable object, then scale with the true photon fraction obtained from MC and data (showermax and preshower radiator)
True photon fraction ~ 30% for photon Et > 13 GeV
Leptons + fake photons from jets: apply jet faking photon rate to the events with lepton candidate + photon candidate + a central jet
W Z + jet+ 2 jets where 1 jet fake leptonW or Z + 2 jets where both jets fake photonsZ + jet where electron fakes a photon
Leptons + fake photons from electrons: apply electron faking photon rate to the events with lepton candidate + photon candidate + an electron
Z where the electron comes from decay of ZZ + jet where the jet fakes a photon
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DOMINANT BACKGROUND
electron channel• ee from Zwhere one electron fakes the photon
muon channel• Z
Z
Z Z
l
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REJECT FAKE PHOTONS USING SILICON TRKElectron can fake a photon due to track-loss, FSR or BREM
Background from BREM can be reduced by removing photons matched to silicon tracks
tracks seeded by event vertex and a cluster in the EM calorimeter
Measure the fake rateCompare Z peak from ee and eGet Et dependence from MC
Normalize to data
Silicon-track rejections reduce the fake rate by a factor of 3-4
0.36% at 45 GeV
Silicon track rejection applied
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ResultBefore Sili rejection After Sili rejection
Channel e e Prediction 6.82±0.75 0.79±0.11 3.79±0.54 0.71±0.10
Obseverd 3 0 1 0
M(e)=129.5 GeV/c2
M(e1)= 93.0 GeV/c2
M(e2)= 88.3 GeV/c2
The event which survives silicon-track rejection.
= Sum Et of observed objects and missing Et
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CONCLUSION
We have measured the Lb relative branching fraction using 173 pb-1We have made the first observation of 4 Lb semileptonic decaysWe have the first evidence that the Lb pt spectrum is softer than that of the B0 meson. Although Bs mixing is already observed, there’re still interesting B physics to do at the Tevatron. With current available data, we could make a more precise measurements of b-baryon properties or search for unobserved b-baryons.
We have searched for anomalous production of diphoton + e/mu events in 1 fb-1 of data. No excess is observed.
Removing photons matched to silicon tracks reduce the electron faking photon rate by a factor of 4Keep looking …
Back Up Slides
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Control Sample DX, D+ K-+ +
Background shapes come from MC
Hadronic SignalInclusive Semileptonic Signal
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Control Sample D*X, D*+ D0 +, D0 K-+ Inclusive Semileptonic Signal
Background shapes come from MC
Hadronic Signal
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Physics Background
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Dominant Systematics Physics background and hadronic signal branching fractions
Measured: from PDG Estimated: multiply the BR by 2 or 0
Mass fitting model Vary the constant parameters in the fit Several background shapes come from inclusive MC
vary BR of the dominant decays
MC modeling of acceptance and efficiency pT spectrum
affect the efficiency and B (b c b semileptonic decay model
size of the independent MC for reweighting the phase space distribution uncertainty on the predicted form factors
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MC Tuning
Flat phase space
Form factor weighted
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b Polarization
cos1
cos bd
dN