b physics at belle koji hara (nagoya university) workshop "new developments of flavor...
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B physics at BelleB physics at Belle
Koji Hara (Nagoya University)
Workshop "New Developments of Flavor Physics" 2009
March 9-10, 2009
New results of tauonic B decays
BandBD
KEKB & BelleKEKB & Belle
e+ source
Ares RF cavity
Belle detector
SCC RF(HER)
ARES(LER)
e- (8.0GeV) × e+ (3.5GeV)
⇒(4S) →BB
⇒Lorentz boost:= 0.425
Finite crossing angle
~11mrad ×2
Operation since 1999.
L peak = 1.71x1034cm-2s-1
2
Total: 895 fb-1
(4S): ~720 fb-1
(5S): ~52.6fb-1
(3S): 2.9 fb-1
(2S): 7.1fb-1
(1S): 5.7fb-1
Yb scan: 8.1fb-1
Off-peak: ~83 fb-1
Total: 895 fb-1
(4S): ~720 fb-1
(5S): ~52.6fb-1
(3S): 2.9 fb-1
(2S): 7.1fb-1
(1S): 5.7fb-1
Yb scan: 8.1fb-1
Off-peak: ~83 fb-1
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BelleBelle DetectorDetector
4 lyr DSSD
He/C2H6
Extreme forward calorimeter
Leptonic decays proceed through W boson annihilation in the Standard Model
Decay rate simply related to B meson decay constant fB and |Vub|
Charged Higgs contribution enhance/reduce the Br
[Wei-Shu Hou Phys. Rev. D48, 2342 (1993)]
CP Violation may be sensitive to “unparticle” physics[ R. Zwicky, Phys.Rev.D77036004(2008), C.-S. Huang and X.-H. Wu, Phys.Rev.D77,075014(2008)]
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BB++IntroductionIntroduction
b
uW/H
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BB Analysis Concepts Analysis Concepts
Require no particle remain after removing products of tagging B and the particle(s) from B decay
Possible only in B factory
More than 2 neutrinos appear in B decay
Tagging side :Semileptonic or Hadronic B Decay
Signal side :
Detect daughter particle(s)
(4S)B- B+
e+
e
B++, +e+eB-X
Most powerful discriminant variable:Extra calorimeter energy EECL
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Belle Hadronic B tag (449x106 BB pairs)[PRL 97, 251802 (2006)]
◦ 3.5 evidence
B(B)=[1.79 (stat) (syst) ] x 10-4
BaBar (383 x 106 BB pairs) [PRD 77, 011107(R) (2008)], [PRD 76, 052002 (2007)]
◦ Hadronic B Tag
◦ Semileptonic (BDlX) Tag
X: , 0,
not reconstructed explicitly
◦ 2.6excess
B(B)=[1.2±0.4(stat)±0.3(bkg)±0.2(syst)]×10-4
Previous BPrevious B++++Measurements Measurements
+0.56 +0.46 -0.49 -0.51
New Belle Result with D(*)l tag using 657M BB pairs
Need more statistics to establish B+ Decay
Belle Hadronic
BaBar DlXBaBar Hadronic
B=1x10-3 Signal
B=3x10-3 Signal
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Signal Selection ConceptSignal Selection ConceptThough Br(BD(*)l)is large (~17%), S/N is expected to be
worse than S/N of hadronic B tags. We only use clean decay modes with high Br x .
Tagging Side◦ B- D*0l+ D0l
D*0D00, D0 D0K-+,K-, K-
◦ Reconstruct D*0lexplicitlypreventadditional fromcontaminating EECL
Signal Side1 prong decay◦ B+
e, ,
Require No additional charged tracks or
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Tagging side◦ Identified using a kinematic relation
Optimized to maximize in EECL<0.2 GeV◦ separately for l and modes
Signal side◦ Nsig extracted from EECL
◦ Clear Signal and BG separation expected
Selection CriteriaSelection Criteria
signal (B =1.79x10-
4)
lDB
lDlDB
lDB PP
MMEEB
(*)
(*)(*)
(*)
2
2cos
22
EECL(GeV)
Eve
nts
/ 0
.05
Ge
V
BGsigsig NNN /FoM
D*l tag,
MC expectation
BG
+ Data+ BG
D*l tag, l + Data+ BG
Semileptonic Tag Semileptonic Tag BBResultResult
)()(154 2122
3635sig syststatN
435.037.0
38.037.0 10)]()(65.1[)(
syststatB B
[arXiv: 0809.3834, BELLE-CONF-0840]
3.8σ significance including systematics.
Confirmation of previous Belle result with hadronic tags (more precise)
Above SM expectation, discrepancy ~1.6σ
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409.013.0SM 10]78.0[)(
BB (CKMfitter 2008 prediction)
Dominant systematic error for B(B): BG MC Statistics (12%), Tagging Efficiency(12%) Peaking BG Uncertainty (8%)
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Determination of fDetermination of fBB
Product of B meson decay constant fB and CKM matrix element |Vub|
Using |Vub| = (4.47±0.30)×10-3 from Belle BXulinclusive
[Belle preliminary, CKM2008]
GeV10)1.17.9(V 40.11.1ubB
f
fB = 216 22 MeV (an unquenched lattice calc.)
[HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ]
MeV 216 2728
2524B
f
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rH=2.110.75
22 2
2(1 tan )B
HH
mr
m
Constraint on Charged HiggsConstraint on Charged Higgs435.038.0
37.037.0 10)65.1() (BB
95% C.L.
409.013.0SM 10]78.0[)(
BB
B→DB→D Introduction Introduction Semileptonic decay sensitive to charged Higgs
T.Miki, T.Mimuta and M.Tanaka:hep-ph 0109244.
1.Smaller theoretical uncertainty of R(D)For B→τν,
There is O(10%) fB uncertainty from lattice QCD
(Ulrich Nierste arXiv:0801.4938.)2.Large expected Br
Compare to B→τν
3.The decay shape of 3 body decay can be used to discriminate W+ and H+
4. Sensitive to different vertex B: H-b-u, BD: H-b-c
W/H
b c Ratio of to ,e could be reduced/enhanced significantly
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Previous B→DPrevious B→D(*)(*) Measurements Measurements
Belle inclusive B tag :
5.2σ observation
Belle B→D*τνB→D was not measured
Babar B→D(*)τνBabar full reconstruction tag :
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BBDD Analysis Method Analysis Method
Similar to B analysis
Υ(4S) BB
e
K
π
νe ντ ντ
Signal Side(B→D)
Tagging Side(B→Hadronic mode)
• Require no remaining particles in the event using EECL
• Additional discriminant variable: Missing Mass square MM2 of the event
to separate BDlBG (MM2 ~ ) from signal (MM2>)14
Tag Side ReconstructionTag Side Reconstructionfully reconstruct B0,B+ 657x106BB
(Belle preliminary) (Belle preliminary)
TotalB+→147 modesB0→133 modes
B+ B0
Beam constraint Mass :
N=6.05x105
eff. = 0.18%Purity = 51%
N=1.01x106
eff. = 0.31%Purity = 58%
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Selection of B→DSelection of B→D(*)(*)D(*) decay modes τ selection
No additional charged particles and π0 remain in the event
Extra calorimeter Energy(EECL) Select signals using Missing Mass square (MM2) 、
PCM(τ→X)
Dτν Selection
e,μ with lower momentum
-Main background: Semileptonic B decays ( D(*)lν )
-signal-Dlν-D*lν-Other BG
EECL
No remaining particles
even
ts/0
.1G
eV
-signal-Dlν-D*lν-Other BG
MM2
Separate D(*)lν and signal
-signal-Dlν-D*lν-Other BG
arb
itra
l
arb
itra
l16
B→DB→D Result Result
EECLMM2B+→Dτν
ObservedClear Signal
GeVGeV2/c4
even
ts/0
.4G
eV2/c
4
even
ts/0
.1G
eV
●data - Dτν - D*τν - BG
●data - Dτν - D*τν - BG
(EECL<0.2GeV) (MM2>2.0GeV2/c4)
EECLMM2B0→Dτν
GeVGeV2/c4
even
ts/0
.4G
eV2/c
4
even
ts/0
.1G
eV
●data - Dτν - D*τν - BG
●data - Dτν - D*τν - BG
(EECL<0.2GeV) (MM2>2.0GeV2/c4)
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(3.8σ)
(2.6σ)
First evidence
•Plots are projection in the signal enhanced region
(Belle preliminary)
B→DB→D** Result Result
(Belle preliminary)
EECLMM2
B0→D*τν
GeVGeV2/c4
even
ts/0
.4G
eV2/c
4
even
ts/0
.1G
eV
●data - Dτν - D*τν - BG
●data - Dτν - D*τν - BG
(EECL<0.2GeV) (MM2>2.0GeV2/c4)
ObservedClear Signal
•Plots are projection in the signal enhanced region
EECLMM2
B+→D*τν
GeVGeV2/c4
even
ts/0
.4G
eV2/c
4
even
ts/0
.1G
eV
●data - Dτν - D*τν - BG
●data - Dτν - D*τν - BG
(EECL<0.2GeV)(MM2>2.0GeV2/c4)
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Determination of R(DDetermination of R(D(*)(*)))
Br(B+→Dτν) = 1.51 ± 0.15 [%]-0.39 -0.19
+0.41 +0.24
Br(B+→D*τν) = 3.04 ± 0.22 [%]-0.66 -0.47
+0.69 +0.40
Br(B0→Dτν) = 1.01 ± 0.10[%]-0.41 -0.11
+0.46 +0.13
Br(B0→D*τν) = 2.56 ± 0.10[%]-0.66 -0.22
+0.75 +0.31
(first error is stat second is systematic, third is D(*)lBr error)
(preliminary)
(preliminary)
Deviation from the SM expectation
B+→Dτν: 1.6σB0→Dτν: 0.5σ
Consistent within errors
Branching fraction
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Working on charged Higgs constraint.
SummarySummary New measurement of Bwith semileptonic
tagging method confirms the evidence obtained by Belle haronic tag.Update of hadronic tagging will also come soon.
First BD measurement in Belle has been performed. We obtained first evidence of B+D0+decay.
Measurement of tauonic B decays are now well established. They are giving tight constraints on charged Higgs.
Future measurements in Super B Factory will be strict tests of new physics beyond the SM.
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Specific Luminosity With Crab Crossing @ Specific Luminosity With Crab Crossing @ KEKBKEKB
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22 mrad crossing
3.06 bucket spacing Simulation
22 mrad
Simulationhead-on
Crab Crossing Data
Not as high as the expectation of simulationStill need more study to achieve the goal (2x specific luminosity)
Crab crossing since January 2007
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For emodes◦ Dominant BG: true D(*)lnu tagged B-decays looser tagging selection◦ -2.1<cosBDL<1.3, -2.6<cosBD*L<1.2, 0.5<P*l
tag<2.5◦ P*l
sig > 0.3For mode
◦ Suppress continuum and combinatorial BG tighter tagging selection◦ -1.1<cosB(*)DL<1.1,1.0<P*l
tag<2.2◦ 1.0<P*
sig < 2.4◦ |costhrust| < 0.9
Reconstruction efficiencyIncluding Br of decay modes and tagging side efficiency◦ e mode: 6.0 x 10-4
◦ mode: 3.8 x 10-4
◦ mode: 4.9 x 10-4
Selection Criteria and EfficiencySelection Criteria and Efficiency
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Systematic Errors of YieldSystematic Errors of Yield
BG PDF Shape +18.1 -17.2Signal PDF Shape +3.1 -3.2Br of Peaking BG +6.4 -13.0Rare B,bul, pair BG +5.9 -5.9Efficiency Ratio +0.5 -0.6
Total +20.3 -22.3
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Br Systematic ErrorBr Systematic Error+(%) -(%)
(Error for Efficiency)MC stat 0.9 0.9PID 1.3 1.3Br of 0.4 0.4Tracking 1.0 1.0Tagging Efficiency 11.6 11.6
Signal Yield 13.2 14.7
NBB 1.4 1.4
Total 21.2 22.2
Systematic errorSystematic errorsource B+→Dτν[%] B+→D*τν[%]
MM2 shape +9.1/-7.9 +10.0/-5.8
EECL shape +10.6/-7.6 +7.0/-9.7
Br(B→D**lν) ±0.4 +0.8/-0.0
D⇄D* cross feed +7.1/-6.9 +5.1/-5.3
Br(τ→lνν) ±0.3 ±0.3
Total 15.7/-12.9 +13.2/-15.4
source B0→Dτν[%] B0→D*τν[%]
MM2 shape +6.4/-5.8 +5.8/-6.1
EECL shape +9.0/-7.3 +9.8/-5.0
Br(B→D**lν) +4.5/-2.6 +0.6/-0.3
D⇄D* cross feed +5.8/-6.0 +3.5/-3.4
Br(τ→lνν) ±0.3 ±0.3
Total +13.3/-11.4 +12.0/-8.6