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Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Measurement of |Vcb| and |Vub|
at
Weak Interactions and Neutrinos 2003
October 7
I. Bizjak, J. Stefan Institute
for Belle collaboration
|Vcb|
|Vcb|
|Vcb|
|Vcb|
|Vcb|
|Vcb|
u�ρπ
|Vub|
u�ρπ
|Vub|
u�ρπ
|Vub|
u�ρπ
|Vub|
u�ρπ
|Vub|
u�ρπ
|Vub|
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
TSUKUBA Area (Belle)
HER LERInteraction Region
OHO Area
High Energy Ring (HER)
for Electron
Low
Ene
rgy
Ring
(LER
)
for P
ositr
on
NIKKO Area
Electron Positron
e +/e -
(TRISTAN Accumulation Ring)
WIG
GLE
R
RF
WIG
GLE
R
RF
RF
RF
RF RFFUJI Area
HER LER
Linac
Belle detector @ KEK-B
Beam energies:e+ (HER): 8.0 GeVe- (LER): 3.5 GeVECM=10.58 GeV
4 years of data taking:Lmax=10.6· 10
33 cm-2s-1
Lint= 158.7fb-1 ... 152 million B meson events
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Measurement of |Vcb| and |Vub|
B physics can determine 2/3 real par.+
complex phase
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Exclusive |Vub|: evidence for B+→ωl+ν
• Events with single lepton (e or µ)
• Reconstructed neutrino momentum from missing momentum
ω decay reconstruction: ω → π+ π¯ π0
σ(pmiss ) ≈ 140MeV/c
Fully reconstruct the final state
Simultaneous fit of the signal m(π+ π¯ π0 ), ∆E, plin three lepton momentum bins
3pmiss = 3Y(4S) - Σ 3p 4pmiss =(|pmiss|, 3pmiss)
B+→ωl+ν
Br (B0→π−l+ν)=(1.33 ± 0.11 ± 0.21) · 10-4 ( 60 fb-1 )Br (B+→ρ0l+ν)=(1.44 ± 0.18 ± 0.23)· 10-4 ( 29 fb-1 )
Previous exclusive results:
ν
l+
ω
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Exclusive |Vub|: evidence for B+→ωl+ν ( 78 fb-1 )
BELLE
0
10
20
30
-1 -0.5 0 0.5 1
∆E (GeV)
Ent
ries
/ 24
0 M
eV 2.4 < p*l < 2.7 GeV/cDataωlνXulνXclνFake/non B
0
10
20
30
40
0.75 0.8 0.85
m(π+π-π0) (GeV/c2)
Ent
ries
/ 20
MeV
/c2
2.4 < p*l < 2.7 GeV/cDataωlνXulνXclνFake/non B
0
100
200
300
-1 -0.5 0 0.5 1
∆E (GeV)
Ent
ries
/ 24
0 M
eV 2.1 < p*l < 2.4 GeV/cDataωlνXulνXclνFake/non B
0
200
400
0.75 0.8 0.85
m(π+π-π0) (GeV/c2)
Ent
ries
/ 20
MeV
/c2
2.1 < p*l < 2.4 GeV/cDataωlνXulνXclνFake/non B
0
500
1000
-1 -0.5 0 0.5 1
∆E (GeV)
Ent
ries
/ 24
0 M
eV 1.8 < p*l < 2.1 GeV/cDataωlνXulνXclνFake/non B
0
500
1000
1500
0.75 0.8 0.85
m(π+π-π0) (GeV/c2)
Ent
ries
/ 20
MeV
/c2
1.8 < p*l < 2.1 GeV/cDataωlνXulνXclνFake/non B
Br (B+→ωl+ν)=(1.3 ± 0.4 ± 0.2 ± 0.3) · 10-4
Dominant systematic uncertainty:• B →Xulν crossfeed ... 14%• Neutrino reconstruct.,
track&cluster finding ... 9%
stat. sys. model
Simultaneous fit of the signal m(π+ π¯ π0 ), ∆E, plin three lepton momentum bins
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Hadronic invariant mass Mx
l±ν invariant mass q2
Lepton energy El
Inclusive |Vub|: the variables
Mx < MD
q2 > (mB-mD)2
El>(mB
2-mD2)
2mB
80%
20%
10%
Part of phase space, where b→c is kinematically suppresed
What part of b→u in this phase space
C.W.Bauer, Z. Ligeti, M. Luke: PLB 479,395 (2000)
How to suppress B→Xclν, which is approx. 60 times more abundant than B→Xulν?
Neutrino
Lepton
Mx
q
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
0
0.005
0.01
0.015
0.02
0.025
0.03
0 0.5 1 1.5 2 2.5 3
GeV/c
∆N/N B → Xc l ν
B → Xu l ν
Electron spectrum endpoint: the method
Deal with large backgrounds:
Non BB backgrounds
• Continuum (e+e- →qq )• QED processes
BB backgrounds
• B→Xclν• Leptons from other decays
(J/ψ, γ conv.)• Fake electrons
Subtraction of continuum
(8.8fb-1 of offresonance data)
Estimated using Ks→π +π¯
Veto on inv. mass
Fox-Wolfram momentsFisher discriminant:Thrust axisVisible energyCharged multiplicity
+
MC simulation:D**eν (ISGW2)D*eν (HQET)Deν (ISGW2)D(*)π (Goity-Roberts)
Using endpoint of momentum spectrum for e±
• Measurement region: 2.3 GeV/c < pe < 2.6 GeV/c (CMS)• Backg. estim. region: 1.5 GeV/c < pe < 2.2 GeV/c (CMS)
Acceptance of selection requirements as a funct. of q2
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Electron spectrum endpoint: the result ( 27 fb-1 )
∆Br =Br (B→Xue ν: 2.3 GeV/c
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
D(*)lν tag : the method• Tag events with both B decaying semileptonically
Requrements:
Reconstructed D(*) meson and 2 leptons with opposite charge
B → D(*) lν & B→XlνSignal sideTag side
Kinematics solvable, if:x2=1 − (cos2θB1+cos2θB2 − 2 cosθB1cosθB2 cosθ12)/sinθ12
Due to experimental resol. : cut x2 > − 0.2
Xu/Xc separation by demandingno detected K± on the signal side
x2
signal
data
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
D(*)lν tag : the result ( 78 fb-1 )
N(B→Xulν: mx < 1.5 GeV/c2 , pl > 1 GeV/c, all charged ) = 82 ± 19N(B→Xulν: mx < 1.5 GeV/c2, pl > 1 GeV/c, π0 associat. ) = 92 ± 21
Br (B→Xulν)=(2.62 ± 0.63 ± 0.23 ± 0.05 ± 0.41)· 10-4stat. sys. b→c b→u
model
|Vub| =(5.0 ± 0.64± 0.53)· 10-3
exp. theo.
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Advanced ν reconstruction tag : the result (78 fb-1 )
exchange of particles
W = PDF(random)PDF(rand.)+PDF(correct)
by minimising:
N(B→Xulν: mx < 1.5 GeV/c2 q2 > 7 GeV2/c4 )= 1148 ± 98
Br (B→Xulν)=(1.64 ± 0.14 ± 0.36 ± 0.28 ± 0.22)· 10-4stat. sys. b→c b→u
model
|Vub| =(3.96 ± 0.47± 0.52)· 10-3
exp. theo.
-150
-100
-50
0
50
100
150
0 0.5 1 1.5 2 2.5 3MX(GeV/c
2)
Nev
ents /
0.05
GeV
/c2
-100
-50
0
50
100
150
200
250
0 5 10 15 20 25 30q2(GeV2/c2)
Nev
ents /
1.0
GeV
2 /c2
q2 for mx < 1.5 GeV/c2mx for q
2 > 7 GeV2/c4
After MC(Xclν) subtraction
PDF(pB, EB, Mmiss , ...)
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
B→Xlν using full reconstruction of the other B
Mb
0
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3000
4000
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6000
5.2 5.225 5.25 5.275 5.3[GeV/c]
B0
Mb
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1000
2000
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5000
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7000
5.2 5.225 5.25 5.275 5.3[GeV/c]
B+
Reconstructed channels:
B0 →D*+π- / D*+ρ- /D*+a1- ; D+π- / D+ρ- /D+a1-
B- →D*0π- / D*0ρ- /D*0a1- ; D0π-
(B- → D+ρ- /D+a1- not used due to low purity)
D* → D0π
D0 →Kπ / Kππ0 / Kπππ / Ksππ
b→creconstructed
l±
ν
Xc
N(B0 )=21915±202 N(B+ )=24529±227
• Measuring B flavour/ lepton charge correlation
• Lepton momentum measurement in B rest-frame
• Subtraction of continuum (8.8fb-1 of offresonance data)• Taking into account other background:
Leptons from J/ψ, γ conv., upper vertex charm• Numbers corrected for mixing in the B0 case
Beam constrained mass: √(Ebeam ,pB )2
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Br (B0→Xlν)=(10.32 ± 0.32 ± 0.29)%Br (B+→Xlν)=(11.77 ± 0.26 ± 0.32)%
Br (B→Xlν)=(11.19 ± 0.20 ± 0.31)%Br (B+)/Br (B0)= 1.14 ± 0.04 ± 0.01
B→Xlν using full rec. of the other B: the results
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 1 2 3
promptsecondary
P in B rest frame (GeV/c)
dB
/dp
(G
eV/c
)-1
B0 e
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
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promptsecondary
P in B rest frame (GeV/c)
dB
/dp
(G
eV/c
)-1
B0 µ
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promptsecondary
P in B rest frame (GeV/c)
dB
/dp
(G
eV/c
)-1
B+ e
0
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0.12
0.14
0 1 2 3
promptsecondary
P in B rest frame (GeV/c)
dB
/dp
(G
eV/c
)-1
B+ µ
Lepton momentum in B rest frame
Consistent with B+/B0 lifetime ratio
|Vcb| =(4.13 ± 0.07 ± 0.25)· 10-2
exp. theo.
stat. sys.
stat. sys.
( 78 fb-1 )
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Mx resolution
H0: 93. H1: 21.
σ0: 166. σ1: 452. (MeV/c2)
x0: -77. x1: -255. (MeV/c2)
Mx resolution
Mx < 1.5 GeV/c2
Mx resolutionMx (GeV/c
2)
Mx > 1.5 GeV/c2
H0: 105.
σ0: 186. (MeV/c2)
x0: -87. (MeV/c2)
b→c MC
0
50
100
-1.5 -1 -0.5 0 0.5 1 1.5
IDEntriesMeanRMS
100 618
0.9170 0.5593
Mx for b→u enhanced sample (joined bins)Mx for b→u enhanced sample (joined bins)Mx for b→u enhanced sample (joined bins)Mx for b→u enhanced sample (joined bins)Mx (GeV/c
2)
data
b→c MC
b→u MC
0
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0 0.5 1 1.5 2 2.5 3
Full reconstruction tag: |Vub| pre-release
Mx (b→c MC subtracted) for b→u enhanced sample (joined bins)Mx (b→c MC subtracted) for b→u enhanced sample (joined bins)Mx (b→c MC subtracted) for b→u enhanced sample (joined bins)Mx (GeV/c
2)
Mx data − Mx b→c MC
Mx b→u MC
0
20
40
60
80
100
0 0.5 1 1.5 2 2.5 3
190MeVσ( Mx ) ≈
• Good Mx resolution• Observed excess of events in the low Mx
After Xclν MC subtraction
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
|Vub| Results
Br (B+→ωl+ν)=(1.3 ± 0.4 ± 0.2 ± 0.3) · 10-4Exclusive:
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
|Vcb| Results
|Vcb| =(4.13 ± 0.07 ± 0.25)· 10-2
exp. theo.
Ilija Bizjak, Ljubljana @ WIN 03, October 2003
Conclusion
Mb
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B0
Mb
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3000
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5000
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7000
5.2 5.225 5.25 5.275 5.3[GeV/c]
B+
|Vub|
Inclusive measurements by using Mx / q
2
Lepton endpoint measurement
Exclusive result for ωl+ν
|Vcb|
Inclusive measurement on fully recon. sample
Finalise the analyses + use the whole data set
Preliminary number for |Vub| with full reconstruction method out soon
Future