Measurement of |Vcb| and |Vub atconferences.fnal.gov/win03/Talks/CKM/SecIII/bizjak.pdf · 2015. 12....

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|


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


Measurement of |Vcb| and |Vub|

B physics can determine 2/3 real par.+

complex phase


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


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


0

200

400

0.75 0.8 0.85


Ent

ries

/ 20

MeV

/c2


0

500

1000

-1 -0.5 0 0.5 1

∆E (GeV)

Ent

ries

/ 24

0 M


0

500

1000

1500

0.75 0.8 0.85


Ent

ries

/ 20

MeV

/c2


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


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


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


Electron spectrum endpoint: the result ( 27 fb-1 )

∆Br =Br (B→Xue ν: 2.3 GeV/c


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


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.


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 , ...)


B→Xlν using full reconstruction of the other B

Mb

0

1000

2000

3000

4000

5000

6000

5.2 5.225 5.25 5.275 5.3[GeV/c]

B0

Mb

0

1000

2000

3000

4000

5000

6000

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


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

0 1 2 3

promptsecondary


dB

/dp

(G

eV/c

)-1

B0 µ

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 1 2 3

promptsecondary


dB

/dp

(G

eV/c

)-1

B+ e

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 1 2 3

promptsecondary


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 )


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

20

40

60

80

100

120

140

160

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


|Vub| Results

Br (B+→ωl+ν)=(1.3 ± 0.4 ± 0.2 ± 0.3) · 10-4Exclusive:


|Vcb| Results

|Vcb| =(4.13 ± 0.07 ± 0.25)· 10-2

exp. theo.


Conclusion

Mb

0

1000

2000

3000

4000

5000

6000

5.2 5.225 5.25 5.275 5.3[GeV/c]

B0

Mb

0

1000

2000

3000

4000

5000

6000

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

Measurement of |Vcb| and |Vub atconferences.fnal.gov/win03/Talks/CKM/SecIII/bizjak.pdf · 2015. 12....

Documents

Transcript of Measurement of |Vcb| and |Vub atconferences.fnal.gov/win03/Talks/CKM/SecIII/bizjak.pdf · 2015. 12....