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Semileptonic B decays at BABAR
Olga Igonkina (University of Oregon) representing BABA collaboration R
March 4, 2004
1.5
excluded area has < 0.05 CL

1

md ms & md K sin 2
WA

0.5

0

| Vub |
cb
-0.5

|Vub/Vcb| V


-1

K

CKM
-1.5

fitter LP 2003

-1

-0.5

0

0.5

1

1.5

2



|Vcb | Lepton energy moments Hadron mass moments OPE fit |Vub | B (B Xu ) B ‘ 0 ,"0 " , Search for physics b eyond SM:



S emileptonic B decay s Olga Igonkina


Measurements of |Vxb | via B X
e+ , ² Vcb , V
ub +

Lepton energy sp ectrum
bc

e , W+ c, u X ïï

²

bu

ï b Bq

|Vcb |

0.04,

B (B X

c

)

10% Hadron mass sp ectrum

this talk

via incl. B (B Xc ) via incl. E , MXc sp ectra via excl. B (B D () ) |Vub | 0.004, B (B X
u

)

0.2%

this talk

via incl. lepton sp ectrum end p oint via incl. MXu sp ectrum via excl. B (B ( ) )
2

S emileptonic B decay s Olga Igonkina


Calculating |Vcb | from inclusive B X

c



Op erator Pro duct Expansion (p ower series in s and 1/mb ) calculates inclusive rate and moments of the E , MX distributions:
Theoretical uncertainty is 1.5%

Rate :



c

=

G2 m F 192

5 b 3

|Vcb |2 (1 + A

ew

)A

per t

A

nonper t

|Vcb |2 f =

OP E

(a i )

up to 2 and 1/m s

3 b

6 parameters

Moments:
(E , M X )


n

> (E

cut

)=

(X - X 0 )
d dX

n d dX

dX
E >E
cut

dX

f =

OP E

(ai )

Cut on lepton energy Calculations are p erformed in different mass schemes
S emileptonic B decay s Olga Igonkina PRD67(2003)054012 NPB665(2003)367

3


Inclusive B X

c

: Electron Momentum Spectrum
a) e+ e
-
BABA R

e e
-

6000 6000

tag

mostly
Electrons / 50 MeV/c
4000 4000 2000 2000

B B
sig

B X e

tag

e

+

e

sig

b) 20000 20000 e‘ e‘
15000 15000 10000 10000 5000 5000 0 0 0

Selection of di-electron events Statistics is large Backgrounds are sizable e‘ identification is imp ortant
N N
+- ‘‘

Data e from same B Fake electrons Dalitz Conversion Continuum

mostly B Xc X e
2 2.5

0.5

1 1.5 * p [GeV/c]

= (1 - ) § NB X e + § N = § NB X e + (1 - ) § N

B Xc X e B Xc X e

+N +N

+- bg r ‘‘ bg r

where is mixing parameter multiplied with fraction of neutral B
S emileptonic B decay s Olga Igonkina

4


Inclusive B X
N (B X e )
Electrons / 50 MeV/c

c

: Electron Momentum Spectrum

15000 10000 5000

BABA R

Ldt = 47.4 fb

-1

B r (B X e ( ))|Ecut >0.6 GeV = (10.36 ‘ 0.06stat ‘ 0.23sys )%
Submitted to PRL
(4S) rest frame

0 0

0.5

1 1.5 * p [GeV/c]

2

2.5
c

Moments of B X
>) < (E - < E M lep2 >(GeV2 )

lepton sp ectrum as function of E
BABA R
lep < (E - < E M>)3 >(GeV3 )

cut

B rest frame

0.10
dE
B lep E 0

BABA R

< M 1 >(GeV) E

1.8 1.7 1.6 1.5 1.4
BABA R

0.15 0.10 0.05 0.5 1.0 1.5 E cut[GeV]

0.00

lep

0.08 0.06 0.04 0.5

M

3

-0.01 -0.02 -0.03 0.5
BABA R

1.0

1.5 E cut[GeV]

0.5

1.0

1.5 E cut[GeV]

2

1.0

1.5 E cut[GeV]

Submitted to PRL
S emileptonic B decay s Olga Igonkina

corrected for efficiency and radiation. p oints are highly correlated.
5


Inclusive B X

c

: Hadron Mass Spectrum
Fully reconstructed tag B No missing information Backgrounds are small Statistics is limited Signal side: B Xc e , B Xc ²

e

-

1097 mo des B B
tag

sig

e

+

sig

N events

BABA R

Fit (4S ) Btag X each event Calibrate MX on MC, check on D data.
Before and after calibration
3.4 Slope= 0.995+0.011 Offset= 0.01+0.02 GeV D() D

[GeV]

7114 events

3.0 2.6 2.2

D

D

1.8 1.8
MX S emileptonic B decay s Olga Igonkina

Slope= 0.799+0.007 Offset= 0.26+0.02 GeV 2.2


2.6 true>

3.0

3.4

[GeV]

6


Inclusive B X

c

: Hadron Mass Spectrum

No dep endence on the relative fractions and masses of various Xc ! Statistically indep endent of lepton energy moments measurement Moments of B X hadron mass sp ectrum as function of E

c

cut

Ldt = 82 fb
BAB(a) A R

-1

Submitted to PRL (including all tables)
[GeV2] [GeV3] [GeV4]
2.08
4.4

(b BABA ) R

10

(cR BABA)

[GeV]

21

BAB(d) A R

2.04

4.2

9

19

2.00

0.9

p*

1.1
min

[GeV]

1.3

1.5

4.0

0.9

p*min [GeV]

1.1

1.3

1.5

8

0.9

1.1 1.3 1.5 p*min [GeV]

17

0.9

p*min [GeV]

1.1

1.3

1.5

corrected for efficiency and radiation

p oints are highly correlated.

S emileptonic B decay s Olga Igonkina

7


Operator Product Expansion: kinetic scheme

Taylor expansion

|Vcb | =

B

B X

c





§ [C 0 +

Ci § (ai - a0 )]

B


n

> (E

cut

) = C0 +

Ci § (ai - a0 )

Obtain parameters ai from the fit with no constraints:
leading order 1/m2 b

1/m3 b

mb (1GeV) and mc (1GeV) - b- and c-quark masses ²2 (1GeV) - kinetic energy of the b-quark in the B -meson ²2 (1GeV) - hyp erfine splitting G 3 D (1GeV) - exp ectation value of Darwin op erator 3 (1GeV) - equivalent of the spin-orbital interaction in atoms LS

B

B X

c



is extrap olation of < E 0 > to E

cut

=0

S emileptonic B decay s Olga Igonkina

8


Simultaneous fit of E and M

X

moments

Calculations are taken from Gambino and Uraltsev hep-ph/0401063.

Simultaneous fit of electron energy moments and hadron mass. Only black p oints are used in the fit preliminary
2 .1 0 4 .5 9 .6 22

hadron mass moments

M2 (GeV2)

M3 (GeV )

M4 (GeV4) (GeV3)

M1X (GeV)

2 .0 6

9 .2 8 .8

3

4 .3

20

X

X

X

2 .0 2

(a) R BABA

(b) 4.1 BABAR

(c) 8.4 BABAR
0.18

18

( AB R Bd) A

0 .1 0 0 .0 8 0 .0 6

M1 (GeV)

(GeV )

BABA R

0 .0 0 - 0 .0 1 - 0 .0 2

1 .7 1 .6 1 .5 1.4 BABAR (f)

0

2

2

M

partial0.04 (e) branching ratio
0 .5

M

1 .0

1 .5

0 .5

1 .0

1 .5

0.02

BABA (g) R

0 .5

1 .0

1 .5

3

0.10

electron energy moments

M

-0.03 Bh) AR ( AB 0 .5 1 .0 1 .5

Ecut (GeV)

Bands corresp ond to the theoretical uncertainties
S emileptonic B decay s Olga Igonkina

Fit quality: 2 = 14.8 ndof 20
9


Fit E and M

X

moments separately
Constrained fit: 2 = 1 ellipses
BABA R preliminary

Different theoretical accuracy for moments: n < MX > miss part of Ecut -dep endent p erturbative corrections n Exp erimental uncertainty for < MX > is larger than for < E n > The variation of s have very small impact on result The separate fit of moments (with constrained ²2 and 3 ) are in very go o d G LS agreement

|Vcb |(10

Lepton Moments

-3

)

42 41 40

All Moments
4.5 4.7

Hadron Moments
4.9
2

mb (1GeV), GeV/c are fitted with < E 0 >

X

S emileptonic B decay s Olga Igonkina

10


|Vcb | determination
preliminary

|Vcb | = (41.25 ‘ 0.45 B
B X
c

exp exp

‘ 0.41 ‘ 0.06

OP E OP E

‘ 0.62th ) 10 )%

-3



= (10.62 ‘ 0.16

indep endent of scheme

mb (1GeV) = (4.65 ‘ 0.05 (mb - mc )(1GeV) = (3.43 ‘ 0.02

exp exp

‘ 0.04 ‘ 0.02

OP E OP E

)GeV )GeV
mb (mb ) = (4.26 ‘ 0.05) GeV ïï

mc (1GeV) = (1.22 ‘ 0.09) GeV
BABA (OPE) R
á

|Vcb |
äå âã

B

B X

c



BABA (OPE fit) R average HFAG


CLEO-1 (OPE) CLEO-2 (OPE) DELPHI (OPE)
æç

BABA (e tag) R Belle (
!

tag) tag)

39

41

43

10

-3

Different OPE schemes

S emileptonic B decay s Olga Igonkina

()

HFAG (excl. D )


10

11

&'

$%

Belle (E )


"#

BABA (E ) R
èé

CLEO (

BABA (breco) R Belle (breco) ARGUS %

11


Inclusive B X

u

, low M

X

spectrum

e

-

B B

tag

sig

e

+

sig

Fully reconstructed tag B . Suppress B Xc on signal side. Get NB X from mE S in each MX bin Fit MX to get NB Xu (Use wide bin for MX < 1.55GeV/c2 to minimize MC systematics) Measure B (B Xu )/B (B X )

Events / (2.5 MeV/c )

BABA R

100 80 60 40 20 0 5.2

b)

Events / Bin

120

400 300 200 100

BA a)BAR

2

Data b u l b c l Other

S B

>2

5.25 5.3 2 m ES [GeV/c ]

0

0

1

2

m X [GeV/c ]

3

4

2

5

S emileptonic B decay s Olga Igonkina

12


Inclusive measurement of V
Accepted by PRL

ub

Ldt = 82 fb = (2.06 ‘ 0.25
stat stat

-1

B (B X

u

)

B (B X ) B (B X
u

‘ 0.23 ‘ 0.26

sy s sy s

‘ 0.36th ) 10 ‘ 0.39th ) 10

-2 -3

) = (2.24 ‘ 0.27
B (bu ) 1.55ps 0.002 b stat

|Vub | = 0.00445 §

§ (1 ‘ 0.056th )
BABA (mX ) R
01

V
PQ

ub

(calculations from 1999)

|Vub | = (4.62 ‘ 0.28

‘ 0.27

sy s

‘ 0.40

MC

‘ 0.26th ) 10

-3

Belle (mX - q 2 ) Belle (mX )
HI

Belle (E )
DE FG

Events / Bin

50
45 67

0
S emileptonic B decay s Olga Igonkina

1

2

m X [GeV/c ]

3

4

2

5

45

23

0

89

No cut on q 2 is applied. Shap e function uncertainty is not fully understo o d

@A

BC

100

BABA R

b)

Data b u l

BABA (E ) R CLEO (E ) LEP Average OPAL DELPHI L3 ALEPH

10-3

13


Exclusive B X
Exclusive decays B X ( Ldt = 82fb-1 ):
B
8 7 6 5 4 3 2 1 0 -0.3 -0.2 -0.1 -0 0.1 0.2 0.3 0.4 mX (GeV/c2)
signal b->ulnu(oth) b->clnu other data

u

channels

u

are identified in the same sample

‘



0


BABA R
9 8 7 6 5 4 3 2 1 0 0.4

B

‘

"0 "
BABA R

B
14 12 10 8 6 4 2 0
signal

‘


BABA R

data events exclusive

data events exclusive

data events exclusive

signal b->ulnu(oth) b->clnu other data

b->ulnu(oth) b->clnu other data

0.5

0.6

0.7

0.8

0.9

1

1.1 1.2 mX (GeV/c2)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1 1.1 1.2 mX (GeV/c2)

preliminary

B (B B (B B (B

‘ ‘ ‘

0 ) = (0.78 ‘ 0.32stat ‘ 0.13sys )10-4 "0 " ) = (0.99 ‘ 0.37stat ‘ 0.19sys )10-4 ) = (2.20 ‘ 0.92stat ‘ 0.57sys )10-4
-

"0 " is +

with 0.65 < m

+

-

< 0.95 GeV/c

2
14

S emileptonic B decay s Olga Igonkina


Different sub ject: LFV

decays

Search for signal of non-SM physics:
e
-

Sensitive to SUSY, heavy sterile neutrino, etc
- e-e+eR


sig

tag

data

signal MC



e

+

0.2 -0

- ²+e-e-

BABAR

1 2 3

-0.2 -0.4

E (GeV)

-0.6 0.2 -0

1-3 top ology events E ( ) = Ecms /2, m( Ldt = 92 fb-1
Decay - - - - - - eee ² + e- e- ² - e+ e- e + ²- ²- e - ²+ ²- ² - ²+ ²-
-+-

- ²-e+e-

- e+²-²-

)=m



-0.2 -0.4

N 1 0 1 0 1 0

Nbgd 1.51 ‘ 0.11 0.37 ‘ 0.08 0.62 ‘ 0.10 0.21 ‘ 0.07 0.39 ‘ 0.08 0.31 ‘ 0.09

B UL @90%C L < 2.0 ½ 10-7 < 1.1 ½ 10-7 < 2.7 ½ 10-7 < 1.3 ½ 10-7 < 3.3 ½ 10-7 < 1.9 ½ 10-7

-0.6 0.2 -0 -0.2 -0.4 -0.6 -0.6 -0.4 -0.2

- e-²+²-

- ²-²+²-

M (GeV/c )

-0

0.2

2

-0.4

-0.2

M (GeV/c )

0

0.2

2 0.4

accepted by PRL
LF V decay s Olya Igonkina 15


Summary

New measurements of semileptonic B decays : moments of lepton energy up to 3rd order as function of Ecut moments of hadron mass up to 4th order as function of Ecut which are used in most precise OPE fit with no external parameters and constrains: |Vcb | = (41.25 ‘ 0.45
exp

‘ 0.41

OP E

‘ 0.62th ) 10

-3

B B Xc = (10.62 ‘ 0.16exp ‘ 0.06OP E )% and precise determination of mb and mc Measurement of B (B X |Vub | = (4.62 ‘ 0.28
stat u

)/B (B X ) on clean sample
sy s

‘ 0.27

‘ 0.40

MC

‘ 0.26th ) 10

-3

New results in physics : upp er limits on the fraction of lepton flavor violation decays B < 1 - 3 § 10-7 at 90% CL More results so on!
S emileptonic B decay s Olga Igonkina