Semileptonic B decays, B mixing and magnitudes of CKM elements at B A B AR

Semileptonic B decays, B mixing Semileptonic B decays, B mixing and magnitudes of CKM elements and magnitudes of CKM elements

at Bat BAABBARAR

David Côté, Université de MontréalDavid Côté, Université de Montréal

for the for the BBAABBARAR collaboration collaborationDAΦNE 2004: Physics at meson factoriesDAΦNE 2004: Physics at meson factories

DAΦNE 2004 David Côté, Université de Montréal 2/14

OutlineOutline

• |V|Vcbcb||

• |V|Vubub||

• BB00 – B – B00 mixing mixing

semileptonic semileptonic B decays: BB decays: BXXcc ll

or Bor BXXuu ll 88106 BB

∫ Lon dt = 82 fb-1

Results presented today used Results presented today used less than half of the data we less than half of the data we have have nownow. .

mmdd, ..., ...

DAΦNE 2004 David Côté, Université de Montréal 3/14

Why studying semileptonic B Why studying semileptonic B decays and Bdecays and B0 0 - B- B00 mixing? mixing?

• To (over-)constrain the To (over-)constrain the Standard Model and Standard Model and determine some of its determine some of its fundamental parameters: mfundamental parameters: mbb, , mmcc and CKM matrix elements and CKM matrix elements

• To know more precisely To know more precisely parameters needed by other parameters needed by other analyses (analyses (mmdd, branching , branching fractions, form factors,...)fractions, form factors,...)

• To learn about QCD and To learn about QCD and effective QCDeffective QCD

DAΦNE 2004 David Côté, Université de Montréal 4/14

Inclusive |VInclusive |Vcbcb| measurement strategy| measurement strategy

• f , f0 : heavy quark expansion (HQE) formulae* • mb and mc : running quark masses (at = 1 GeV)• G, , LS, D : non-perturbative QCD parameters

*Gambino & Uraltsevhep-ph/0401063hep-ph/0403166

3322

000

3322

,,,,,,,

,,,,,

DLSGcbcc

DLSGcbB

ccb

mmEfEEXBBrXBBr

mmfXBBr

V

Problem: large uncertainties in mb, mc, ’s and ’s

Solution: Measuring mb, mc, G, , LS, D, simultaneously to Br(BXc e ) and |Vcb| using HQE’s predictions of El and MXc moments.

3322

00

332200

,,,,,,,

,,,,,,,

DLSGcbXciXc

Xci

DLSGcbii

mmEfEEMM

mmEfEEEM

i=1..3

i=1..4

DAΦNE 2004 David Côté, Université de Montréal 5/14

electron energy momentselectron energy moments

eesigsigee--

ee++BBtagtag

BBsigsig

νν eetagtag

Data sample:∫ L dt = 47.4 fb-1 400,000 events!

Strategy: identify B Xc e decays with di-electron events

– Require typical B-B event topology, one high momentum etag and one opposite charge esig

– Subtract remaining backgrounds (mostly from data control samples)

– Corrections applied for Bremsstrahlung, e ID efficiency, etc.

Accepted by Phys. Rev. Dhep-ex/0403030

esig energy spectrum used for moments measurement

DAΦNE 2004 David Côté, Université de Montréal 6/14

hadronic mass momentshadronic mass momentsStrategy: identify B Xc l decays on the recoil of fully reconstructed B’s

• Semileptonic side requirements : – exactly one e or with p* > 0.9 GeV/c

– Emiss, Pmiss consistent with a neutrino and net event charge 1

• MXc reconstructed with a kinematic fit to all remaining particles

• Corrections for small MXc reconstruction bias computed from Monte Carlo

DD**

ll

ee++

BBrecoreco

BBrecoilrecoil

XXcc νν

ee--

Accepted by Phys. Rev. D hep-ex/0403031

BABAR

El* > 0.9 GeV

Clear sign of higher charm resonances

DAΦNE 2004 David Côté, Université de Montréal 7/14

Excellent agreement between lepton and hadron moments!

Fit resultsFit resultsAccepted by

Phys. Rev. Lett.hep-ex/0404017

χ2 = 15Ndof = 20

MXc and El moments as a function of minimum El cut

used in global fitnot used in global fit

Excellent agreement between data and HQE predictions!

DAΦNE 2004 David Côté, Université de Montréal 8/14

|V|Vcbcb|: result and comparison|: result and comparison

)%06.016.061.10()(

10)6.02.04.04.04.41(||

HQEexp

3HQEexp SL

eXBBr

V

c

cb s

2% error on |Vcb|!

Br(BBr(BX X ll ))|V|Vcbcb||

DAΦNE 2004 David Côté, Université de Montréal 9/14

mmbb, m, mcc: result and comparison: result and comparison

GeVGeVm

GeVGeVm

c

b

)02.006.007.018.1()1(

)02.004.005.061.4()1(

s

s

HQEexp

HQEexp

ki

neti

c m

ass

sche

me

theorytheory

Conversion of mb and mc from kinetic mass to MS scheme by N. Uraltsev (hep-ph/9708372, hep-ph/0302262 , hep-ph/0304132)

DAΦNE 2004 David Côté, Université de Montréal 10/14

Inclusive |VInclusive |Vubub||Phys. Rev. Lett.92:071802,2004

Strategy: same B X l selection as hadron mass moments (slide 6)

• BXu l selection: kaon veto, low MX

• Measurement of for systematic

errors cancellation

•

XBBr

XBBrR uu

∫ L dt = 82 fb-1*Br(BXu l ) extracted from Ru using ref Phys.Rev.D67:031101,2003

3*

3

10)(39.0)(26.0)(27.024.2

10)(48.0)(27.0)(28.062.4

theosyststatXBBr

theosyststatV

u

ub

Several avenues currently considered in order to reduce further the theoretical uncertainties.

Monte CarloMonte Carlo

DAΦNE 2004 David Côté, Université de Montréal 11/14

Exclusive |VExclusive |Vubub||Phys. Rev. Lett.90:181801,2003

Much more to be expected soon: larger dataset additional decay modes reduced theoretical uncertainties form factor(s) measurement new recoil techniques

∫L dt = 50.5 fb-1

0B 40

339.056.0

10)(60.0)(47.0)(42.029.3

10)()(25.0)(22.064.3

theosyststateBBr

theosyststatVub

Strategy: untagged identification of B e decays with “ reconstruction”

• Signal extracted by requiring:– very high momentum electron E = Ebeam - E - El - Emiss compatible with zero

– M compatible with mass

• Rather high theoretical uncertainties (~15%)

• Relatively high yield: 834 102 events (only electrons and 50.5 fb-1)GeV/c

exclusiveanalysisadvantage MCMC

DAΦNE 2004 David Côté, Université de Montréal 12/14

The B0 – B0 mixing technique is well-known and well-documented:

1. Determination of vertex and flavor of the two B’s

2. “t” between the two B’s estimated from distance between vertices

(1) Phys.Rev.Lett.88:221802,2002 (2) Phys.Rev.Lett.88:221803,2002 (3) Phys.Rev.Lett.89:011802,2002 (4) Phys.Rev.D66:032003,2002 (5) Phys.Rev.D67:072002,2003

1006.0008.0500.0 psmd

psB

029.0012.0529.10

Results (23106 BB):

(3)

(averaged 1,2,5)

« classic » B« classic » B00 - B - B00 mixing mixing

000000 / BBBBBB “mixed”

0000 BBBB “unmixed”

dmT

2

tme

mtN d

t

d

cos14

;

tm

tNtN

tNtNtAsymmetry d

cos

DAΦNE 2004 David Côté, Université de Montréal 13/14

Generalized BGeneralized B00 - B - B00 mixing analysis mixing analysis B0 – B0 total decay-rate difference, CP violation in mixing and CPT

violation were always neglected in mixing and CP measurements The validity of these assumptions was recently confirmed in a

generalized B0 - B0 mixing analysis using 82 fb-1

Phys.Rev.Lett.92:181801,2004 hep-ex/0403002, submitted to PRD

0000 BBPBBP |q/p| 1: imply

dd

dd

im

imz

)2/(

)2/(

(): difference between flavor (mass) eigenstates

z (0,0): imply CPT violation

CP

CPCP A

Ap

q

ACP (ACP) is the amplitude for B0fCP (B0fCP)

d/d : lifetime difference between BH and BL mass eigenstates (not “Bshort” and “Blong”)

DAΦNE 2004 David Côté, Université de Montréal 14/14

SummarySummary

New BaBar precision measurement of |VNew BaBar precision measurement of |Vcbcb|, Br(B|, Br(BXXcc

ll ), m), mbb, m, mcc and 4 HQE parameters. and 4 HQE parameters.

13% (18%) inclusive (exclusive) |V13% (18%) inclusive (exclusive) |Vubub| measurement at | measurement at

BaBar using BBaBar using BXXuu ll decays (currently dominated by decays (currently dominated by

theory errors, but much progress to be expected soon).theory errors, but much progress to be expected soon).

New measurement of New measurement of dd//dd, |q/p| and z generalized , |q/p| and z generalized

mixing parameters validate the assumptions used for mixing parameters validate the assumptions used for previous BaBar’s mixing and CP measurements.previous BaBar’s mixing and CP measurements.

backup slidesbackup slides

DAΦNE 2004 David Côté, Université de Montréal 16/14

-- plane plane

DAΦNE 2004 David Côté, Université de Montréal 17/14

mmd,sd,s vs V vs Vtd,std,s

dd BBtdtbd BfVVm 22* [known factors]

needs latttice QCD calculations

ss

dd

BBts

BBtd

s

d

BfV

BfV

m

m2

2

[known factors]

also needs latttice QCD calculations,but easier to compute.

DAΦNE 2004 David Côté, Université de Montréal 18/14

electron energy momentselectron energy moments

We measured...

0

/,0 E eei

ei dEdEdEER

• the first moment: 0,

0,

00

0101 ER

EREM

• the central moments: 0,

,

00

0100 ER

EMEREM n

n n = 2,3

Defining:

• the partial branching fraction (0th moment): 0,000 EREB B

DAΦNE 2004 David Côté, Université de Montréal 19/14

HQE parametersHQE parametersWe use calculations in kinetic mass scheme by Gambino and Uraltsev

hep-ph/0401063hep-ph/0403166

(HQE to order 1/mb3, s

2 )

• μπ2 - exp. value of kinetic energy of b quark inside B meson

• μG2 - exp. value of chromomagnetic moment operator

• ρD3 - exp. value of Darwin operator

• ρLS3 – exp. value of Spin-Orbit operator

Ơ(1/mb2){

Ơ(1/mb3){

3HQEexp

3

3HQEexp

3

2HQEexp

2

2HQEexp

2

)01.007.004.009.0(

)00.002.002.020.0(

)02.003.006.027.0(

)01.004.004.045.0(

s

s

s

s

GeV

GeV

GeV

GeV

LS

D

G