6/2/2015Attila Mihalyi - Wisconsin1 Recent results on the CKM angle from BaBar DAFNE 2004,...

04/18/23 Attila Mihalyi - Wisconsin 1

Recent results on the CKM angle from BaBar

DAFNE 2004, Frascati, Italy

Attila MihalyiUniversity of Wisconsin-Madison


The CKM matrix and Unitarity TriangleThe CKM mixing matrix relates the quarks in the weak interaction basis (d’,s’,b’)

and the quark mass eigenstates (d,s,b): (d’,s’,b’)=VCKM (d,s,b)

tbtstd

cbcscd

ubusud

CKM

VVV

VVV

VVV

V

Wolfenstein parametrization:

1)1()1(2

11)1(

)(2

11

223

2242

32

iAiA

AiA

iA

VCKM

=sinC (Cabibbo angle)

Independent parameters: , A

Unitarity leads to:

0 tbtdcbcdubud VVVVVV

*

*

cbcd

tbtd

VV

VV

*

*

cbcd

ubud

VV

VV

1

(,)

The angles of the triangle are related to CP–violation.

Measure from CP-asymmetries in b→uud processes.

B→B→B→


B-decay modes sensitive to Time dependent asymmetry of a B-B system (h=):

Decay amplitudes: PeTeAPeTeA iihh

iihh

,

Due to the presence of both tree and penguin amplitudes we have:

effi

i

ii

hh eeTP

eTPe

22

1

1

The extraction of is complicated by penguins!

)sin()cos())(())((

))(())(()(

00

00

mtSmtChhtBNhhtBN

hhtBNhhtBNtA hhhhCP

21

Im2

hh

hhhhS

2

2

1

1

hh

hhhhC

hh

hhhh A

A

p

q ie

p

q 2where

eff directly related to Shh

T=TreeP=penguin


Isospin analysis for B→ and B→Two triangular (isospin) relations can be constructed from the decay amplitudes.

M. Gronau, D. London, Phys. Rev. Lett., 65, 3381 (1990)

00 hhhh~ BABA

hh~

2

1 0BA

hh2

1 0BA

000 hhBA

000 hh~

BA

if no penguins

One can set a limit on the shift from penguins, -eff (useful only if the

B→ h0h0 BR is small):Gronau-London-Sinha-Sinha Phys. Lett. B514, 315 (2001)0

2000

0

00

4

)22(21)22cos(

BB

BBB

B

Beff

Y. Grossman, H. R. Quinn, Phys. Rev., D58, 017504 (1998)

Unknowns: Decay amplitudes

Observables: Branching ratios, CP asymmetries

Solvable but a 4-fold ambiguity on remains:

21)2sin( CS

Common base: EW penguins neglected


Prospects of from B0→+-

The B0→ 00 BR was recently measured at BaBar, PRL 91 241801 (2003), and also at Belle.

60 10)5.090.1()( BBR

05.019.019.0

03.022.040.0

C

S113 fb-1 of data Preliminary,LP03

02.003.0

10)6.05.5()(

10)2.06.07.4()(

18.017.0

60.19.0

0

60

A

BBR

BBR

From 81fb-1 of data, taken in 1999-2001: PRL 89 281802 (2002), PRL 91 021801 (2003)

Implies large penguin contributions: eff | at 90% c.l. Not easy to get from B→

0B

0B

BR comparable to B0→ +- and B+→ +0 but not large enough to measure the B0 - B0 asymmetry.

0B

HFAG average:


Prospects of from B→Both tree and penguin processes contribute.

Time dependent decay rate:

S: CPV in interference between mixing and decay

C: direct CPV

C, S: parameters related to not being a CP eigenstate.

ACP: asymmetry between and

Babar Results from 113 fb-1 with a quasi-2-body approach. (Select the bands on the Dalitz plot)

03.006.011.0

05.013.020.0 , 03.018.033.0

05.013.035.0 , 04.018.013.0

CPA

CS

CS

0B

0B

is not a CP eigenstate:

))cos()()sin()(1)(1()( 0 tmCCtmSSAB CP

PRL 91 201802 (2003)


Isospin Analysis

0000 221 AAAAA

00000

00

00

)(

)( , )(

)( , )(

ABA

ABAABA

ABAABA

Neutral and charged B decay amplitudes:

0000 )()( ABAABA ,

Construct an SU(2) pentagon relationship to solve for :

Lipkin, Nir, Quinn, Snyder, PRD 44, 1454,1991

Even in the absence of penguins there’s an eightfold ambiguity on

2

effˆ1 sin 2S S C C

*ˆ arg A A

Analysis is complicated by penguins (eff) and the non-CP eigenstates )ˆ(

No model independent constraints yet on from B→ The next step is a full Dalitz analysis. (Quinn-Snyder, PRD 48, 2139, 1993)


Prospects of from B→Both tree and penguin amplitudes contribute.

If no penguins:

)2sin(

0

S

C

With penguin contributions:

)2sin(1

)sin(

2effCS

C

.

0

.

000

2

)(

)()(sin

Long

Long

BBR

BBR

Using the Grossman-Quinn bound to limit =|-eff|

B0→ branching ratio is small compared to B+→ !

61.64.6

0

672.060.0

000

10)4.26()(

10)12.063.0()(

BBR

BBR

)%68(9.12

)%90(7.14

CL

CL

eff

eff

Decay is penguin dominated.

Penguin

Tree


The B→ decay B0 + - is a VV-decay The decay can proceed through 3 partial waves:

S (L=0, CP even), P (L=1, CP odd), D( L=2, CP even) 3 helicity amplitudes:

=0 → longitudinal polarization. Pure CP even eigenstate. =±1→ transverse polarization. Mix of CP even and odd eigenstates.

The decay B0 + - has been observed at BaBar and its BR and polarization measured: (PRD 69, 031102 (2004) and hep-ex/0404029, submitted to PRL)

B0 + - is an excellent candidate for measuring

§ Longitudinally saturated

§ Relatively large BR

§ Small penguin pollution

§ Two charged tracks in the decay for vertexing

03.003.099.010)5430( 6 longfBR ,


Analysis Strategy

In a simultaneous fit we measure: signal yield, polarization, Clong and Slong..Use a Maximum Likelihood fit to model: True-signal, Misreconstructed

signal (42% long., 15% trans.), Continuum and 17 B-background modes.

B-background: 209 decay modes simulated. Dominant modes:

,

, , 0

BB

aBaBcharmB0

11,

Simple assumptions

§ We neglect interference with other decays to final states (includes non-resonant contributions).

§ I=1 decay amplitudes are also neglected. I=1 absent due to Bose statistics but reintroduced by the finite (Falk, Ligeti, Nir, Quinn, Phys. Rev. D69:011502,2004)


B→Signal Selection

Also use the -mass and -decay angle (helicity) to distinguish signal from background.

B-decay: isotropic Continuum qq: jet-like

Combine event shape variables into a Neural Network.

Events with clean tags.

2*2beamES

*BpEm B-mass: *

beam* EEE B Missing energy:

Full likelihood Background

Data


Results:)(14.0)(27.017.0

)(14.0)(42.042.0

syststatC

syststatS

long

long

Babar result from 81fb-1 of data (taken between 1999-2001)

Submitted to PRL

hep-ex/0404029

Recent preliminary Babar result from 113fb-1 of data (presented at Moriond EW):

penguinsyststat 1341096

)(14.0)(24.023.0

)(11.0)(33.019.0

syststatC

syststatS

long

long

0B

0B


Global CKM FitsMore plots at: http://ckmfitter.in2p3.fr

Can’t exclude a large region with .Includes the Belle B→result.

The B→system provides the most stringent constraint on !

Other B→used in the SU(2) analysis.

(assumed) 0.1)(

6.0)(

96.0)(

4.26)(

0

8.06.0

000

05.007.0

0

1.64.6

0

Bf

BBR

Bf

BBR

L

L

Includes Belle


Summary

No significant constraint on from B→ Non optimal B0→BR (large penguins).

B→ quasi-2-body analysis performed but no model-independent constraints on Non-CP eigenstate and penguins not under control.

B→provides the most stringent constraint on . This analysis has been carried out at BaBar, and the result is (with some simple assumptions):

penguinsyststat 1341096

6/2/2015Attila Mihalyi - Wisconsin1 Recent results on the CKM angle from BaBar DAFNE 2004,...

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