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Multi-body B-decays studies in BaBar

Ben Lau (Princeton University) On behalf of the BABAR collaboration

The XLIrst Rencontres de Moriond

QCD and high energy hadronic interactions

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Multi-body decay and CP violation 0*** tbtdcbcdubud VVVVVV

Sides are determined from the rates for various processes involving b

quarks

Angles are determined from CP-violating

asymmetries

Area is proportional to the amount of CP

violation*cbcdVV

*tbtdVV

*ubudVV

),(

*cbcdVV

*cbcdVV

)0,1()0,0(

CP 0

“The” Unitarity Triangle

Surprising, the best and estimation are coming from multi-body decay!

B0

B+Ddalitz

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Introduction to analysis technique

(mES) 3 MeV

e- (9 GeV) e+

(3.1 GeV)(4S)

B background

signal

Event selection:Quality cuts for tracks and showersContinuum rejection using event

shape variables Kinematic signal identification with

mES and E:

Maximum Likelihood Fit

to determine yields and asymmetries

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Measuring in b → uud

ubud

tbtdargVV

VV

WW

b

d b

d

0B

b

d

t

td

u

u

da1

+

0B ,a1-

)2sin(1

)sin(

eff2

ff

f

CS

C

(direct CPV)

)cos()sin(

)()(

)()(00

00

tmCtmS

fBfB

fBfBA

CPCP ff

CPCP

CPCPCP

Goal: Measure time dependent ACP

B0large penguinB0 need time-dependent dalitz plotB0small penguin, mostly longitudinal polarization

W

b

d

d

u

u

d

gtcu ,,

)sin(2sin tmACP If tree dominated:

Unfortunately, there is penguin pollution

“effective” value of

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CKM and Isospin Analysis Isospin Analysis disentangles penguin contributions to S=sin2αeff using

SU(2) symmetry relations between the B→ modes (analogous to B → ππ system)

We need branching fraction measurements: B(B±→ρ±ρ0), B(B0→ ρ+ρ-), B(B0→ ρ+ρ-), B(B0→ ρ0ρ0), B(B0→ ρ0ρ0)

BaBar has an improved measurement on Bf(B±→ρ±ρ0)

•Gronau-London Method (PRL 65, 3381)

•In this construction κ = 2(αeff-α)

•S and C are parameters relating to the CP asymmetry of the ρ+ρ- mode.

κ

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BaBar Updated Results (230M BB)Branching Fractions:

Previous measurement:

Consistent with hypothesis thatEW penguin pollution is small

Differential decay rate:

Charge Asymmetry:

The new measurement is in better agreementwith the isospin symmetry

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Motivation:Can be used to give a new measurementof by time-dependent ACP analysis

Observation of B0a1(1260)+ ± events

Branching Fractions:

Fitted a1(1260) resonance parameters:

Next step:

Measure using time-dependent CP analysis

0 61( (1260) ) 40.2 3.9 3.9 10BF B a

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Motivated by B, with sufficient statistics one can measure Little is known about these 5-body states

0

1a

0BTheory prediction for Branching Fraction (from 1987):

BR(B0a1)=43x10-6

Search for B0a1

Place an upper Limit < 30 × 10-6 (90% C.L.)

extraction will be difficult due to smallstatistics

BaBar performed a search using 110M BB events

BaBar Preliminary

Fit results: 68 ± 34 events

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sin(2+) in B0D(*),D

Favoredb c transition

2 *2i i i iu cdbAe e e V er V

c0B

d

bu

d

*D

h

*cb udA V V

Doubly-Cabibbosuppressedb u transition

d

bc

d

0B

u

*D

h0B

u,c,t

u,c,t

V*ub

Interference between:

= strong phase difference

Vcd

Vcb

V*ud

)(

)((*)0

(*)0

hDBA

hDBAr

- CP asymmetry proportional to ratio r of amplitudes

r~0.02 (from CKM elements) small CP asymmetry

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B0Ds*and SU(3) Such an important parameter |rD| cannot be calculated accurately… need measurement..

Need Ds mode. Because |rD| is extremely difficult to measure (background too huge)

Measurement of B (B0Ds+-) would help measure |rD | using SU(3)*

s

b

d d

uc

B0 -

Ds+

W

b

d d

uc

B0

D+

Wd flavor

SU(3)

SU(3) first ordercorrections

(*)

(*)

)/(

)/((*)0

(*)0

sD

D

cs

cdsD f

f

V

V

DBBR

DBBRr

*W exchange amplitude assumed to be small and neglected in this SU(3) analysis

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B0Ds*/K results

6 sigma

5 sigma

First observation of B0 Ds*+- /Ds

*+K- !

D mode D* mode

rD

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Direct CP Violationand Polarization in BK*•An interesting mode: B → K* ρ are charmless hadronic B decays.•Proceed through the dominant gluonic penguin and Cabibbo-suppressed tree level diagram Buus

Goal: Measure the polarization:Will fL ~ 100% like tree dominated Or fL ~ 50% like penguin dominated K* ?It is interesting to look for the connection

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Results for B+f0(980)K*+

08.091.0 22.020.0L

f

20.021.0

*0 34.0)(

KfBACP

Branching Fractions

Direct CP violation:

B+f0(980)K*+

5 sigma

B+0K*+

2.6 sigma

Upper Limit: <5.9 x 10-6 (90% C.L.)

Branching Fraction:

K* is a vector-vector decay•efficiency depends on polarization•need to extract fL from the fit:

Results for B+K*+

62.12.1

*0 106.02.5)(BF

KfB

67.16.1

*0 108.06.3)(BF

KB

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Summary Multibody B decays are playing a critical role in

the study of CP violation at the B Factories Currently, the best measurements of and are coming

from multibody decays

BaBar measurements of : Updated measurement of

Expanding into a1X modes: First observation of B0 → a1(1260)+

search for B0 → a1+

Measurement of /direct CP violation First observation of Ds(*)/K, useful in getting sin(2+)

in D* Searching for direct CP violation in B K*