August 20, 2007 Charmless Hadronic B decays at BaBar1 Charmless Hadronic B Decays at BaBar Woochun Park University of South Carolina Representing the BaBar

August 20, 2007 Charmless Hadronic B decays at BaBar

1

Charmless Hadronic B Decays at BaBar

Woochun ParkUniversity of South Carolina

Representing the BaBar Collaboration

Physics Seminar @Yonsei UniversityAugust 20, 2007

August 20, 2007 Charmless Hadronic B decays at BaBar 2

Standard Model Supersymmetry

Introduction to Charmless Decays

Dominated by SM-suppressed bu tree amplitudes. Also, transitions involving bs and bd penguin amplitudes. Small branching fractions, ~10-6 in Standard Model Virtual loops sensitive to new physics contributions.

Important probes of the CKM mechanism (, , and )

Rich program at the B factories Branching fractions and CP asymmetry measurements Polarization measurements in vector-vector and vector-

tensor modes.


Overview of This Talk

Vector-Vector and Vector-Tensor modes B+K*(892)+ [arXiv:0705.1798[hep-ex]] B0K*(892)0 and K*

2 (1430)0 [PRL 98

051801(2007)] Search for B0(K)* with large Kinvariant

mass[arXiv:0705.0398 [hep-ex]]

BK* [PRL 97 201801 (2006)] BR’s, CP asymmetries, and polarization

measurements


BaBar Dataset and Detector

Need large data samples to probe BF~10-6

> 420 fb-1 delivered. 223M or 384M B pair

samples used for analyses presented here.

BaBar Detector for Charmless B decay analyses Good neutral energy

resolution Charged K/separation

more than with Cherenkov angle + dE/dx .

Cherenkov angle


Analysis Method

Perform maximum likelihood fit Kinematic variables: beam

energy substitute mass (mES), E, resonance invariant masses and helicity angles.

Event-shape variables to distinguish from continuum event

Simultaneous fit to extract Branching fraction, CP asymmetries, and polarization parameters.

Be

e

B

Kinematics

*beam

* EEB cepB /V M300~*

Be

B2*2

beamES*BpEm *

beam* EEE B

|coss|


BVV, VT Decays : Helicity Amplitude and Angular analysis

2212

2121

sinsin4

11coscos

coscos

LL ff

dd

dN

Full amplitude ananlysis can be simplified to separate longitudinal and transverse events with low statistics and measure: Longitudinal polarization fraction fL

Integrate over

21

21

20

20

L |Α||Α||Α|

|Α|f

BK* analysis

BK* analysis


Amplitude

Standard Model: left-handed quarks and spin flip suppression:


Expectation of fL

We expect longitudinally polarized decays to dominate: Confirmed (fL ~ 0.82-0.98) in B, (tree-dominated). Need to investigate pure penguin or penguin-dominated VV and VT

decays. Other amplitudes could decrease fL:

SM: annihilation contribution, re-scattering effect, magnetic penguin, small BK* form factor……

NP: Right-handed supersymmetric mass insertions, tensor Z”,…

fL

0.82±0.11

0.91±0.05

0.86±0.13

0.97±0.02

Tree-dominated VV results


Major Background

Continuum Background |cos| < 0.8 and Fisher PDF with cosB and L0, L2.

Charmed B Background Ds/D cut on 12 MeV of the nominal mass values.

K S-wave LASS shape is used with interference considered

in the nominal fit. f0 KK

Interference effect is estimated as systematics.


Finding B+K*+(892)

Q is charge of pion.


Finding B0K*0(892) and B0K*20(1430)


Angular Distribution in Slices

|A0|2 expected to be dominant


Measurement of fL

K*(892)0

K*2(1430)0

K*(892)+

VV

VV and VT different


Resolved Ambiguity in B+K*(892)+

with Interferencewithout Interference


Resolved Ambiguity in B0K*(892)0


Puzzles

K*(892)+

the difference b/w the Qprojections for eventswith coscosand with coscos

0 or

Indicating the presence of final state interactions for VV.(not accounted for by naïve factorization).

fL(VV) ≠ fL(VT) (puzzle)

Indication of a new physics contribution

FSI Effect


Theoretical Efforts

FPCP 2007 presented

hep-ph/0405134,PLB 601,151 (2004).

hep-ph/0409317, PLB 597,291 (2004),PRD 71, 014030 (2005),PRD 70, 114025 (2004).

http://indico.cern.ch/contributionDisplay.py?contribId=2&sessionId=29&confId=5905




Search for (K)*0 with large Kinvariant mass

We extend the BK*(892)0 analysis to higher-mass and higher-spin resonances.

However, BD0 is highly suppressed in the SM.

As a first measurement, we report several BF upper limits.

D0 mass peak is predominantly due to f(980)0D0 and continuum.

384 M BB arXiv:0705.0398 [hep-ex]


B →K*

More pure-penguin or penguin dominated VV decay studies are desirable to resolve puzzles.

K*ρ is the best candidate mode. Dominated by bsg penguin diagram. Tree is doubly cabbibo-suppressed. K*0is pure penguin.

As in the K(892)* mode, it is critical to understand the non-resonant background and f0(980)K*.

Use BF and fL from K*0to reduce penguin error on Beneke, et al, hep-ph/0604005]


Strategy

Simultaneous measurements of :

• Signal yield

• fL (longitudinal signal fraction)

• Charge Asymmetry

Integrating over the angle :

2212

2121 4

11

sinsincoscos

coscos LL ff

dd

dN

Likelihood analysis over 7 variables :

• E and mES

• Reconstructed masses mV1 & mV2

• Helicity angles cos1 & cos2

• NNO

N

i jbackgroundijj

totalisignalsignal

N PnPneL1

)(,

,,'

N’(N) number of expected(observed) events.

232 M BB data samples


Strategy to identify signal

N

i jbackgroundijj

totalisignalsignal

N PnPneL1

)(,

,,'

Signal PDF

• PDFs for true and SCF(Self-cross feeding) respectively. Then, combine them with the fraction given by MC simulation.

•Two different PDFs for longitudinal and transverse-signal

fLobs = NLg / NSig fL : Efficiency corrected


Efficiencies and SCF rate

MES ΔE

True-signal

SCF signal

MES

ΔE

K*+ Monte Carlo


Cut and Control Variables

Signal-longitudinal, transverse, B0B0, B+B-, and off-resonance after skim with (K*+)|MK-0.892| < 0.125 (150),

|M,-0.771| < 375 (290) MeV/c2. -0.8 < cos< 0.98

(cos> -0.5 (-0.9) for K+π0 (π+π-)

|cos| < 0.95 )

to get rid of slow neutral pions or low acceptance region.

(Vertex fit cut) MES > 5.23 (5.25) GeV/c2

-0.15 < ΔE < 0.12 GeV (|ΔE| < 0.1)

• For π0 , at least 50 (30) MeV and 0.01 <LAT< 0.6 photons used. 0.10 (0.12) < mγγ < 0.16 (0.15) GeV/c2

• For π+ id, we veto electron, kaon and proton candidates. K+ id used.

MESE

MK M

cos cos

NNO

K*+ MC/Off-resonance


D0 veto

To veto B0D0(Kππ0)π0

To veto B0D*0(Kππ0)π0

From MC

From MC

K*+

K*+ K+ K0s

Then, allow charm bg yield to float.


Charmless background

K*+

K*+K+

K0s


ρ-K+π0 / K*+π-π0 Yield Estimate

Estimated using extended MKπ0 and Mππ0 region, [0.77,1.07] [0.77,1.51] and [0.40,1.15] [0.40,1.55] GeV/c2.

K*0

sPlot

Interference is not considered. Estimated as systematics.

sPlot

K*0


ρ-K+π0 / K*+π-π0 Yield Estimate (II)

K*+

K+

K0s

Before adding ρ-K+π0 After


BK(892)*232M BB PRL 97 201801 (2006)

K*+ K*0

K*0

f(980)K*0

K*+

f(980)K*+

Projection Plot


BK*PRL 97 201801 (2006)

1,2,3,4,5 contours (statistical only)


Belle’s K*0

fb-1


Conclusion

fL measurements have been done in VV and VT decays and it’s a puzzle.

Better theoretical explanation is needed.

Hot news!! BK*K*bar analysis is observed at BaBar. fL = 0.81±0.14 BF 5x10-7 6 (arXiv:0708.2248)

fL

K*(892) 0.49±0.06

K*(892) 0.51±0.05

K*(892)0 0.52±0.11

K*(892)0 0.57±0.13

K*2(1430)

0

0.85±0.07


Feynman Diagram

Documents

August 20, 2007 Charmless Hadronic B decays at BaBar1 Charmless Hadronic B Decays at BaBar Woochun Park University of South Carolina Representing the BaBar