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August 20, 2007 Charmless Hadronic B decays at BaBar
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Charmless Hadronic B Decays at BaBar
Woochun ParkUniversity of South Carolina
Representing the BaBar Collaboration
Physics Seminar @Yonsei UniversityAugust 20, 2007
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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.
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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
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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
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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|
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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
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Amplitude
Standard Model: left-handed quarks and spin flip suppression:
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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
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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.
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Finding B+K*+(892)
Q is charge of pion.
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Finding B0K*0(892) and B0K*20(1430)
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Angular Distribution in Slices
|A0|2 expected to be dominant
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Measurement of fL
K*(892)0
K*2(1430)0
K*(892)+
VV
VV and VT different
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Resolved Ambiguity in B+K*(892)+
with Interferencewithout Interference
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Resolved Ambiguity in B0K*(892)0
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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
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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
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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]
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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]
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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
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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
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Efficiencies and SCF rate
MES ΔE
True-signal
SCF signal
MES
ΔE
K*+ Monte Carlo
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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
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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.
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Charmless background
K*+
K*+K+
K0s
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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
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ρ-K+π0 / K*+π-π0 Yield Estimate (II)
K*+
K+
K0s
Before adding ρ-K+π0 After
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BK(892)*232M BB PRL 97 201801 (2006)
K*+ K*0
K*0
f(980)K*0
K*+
f(980)K*+
Projection Plot
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BK*PRL 97 201801 (2006)
1,2,3,4,5 contours (statistical only)
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Belle’s K*0
fb-1
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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
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Feynman Diagram