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The XLIrst Rencontres de Moriond. QCD and high energy hadronic interactions. Multi-body B-decays studies in BaBar. Ben Lau (Princeton University) On behalf of the B A B AR collaboration. “The” Unitarity Triangle. . . Multi-body decay and CP violation. - PowerPoint PPT Presentation
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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*
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