Gagan Mohanty

1
Dalitz Plot Analysis in the Charmless three-body
B decays

_at_

• Gagan Mohanty
• University of Warwick

Representing
2
Outline of the talk

• Introduction
• Theoretical Framework
• Experiment Dataset
• Event Selection
• DP Analysis Methodology
• Results and Discussion
• Conclusions and Outlook

() DP Dalitz Plot
3
Introduction Timeline (1993)

• 1st observation of charmless B decays by CLEO

PRL 71, 3922 (1993)

• Since then

4
Introduction Timeline (2006)

• A vast amount of results in the charmless sector
  is pioneering

BaBar PRL 93, 131801
Kp-

• test of QCD factorization
• direct CP
• search for new physics

K-p

• A natural extension quasi-two-body B decays to
  three-body final states

5
Theoretical Framework

• The dominant contributions to charmless
  three-body final state

b ? s/d
b?s penguin transition contributes only to
final states with odd number of kaons due to
presence s quark e.g. Kpp, KKK
b?u tree and b?d penguin transitions
contribute mainly to final states with even
number of kaons such as ppp, KKp. Contribution to
odd number kaon states is Cabibbo suppressed
sin?c
b ? u
wrong flavor final states such as KKp-
and K-pp are expected to be exceedingly
small at o(10-11) in the Standard Model, and
offer an excellent window for new physics
6
Typical final states

• Shall focus on the Dalitz Plot analysis of above
  five charmless three-body decay modes from BaBar

7
PEP-II asymmetric B factory
9 GeV e- ??(4S)? 3.1 GeV e ?ß 0.56 lt?zgt
260 µm
This talk includes
Daily luminosity
Lint gt 300 fb-1
(10 off-peak)
Run 5
8
3x
Design 3x1033 cm-2 sec-1
Design 100 pb-1
9
BaBar Detector
Electromagnetic Calorimeter 6580 CsI(Tl) Crystals
1.5T solenoid
Cerenkov Detector (DIRC) 144 Quartz bars and
11000 PMTs

• e? ID
• reco.

?E/E 2.32 E-1/4 ? 1.85
Particle ID
e (3.1GeV)
Drift Chamber 40 layers
e- (9GeV)
Instrumented Flux Return Resistive Plate
Chamber ? Limited Streamer Tube
Silicon Vertex Tracker 5 layers, double strip
?? KL ID
10
Event Selection

• Wish to select B ? hhh (hK/p) event out of sea
  of continuum and other type B events
• Done in several steps
• Continuum rejection (Event topology)
• p vs. K vs. e/µ (Particle flavour
  Identification)
• Reconstruct Ks/p0 from their decay products
• on vs. off resonance (Kinematical variables)
• Veto on charmed resonances D, J/?, ?(2S)

11
Continuum Rejection

• Bs are produced at rest (spherical) vs. jetty
  udcs events
• Cuts on event thrust Fisher discriminant/NN
  constructed out of the topological variables

Background
Signal
12
Particle Identification

• PID is crucial for the analyses
• distinguish K vs. p (DIRC)
• veto the electron (DCH/EMC)

• Reconstruct p0? ?? (EMC) and Ks? pp

13
Kinematical Variables
B ? Kpp-

• Utilize precise beam energy information (E,p)
  conservation

Signal box
Sideband
Background DP fit
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DP Analysis Technique 1

• Dalitz Plot is a powerful technique relying on
  Lorentz invariant phase-space variables in a
  three-body decay

1
sij m2ij
2
B

3
2
1
13
Resonance
3
B
15
DP Analysis Technique 2

• Extract ci and ?i by performing a max likelihood
  fit

• ?i has two terms
• CP violating weak phase (ve)
• CP conserving strong phase same

B ? B

• Separate fit of B and B samples

16
Efficiency Variation
B ? ppp-
D
J/?
?(2S)

• Smooth variation of efficiency across the DP
• Use 2D parameterization in the likelihood fit
• Combinatorics is very small (mostly ignored)

17
Background Parameterization
B ? ppp-
D
Continuum
J/?
?(2S)

• Use 2D histogram to model the DP distribution
• Continuum off res on res data sideband and B
  bkg Monte Carlo subtracted from latter
• Square DP for better describing peaking edge

18
B? ppp- fitting the signal
PRD 72, 052002 (2005)
?(770)
B
f2(1270)
210 fb-1
Coupled BW
?(770)
B-
f2(1270)
Phase-space
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B? ppp- Summary

• ?0(770) is the dominant component
• 3s indication for f2(1270) NR mode
• Little evidence for s (seen by BES)

PRD 72, 052002 (2005)

• Can be utilized to measure ?

PRL 81, 4067 (1998)
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B? ppp- prospect for ?

• proposes to use B??c0p, which
  carries a null weak phase, as the reference mode
• However, no indication of the ?c0p mode
• new reference mode needs to be studied
• Iso-scalar pp resonances e.g. f0(980) are
  proposed as alternatives
• Again statistics disallows
  any meaningful conclusion
• Lint is the need of the hour!

PRL 81, 4067 (1998)
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B? Kpp- fitting the signal
PRD 72, 072003 (2005)
Fit
qq
BB
B-
B-
205 fb-1
B
B
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B? Kpp- Summary
PRD 72, 072003 (2005)

• Total BF differs significantly from Belle
• (Kp)0 gt K0(1430) resonance Effective range
  NR component (again different in Belle)
• Evidence for direct CP violation in ?0(770)K mode

23
CP in charged B decays?

• Large ACP in agreement with predictions based on
  global SU(2) fits T/P0.3

PRD 72, 072003 (2005)
BABAR
PRD 69, 034001 (2004)
Belle

• Eagerly looking forward to more data

hep-ex/0512066 (2005)
24
B0? pp-p0 time-dependent DP

• Parameterize B0(B0) ? pp-p0 amplitude in terms
  of ?(?pp0)p-, ?-(?p-p0)p and ?0(?pp-)p0

PRD 48, 2139 (1993)

f?(? ,-,0) are BW functions dependent on the
DP variables

• Time-dependent decay rate

• Determine U? and I? (27 ?16 parameters for small
  ?0p0 contribution) in the likelihood fit

25
B0? pp-p0 DP fit and result

• Likelihood built using PDFs for the
  discriminating variables ?E, mES, NN, ?t DP
  variable (square)

hep-ex/0408099 (2004)
m
?
192 fb-1
Event yield 1184 58

• Extract physics parameters from the fitted U? and
  I?

26
B0? pp-p0 a and direct CP

hep-ex/0408099 (2004)

1?
2?
Direct CP violation _at_ 2.9s level
27
Overall ? from BaBar
a from rr, rp and pp

• from a full CKM fit
• (eK, Vub, Dmd,s, sin(2b))

• Mirror solutions being disfavored!
• rp mode particularly plays an important role
• From rr, rp, pp (combined)

(preliminary)
28
B0? Kp-p0 fitting the signal
hep-ex/0408073 (2004)

Fit
qq
BB

• Gounaris-Sakurai
• LASS shape
• Uniform phase-space

PRL 21, 244 (1968)
NP B296, 493 (1988)
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B0? Kp-p0 Summary
hep-ex/0408073 (2004)
193 fb-1

• 4.2s evidence of K0(892) mode, UL from Belle
• Negligible non-resonant contribution 90 CL UL
• Measured BF of the benchmark process B0 ? D0p0 in
  agreement with current world average (270
  80)x10-6
• No significant ACP observed in any of the modes

30
B0? KK-Ks fitting the signal

• 1st attempt to study the KK-Ks Dalitz plot
• Narrow F(1020) signal gt use convoluted BW
• Handful events to claim any other resonances
• Try combinations of known 0 and non-flat NR
  model to best parameterize the data

f0(980)
210 fb-1
X(1500)
NR
31
B0? KK-Ks Summary
hep-ex/0507094 (2005)

• Ad hoc model to describe S-wave
• Need theory hand more data

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Summary

• Charmless three-body decays move to the era of
  Dalitz plot analysis
• Branching fractions of many quasi-two-body decays
  are measured, some are the 1st time measurements
• Evidence of large CP asymmetry in the ?0(770)K
  mode of the Kpp final state
• Time-dependent Dalitz measurement of B0?(?p)0
• direct CP violation at 2.9s level and measured a
  
• Mostly covered from BaBar, competitive results
  are available from Belle for many modes

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Backup Slides
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Future Prospects
Double again from 2006 to 2008 1 ab-1
Double from 2004 to 2006
Lint fb-1
?
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Square Dalitz Plot
?-
?0
?
Jacobian
blow up r bands interference regions
36
B?ppp nominal fit results
PRD 72, 052002 (2005)
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B?Kpp nominal fit results
PRD 72, 072003 (2005)