Measurements of a and future projections

1
Measurements of a and future projections

• Fabrizio Bianchi
• University of Torino and INFN-Torino
• Beauty 2006
• The XI International Conference on B-Physics at
  Hadron Machines

2
Outline

• Introduction to the measurement of a
• Results from the B-factories
• B p p-, p p0, p0 p0
• B r r-, r r0, r0 r0
• B0 (r p)0
• Summary and outlook
• Will not cover expectations at LHC and Super
  B-Factories
• See talks of P. Robbe and A. Bevan

3
Measuring a
Access to a from the interference of a b?u decay
(g) with B0B0 mixing (b)
Inc. penguin contribution
4
From aeff to a Isospin Analysis
Gronau and London, Phys. Rev. Lett. 65, 3381
(1990)
Assume SU(2) symmetry among amplitudes
Neglecting EW Penguins is a
pure tree mode. The triangles share a common side.
5
Time Dependent Analysis Outline

• Fully reconstruct the B decaying to a CP
  eigenstate.
• Tag the flavor of the other B.
• Mis-tag probability measured in Bflav sample.
• Measure Dt.
• Extract S and C with a ML fit on a signal
  enriched sample.
• Signal PDF from MC.
• Background PDF from MC or sidebands

6
Variables used in the ML fit
Event Topology Combine variables in F or N
signal
signal

• PID info
• DIRC dE/dX (BaBar)
• Aerogel dE/dX (Belle)
• Dt

background
background
7
results (preliminary)
347 million BB
hep-ex/0607106
Background Signal
B0tag
mES
B0tag
mES
DE
DE
Npp 67542
sPlot
8
results (preliminary)
535 million BB
hep-ex/0608035

Npp 146465
9
results (preliminary)
C -A
347 million BB

Cpp - 0.16 0.11 0.03 Spp - 0.53 0.14
0.02
BaBar
(Spp, Cpp) (0.0, 0.0) excluded at 3.6 s
Average
535 million BB
Belle
Cpp - 0.55 0.08 0.05 Spp - 0.61 0.10
0.04
2.3 s discrepancy
Observation of Direct CPV at 5.5 s Observation of
mixing-induced CPV at 5.6 s
10
(preliminary)
347 million BB
hep-ex/0607106
Np0p0 140 25
Npp0 572 53
11
a constraint from
Da a - aeff
Da
1- C.L.
Da lt 41o at 90 C.L.
a
a
Frequentist interpretation use only the
B?pp branching fractions and isospin-triangle
relations.
1- C.L.
No stringent constraint from pp system alone ?
need rr and rp
12
The analysis

• Worse than pp at first sight
• V V final state. Mixture of CP 1 and -1 need
  to know each fraction
• However
• 100 longitudinally polarized (pure CP-even
  state)
• no need for elaborate angular analysis
• Branching fraction for B0 g rr- is larger than
  pp-
• Branching fraction for B0 g r0r0 is small
  (1.1x10-6)
• small penguin pollution

13
results (preliminary)
347 million BB
hep-ex/0607098
14
results
275 million BB
PRL 96, 171801 (2006)
Nrr 19432
15
results (preliminary)
16
results (preliminary)
232 million BB
hep-ex/0607092
Nrr0 390 49
17
results (preliminary)
347 million BB
hep-ex/0607097
Nr0r0 98 32 22
3.0 s evidence
18
a constraint from
PRL 96, 171801 (2006)
hep-ex/0607098
71, 105o at 68.3 C.L.
Use BR(B-gtr0r0)lt1.1 X 10-6
a
Frequentist interpretation use only the
B??? branching fractions, polarization fractions
and isospin-triangle relations. First evidence
of B?r0r0 Constraint on a is less stringent
19
The Dalitz analysis
A. Snyder and H. Quinn, Phys. Rev. D, 48, 2139
(1993)
rp- r-p r0p0
B0
pp-p0
B0
Monte Carlo

• Time-dependent Dalitz-plot analysis assuming
• isospin simmetry.
• 26 coefficients of the bilinear form factor
• terms occurring in the decay rate are
• measured with a UML fit.
• Physically relevant quantities are derived
• from subsequent fits to these coefficients.

Interference provides information on strong phase
difference
r(1450) and r(1700) are included
20
analysis (preliminary)
hep-ex/0608002
347 million BB
m and q are the transformed Dalitz variables
21
analysis (preliminary)
hep-ex/0609003
449 million BB

• Dalitz Isospin (pentagon) analysis
• 26(Dalitz) 5(Br(r?p?), Br(rp0), Br(r0p),
  A(rp0), and A(r0p))

rp- r-p
r0p0
Signal SCF BB bkg continuum
mass
helicity
22
a constraint from
(preliminary)
0,8o U 60,95o U129,180o at 68.3 C.L.


1- C.L.
1- C.L.
a (deg)
a (deg)
23
a constraints
Belle rp result is not included. It will weakens
the suppression of solutions around 0o and 180o.
CKMfitter http//ckmfitter.in2p3.fr/ UTf
it http//utfit.dreamhosters.com/
Global Fit
B-Factories
aB-Factories 92 7o (SM Solution) aGlobal
Fit 93 6o
Nice agreement
24
Pending Issues

• Discrepancy on Cpp
• Solutions at 0o and 180o should be (more)
  suppressed.
• Using rp nice suppression from BaBar, not from
  Belle.
• Background modeling.
• Interference with other resonances or
  non-resonant component in rp, rr modes.
• Subtleties on statistical analysis with small
  statistics.

Cpp - 0.16 0.11 0.03 Cpp - 0.55 0.08
0.05
25
Uncertainties on a extraction

• Possible contribution of EW penguin and isospin
  breaking effect.
• EW penguin effect seems to be small (2).
• Other isospin breaking effect O(1).
• M.Gronau and J.Zupan PRD 71, 074017(2005)
• I1 contribution due to finite width of r mass
  (rr mode).
• A.Falk et al. PRD 69, 011502(R)

Too small to be an issue at B-factories
26
Summary and Outlook

• The three modes are complementary.
• Need to study them all.
• Good agreement between the CKM fit (a determined
  by others) and direct measurements.
• Still a lot to do.
• Refine previous analysis and exploit new ideas
• a from B-gta1p ?
• Constraint on a from B0-gtrr- and B-gtK0r
• M. Beneke et al., Phys. Lett. B638, 68(2006)
• Doubling of statistics at the B-factories is much
  needed.
• Looking forward to LHC and to a Super B-Factory.

27
Backup Slides
28
Time Dependent CP Asymmetry
mixing
decay
Amplitude ratio
CP eigenvalue
29
BABAR Detector
30
DIRC Control samples for p and K
p
K
Projection for 2.5 lt p lt 3 GeV/c
31
(No Transcript)
32
results (preliminary)
Cpp - 0.16 0.11 0.03 Spp - 0.53 0.14
0.02
(Spp, Cpp) (0.0, 0.0) excluded at 3.6 s
33
results (preliminary)
App 0.55 0.08 0.05 Spp - 0.61 0.10
0.04
Observation of Direct CPV at 5.5 s Observation
of mixing-induced CPV at 5.6 s
34
a constraint from
35
a constraint from
36
formalism
Direct CP Violation
CP violation in the interference with and without
B mixing.
37
parameters (prelim)
38
Direct CP violation in
Significance for non-zero DCPV BaBar 3.0 s
Belle 2.4 s