Transcript Measurements of a and future projections

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
Outline


Introduction to the measurement of a
Results from the B-factories:
 B
p+ p-, p± p0, p0 p0
 B
r + r -, r ± r 0 , r 0 r 0
0
 B
(r p)0

Summary and outlook

Will not cover expectations at LHC and Super B-Factories

See talks of P. Robbe and A. Bevan
2
Measuring a
Access to a from the interference of a b→u decay () with B0B0 mixing ()
ACP (t ) 
( B 0 (t )  f ) - ( B 0 (t )  f )
( B 0 (t )  f ) + ( B 0 (t )  f )
 S sin (mBd t ) - C cos(mBd t )
q A

 e -2i e -2i  e -2ia
p A
S  sin(2a )
Inc. penguin contribution
C 0
  ei 2a
T + P e + i ei
T + P e -i ei
S  1 - C 2 sin( 2a eff )
C  sin 
3
Gronau and London, Phys. Rev. Lett. 65, 3381 (1990)
From aeff to a: Isospin Analysis
Assume SU(2) symmetry among amplitudes
B   h  h0
A+ -  A( B 0  h + h - )
0
~ +A  A( B  h + h - )
A+ 0  A( B +  h + h 0 )
~
A -0  A( B -  h - h 0 )
~ -0
A A
A00  A( B 0  h 0 h 0 )
0
~ 00
A  A( B  h 0 h 0 )
+0
Neglecting EW Penguins:
+
+ 0
B  h h is a pure tree mode.
The triangles share a common side.
4
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 t.
 Extract S and C with a ML fit on a signal enriched sample.
 Signal PDF from MC.
 Background PDF from MC or sidebands
5
Variables used in the ML fit
*2
mES  Ebeam
- pB*2
signal
*
E  EB* - Ebeam
Event Topology
Combine variables in F or N
signal
 PID info:
 DIRC + dE/dX (BaBar)
 Aerogel + dE/dX (Belle)
background
background
 t
6
347 million BB
hep-ex/0607106
B  p p :results (preliminary)
0
+
-
Background
Signal
B0tag
mES
B0tag
mES
B 0  p +p -
E
E
Npp = 675±42
sPlot
7
535 million BB
hep-ex/0608035
B  p p :results (preliminary)
0
+
-
Npp = 1464±65
8
C =−A
B  p p :results (preliminary)
0
+
-
347 million BB
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
BaBar
Average
535 million BB
Cpp = - 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
Belle
2.3 s discrepancy
9
347 million BB
hep-ex/0607106
B  p p , p p (preliminary)
0
+
0
Np±p0 = 572 ± 53
0
0
Np0p0 = 140 ± 25
B   r p 0
10
a  a - aeff
1- C.L.
a constraint from B
 pp
a
|a| < 41o at 90% C.L.
a
1- C.L.
a
Frequentist interpretation: use only the B→pp
branching fractions and isospin-triangle relations.
No stringent constraint
from pp system alone
 need rr and rp
11
The B  r r analysis
0

-
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 r+r- is larger than p+pBranching fraction for B0 g r0r0 is small (~1.1x10-6)
 small penguin pollution
12
347 million BB
hep-ex/0607098
B  r r results (preliminary)
0
+
-
13
275 million BB
PRL 96, 171801 (2006)
B  r r results
0
+
-
B0  r + r -
BR  (22.8  3.8+-22..86 ) 10-6
Clong  0.00  0.30  0.09
S long  0.08  0.41  0.09
f L  0.941+-00..034
040  0.030
Nrr =
14
B  r r results (preliminary)
0
+
-
15
232 million BB
hep-ex/0607092
B  r r results (preliminary)


0
Nr+r0 =390 ± 49
16
347 million BB
hep-ex/0607097
B  r r results (preliminary)
0
0
Nr0r0 = 98 ± 32 ±
22
0
3.0 s evidence
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hep-ex/0607098
PRL 96, 171801 (2006)
a constraint from B  rr
[71, 105]o
at 68.3% C.L.
Use BR(B->r0r0)<1.1 X 10-6
a
Frequentist interpretation: use only the B→ρρ
branching fractions, polarization fractions and
isospin-triangle relations.
First evidence of B→r0r0
Constraint on a is less stringent
18
A. Snyder and H. Quinn, Phys. Rev. D, 48, 2139 (1993)
The B  ( rp) Dalitz analysis
0
B0
B0
r+pr-p+
r0p0
0
p+p-p0
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
19
347 million BB
hep-ex/0608002
B  ( rp) analysis (preliminary)
0
0
m’ and q’ are the
transformed Dalitz variables
20
449 million BB
hep-ex/0609003
B  ( rp) analysis (preliminary)
0


0
Dalitz + Isospin (pentagon) analysis
26(Dalitz) + 5(Br(rp), Br(r+p0), Br(r0p+), A(r+p0), and A(r0p+))
r+p-
mass
r-p+
r0p0
Signal
SCF
BB bkg
continuum
helicity
21
a constraint from B  ( rp)
(preliminary)
0
0
1- C.L.
1- C.L.
[0,8]o U [60,95]o U[129,180]o
at 68.3% C.L.
a (deg)
a (deg)
22
Belle rp result is not included.
It will weakens the suppression
of solutions around 0o and 180o.
CKMfitter
http://ckmfitter.in2p3.fr/
UTfit
http://utfit.dreamhosters.com/
a constraints
Global Fit
B-Factories
aB-Factories = [ 93
aGlobal Fit = [ 98
+11
]
-9
+5
]
-19
º
Nice agreement
º
aB-Factories = [92 ± 7]o (SM Solution)
aGlobal Fit = [93 ± 6]o
23
Pending Issues
Cpp = - 0.16 ± 0.11 ± 0.03

Discrepancy on Cpp

Solutions at 0o and 180o should be (more) suppressed.




Cpp = - 0.55 ± 0.08 ± 0.05
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.
24
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)]
I=1 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
25
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->a1p ?
Constraint on a from B0->r+r- and B+->K*0r+
[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.
26
Backup Slides
Time Dependent CP Asymmetry
A f CP (t ) 
0
0
( B phys
(t )  f CP ) - ( B phys
(t )  f CP )
(t )  f CP ) + ( B
0
phys
(t )  f CP )
 + S f CP  sin (mBd t ) - C f CP  cos(mBd t )
B0
mixing
( B
0
phys
t 0
B0
C f CP 
Sf CP 
1 - |  f CP | 2
1 + |  f CP | 2
- 2 Im  f CP
λ f CP  ηf CP
CP eigenvalue
q A f CP

p A f CP
Af CP
t
CP
f CP
Af CP
Amplitude
ratio
 e - 2i
1 + |  f CP | 2
28
BABAR Detector
29
DIRC: Control samples for p and K
From D *+  D 0 ( K -p + )p +
p
K
Projection for
2.5 < p < 3 GeV/c
30
31
B  p p :results (preliminary)
0
+
-
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
32
B  p p :results (preliminary)
0
+
-
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
33
a constraint from B
 pp
34
a constraint from B  rr
35
B  ( rp) formalism
0
0
-|t |/
e
( B  r + -p -+ (t ))  (1 + - ACP ( rp))

8
[1 + Qtag ( S rp + -S rp ) sin(mt ) - Qtag (Crp + -Crp ) cos((mt )]
A ( r p)  +-
A ( r p) 
-+
S rp
ACP ( r p ) + C rp + ACP ( r p )C rp
1 + C rp + ACP ( r p )C rp
ACP ( r p ) - C rp - ACP ( r p )C rp
Direct CP Violation
1 - C rp - ACP ( r p )C rp
CP violation in the interference with and without B mixing.
36
B  ( rp) parameters (prelim)
0
0
37
Direct CP violation in B  ( rp)
0
Significance for non-zero DCPV:
BaBar: 3.0 s
Belle: 2.4 s
0
38