CP violation in B → pp , rp
description
Transcript of CP violation in B → pp , rp
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CP violation in B → ,
Hiro Sagawa (KEK)
FLAVOR PHYSICS & CP VIOLATION,
Ecole Polytechnique, Paris, France
on June 3-6, 2003
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Outline
• CPCP asymmetries in asymmetries in B B00 →→ decaydecay – CP violating parameters : S and A(= C)
• Belle : hep-ex/0301032 ( to be appeared in PRD )
• BaBar : Phys. Rev. Lett. 281802
– Bound on Penguin Pollution from isospin
relation ( B→ anddecays )
• CPCP asymmetries inasymmetries in B B00 →→ decay ( decay ())– Quasi-two-body analysis
• BaBar : update at Recontres de Moriond 2003
Belle BaBar
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Introduction
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Introduction
B Unitarity triangle b uud
Quark mixing is described by the 3x3 Cabibbo-Kobayashi-Maskawa(CKM) matrix. (Wolfenstein parametrization)
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1 2 31 ( )2
1 2 212
3 2(1 ) 1
( )ud us
cd cs cb
ts tb
ub
td
A i
A
A i A
V V
V V V V O
V
V
V V
1()3()
2()* * * 0ud ub cd cb td tbV V V V V V
One irreducible complex phasederives CP violation .
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CP violation in mixing and decay
0
0
0
0
CP CPf
B
BB f
B
CPfA
CPfA
CPfA
CPfAmixing mixing
decay decay
CP
CP
CPf
ff
Aq
p A
CP violation in neutral B meson results fromthe interference between decays with and without mixing.
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Time evolution in B0 π+π–
0
0
| |/
( ) [1 { sin( )
cos( )}]
Bt
qd
d
eP q St m t
m tA
q= +1 for B0 tag 1 for B0 tag
t=z/(c)2
2 2
2Im | | 1,
1 | | | | 1AS C
(Belle)
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CP violation in B0 π+π–
* *
**tb td
tb td
ud ub
ud ub
V VV V
V V VV
B0
b
dB0 t t
d
b
B0
mixing
b
b
dud
B0
udW+
Tree(T)
b
dB0
duud
gt
Penguin(P)decay
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2
0
sin(2 )
i
A
T
S
ree only
e
22
22
2
2
1 | / |, ( )
1 | / |
sin( ) , ( )
1 sin(2 ) .
i i
f
i
e
ii
f
Tree Penguin
e ee
e e
direct CP violation
C related to thru isospin ana
P
P
A
lys
T
C
S
T
A
is
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Analysis Procedure
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Data sampleEventSelection
Flavortagging
Vertexand t
Continuumsuppression
: charmless B decays BR ~ 10-5-10-6 : rare decays world average (10-6)
Need a lot of data
0 0
4.8 0.5
25.4 4.2
(
5.3
)
( )
( )
BR
BR
BR
Data sample Belle 85 million BB pairs BaBar 88 million BB pairs BaBar 89 million BB pairs
(HFAG table)
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Kinematics: Reconstruction of CP side
EventSelection
Flavortagging
Vertexand t
Continuumsuppression
Kinematics
*
*
*2
*
2b beam
beamB
Bc p
Beam constrained mass
Energy d
E
ifference
EM
EE
*
*
*
:
:
:B
be m
B
a cms beam energy
cms energy of B candidate
cms momentum of B cand
E
E
p idate
Mbc(GeV/c2) E(GeV)
Signal MC
backgqq roundbackgqq round
Signal MC
K
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Good K/ separationEventSelection
Flavortagging
Vertexand t
Continuumsuppression
Belle ACC(Aerogel Cherenkov Counter) + CDC dE/dx
For the tracks in the momentum range that covers the B0 signal, effciency = 91% 10.3% of kaons are misidentified as pions. 10.0 0.2% from K
10.6 0.2% from K+
The effect of asymmetry of this misidentification is negligible for the measurement of A and S.
Threshold type
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Good K/ separationEventSelection
Flavortagging
Vertexand t
Continuumsuppression
BaBar DIRC (Detector of Internally Reflected Cherenkov light)
/K separation8 2
2.5
/
4 /C
C
at GeV c
at GeV c
Cherenkov angle ( , )is used separately as PDF for maximum likelihood fit.
, :C C
, :C C
Cherenkov angle for positivelyand negatively charged tracks
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Flavor taggingEventSelection
Flavortagging
Vertexand t
Continuumsuppression
Use flavor specific
properties and correlations
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Continuum backgroundEventSelection
Flavortagging
Vertexand t
Continuumsuppression
use kinematics and topology to separate spherical B decays from jetty qq events
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Continuum suppression
B0 for the case of BelleCut on a likelihood ratio (LR) that combines an event topology variable (SFW) and B flight direction (cosB )
SFW: Super Fox Wolfram Fisher discriminant using modified Fox-Wolfram moments
qqSignal Signal
SFW cosB LR
Signal
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Vertex reconstruction
Flavortagging
Vertexand t
Continuumsuppression
• The same algorithm as that used for sin21 meas.
• Resolution mostly determined by the tag-side vtx.
Example vertices
B0 lifetime of control sample1.5510.018(stat) ps
Time resolution (rms)1.43ps
(PDG02: 1.542±0.016 ps)
EventSelection
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CP asymmetries in B0
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Event reconstruction (Belle)Beam-constrained mass (Mbc) energy difference (E)
(in E signal region) (in Mbc signal region) B-candidate energy – beam energy (CMS)
K
K
other rare B decays
qq continuum
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Fit results (Belle)
5-5 0
5-5 0 5-5 0
Large CP Violation is seen !
B0 tag B0 tag
sin term
sin term
cos term hep-ex/0301032accepted forPhys. Rev. D
0.080.07
0.77 0.27( ) 0.08( )
1.23 0.41( ) ( )
A stat syst
S stat
C
syst
LR>0.825
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Confidence Regions (Belle)
Feldman-Cousins frequentist approach
1) Evidence for CP violationin B0 π+π–
2) “Indication” of direct CP Violation (A>0)
CL for CP conservation 3.4
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21 12
21
2
12
2
| / | | / |
|
[sin 2 2 sin( )cos sin 2 ]/ ,
[2 sin( )sin ]/ ,
1 2 cos( )c
/ |
| / | | / |os
P T PS R
A R
T
P T
P T P TR
P T
Constraints on the CKM angle 2()
|P/T| 0.15-0.45 (representative) Theory ~0.3
1 23.5deg (=)
(Belle & BaBar combined)
2 (=) strong phase difference
78o<2<152o
(95.5%C.L.)
<0 favored
2
|P/T|=0.45
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Constraint on -
2=78o
2=118o
2=152o1
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Belle’s resultsof 1 and 2
are consistentwith othermeasurements.
PDG2002 + ( Belle 1 & 2 )
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mES and E (BaBar)
-enhanced eventsPhys Rev Lett 89, 281802 (2002)
K-enhanced events
backgr dq nKq ou
backgr dq unq o
mES
mES
E
E
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CP asymmetry result (BaBar)
Projection in signal -enhanced events
0.02 0.34 0.05
0.30 0.25 0.04
S
C
Phys Rev Lett 89, 281802 (2002)
Asy
mm
etry
E
ven
ts/1
ps
( )t ps
0B tags
0B tagqq K
0
0
0
0
( ) ( )( )
( ) ( )
sin( ) cos( )
tag
t
ta
tg
g
aga
d d
N N
N N
BAs t
t
B
Bym
S Cm m
B
t
( )C A
(A=+0.30)
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The difference is at 2.2 level.
It’s early to say conclusively for the difference.
Fit results (Belle&BaBar)
&
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Comparison with predictions
PQCD
A Belle BaBar PQCD QCDFhep-ex/0301032 PRL,281802
(2002)PRD67,054009 (2003)
NPB606,245 (2001)
(%) 77 27 8 30 25 4 16 ~ 30 6 12
0.30(
,
0
0.4
.23
0.18(
( )
)
),
.5(
,
)
c
purp
p
le
R lines
g
i
r
blue
k
een
n
Purple regions : PQCD favoredRegion for each 2 (60o, 100o,150o)
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A bound on =|eff-|with an upper limit on
can constrain on using isospin relation.
2
0 0 0
2
2
: , , (limit)
: , ( 1 sin 2( ))
( , )
BRs
CP asymmetries A S A
A C
1
2A
1
2A
00A00A
0 0A A
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00 0 0 0
0
0
00 0
0 00
( ) ( )
( ) ( )
( ) ( ) ( )
A B
A B
Amplitude for
A B
B
B
A BA
A
32ij ij
A e A
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A bound on =|eff-|• Gronau/London/Sinha/Sinha bound (PL B514, 315 (2001))
2000
0
12
2
0
cos21 A
B BB
B B
B B
0 0 0
6
60
0 60
, ,
( 0.5) 10 ,
( 0.9) 1
4.8
0 ,
10 ,
0.48 0.1
5.6
9.
3.6
Average branching rat
B
ios
for
A
B
B
| | 48 @90% . .o C L
00 /B B
00 6(limit) 3.6 10B
(de
g)
HFAV table
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CP asymmetries in B0
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CP-Violating Asymmetries in B
→ ,• Principle: measure directly, even with penguins using
full Dalitz-plot analysis– difficulty
• Combinatorics and lower efficiency in three-body topology with 0
• Large backgrounds from misreconstructed signal events and other B decays
Need large statistics to extract cleanly
• “quasi-two-body” analysis:– Select the -dominated region of the K Dalitz pla
ne (Rejected when .)
– Suppression of qq backgrounds– Simultaneous fit for and
0 0 20.4 ( ), ( ) 1.3 /m m GeV c
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0000 and BBBB
Final state : not a CP eigenstate
Basically there are four tree amplitudes:
CP Violation Study in B0 →π decay
0B
0B
0B
0B
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B0 →π Time-dependence
Decay rate distribution ( for charge )
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)()(
)()(
hNhN
hNhNA h
CP
)cos()(
)sin()(
tmCQC
tmSQS
dhh
dhh
direct CP violation → ACP and C = 0
indirect CP violation → S = 0
C and S are insensitive to CP violation
Time evolution includes:
Time-integrated asymmetry:
Q is the charge
K is self-tagging: 0 ,0 ,1 ,0 KKKK SSCC
Fit for:
SSCCAA KCPCP , , , , ,
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Preliminary
The results with 89 million BB pairs @2003 Moriond EW
0.28 0.17 0.08
0.18 0.08 0.03
KA
A
BR of and K
Charge asymmetry of and K
6
1.3 61.2
( ) (22.6 1.8 2.2) 10
( ) (7.3 1.3) 10
B B
B B K
B0 →π/K (BaBar) Yields and Charge Asymmetries
B0 →π B0 →K
B rel eqq at d
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B0 →π/K (BaBar) : t distributions
B+continuumbackground
B-related background
2 (or more)from zero
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Direct CP violation in B0 →
0 0
0 0
0 0
0 0
( ) ( )
1( ) ( )
( ) ( )
1( ) ( )
CP CP
CP
CP CP
CP
N B N B A C A CA
C A CN B N B
N B N B A C A CA
C A CN B N B
0.240.28
0.160.17
0.62 0.06
0.11 0.04
A
A
A
A (0,0)
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Comparison with predictions
BaBar:
A = -0.18 0.08 0.03C = +0.36 0.15 0.04C = +0.28 0.19 0.04
QCDF: A = -0.015 C = 0.019 C = 0.250
w/ Charming Penguin(CP): S = -0.015 C = 0.092 C = 0.228
Phys. Rev. D67,094019, 2003
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Prospect (B0 →π-)
L(fb) L(fb)
A
S
0.77 0.28 (
0.30 0.25 ( )
)
A
A B
BaBar
elle
1.23 0.42 (
0.02 0.34 ( )
)
S
S B
BaBar
elle
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Prospect (B0 →π)
L(fb-1)
L(fb-1)
L(fb-1)
A
C
S
0.18 0.08A 0.36 0.18C
0.19 0.24S
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Summary• Measurement of CP asymmetries in B0 →
• Still early to say conclusively for the difference.
• Measurement of CP asymmetries in B0 → – Quasi-two-body analysis was performed by BaBar.– Hint of Direct CPV ?
0.080.07
( )
0.77 0.27 0.08 1.23 0.41
0.30 0.25 0.04 0.02 0.34 0.05
C A S
Belle
BaBar
0.24
0.160.1
0 28
7
. 0.06
0.11 0.
0
04
.62A
A
(0,0)
2 lines
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end