Transcript hepweb.ucsd.edu

Experimental Aspects of CP
Violation in B Decays : Lecture III
Vivek Sharma
University of California, San Diego
http://vsharma.ucsd.edu/prague/cpv.pdf
Outline of Lecture II: Yesterday
• PEP-II and KEK-B Colliders : Notable features
• Detectors at the Asymmetric energy collider
– General requirements for CPV measurements
• Implementation in BaBar & Belle (similar but different)
• General Data analysis methods
– B Meson Reconstruction & Continuum background rejection
– B meson flavor determination : B or a B ??
– Blind analysis !
2
Outline of Lectures 3 & 4
• Lecture 3
• Three types of CP violation & SM expectations in B Decays
– Decay amplitude Weak phase structure
– Decay asymmetry prediction in SM
• General strategy for time-dependent CP asymmetry measurement
– Observables that probe angle 
• Time dependent CP asymmetry in B -> Charmonium KS modes Step-by-Step
• Other modes with subdominant or dominant Penguin
• Lecture 4
– Observables that probe angle
– Observables that probe angle 
– Summary of current measurements
– Future prospects
3
CP Violation In B Decays: SM Expectations
Decay Amplitude Weak Phase Structure in CPV
b  q qq Decays
• Most B decay final states have contributions from both “Tree” and
3 “Penguin” (Pt,Pc,Pu) diagrams.
– All Tree diagrams (Spectator, W-exchange, W-Annihilation,
rescattering) have same weak phase
– The three Pi can have different Weak and Strong phases
– EW penguins “suppressed” due to EW coupling
5
B Decay Amplitude Weak Phase Structure
Classification of b  q qq Decays
A(ccs )  VcbVcs* Tccs  Psc  Pst   VubVus*  Psu  Pst 
A(uus)  V V
*
cb cs
A( sss)  VcbVcs*
 P  P   V V T
 P  P  V V P
c
s
t
s
*
ub us
uus
c
s
t
s
*
ub us
u
s
P P
u
s
t
s

 Pst 
A(ccd )  VtbVtd*  Pdt  Pdu   VcbVcd* Tccd  Pdc  Pdu 
A(uud )  V V
*
tb td
A( ssd )  VtbVtd*
 P  P   V V T
 P  P  V V P
t
d
c
d
*
ub ud
uud
t
d
u
d
*
cb cd
c
d
P P
u
d
c
d

 Pdu 
6
Decay Amplitude Weak Phase Structure in CPV
7
Decay Amplitude Weak Phase Structure in CPV
b  qqd Decay Modes
8
Five “Classes” of B Decays For CPV
1. Decays dominated by single term: b  ccs & b  sss
SM  Small Direct CPV since second term is CKM suppressed
Any large Direct CPV  New Physics ( e.g. B+   K  ,  K  )
B0 modes have cleanly predicted relationship between CKM angle
and measured asymmetry from CPV due to interference between
decays with/Without Mixing
2. Decays with small second term: b  ccd ; b  uud
Expectation that P/T << 1  small Direct CPV possible
Approximate predictions in B0 decay for relation between
measured CPV and CKM phase
9
Five “Classes” of B Decays For CPV
3. Decays with suppressed (Vub Vus* )Tree as in b  uus
 Large interference effects. Example: B  K
4. Decays with no Tree contrib: b  ssd .
Interference comes from Penguin diagrams
with different Q=2/3 quarks in loop. e.g. B  KK
5. Radiative Penguin Decays: b  s .
Situation same as in (4) but leading contribution
from EM penguin. e.g: B  K*
10
Some Examples of Class I (b c c s): B0 KS
 p
VcsVcd* 2iK
   * e
 q K VcsVcd
A K S
  K S
A K S
f  f
CP
CP
q A f CP
p AfCP
 VcbVcs*   VcsVcd*  2i B
 *  * e
 VcbVcs   VcsVcd 
 K  1
 Vtb*Vtd  Vcb*Vcs  Vcs*Vcb 
  B  K S   

* 
* 
* 
 VtbVtd  VcbVcs  VcsVcb 
S
Im K
S
 sin(2 )
11
Another Example of Class I (b u u d): B0 +Neglecting Penguin diagram
A
 
A
 VubVud*
 *
 VubVud
 2i B
e

  1
 Vtb*Vtd  Vud* Vub 
 B     
 Im  sin(2  2  2 )  sin(2 )
* 
* 
 VtbVtd  VudVub 


Weak Phase in Penguin term is arg(Vtd*Vtb ) different from Tree so it will modify
Im and  depending on its relative strength w.r.t Tree. (Penguins are large!)
12
An Example of Class II (b c c d): B0 D+ D-
Ignoring Penguin Diagram (?)
*
*



V
V
V
 
tb td
cdVcb
  B  D D    D D 

* 
* 
 VtbVtd  VcdVcb 
ImDD   sin(2 )
13
B
CPV in Decay aka Direct CP Violation
2
B

f
A(B f )
A1
A(B  f )
B f
i wk
( B  f )  A1  A2e
ACP 
B
f
A2e
2
e i st
iwk i st 2
e
f
wk
A2
, ( B  f )  A1  A2e
Br  B  f   Br  B  f 
Br  B  f   Br  B  f 

Af
Af
2
 Af
2
 Af
2
B f
 st
A1
2
wk
 iwk i st 2
e
 0  Direct CPV
14
Observation of Direct CPV in B0K- +
SM amplitude   2e i T  P AK
sin   
K separation
E (GeV)
K separation()
• Loop diagrams from New Physics (e.g. SUSY) can modify SM asymmetry
• Clean mode with “large” rate : BF  B 0  K     18.2  0.8 106
• Measure charge asymmetry, reject B background with Particle ID
signal
B background
15
BaBar: First Observation of Direct CPV in B decay !
n  B0  K     910
nK  1606  51
AK  0.133  0.030  0.009
B0K+
n  B 0  K     696
BABAR
4.2, syst.
included
B0K+
BABAR
background
subtracted
signal enhanced
16
Confirmation of Direct CPV by Belle at ICHEP04
ACP = -0.101  0.025  0.005
_
B0 K
3.9 significance
B0 K
274M BB
Signal=2139 53
Combined BaBar & Belle significance = 5.7
Establishes CPV not just due to phase of B Mixing (M12)
Theoretical (npQCD) uncertainties insufficient to prove or rule out NP
17
Direct CPV in B- K- 0
Not in BK- +
Belle
Belle
ACP(K0 ) = 0.04  0.05  0.02
BaBar
ACP(K0 ) = 0.06  0.06  0.01
Average ACP ( K  0 )  0.049  0.040, Average ACP ( K   )  0.10  0.02
Expect both ACP to be same, difference is 3.6 ...(EW Penguin ??)
18
19
CPV in B0 Mixing
2
B0
B0
f
2

B0
A( B 0  B 0 )
B0
f
A( B0  B0 )
Occurs when Mass eigenstates CP eigenstates
(|q/p|1 and<BH|BL> 0)
The Box diagrams provide the required 2 phases
Strong phases depend on quark masses and
non-perturbative physics.
Asymmetries are small and hard to calculate precisely


B
 B
asl
0
phys
0
phys

 X   B
0
(t )   X    Bphys
(t )   X 
(t ) 

0
phys
(t )   X 


1 q / p
4
1 q / p
4
 O(104 )
20
CPV in B0 Mixing
2
B0 B0
f
A( B 0  B 0 )
B0
M 12
off-shell states f
i
12
2

B0
on-shell
states f
| BL,H   p | B 0   q | B 0  
1   Bd
q

p
1   Bd
2
B0 B0
A( B  B )
0
f
0
CPV in the B 0 B 0 mixing matrix
results from:
Mass eigenstates | BL , H   CP eigenstates | B 
1
1 | Bd |
2
(| B   Bd | B )
 1  Prob(B 0  B 0 )  Prob(B
0
 B 0)
21
CPV in B0 Mixing
Time-dependent CP Asymmetry:
AT (t ) 
0
0
( Bphys
(t )   X )  ( Bphys
(t )   X )
( B
0
phys
(t )   X )  ( B

In the B System, md  mBH  mBL
0
phys
(t )   X )


4 Re( Bd )
1 |  Bd | 2
 d  εd ~ purely imaginary
SM: AT  2  10 3 ; hence AT  10 2  New Physics
Babar  Search for asymmetry in same-sign dilepton sample containing 20381 events
N(
ATobs (t ) 
N(
, t )  N (

, t )  N (
, t )
S ( t )

A

T

, t )
S ( t )  B ( t )
 
 


S ( t )  signal
B ( t )  background from B decay and continuum
22
CPV in B0 Mixing
BABAR
20.7 fb1
Sample backgrounds B(t):
4.3% continuum
24% direct+cascade
12% direct+fake
B 0B 0 , B 0B 0 signal S (t )
Measurement region > 200mm
23
CPV in B0 Mixing
BABAR
20.7 fb1
Find:  0.005  0.012(stat )  0.014(syst )
Conclude: Re( Bd ) /(1 |  Bd |2 ) 
0.0012  0.0029( stat )  0.0036( syst )
q / p  0.998  0.006(stat )  0.007(syst )
BABAR PRL 88, 231801 (2002)
So far, no experimental evidence
of large CP violation in B0 mixing
To a good approximation:
q / p  1 and q / p  e 2i M   | M12 | / M12
24
CPV In Interference Between Mixing and Decay
B0
fcp
+
B0 B0
fcp
2
B0

B0
fcp
+
B
2
ACP e i f
B0
M 12 
0
fcp
B
ie 2i M
0
fCP
ACP e i f
Neutral B Decays into CP final state fCP accesible by both B 0 & B 0decays
This is CPV when
q
A f CP
q A f CP
 1 and
 1 and the Quantity of interest is  fCP   fCP
p
AfCP
p AfCP
CPV is defined as
a fCP 
B
B
0
phys
0
phys
(t )  fCP     B
(t )  fCP     B
0
phys
0
phys
(t )  fCP 
(t )  fCP 


2Im fCP sin  mBt   1   fCP
1   fCP
2
 cos  m t 
B
2
When B decay is dominated by a single diagram,  fCP  1  a fCP  Im fCP sin  mBt 
CP asymm. can be very large and can be cleanly related to CKM angles
25
CPV In Interference Between Mixing and Decay
Requires measurement of proper time difference t=t between the
decay of Btag and BCP. Time dependent rates for a
B0  fCP denoted by F (t) and a B0  fCP denoted by F (t) is
+
-
 1  λf 2

2 Im(λf )
F (t )  exp(t ) 1
cos(mt ) 
sin(mt ) 
2
2
1  λf
 1  λ f

S
C
26
Time-Dependent CP Asymmetry with a Perfect
Detector
B0
B0
Asymmetry ACP
• Perfect measurement of time interval t=t
• Perfect tagging of B0 and B0 meson flavors
•For a B decay mode such as B0Ks with |f|=1
sin 2
ACP (t )  sin2β sin(ΔmΔt )
27
Time Dependent CPV Measurement Technique
Since the techniques of time-dependent analysis is common
to many modes, I will now describe this in detail using the
“golden” mode B0 (cc) K0 from which CP violation in
B0 decays was first established.
The analysis (from 2002) based on 88 fb-1 is “old” but
forms basis for all other new (2004) analysis results that I
will present later
CP Violation in Picture
z
Separate
B0 and B0

m
(4S) = 0.55
e-

Btag
  4s 
K
e+
B0
μ-
Brec
K
B0
Coherent BB pair
Δz
Δt 
 βγ  c
z
Vivek Sharma , UCSD
μ
0
s
π-
+
π
+
B0  J/ Ks
29
Sin2 Analysis Strategy
Factorize the Time Dependent analysis into building blocks
Obtain All analysis ingredients from DATA
Measurements
 B±/B0 Lifetimes
 B0 B0-Mixing
 CP-Asymmetries
Analysis Ingredient

Reconstruction of B mesons
in flavor eigenstates
B vertex reconstruction

Flavor Tagging + a + b


Reconstruction of neutral
B mesons in CP eigenstates
+a+b+c
Vivek Sharma , UCSD
30
Calibrating The BaBar Clock With B Meson
Lifetime Measurement
0
+
Measurement of the B and B Lifetime
Tag B
z ~ 110 mm
K+
K0

Reco B
z ~ 65 mm
(4s)
 = 0.55
3. Reconstruct Inclusively
the vertex of the “other”
B meson (BTAG)
z
-
-
D-
+
t @ z/c
1. Fully reconstruct one B meson
in flavor eigenstate (BREC)
2. Reconstruct the decay vertex
4. compute the proper time difference t
5. Fit the t spectra
Vivek Sharma , UCSD
32
Fully-Reconstructed B sample
Flavor eigenstates Bflav : for lifetime and mixing measurements
Cabibbo-favored hadronic decays
bc u d
Neutral
B Mesons
“Open Charm” decays
~21000 signal
Purity: 85%

B0  D(  ) π  /ρ /a1
B  D(  )0π 
Charged
B Mesons
Hadronic decays into final states
with Charmonium
b  (c c ) s
B0  J / K *0 ( K   )
B  J / K  ,  (2S ) K 
~20000 signal
Purity: 85%
cm
2
[GeV]
mES = (Ebeam
)2 - (pcm
)
B
Vivek Sharma , UCSD
33
Vertex and t Reconstruction
BREC direction

Reconstruct Brec vertex from


charged Brec daughters
Determine BTag vertex from



charged tracks not
belonging to Brec
Brec vertex and
momentum
beam spot and (4S)
momentum
BREC Vertex
BREC daughters
Interaction Point
Beam spot
TAG Vertex
z
BTAG direction
TAG tracks, V0s

High efficiency (97%)

Average z resolution is 180 mm (<|z|> ~ ct = 260 mm)

t resolution function measured from data
Vivek Sharma , UCSD
34
tB Measurement in BaBar
true t
t resolution
measured t
LEP/SLD
e-t/t

B production
point known
eg. from
beam spot
BaBar
Either Brec or
Btag can decay
first (this
analysis)
e-|t|/t

=
Resolution
function
=
lifetime
Resolution
Function +
Lifetime
Need to disentangle resolution function from physics !
Vivek Sharma , UCSD
35
t Resolution Function


z
event-by-event (t) from vertex errors
Lifetime-like bias to
 Small correlation between lifetime
and Resolution Function parameters
R  (1  ftail  f outlier )G ( S t , mcore  0)
 ftail G ( S t , m  0)  exp(t /  bias t )
~0.6 ps
Signal
MC (B0)
 f outlier G ( outlier , moutlier )
tracks from long-lived D’s
in tag vertex
asymmetric Resolution
Function
Vivek Sharma , UCSD
t (meas-true)/t
36
Lifetime Likelihood Fit


Simultaneous unbinned maximum
likelihood fit to B0/B+ samples
Use data to extract the properties of
background events


B0 mES
Mass distribution provides the
signal probability
Use the events in the sideband
(mES < 5.27) to determine the
t structure of the background
events under the signal peak
B0 Bkg t

19 free parameters



t(B+) and t(B0)
t signal resolution
empirical background
description
2
5
12
Vivek Sharma , UCSD
37
B Lifetime Fit Results
20
B0/ B0
fb-1

World’s best measurement



Main source of systematic
error


B
signal
+ bkg
2 % statistical error
1.5% systematic error
Parameterization of the t
resolution function
Description of events with large
measured t (outliers)
PRL 87, 201803 (2001)
t0
= 1.546  0.032  0.022 ps
PDG: 1.548
t
background
= 1.673  0.032  0.022 ps
PDG: 1.653
t (ps)
 0.032 ps
 0.028 ps
t/t0 = 1.082  0.026  0.011
Vivek Sharma , UCSD
PDG: 1.062
 0.029
38
B Flavor Mistag Knowledge From Data
sin2 results from charmonium modes
P ( B 0  B 0 )  et 1  cos( m t ) 
Start with a B0 beam, slowly (compared to the lifetime) a B0 component builds up
But no “Mixed” events at t=0. If the detector measures some “mixed” events, it
must be because it has measured the flavor of the B incorrectly ( mistag)
0
B
0
0
BB
B Lifetime
40
Analysis Strategy (II)
Measurements
Analysis Ingredient
 B±/B0 Lifetimes
 Reconstruction of B mesons
in flavor eigenstates
 B vertex reconstruction
 B0 B0-Mixing
 Flavor Tagging + a + b
 CP-Asymmetries
 Reconstruction of neutral
B mesons in CP eigenstates
+a+b+c
Vivek Sharma , UCSD

41
Measurement of B0B0 Mixing rate Vs t
Tag B
z ~ 110 mm
K+
K0

Reco B
z ~ 65 mm
(4s)
 = 0.55
z
-
-
D-
+
t @ z/c
3. Reconstruct Inclusively
the vertex of the “other”
B meson (BTAG)

4. Determine flavor of BTAG to
separate Mixed and Unmixed
events
1. Fully reconstruct one B meson
in flavor eigenstate (BREC)

2. Reconstruct the decay vertex 
5. compute the proper time difference t

6. Fit the t spectra of mixed and unmixed events
Vivek Sharma , UCSD
42
t Spectrum of Mixed and Unmixed Events
perfect
flavor tagging & time resolution
realistic
mis-tagging & finite time resolution
Decay time diff (t) in ps
 | Δ t |/τ Bd
e
f Unmix (Δ t)   Unmix
4τxB
Mix
 Mi
d

f
Decay time diff (t) in ps
| Δ t |/τ Bd
4τ Bd
0
0
Unmixed: B0flav Btag
or B0flav Btag
Mixed:


cos(
t ) Δm
 1Δm
d Δcos(
Δt )
  dResolutionFunction



+
_ 1  2w
(Δ t)1 

e
0
0
B0flav Btag
or B0flav Btag

w: the fraction of wrongly tagged
events
md: oscillation frequency
Vivek Sharma , UCSD
43
B Flavor Tagging Methods
Hierarchical Tagging Categories
For electrons, muons and Kaons use the charge correlation
l

b
W-
D, D*
d

l B
d
b
c
 Q 0 B
s
K
B0
Lepton Tag
0
kaons
0
c
B0
 Q0 B
l   B0
-
d
Multivariate analysis exploiting the other
kinematic information of the event, e.g.,
 Momentum spectrum of the charged particles
 Information from non-identified leptons and kaons
 Soft  from D* decay
Neural Network
*0
0
kaons
d
Kaon Tag
NN output
Each category is characterized by the probability of
giving the wrong answer (mistag fraction w)
Vivek Sharma , UCSD
44
Flavor Tagging Performance in Data
The large sample of fully reconstructed events provides the precise
determination of the tagging parameters required in the CP fit
Tagging
category
Fraction of tagged
events (%)
Wrong tag
fraction w (%)
Lepton
10.9  0.3
9.0  1.4
0.9  2.2
7.4  0.5
Kaon
35.8  1.0
17.6  1.0
-1.9  1.5
15.0  0.9
NT1
7.7  0.2
22.0  2.1
5.6  3.2
2.5  0.4
NT2
13.8  0.3
35.1  1.9
-5.9  2.7
1.2  0.3
ALL
68.4  0.7
Highest “efficiency”
Mistag fraction
difference w
(%)
Q =
(1-2w)2 (%)
26.1  1.2
Error on sin2 and md depend on
the “quality factor” Q approx. as:
  sin 2 
Smallest mistag fraction
1
BABAR
Q
29.7 fb1
Vivek Sharma , UCSD
45
Flavor Tagged B Meson Sample For Mixing Studies
Lepton
Lepton
psig,i ~ 0
psig,i ~ 0.96
Kaon
Nsignal  3156  63
Purity  (84.6  0.7)%
Nsignal  1097  34
Purity  (96.0  0.7)%
Background properties
from sideband events
NT1
NT2
Nsignal  798  31
Purity  (88.9  1.2)%
Nsignal  1293  43
Purity  (79.4  1.3)%
Gaussian
ARGUS function
Vivek Sharma , UCSD
46
t Resolution Function
R  t   1  ftail  foutl   Gcore  t , Score , core,i 
 ftail  Gtail  t , Stail , tail 
Outlier
Core
Tail
 foutl  Goutl  t , outl  0 ps, outl  8 ps 
core  Score  evt
t
tail  Stail  evt
t
Use the event-by-event
uncertainty on t
R(t)
B0 flavour
sample
CP sample
t Residual (ps)
Different bias scale factor
For each tagging category
t (ps)
Vivek Sharma , UCSD
47
Mixing Likelihood Fit on Reconstructed B0 Sample
Unbinned maximum likelihood fit to flavor-tagged neutral B sample
 | Δ t |/τ Bd
e
f Unmix (Δ t)  
Mix
 4τ Bd


 1  1  2w cos( Δmd Δt )
Fit Parameters
md
Mistag fractions for B0 and B0 tags
Signal resolution function
Empirical description of background t
B lifetime fixed to the PDG value
44 total free parameters



 R


1
8
2x8
16+3
tB = 1.548 ps
All t parameters
extracted from data
Vivek Sharma , UCSD
48
Mixing with Hadronic Sample
Bgnd:
mES<5.27
Signal:
mES>5.27
BABAR
29.7 fb1
Precision measurement consistent with world average
Δmd  (0.516  0.016(stat)  0.010(syst) ) ps 1
Vivek Sharma , UCSD
BABAR PRL 88, 221802 (2002)
49
md Measurement in Comparison With World
Precision md measurement
 3% statistical error
 2% systematic error
dominated by MC
correction
BaBar Measurements
World Average: 0.496 ± 0.007 ps-1
Vivek Sharma , UCSD
50
B0 B0 Mixing Asymmetry with Hadronic Sample
Unfolded raw asymmetry
Amixing ( t ) 
1  2ω  cos ΔmBd Δt
Folded raw asymmetry
t [ps]
~ 1  2
Flavor mistag rate
well calibrated from
mixing measurement
~ π /md
Vivek Sharma , UCSD
BABAR
29.7 fb1
|t| [ps]51
Mixing Measurement at Belle (Hadronic Modes)
Mistag rate
BELLE
29.1 fb1
Δmd  (0.528  0.017(stat)  0.011(syst) ) ps 1
Vivek Sharma , UCSD
52
CP Analysis Analysis Strategy (Step III)
Measurements
Analysis Ingredient
 B±/B0 Lifetimes
 Reconstruction of B mesons
in flavor eigenstates
 B vertex reconstruction

 B0 B0-Mixing
 Flavor Tagging + a + b

 CP-Asymmetries
 Reconstruction of neutral
B mesons in CP eigenstates
+a+b+c
Vivek Sharma , UCSD
53
Measurement of CP Asymmetry
Tag B
z ~ 110 mm
-
K0

CP B
z ~ 65 mm
+
Ks0
m-
(4s)
 = 0.55
3. Reconstruct Inclusively
the vertex of the “other”
B meson (BTAG)
4. Determine the flavor of
BTAG to separate Mixed and
Unmixed events
z
t @ z/c

m+
1. Fully reconstruct one B meson
in CP eigenstate (BCP)
2. Reconstruct the decay vertex 

5. compute the proper time difference t

6. Fit the t spectra of B0 and B0 tagged events
Vivek Sharma , UCSD
54
Charmonium+K0 CP Sample for BABAR (’02)
f   1 modes
1506 signal
candidates,
purity 94%
 f  1 modes
0
BCP
 J/ψK S0 {  π  π  }
0
BCP
 J/ψK S0 {  π 0π 0 }
0
BCP
 ψ  2 S  {    or
J/ψπ  π  }K S0
0
BCP
 χ c1{  J/ψγ}K S0
0
BCP
 c {  KK }K S0
988 signal
candidates,
purity 55%
 f  1 mode
0
BCP
 J/ψK L0
BABAR
81.3 fb1
(after tagging & vertexing)
Vivek Sharma , UCSD
55
t Spectrum of CP Events
perfect
flavor tagging & time resolution
B0tag  B 0
Mistag fractions w
And
resolution function R
determined by
flavor sample
realistic
mis-tagging & finite time resolution
B0tag  B0
B0tag  B 0
B0tag  B0
CP PDF









| Δ t |/τ
|Δt|/τ
e B Bd












d
e


(

t
)


1
η
sin
2
β
sin(
Δm
Δt
) R
f f(Δt)


1
η
sin2
β
(1

2
w
)sin
(
Δm
Δ
t
)

 
f
d
B0
f
d


4 τB4d τ B 

0
B
d
Mixing PDF







|Δt|/τBd
f mixing,(Δt)  e
4τ
Bd
Vivek Sharma , UCSD















 1 (1 2w)cos( Δmd Δt)  R
56
Sin2 Likelihood Fit
Combined unbinned maximum likelihood fit to t spectra
of flavor and CP sample
Fit Parameters
tagged CP samples
sin2
Mistag fractions for B0 and B0 tags
Signal resolution function
Empirical description of background t
1
8
8
17
B lifetime fixed (PDG value)
Mixing Frequency fixed (PDG value)
tB = 1.548 ps
tagged flavor sample
md = 0.472 ps-1
 All t parameters extracted
35 total free parameters
from data
 Correct estimate of the error and
correlations
57
sin2 Likelihood Fit Description
Combined unbinned maximum likelihood fit to t spectra of Bflav
and CP samples
Fit Parameters
#
Main Sample
Sin2
1
Tagged CP sample
Mistag fractions for B0 and B0 tags
8
Tagged flavor sample
Signal resolution function
8
Tagged flavor sample
Empirical description of background t
17
Sidebands
B lifetime from PDG 2002
0
tB = 1.542 ps
Mixing frequency from PDG 2002
0
md = 0.489 ps-1
Total parameters
34
Global correlation coefficient for sin2: 13%
 All t parameters extracted from data
 Correct estimate of the error and correlations
58
Check “null” Control Sample at BABAR
Input Bflav sample to CP fit
No asymmetry expected
Sample
“sin2”
Bflav
0.021±0.022
B+
0.017±0.025
59
BABAR Result for sin2 (July 2002)
CP = -1
CP = +1
sin2 = 0.755  0.074
sin2  0.741  0.067(stat)  0.033(syst)
60
Pure Gold : Lepton Tags Alone
BABAR
81.3 fb1
220 lepton-tagged
f = -1 events
98% purity
3.3% mistag rate
20% better t
resolution
CP asymmetry
is obvious !
sin2β  0.79  0.11
61
Systematic Errors on sin2 from BABAR
[sin2]
Description of background events
0.017
CP content of background components
Background shape uncertainties, peaking component
Composition and CP content of J/KL background
0.015
t resolution and detector effects
0.017
Silicon detector residual misalignment
t resolution model (Gexp vs 3G, Bflav vs BCP)
Mistag differences between BCP and Bflav samples (MC)
0.012
Fit bias correction and MC statistics
0.010
Fixed lifetime and oscillation frequency
0.005
Total
0.033
62
Updated (ICHEP04) sin2 results from Charmonium
Modes
205fb 1 on peak or 227M BB pairs
7730 CP events (tagged signal)
(cc )KS0 (CP odd) modes
BABAR
Limit on
direct CPV
(cc )KL0 (CP even) modes
BABAR
sin2  0.722  0.040  0.023
  A / A  0.950  0.031  0.013
(cc ) K S0 +
(cc ) K L0
63
Belle Results on sin2 from Charmonium Modes
Belle
2003
140 fb 1 on peak or 152M BB pairs
4347 CP events (tagged signal)
sin 2   0.728  0.056  0.023
  A / A  1.007  0.041  0.033
64
Lessons From sin2 Measurement With B0K0
• In 2001, CP Violation in B system was discovered in this mode by
BaBar and Belle. It was the first instance of CPV outside the Kaon
system.
• It was also the first instance of a CPV effect which was O(1) in
contrast with the Kaon system and confirms the conjecture of
Kobayashi & Maskawa made in 1972 for CPV phenomenon. It
excludes models with approximate CP symmetry (small CPV).
• In 2004 sin2 is a precision measurement (5%) and agrees well
with the constraints in the - plane from measurements of the
CKM magnitudes.
• Now it appears unlikely that one will find another O(1) source of
CPV and the enterprise now moves towards looking for
corrections rather than alternatives to the SM/CKM picture
• Focus now shifts to measurements of time-dependent asymmetries
in rare B decays which are dominated by Penguin diagrams in the
SM and where New Physics could contribute to the asymmetries
65
sin2 From Penguin Modes: B0K0
V V ~ 

tb ts
2
V V  ~  4R ei
ub us
u
No tree level SM diagram, PT Penguin dominates
Expect little direct CPV and -f S K0 @ S K0 in SM
NP can change this picture in unpredictable way
+1.3
Exptal challenge is the small rate BF=  7.6-1.2
±0.5×10-6
66
CP Asymmetry In Penguin Modes: B0K0
Analysis based on 227 Million BB pairs
B   K  K K (  )
0
0
S


114  12 signal events


B0  KL0

 KL0
 K 0
S

98  18 signal events
full background
continuum bkg
Sample orthogonal to the non-resonant BKKK0 data
67
CP Asymmetry In Penguin Modes: B0K0
B0KS
SK 0  0.29  0.31
S
0
Btag
K  1
B 0  KS0 114  12 events
SK  0.29  0.31
0
Btag
0
S
0
S
B 0  KL0 98  18 events
SK  1.05  0.51
0
B0KL
SK 0  1.05  0.51
L
0
tag
B
K  1
0
L
L
0.07
0.04
 0.00  0.23  0.05
CP  SK 0  0.50  0.25
CK
0
0
Btag
Also, Direct CP Asymm in complementary mode
B-   K - : C K-  0.054  0.056  0.012
68
CP Asymmetry In Penguin Modes: B0K0
Belle 274M BB
KS
Nsig=139 14
purity 0.63
KL
Nsig= 36 15
purity 0.17
pB*
69
CP Asymmetry In Penguin Modes: B0K0
Belle 274 M BB
K0
S = 0.736
fit
Good tags
Poor tags
Good tags
KS + KL : S (K0) = +0.06 ±0.33 ±0.09
C (K0) = -0.08 ±0.22 ±0.09
~2.2 away from SM
70
CP Asymmetry In Penguin Modes: B0/ K0
 VtbVts ~  2
W
B0
b
t
s  ', f
0
s
g
s
d
d
BaBar
 V V ~  Rue

ub us
K
227 M BB
0
B
0
4
b
d
W
i
u  ', f
0
u
s
K0
d
Belle 274M BB
B0  KS0
819  38 signal
Nsig=512 27
71
CP Asymmetry In Penguin Modes: B0/ K0
0
Btag
Raw Asymmetry
Belle 274M BB
0
Btag
S = 0.736
fit
Good tags
Asymmetry
sin2 [cc] @ 3.0
S = +0.65  0.18  0.04
C = +0.19  0.11  0.05
S K 0  0.27  0.14  0.03
S
C K 0  0.21  0.10  0.03
S
72
Results on sin2 from s-penguin modes
All new!
All new!
2.7 from s-penguin
to sin2(cc)
2.4 from s-penguin
to sin2(cc)
73
Summary of sin2eff
74
World Averages for sin2 and s-penguin modes
3.6 from s-penguin
to sin2(cc)
No sign of Direct CP in averages
Beginning to look suspicious but must wait for 5/expt to get exciting 75
Projections for Penguin Modes
0.40
f0 KS
KS0
KS
’KS
KKKS
0.30
0.25
0.20
 (S )  0.30
Luminosity
expectations
:
2004=240 fb-1
2009=1.5 ab-1
K*
Similar
projections for
Belle as well
0.15
2009
Jul-09
Jan-09
Jan-08
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jan-04
Jul-03
0.00
5 discovery region if non-SM
physics is 30% effect
2004
Jul-04
0.05
Jul-08
0.10
Jan-03
Error on sine amplitude
0.35
Projections are statistical errors only;
but systematic errors at few percent level
76
PEP II Luminosity Projections
1200
30
Yearly Integrated Luminosity [fb-1]
Cumulative Integrated Luminosity [fb-1]
25
Peak Luminosity [10**33]
800
20
600
15
Peak Luminosity [10**33]
Integrated Luminosity ( fb-1)
1000
0.5 ab-1
400
10
200
5
0
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Yearly Integrated Luminosity [fb-1]
3
23
41
39
62.6
66.1
120.1
151
160.1
217
216
Cumulative Integrated Luminosity [fb-1]
3
26
67
106
168.6
234.7
354.8
505.8
665.9
882.9
1098.9
Peak Luminosity [10**33]
1
2
4.4
5
7.5
10
13
16
20
22
25
0
Year
2004 2006
1.6 x 1034
77
CP Asymmetries in bc cd Modes
Statistics limited, may get interesting in about 2 years !
78