Experimental Aspects of CP Violation in B Decays : Lecture III Vivek Sharma University of...
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Transcript of Experimental Aspects of CP Violation in B Decays : Lecture III Vivek Sharma University of...
Experimental Aspects of CP Violation in B Decays : Lecture
III
Experimental Aspects of CP Violation in B Decays : Lecture
III
Vivek Sharma University of California, San Diego
http://vsharma.ucsd.edu/prague/cpv.pdf
2
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 !
3
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
CP Violation In B Decays: SM Expectations
5
Decay Amplitude Weak Phase Structure in CPV
• 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
Decaysb q qq
6
B Decay Amplitude Weak Phase Structure
* *
* *
* *
( )
( )
( )
c t u tcb cs s s ub us s sccs
c t u tcb cs s s ub us s suus
c t u tcb cs s s ub us s s
A ccs V V T P P V V P P
A uus V V P P V V T P P
A sss V V P P V V P P
Classification of Decaysb q qq
* *
* *
* *
( )
( )
( )
t u c utb td d d cb cd d dccd
t c u ctb td d d ub ud d duud
t u c utb td d d cb cd d d
A ccd V V P P V V T P P
A uud V V P P V V T P P
A ssd V V P P V V P P
7
Decay Amplitude Weak Phase Structure in CPV
8
Decay Amplitude Weak Phase Structure in CPV
Decay Modesb qqd
9
Five “Classes” of B Decays For CPV
+
0
1. Decays dominated by single term: b ccs & b
SM Small Direct CPV since second term is CKM sup
Any large Direct CPV New Physics ( e.g. B
B modes have cleanly predicted r
pre
elat
sse
o
,
d
)
i
s
K
ss
K
nship between CKM angle
and measured asymmetry from CPV due to interference between
decays with/Without Mixing
0
2. Decays with small second term: ;
Expectation that P/T << 1 small Direct CPV possible
Approximate predictions in B decay for relation between
measured CPV and CKM phase
b ccd b uud
10
Five “Classes” of B Decays For CPV
*ub us3. Decays with suppressed (V V )Tree as in
Large interference effects. Example: B K
b uus
4. Decays with no Tree contrib: .
Interference comes from Penguin diagrams
with different Q=2/3 quarks in loop. e.g. B KK
b ssd
*
5. Radiative Penguin Decays: b s .
Situation same as in (4) but leading contribution
from EM penguin. e.g: B K
11
Some Examples of Class I (b c c s): B0 KS
*2
*Kics cd
cs cdK
V Vpe
q V V
* *2
* *S B
S
S
K icb cs cs cdK
K cb cs cs cd
V V V VAe
A V V V V
* * *
* * *sin(2 )
S
tb td cb cs cs cbS K
tb td cb cs cs cb
V V V V V VB K
V V V V V V
Im
CP
CP CP
CP
f
f ff
q A
p A 1
SK
12
Another Example of Class I (b u u d): B0 +-
*2
*Biub ud
ub ud
V VAe
A V V
* *
* *sin(2 2 2 ) sin(2 )tb td ud ub
tb td ud ub
V V V VB
V V V V
Im
Neglecting Penguin diagram
1
*
and depending on its relative strength w.r.t Tree. (Penguins are large!)
Weak Phase in Penguin term is arg( ) different from Tree so it will modifytd tbV V
Im
13
An Example of Class II (b c c d): B0 D+ D-
Ignoring Penguin Diagram (?)
* *
* *sin(2 )tb td cd cb
DDD Dtb td cd cb
V V V VB D D
V V V V
Im
14
CPV in Decay aka Direct CP Violation
( )A B f
2 2
B
f fB
( )A B f
2
wk sti iA e e
1AB f
1Ast
B f2A
wkB fwk
2
1
2
1 22( ) , ( ) wk s w stt ki ii i B fB f A A A e ee e A
2 2
2 20 Direct
ff
CP
ff
A ABr B f Br B fA CPV
Br B f Br B f A A
15
Observation of Direct CPV in B0K- +
2 iSM amplitude e T P sinKA
• Loop diagrams from New Physics (e.g. SUSY) can modify SM asymmetry
• Clean mode with “large” rate :• Measure charge asymmetry, reject B background with Particle ID
0 618.2 0.8 10 BF B K
B background
signal
E (G
eV
)
K separation
K
sep
ara
tion()
16
B0K+
B0K+
BABAR
BaBar: First Observation of Direct CPV in B decay !BaBar: First Observation of Direct CPV in B decay !
4.2, syst. included
BABAR
1606 51
0.133 0.030 0.009K
K
n
A
0
0
9
696
10
n B K
n B K
signal enhanced
background
subtracted
17
Confirmation of Direct CPV by Belle at ICHEP04
ACP = -0.101 0.025 0.005
274M BB
3.9 significance
B0 K _B0 K
Signal=2139 53
Combined BaBar & Belle significance = 5.7Establishes CPV not just due to phase of B Mixing (M12)Theoretical (npQCD) uncertainties insufficient to prove or rule out NP
18
Direct CPV in B- K- 0
Belle
ACP(K) = 0.04 0.05 0.02
Belle
ACP(K) = 0.06 0.06 0.01
BaBar
0 ,
Expect bot
( ) 0.049 0.040 ( ) 0.10 0.02Average
h to be same, difference is 3.6 ...(EW Penguin ?
Average
?)CP
CP
CPA K K
A
A
Not in BK- +
19
20
CPV in B0 Mixing
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
0 0 4
440 0
( ) ( ) 1 /(10 )
1 /( ) ( )
phys phys
sl
phys phys
B t X B t X q pa O
q pB t X B t X
0 0( )A B B
2
2
B0 B0
ffB0
0 0( )A B B
B0
21
CPV in B0 Mixing
122i
12M0B 0B
off-shell states f
on-shell
states f
0 0( )A B B
2
2
B0 B0
ffB0
0 0( )A B B
B0
0 0
,
in the mixing matrix
results from:Mass eigenstates | eigenstates | L H
CPV B B
B CP B
0 0
, 2
1| | | (| | )
1 | | d
d
L H B
B
B p B q B B B
0 0 0 01
1 Prob( ) Prob( )1
d
d
B
B
qB B B B
p
22
CPV in B0 Mixing
3 2SM: 2 10 ; hence 10 New Physics T TA A
0 0
0 0 2
4Re( )( ( ) ) ( ( ) )( )
( ( ) ) ( ( ) ) 1 | |
d
d
Bphys physT
phys phys B
B t X B t XA t
B t X B t X
Time-dependent CP Asymmetry:
In the System, ~ purely imaginary H Ld B B d dB m m m ε
Babar Search for asymmetry in same-sign dilepton sample containing 20381 events
( , ) ( , ) ( )( )
( , ) ( , ) ( ) ( )T
obsT
N t N t S tA t A
N t N t S t B t
( )
( ) f rom B decay and continuum
S t signal
B t background
23
CPV in B0 Mixing
BBAABBARAR20.7 fb20.7 fbBBAABBARAR20.7 fb20.7 fb
Sample backgrounds B(t):
4.3% continuum24% direct+cascade
12% direct+fake0 0 0 0, signal ( )B B B B S t
Measurement region > 200m
24
CPV in B0 Mixing
BBAABBARAR20.7 fb20.7 fbBBAABBARAR20.7 fb20.7 fb
2
( ) ( )
( ) ( )
Conclude: Re( )/ (1 | | )
0.0012 0.0029 0.0036
/ 0.998 0.006 0.007
d dB B
stat syst
stat systq p
( ) ( )Find: 0.005 0.012 0.014stat syst
BABAR PRL 88, 231801 (2002)
To a good approximation:
212 12/ 1 and / | | /Miq p q p e M M
So far, no experimental evidence of large CP violation in B0 mixing
25
CPV In Interference Between Mixing and Decay
0 0
0
Neutral B Decays into CP final state accesible by both & decays
This is CPV when 1 and 1 and the Quantity of interest is
CPV is defined as
( )
C CP
CP C
CP
P
CP
P
CP
f
f
phy
ff
CP
f
s
f
CPf
f B B
q A
p A
B t
A
f B
q A
p
a
20
20 0
When B decay is dominated by a
2 sin 1 c
single diagram, 1 si
os( )
( )
n
( ) 1
CP CP
C
CP CP P
P
C
f B f Bphys CP
phys CP phys CP
f f f B
f
m t m tt f
B t f B t
a m t
f
Im
Im
+
2
+
2
B0
B0
B0
fcpB0
fcpB0
B0
fcpfcp
CP asymm. can be very large and can be cleanly related to CKM angles
0B
fiCPA e
CPf
0B
12
2 Mi
M
ie
fiCPA e
26
CPV In Interference Between Mixing and Decay
2
f f2 2
f f
1 λ 2Im(λ )( ) exp( ) 1 cos( ) sin( )
1 λ 1 λ
t t mt mtF
0 0B denoted by and a B denoted by is(t) (t) CP CPf fF F+ -
Requires measurement of proper time difference t=t between thedecay of Btag and BCP. Time dependent rates for a
S C
27
Time-Dependent CP Asymmetry with a Perfect Detector
sin2( ) sin(ΔmΔβ )CPA t t sin2( ) sin(ΔmΔβ )CPA t t
• Perfect measurement of time interval t=t• Perfect tagging of B0 and B0 meson flavors•For a B decay mode such as B0Ks with |f|=1
sin 2
B0B0
Asy
mm
etry
AC
P
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
Vivek Sharma , UCSD 29
+e-e
B0 J/ KsB0 J/ Ks
CP Violation in Picture
z
Δ zΔ tβγ c
Brec
Btag 4s
(4S) = 0.55
z-π
0sK
+π
+μ-μ
Coherent BB pair
B0
B0
Separate
B0 and B0
Separate
B0 and B0
Vivek Sharma , UCSD 30
Sin2 Analysis Strategy
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 neutralB mesons in CP eigenstates + a + b + c
Hig
her p
recisio
n
Incre
asin
g co
mple
xity
Factorize the Time Dependent analysis into building blocks
Obtain All analysis ingredients from DATA
Calibrating The BaBar Clock With B Meson Lifetime Measurement
Vivek Sharma , UCSD 32
Measurement of the B0 and B+ Lifetime
3. Reconstruct Inclusively the vertex of the “other” B meson (BTAG)
4. compute the proper time difference t5. Fit the t spectra
(4s)
= 0.55
Tag B
z ~ 110 m Reco Bz ~ 65 m
+z
t z/c
K0
D-
--
K+
1. Fully reconstruct one B mesonin flavor eigenstate (BREC)
2. Reconstruct the decay vertex
Vivek Sharma , UCSD 33
( )b c c s
Cabibbo-favored hadronic decays
“Open Charm” decays
Fully-Reconstructed B sample
Neutral B Mesons
ducb
Flavor eigenstates Bflav : for lifetime and mixing measurements
0 *0/ ( )B J K K / , (2 )B J K S K
0( )B D π 0
1( )B D π /ρ /a
Hadronic decays into final stateswith Charmonium
Charged B Mesons
cm 2 cm 2ES beam Bm = (E ) - (p ) [GeV]
~21000 signalPurity: 85%
~20000 signalPurity: 85%
Vivek Sharma , UCSD 34
Vertex and t Reconstruction
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
High efficiency (97%)
Average z resolution is 180 m (<|z|> ~ c = 260 m)
t resolution function measured from data
Beam spot
Interaction Point
BREC Vertex
BREC daughters
BREC direction
BTAG direction
TAG Vertex
TAG tracks, V0s
z
Vivek Sharma , UCSD 35
e-|t|/
Either Brec or Btag can decay first (this analysis)
BaBar
t resolution
e-t/
true t
B production point known eg. from beam spot
LEP/SLD
B Measurement in BaBar
Need to disentangle resolution function from physics !
measured t
Resolutionfunction lifetime
Resolution Function + Lifetime =
=
Vivek Sharma , UCSD 36
event-by-event (t) from vertex errors
Lifetime-like bias to Small correlation between
lifetimeand Resolution Function parameters
t Resolution Function
(1 ) ( , 0)
( , 0) exp( / )
( , )
tail outlier t core
tail t bias t
outlier outlier outlier
R f f G S
f G S t
f G
z
Signal MC (B0)
t (meas-true)/t
tracks from long-lived D’s in tag vertex
asymmetric Resolution Function
~0.6 ps
Vivek Sharma , UCSD 37
Lifetime Likelihood Fit
Simultaneous unbinned maximum likelihood fit to B0/B+ samples
Use data to extract the properties ofbackground events Mass distribution provides the
signal probability Use the events in the sideband
(mES < 5.27) to determine thet structure of the backgroundevents under the signal peak
19 free parameters (B+) and (B0) 2 t signal resolution 5 empirical background 12
description
)2
Beam-Energy Substituted Mass (MeV/c5200 5210 5220 5230 5240 5250 5260 5270 5280 5290 5300
2E
ve
nts
/ 1
Me
V/c
0
200
400
600
800
1000
1200
1400 BAB
B0 mES
B0 Bkg t
Vivek Sharma , UCSD 38
B Lifetime Fit Results
World’s best measurement 2 % statistical error 1.5% systematic error
Main source of systematic error Parameterization of the t
resolution function Description of events with large
measured t (outliers)
B0/ B0
B
t (ps)
0 = 1.546 0.032 0.022 ps
PDG: 1.548 0.032 ps
= 1.673 0.032 0.022 ps
PDG: 1.653 0.028 ps
/0 = 1.082 0.026 0.011
PDG: 1.062 0.029
20 fb-1
background
signal + bkg
PRL 87, 201803 (2001)
B Flavor Mistag Knowledge From Data
40
sin2 results from charmonium modes
0 0( ) 1 cos( )tBP mB e t
Start with a B0 beam, slowly (compared to the lifetime) a B0 component builds upBut 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)
B0
B0 B0
B Lifetime
Vivek Sharma , UCSD 41
Analysis Strategy (II)
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 42
Measurement of B0B0 Mixing rate Vs t
3. Reconstruct Inclusively the vertex of the “other” B meson (BTAG) 4. Determine flavor of BTAG to separate Mixed and Unmixed events
5. compute the proper time difference t 6. Fit the t spectra of mixed and unmixed events
(4s)
= 0.55
Tag B
z ~ 110 m Reco Bz ~ 65 m
+z
t z/c
K0
D-
--
K+
1. Fully reconstruct one B meson in flavor eigenstate (BREC) 2. Reconstruct the decay vertex
Vivek Sharma , UCSD 43
t Spectrum of Mixed and Unmixed Events
0 0
0 0
0 0
0 0Mixed:
Unmixed: tagflav
tagflav
tag flav
tagflav
or
or
B B
B B
B B
B B
perfect flavor tagging & time
resolution
Decay time diff (t) in ps
MiU
xnmix 1 cos( )
4f (Δ t)
Bd
d
| Δ t |/τ
Bd
eΔm Δt
τ
Unmix
xMi
f (Δ t) 1 1 2 cos( ) ResolutionFunction4
Bd
d
d
| Δt |/τ
B
e tτ
mw Δ Δ
_+
w: the fraction of wrongly tagged eventsmd: oscillation frequency
realistic mis-tagging & finite time
resolution
Decay time diff (t) in ps
Vivek Sharma , UCSD 44
NN output
Not U
sed
B Flavor Tagging Methods
For electrons, muons and Kaons use the charge correlation
b c
d d
l-
B0 D, D*
W-
0
0
l
l
B
B
Lepton Tag
b
d
B0
W- W+c s
K*0
d
0
0
0
0
kaons
kaons
Q
Q
B
B
Kaon Tag
Each category is characterized by the probability of giving the wrong answer (mistag fraction w)
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
Hierarchical Tagging CategoriesHierarchical Tagging Categories
Vivek Sharma , UCSD 45
Flavor Tagging Performance in Data
Tagging category
Fraction of tagged
events(%)
Wrong tag fraction w (%)
Mistag fraction difference w
(%)
Q =
(1-2w)2 (%)
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 26.1 1.2
The large sample of fully reconstructed events provides the precise determination of the tagging parameters required in the CP fit
Highest “efficiency” Smallest mistag fraction
BBAABBARAR29.7 fb29.7 fbBBAABBARAR29.7 fb29.7 fb
Error on sin2 and md depend on the “quality factor” Q approx. as:
1sin 2
Q
Vivek Sharma , UCSD 46
Flavor Tagged B Meson Sample For Mixing Studies
1097 34(96.0 0.7)%
signalNPurity
798 31(88.9 1.2)%
signalNPurity
3156 63(84.6 0.7)%
signalNPurity
1293 43(79.4 1.3)%
signalNPurity
Gaussian
ARGUS function
psig,i ~ 0 psig,i ~ 0.96
Background properties from
sideband events
Lepton KaonLepton
NT2NT1
Vivek Sharma , UCSD 47
,1
, 0
,
, 8
,
, ,
tail
tail tai
outl
outl outl outl o
l tai
core core c
utl
or
l
e i
tail
f
f G t p
G
s
R t
p
f
f G t
t
S
S
s
t Resolution Function
t
ttail tail
core coevt
evt
reS
S
Tail
Core
OutlierUse the event-by-eventuncertainty on t
t Residual (ps)
R(t)
Different bias scale factor
For each tagging category
B0 flavoursample
CP sample
t (ps)
Vivek Sharma , UCSD 48
UnmixMix
f (Δ t) 1 1 2 cos( )4
Bd
d
| Δ t |/τ
Bd
e ΔtΔmw Rτ
Fit Parametersmd 1Mistag fractions for B0 and B0 tags 8Signal resolution function 2 x 8Empirical description of background t 16+3B lifetime fixed to the PDG value B = 1.548 ps
Mixing Likelihood Fit on Reconstructed B0 Sample
Unbinned maximum likelihood fit to flavor-tagged neutral B sample
44 total free parameters
All t parameters extracted from data
Vivek Sharma , UCSD 49
1(0 516 0 016 0 010 ) ps d (stat) (syst)Δm . . . BABAR PRL 88, 221802 (2002)
Mixing with Hadronic Sample
BBAABBARAR29.7 fb29.7 fbBBAABBARAR29.7 fb29.7 fb
Precision measurement consistent with world average
Signal: mES>5.27
Bgnd: mES<5.27
Vivek Sharma , UCSD 50
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 51
dm/π~
21~
Folded raw asymmetry
|t| [ps]
Flavor mistag ratewell calibrated frommixing measurement
)
1 2 cosd
mixing
B
A ( tω Δm Δt
B0 B0 Mixing Asymmetry with Hadronic Sample
Unfolded raw asymmetry
t [ps]
BBAABBARAR29.7 fb29.7 fbBBAABBARAR29.7 fb29.7 fb
Vivek Sharma , UCSD 52
Mixing Measurement at Belle (Hadronic Modes)
1(0 528 0 017 0 011 ) ps d (stat) (syst)Δm . . .
BELLEBELLE29.1 fb29.1 fb
BELLEBELLE29.1 fb29.1 fb
Mistag rate
Vivek Sharma , UCSD 53
CP Analysis Analysis Strategy (Step III)
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 54
Measurement of CP Asymmetry
3. Reconstruct Inclusively the vertex of the “other” B meson (BTAG) 4. Determine the flavor of BTAG to separate Mixed and
Unmixed events
5. compute the proper time difference t 6. Fit the t spectra of B0 and B0 tagged events
1. Fully reconstruct one B meson in CP eigenstate (BCP)2. Reconstruct the decay vertex
(4s)
= 0.55
Tag B
z ~ 110 m CP Bz ~ 65 m
+z
t z/c
K0
+
-
Ks0
-
Vivek Sharma , UCSD 55
Charmonium+K0 CP Sample for BABAR (’02)
1 modesf
0 0
0 0 0 0
0
0
0 01
0 0
2
CP S
CP S
CP
S
CP c S
CP c S
B J/ψK { π π }B J/ψK { π π }B ψ S { or
J/ψπ π }KB χ { J/ψγ}KB { KK }K
(after tagging & vertexing)
988 signal candidates,purity 55%
1506 signal
candidates,purity 94%
modes 1f
1 modef 0 0CP LB J/ψK
BBAABBARAR81.3 fb81.3 fbBBAABBARAR81.3 fb81.3 fb
Vivek Sharma , UCSD 56
00tag BB 00
tag BB
perfect flavor tagging & time
resolution
t Spectrum of CP Events
Mistag fractions wAnd resolution function R
1 (1 2 )sin4
sin2 ( )d
d
B
B|Δt|/τ
f def (Δt) η Δm
τw Δβ t
R1 (1 2 )sin
4sin2 ( )
d
d
B
B|Δt|/τ
f def (Δt) η Δm
τw Δβ t
R
CP PDF
00tag BB 00
tag BB
realistic mis-tagging & finite time
resolution
1 (1 2 )cos( )4
dB
Bd|Δt|/τ
mixing, dwef (Δt) Δm Δt
τ
R1 (1 2 )cos( )
4dB
Bd|Δt|/τ
mixing, dwef (Δt) Δm Δt
τ
R
Mixing PDFdetermined byflavor sample
0
0
( ) 1 sin(sin 2 )4
Bd
d
| Δ t |/τ
f dBBB
ef t η Δm Δt
τβ
57
Sin2 Likelihood Fit
Combined unbinned maximum likelihood fit to t spectraof flavor and CP sample
35 total free parameters
All t parameters extracted from data Correct estimate of the error and correlations
Fit Parameterssin2 1Mistag fractions for B0 and B0 tags 8Signal resolution function 8Empirical description of background t 17
B lifetime fixed (PDG value) B = 1.548 psMixing Frequency fixed (PDG value) md = 0.472 ps-
1
tagged flavor sample
tagged CP samples
58
sin2 Likelihood Fit Description
Combined unbinned maximum likelihood fit to t spectra of Bflav and CP samples
All t parameters extracted from data Correct estimate of the error and correlations
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 B = 1.542 ps
Mixing frequency from PDG 2002 0 md = 0.489 ps-1
Total parameters 34
Global correlation coefficient for sin2: 13%
59
Check “null” Control Sample at BABAR
Input Bflav sample to CP fitNo asymmetry expected
Sample “sin2”
Bflav 0.021±0.022
B+ 0.017±0.025
60
BABAR Result for sin2 (July 2002)
sin2 = 0.755 0.074
CP = -1 CP = +1
sin2 0 741 0 067 0 033(stat) (syst). . .
61
Pure Gold : Lepton Tags Alone
BBAABBARAR81.3 fb81.3 fbBBAABBARAR81.3 fb81.3 fb
sin2 0 79 0 11β . .
98% purity3.3% mistag rate
20% better t resolution
220 lepton-tagged
f = -1 events
CP asymmetryis obvious !
62
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
63
Updated (ICHEP04) sin2 results from Charmonium Modes
sin2 0 722 0.040 0.023/ 0.950 0.031 0.013
.A A
0( ) ( odd) modesScc K CP
1205 on peak or 227 pairs7730 CP events (tagged signal)
f b M BB
Limit on direct CPV
BBAABBARARBBAABBARAR
0
0
( ) +
( )
S
L
cc K
cc K
0( ) ( even) modesLcc K CP
BBAABBARARBBAABBARAR
64
Belle Results on sin2 from Charmonium Modes
1140 on peak or 152 pairs4347 CP events (tagged signal)
fb M BB
sin 2 0 728 0.056 0.023/ 1.007 0.041 0.033
.A A
BBelleelle20032003BBelleelle20032003
65
Lessons From sin2 Measurement With B0K0
• 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
66
sin2 From Penguin Modes: B0K0
4~ iV V R eub us u
2~tb tsV V
0 0
T
f K K
No tree level SM diagram, P Penguin dominates
Expect little direct CPV and - S S in SM
NP can change this picture in unpredictable way
+1.3 -6-1.2Exptal challenge is the small rate BF= 7.6 ±0.5 ×10
67
CP Asymmetry In Penguin Modes: B0K0
0 0 ( )SB K K K 0 0
LB K
full background
continuum bkg
0 0L SK K
114 12 signal events 98 18 signal events
Analysis based on 227 Million BB pairs
Sample orthogonal to the non-resonant BKKK0 data
68
CP Asymmetry In Penguin Modes: B0K0
B0KSB0KS
B0KLB0KL 0 1.05 0.51
LKS
0 0.29 0.31SK
S
0tagB
0tagB
0tagB
0tagB0 1
LK
0 1SK
0
0
0.070 50 0.25 0.040 00 0.23 0 05
CP K
K
S .
C . .
0
98 18 events1.05 0.51
LKS
0 0LB K
0
114 12 events0.29 0.31
SKS
0 0SB K
-
- -
K
Also, Direct CP Asymm in complementary mode
B K : C 0.054 0.056 0.012
69
CP Asymmetry In Penguin Modes: B0K0
KS
Nsig=139 14purity 0.63
pB*
Nsig= 36 15
KL
purity 0.17
Belle 274M BB
70
CP Asymmetry In Penguin Modes: B0K0
K0
KS + KL
: S (K0) = +0.06 ±0.33 ±0.09
C (K0) = -0.08 ±0.22 ±0.09 ~2.2 away from SM
KS + KL
: S (K0) = +0.06 ±0.33 ±0.09
C (K0) = -0.08 ±0.22 ±0.09 ~2.2 away from SM
Good tags
Poor tags
S = 0.736fit Good tags
Belle 274 M BB
71
CP Asymmetry In Penguin Modes: B0/ K0
b
dg
t0B
d
ss
s
W
2~tb tsV V
0', f
0K
4~ iub us uV V R e
W b
d
0B
d
uu
0', f
s 0K
Nsig=512 27
Belle 274M BB0 0
SB K
819 38 signal
BaBar 227 M BB
72
CP Asymmetry In Penguin Modes: B0/ K0
0tagB
0tagB
Asymmetry
Raw
Asy
mm
etry
Good tags
S = 0.736fit
Belle 274M BB
0
0
0.10.27 0.034
0.100.21 0.03S
S
K
K
S
C
sin
2
[cc]
@ 3
.0
S = +0.65 0.18 0.04 C = +0.19 0.11 0.05
73
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)
74
Summary of sin2eff
75
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
76
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40Ja
n-03
Jul-
03
Jan-
04
Jul-
04
Jan-
05
Jul-
05
Jan-
06
Jul-
06
Jan-
07
Jul-
07
Jan-
08
Jul-
08
Jan-
09
Jul-
09
Err
or
on
sin
e am
pli
tud
eProjections for Penguin Modes
K*
5 discovery region if non-SM physics is 30% effect
2004=240 fb-1
2009=1.5 ab-1
Similar projections for Belle as
well
Projections are statistical errors only; but systematic errors at few percent
level
Luminosity expectation
s:
20092004
( ) 0.30S f0KS
KS0
KS
’KS
KKKS
77
PEP II Luminosity Projections
2006 1.6 x 10342004
0
200
400
600
800
1000
1200
Year
Inte
gra
ted
Lu
min
os
ity
( fb
-1)
0
5
10
15
20
25
30
Pe
ak
Lu
min
os
ity
[10
**3
3]
Yearly Integrated Luminosity [fb-1]
Cumulative Integrated Luminosity [fb-1]
Peak Luminosity [10**33]
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
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
0.5 ab-1
78
CP Asymmetries in bc cd Modes
Statistics limited, may get interesting in about 2 years !