Measurement of CP Violation in Bs → J/ψφ at CDF
Michal Kreps for the CDF collaboration
Physics Department
0.6
0.4
L = 1.35 fb-1
95% C.L.
68% C.L.
SM prediction
⇒
0.2
0.0
-0.2
-0.4
∆Γ (ps-1)
∆Γ (ps-1)
CDF Run II Preliminary
0.6
CDF Run II Preliminary
SM prediction
95% C.L.
68% C.L.
L = 2.8 fb-1
0.4
⇒ ?
0.2
0.0
-0.2
-0.4
New Physics
-0.6
-0.6
-1
0
1
βs (rad)
-1
0
1
βs (rad)
www2.warwick.ac.uk
Discovery of CP violation
Neutral kaon puzzle in late 1950s
Two particles (K1 , K2 ) with same mass, but
different lifetime and different decay mode
K2 is CP odd and if CP is conserved can
decay only to 3 π
Observation of K2 → π + π − in 1964 by
Cronin and Fitch ⇔ CP is not conserved
2 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Explaining CP violation
Observation by Cronin and Fitch requires ≈ 10−3 admixture of
wrong CP state in wave function
In 1973 Kobayashi and Maskawa concludes that
No reasonable way to include CP violation in model with 4
quarks
Introduction of CP violation needs new particles
One of the suggested ways uses 6 quark model
CP violation ⇔ complex phase in quark mixing (CKM) matrix

 

2
3
Vud Vus Vub
1 − λ /2
λ
Aλ (ρ − i η )

 

2
2
=
V
V
V
−λ
1
−
λ
/
2
A
λ
 cd


cs
cb 
Vtd Vts Vtb
Aλ3 (1 − ρ − i η )
− A λ2
1
Nobel prize in 2008
3 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Implications
When Kobayashi and Maskawa proposed their explanations, only
3 quarks were known
(a) Combined
1
0.5
0
0
-1
−
(b) (cc)K
S (ξf = −1)
0
-0.5
-1
1
0.5
-1
0
(c) J/ψKL (ξf = +1)
-0.5
1
-1
0
-5
-1
ln(L/Lmax)
Since then many measurements performed to check idea
1
Asymmetry
In 2001 Belle and Babar
experiments observe large CP
violation in B 0 decay
BABAR
1
Asymmetry
Start of dedicated B physics
experiments
sin2φ1 . sin(∆md∆t)
The six quark model had several implications:
Existence of another 3 quarks to be seen by experiment
In 1980/1981 several people predicted large CP violation in B
system
(d) Non-CP sample
1
0
5
∆t (ps)
0
-1
-2
-3
0
-4
-1
-1
0
1
2
sin2β
-8
4 18 March 2011
-4
0
∆t (ps)
4
8
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Global status
VCKM


1 − λ2 /2
λ
Aλ3 (ρ − i η )


2
2
= 
−λ
1 − λ /2
Aλ

Aλ3 (1 − ρ − i η )
− A λ2
1
exc
1.5
lude
excluded area has CL > 0.95
t CL
da
γ
>0
∆md & ∆ms
.95
1.0
sin 2β
0.5
∆md
η
εK
0.0
-0.5
α
β
γ
α
Vub
Vub
SL
α
τν
εK
-1.0
CKM
γ
fitter
ICHEP 10
-1.5
-1.0
-0.5
0.0
sol. w/ cos 2β < 0
(excl. at CL > 0.95)
0.5
ρ
5 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
1.0
1.5
2.0
Are we done?
Does not look to be case
Many unanswered questions
SM has many free parameters
What is the meaning of generation, why we need more than
one?
What is the origin of dark matter and dark energy?
How current matter-antimatter asymmetry is generated?
No baryon number violation in SM
CP violation in SM is many order of magnitude too small
In SM cannot generate needed phase transition
SM is probably just low energy approximation of final big theory of
everything
6 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Role of flavor physics
Several extensions of SM exists, each postulating new particles
Some examples
Fourth generation introduces two additional quark, VCKM is
changed to 4 × 4 matrix
Supersymmetry has partner for each SM particle
In supersymmetry squarks/sleptons mix through 3 × 3 matrix


2
2
2
m11 m12 m13
 2
2 
2
m
m
m
 21
23 
22
2
2
2
m33
m32
m31
Looking for indirect effects of new physics to discover it
If new physics is discovered, understand which model is right one
7 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
CPV in Bs → J/ψφ

Vud

 Vcd
Vtd



Vus Vub
1 − λ2 /2
λ
Aλ3 (ρ − i η )
 

2
2
Vcs Vcb  = 
−λ
1 − λ /2
Aλ

Vts Vtb
Aλ3 (1 − ρ − i η )
− A λ2
1
Vts known from unitarity
Need to check also by experiment
Best testing ground is decay Bs → J/ψφ
t, c, u
s
c
b
W+
b̄
s
s̄
c
c̄
s
W−
t̄, c̄, ū
s
s̄
b̄
c̄
New physics in mixing can have large effect on CP violation
Search for large CP violation in Bs → J/ψφ
8 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Sidenote on phases
Bs system is described by equation
0 ! Bs (t)
i
d
= M− Γ
i
dt B̄s0 (t)
2
0 !
Bs (t)
0 B̄s (t)
Box diagram of mixing give rise to M12 and Γ12
Interesting quantities and relation to observables:
SM
∆Ms = 2|M12,s
| · |∆s |
∆ , in SM φ = (4.2 ± 1.4) · 10−3
φs = arg(−M12 /Γ12 ) = φSM
+
φ
s
s
s
∆
∆Γs = 2|Γ12,s | · cos φSM
s + φs
CP Violation in Bs → J/ψφ measures
J /Ψφ
SM
NP
φs
= −2βs + φ∆
+
δ
+
δ
s
Peng.
Peng.
∗
in SM 2βs = 2 arg(−Vts Vtb∗ /Vcs Vcb
) ≈ 0.04
With current CDF precision we really test presence of large φ∆
s
9 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Analysis logic
Principle is to measure time dependent asymmetry of CP
eigenstate
A=
N(B, t) − N(B, t)
N(B, t) + N(B, t)
We need to find in data
Bs → J/ψφ decays
Measure decay time
Find out whether it was produced as B or B
K
l
K
Bq
10 18 March 2011
Bs
µ−
µ+
K−
K+
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Likelihood anatomy
Signal PDF for single tag
1 + ξD
P(t, ρ~|σt )(ρ~)
Ps (t, ρ~, ξ|D, σt ) =
2
1 − ξD
+
P̄(t, ρ~|σt )(ρ~)
2
ξ = −1, 0, 1 is tagging decision
D is event-specific dilution
(ρ
~) - acceptance function in angular space
P(t, ρ~|σt ) (P̄(t, ρ~|σt )) is PDF for Bs (B s )
11 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Likelihood anatomy
d 4 P(t, ρ~)
∝ |A0 |2 T+ f1 (ρ
~) + |Ak |2 T+ f2 (ρ
~) + |A⊥ |2 T− f3 (ρ
~)
dtd ρ~
+ |Ak ||A⊥ |U± f4 (ρ~) + |A0 ||Ak | cos(δk )T+ f5 (ρ~)
+ |A0 ||A⊥ |V± f6 (ρ~)
T± = e−Γt
U± = ±e−Γt
V± = ±e−Γt
12 18 March 2011
× [cosh(∆Γt /2) ∓ cos(2βs ) sinh(∆Γt /2)
∓ η sin(2βs ) sin(∆ms t)] ,
× sin(δ⊥ − δk ) cos(∆ms t)
− cos(δ⊥ − δk ) cos(2βs ) sin(∆ms t)
±
cos(δ⊥ − δk ) sin(2βs ) sinh(∆Γt /2) ,
× [sin(δ⊥ ) cos(∆ms t)
− cos(δ⊥ ) cos(2βs ) sin(∆ms t)
± cos(δ⊥ ) sin(2βs ) sinh(∆Γt /2)] .
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Issue of s-wave
We reconstruct Bs → J/ψφ with φ → K + K −
But wide resonance f0 (980) can also decay to K + K − and
Bs → J/ψ K + K − is also possible (called s-wave)
There are arguments that s-wave can be large
Stone et al, PRD79, 07024 (2009) predicts
B(Bs → J/ψ f0 (980))B(f0 (980) → ππ )
R=
' 0.2 − 0.3
B(Bs → J/ψφ)B(φ → KK )
S-wave can contribute to reconstructed signal
It is CP-odd eigenstate with its own angular and time dependence
Sizeable contribution which is not accounted for can bias result
⇒ Account for it in the likelihood
13 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Decay Bs → J/ψ f0(980) observed
40
Events/(5 MeV)
Decay Bs → J/ψ f0 (980) observed
independently by three experiments
Measured R is about 0.25-0.29
35
LHCb
s = 7 TeV Data
(a)
30
25
20
15
10
5
Events/(5 MeV)
0
5200
5300
5400
5500
5300
5400
5500
m(µ+µ-π+π-) (MeV)
20
(b)
15
10
5
0
5200
m(µ+µ-π+- π+-) (MeV)
L=3.8 fb-1
CDF Run 2 Preliminary
Candidates per 5 MeV/c2
Events/(20 MeV/c2)
We don’t use this information in current
version of the analysis
12
10
Belle
8
6
4
2
00.2
14 18 March 2011
200
Data
180
Fit
160
Background
140
120
100
80
60
40
20
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2
Mππ (GeV/c )
0
5.30
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
5.35
5.40
5.45
5.50
M(J/ψππ) [GeV/c2]
Treatment of s-wave
Add amplitude for s-wave ⇔ four angular terms (amplitude2 + 3
interference terms)
S-wave amplitude is pure CP-odd eigenstate with its own angular
dependence
Strong phases vary over resonance
⇒ Need to start with K + K − mass included
Relativistic Breit-Wigner propagator for p-wave
Constant for s-wave
Keep K + K − mass as unobserved ⇔ integrate over it
Interference between p-wave and s-wave could break last
symmetry
Full math spelled out in arXiv:1008.4283
15 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Previous results
0.6
0.4
L = 1.35 fb-1
95% C.L.
68% C.L.
SM prediction
∆Γ (ps-1)
∆Γ (ps-1)
CDF Run II Preliminary
CDF 1.35 fb−1
p-value = 15%
0.2
0.6
CDF Run II Preliminary
SM prediction
95% C.L.
68% C.L.
L = 2.8 fb-1
0.4
0.2
0.0
0.0
-0.2
fb−1
CDF 2.8
p-value = 7%
-0.4
-0.6
-1
0
1
βs (rad)
-0.2
-0.4
New Physics
-0.6
-1
0
1
βs (rad)
CDF 2.8 fb−1 + DØ 2.8 fb−1
p-value = 3.4%
What next?
16 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Tevatron and CDF experiment
√
pp collisions at s = 1.96 TeV
Peak luminosity ≈
3.5 − 3.8 · 1032 cm−2 s−1
Collected about ≈ 7fb−1
-1
CDF Acquired Luminosity (pb )
2000
1750
1500
2010
1250
2009
1000
750
2008
2007
2005
500
2006
2004
250
0
0
17 18 March 2011
50
100
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
150 200
2003
2002
2001
250 300
350
Day
Selection
Candidates per 0.02
Latest analysis uses 5.2 fb−1
Events selected using dimuon trigger
Typical event has few dozens tracks ⇒
lot of background
Neural network to select interesting
events
0.140
0.135
CDF Simulation
Input βs = 0.02
0.130
0.125
0.120
0.115
0.110
-0.5
18 18 March 2011
0.0
0.5
1.0
Neural Network Cut
Signal
Background
105
104
103
-1.0
-0.5
0.0
0.5
1.0
Network output
CDF Run II preliminary
Candidates per 2 MeV/c2
βs parabolic error
Select ≈ 6500 Bs → J/ψφ decays
L=5.2 fb-1
CDF Run II Preliminary
L = 5.2 fb-1
900
800
700
600
500
400
300
200
100
0 5.28 5.3 5.32 5.34 5.36 5.38 5.4 5.42 5.44 5.46
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Mass(J/ψ φ) [GeV/c2]
Flavor tagging
b
SST
Bs
+
K
b
−
K
a
OST
l
−
b
s/d
Bs /d
s /d
u
Κ /π
u
Determination of the flavor at
production time
Difficult task due to large number of
tracks
Benefits from PID
Calibrated with data
19 18 March 2011
+ +
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
OST Calibration
Flavor tagging algorithm is characterized by
Efficiency Dilution D = 2 · P − 1
Quantity D 2 defines effective statistics
Opposite side tagging is independent of studied hadron
Effective power of OST is D 2 = 1.2%
51,920 +/- 388 Signal Events
12000
10000
8000
6000
4000
CDF Run II Preliminary
1.5
B+ events
Slope = 0.93 ± 0.09
-1
L = 5.2 fb
B
+
1.0
0.5
0.0
-0.5
2000
0
2.0
5.20 5.25 5.30 5.35 5.40
2
J/ψ K+ invariant mass [GeV/c ]
20 18 March 2011
-1.0
0.0
OST Measured Dilution
14000
OST Measured Dilution
2
entries/(5 MeV/c )
-1
CDF II Preliminary, 5.2 fb
2.0
CDF Run II Preliminary
1.5
B- events
Slope = 1.12 ± 0.10
-1
L = 5.2 fb
B−
1.0
0.5
0.0
-0.5
0.2
0.4 0.6 0.8 1.0
OST Predicted Dilution
-1.0
0.0
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
0.2
0.4 0.6 0.8 1.0
OST Predicted Dilution
SSKT Calibration
SSKT depends on the meson we study
Fortunately Bs oscillation is sensitive to
quality of tagging
2
Total tagging power D = 3.2 ± 1.4%
∆ms = 17.79 ± 0.07(stat)
21 18 March 2011
-1
CDF Run 2 Preliminary, L = 5.2 fb
400
Data
Fit Function
Bs → Ds π
Bs → Ds K
Comb. Backgr.
B → Ds X
350
300
250
200
S = 5613 ± 75
150
B = 1070 ± 33
S/B = 5.25 ± 0.17
100
Principle
−Nunmix
A = NNmix
= A · D cos (∆mt)
mix +Nunmix
In total ≈ 12900 signal events
+
2
Candidates per 3 MeV/c
Only way to calibrate is to use Bs itself
S/ S+B = 68.66 ± 0.70
50
(data - fit)
data
0
5.4
5.5
5.6
5.5
5.6
2
0
-2
5.4
Invariant Mass in GeV/c2
-1
CDF Run 2 Preliminary, L = 5.2 fb
Amplitude
Use decays:
Bs → Ds π with Ds → φπ , Ds → K ∗ K and
Ds → πππ
Bs → Ds πππ with Ds → φπ
-
-
B0s → D-s π+, Ds → φ π , φ → K K- (+ cc)
2.0
1.5
Amplitude A
Sensitivity: 37.0 ps-1
1.0
0.5
0.0
-0.5
-1.0
-1.5
10
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
20
30
Mixing Frequency in ps-1
Angular efficiencies
Derived from large statistics MC
Parameterized in three dimensions
CP Violation relatively insensitive to exact details
Efficiency compares well with angular distributions of combinatorial background
CDF Run II Preliminary, L=5.2 fb−1
22 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Lifetime and width difference
L = 5.2 fb-1
Distribution for BsL
Distribution for BsH
Signal mass region
events per 50 µm
CDF Run II Preliminary
Data - signal region
Fit
Signal
Light
Heavy
Background
103
102
10
1
pull
-0.2
-0.1
0
0.1
0.2
4
2
0
-2
-4
Under SM assumption (βs = 0) we measure:
c τ = ΓH2+ΓL = 1.529 ± 0.025(stat) ± 0.012(syst) ps
∆Γs = 0.075 ± 0.035(stat) ± 0.01(syst) ps−1
23 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
0.3
ct (J/ψ KK) [cm]
Polarization amplitudes
|A|| |2 = 0.231 ± 0.014(stat) ± 0.015(syst)
|A0 |2 = 0.524 ± 0.013(stat) ± 0.015(syst)
φ⊥ = 2.95 ± 0.64(stat) ± 0.07(syst)
Data
600
Fit
500
400
300
700
Entries per 0.42 rad
Entries per 0.12 rad
Signal
Entries per 0.12 rad
CDF Run II Preliminary, L = 5.2 fb
700
Data
600
Fit
500
400
300
700
600
400
300
200
200
100
100
100
-0.5
0.0
0
-1.0
0.5
cos(ψ)
-0.5
0.0
0
0
0.5
cos(θ)
Fit
500
200
0
-1.0
Data
2
4
6
φ
4
6
φ
Data
700
Fit
600
500
400
Data
700
Fit
600
500
400
800
Data
700
Fit
600
500
400
300
300
300
200
200
200
100
100
100
0
-1.0
24 18 March 2011
800
Entries per 0.42 rad
800
Entries per 0.12 rad
Background
Entries per 0.12 rad
CDF Run II Preliminary, L = 5.2 fb
-0.5
0.0
0.5
cos(ψ)
0
-1.0
-0.5
0.0
0.5
cos(θ)
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
0
0
2
CP Violation
SM p-value is 44%
SM p-value is 31%
Corresponds to 0.8σ
Comparable to 2D case ⇔ ∆Γ
consistent with SM
Significant improvement
βs ∈ [0.02, 0.52] ∪ [1.08, 1.55]
@ 68% C.L.
Strong phases free
-1
L = 5.2 fb
18
0.6
95% CL
68% CL
0.4
SM prediction
0.2
-1
L = 5.2 fb
95% CL
16
14
12
68% CL
SM prediction
10
8
0.0
-0.2
6
4
-0.4
-0.6
-1
25 18 March 2011
CDF Run II Preliminary
2 ∆ log (L)
-1
∆Γ (ps )
CDF Run II Preliminary
0
βs (rad)
1
2
0
-1
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
0
1
βs (rad)
Comparison to previous result
0.6
95% CL
68% CL
0.4
SM prediction
-1
L = 5.2 fb
∆Γ (ps-1)
-1
∆Γ (ps )
CDF Run II Preliminary
0.2
0.6
CDF Run II Preliminary
SM prediction
95% C.L.
68% C.L.
L = 2.8 fb-1
0.4
0.2
0.0
0.0
-0.2
-0.2
-0.4
-0.4
New Physics
-0.6
-0.6
-1
0
βs (rad)
1
-1
0
1
βs (rad)
Concentrate on size of the allowed region
Significant improvement compared to our previous result
26 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Size of the adjustment
-1
0.6
5.99
2.30
0.4
SM prediction
L = 5.2 fb
0.2
0.0
-0.2
L = 5.2 fb
68% CL
1
95% CL
10-1
-0.4
-1
10-2
SM prediction
ideal
0
βs (rad)
∆Γ (ps )
-1
95% CL
68% CL
0.6
1
0.4
0.2
0.0
0
5
-0.2
-0.4
-0.6
-1
0
βs (rad)
1
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
randomized nuisance
parameters
-0.6
-1
L = 5.2 fb
non-Gaussian errors
CDF Run II Preliminary
27 18 March 2011
-1
CDF Run II Preliminary
1-CL
-1
∆Γ (ps )
CDF Run II Preliminary
10
15
2∆ln(Lp)
S-wave check
Q: Is change since last time due to
previously omitted s-wave?
-1
∆Γ (ps )
CDF Run II Preliminary
A: No, likelihood almost same with s-wave
fixed to zero
Q: Is the K + K − mass consistent with our
fit model?
0.6
S-wave not included
0.4
5.99
S-wave included
2.30
0.2
0.0
-0.2
-0.4
-0.6
L = 3.8 fb-1
data
total fit
0
Bs signalProb 0.3225
combinatorial bkg
0
misreconstructed B
4000
3500
3000
2500
2000
1500
1000
2500
3.8 fb-1
CDF Run II Preliminary
data
total fit
combinatorial background
2000
misreconstructed B0
f
0
1500
1
βs (rad)
8
-1
L = 5.2 fb
95% CL
7
6
68% CL
5
4
1000
3
2
500
1
500
0
0
9 CDF Run II Preliminary
2 ∆ log (L)
4500
-1
Candidates per 2 MeV/c2
Candidates per 4 MeV/c2
A: Yes it is
CDF Run II Preliminary
-1
L = 5.2 fb
5.30
5.35
5.40
5.45
+ J/ψ K K Mass (GeV/c2)
28 18 March 2011
0
1.00
1.05
K+K Mass (GeV/c2)
0
0.00 0.02 0.04 0.06 0.08 0.10
S-wave fraction
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Effect of flavor tagging
With tagging of D 2 ≈ 5% we
don’t gain lot in precision
Main effect in reducing
ambiguities
Untagged case symmetric under
each
2βs → −2βs
δ⊥ → δ⊥ + π
∆Γ → −∆Γ
2βs → 2βs − π
Tagged symmetry
2βs → π − 2βs
∆Γ → −∆Γ
δ|| → 2π − δ||
δ⊥ → π − δ⊥
29 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Different parts of data
30 18 March 2011
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Different parts of data
-1
L = 5.2 fb
CDF Run II Preliminary
-1
L = 5.2 fb
5.99
2.30
0.6
5.99
2.30
0.6
5.99
2.30
0.4
SM prediction
0.4
SM prediction
0.4
SM prediction
0.0
-0.2
-0.4
-0.6
0.2
-1
-1
0.2
∆Γ (ps )
0.6
∆Γ (ps )
-1
∆Γ (ps )
CDF Run II Preliminary
0.0
-0.2
-0.4
-1
Data 0-1.35 fb
S-wave not included
-1
30 18 March 2011
0
βs (rad)
-0.6
1
0.2
0.0
-0.2
-0.4
-1
Data 1.35-2.8 fb
S-wave not included
-1
0
βs (rad)
-0.6
1
-1
Data 2.8-5.2 fb
S-wave not included
-1
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
0
βs (rad)
1
Conclusions
Significantly improved measurement of the CPV in Bs → J/ψφ
βs ∈ [0.02, 0.52] ∪ [1.08, 1.55] @ 68% C.L.
CDF data now agree on the ≈ 1σ level with SM
Best measurement of
Mean lifetime
Width difference between mass eigenstates
Polarization amplitudes
-1
∆Γ (ps )
CDF Run II Preliminary
0.6
95% CL
68% CL
0.4
SM prediction
-1
L = 5.2 fb
0.2
0.0
-0.2
-0.4
-0.6
-1
31 18 March 2011
0
βs (rad)
1
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF
Prospects
Couple of improvements possible beyond collecting data
Include other triggers gives ≈ 25% more statistics
Add Bs → ψ (2S)φ
Look for Bs → J/ψ f0 (980) with f0 (980) → π + π −
Add K + K − mass as fit variable - helps in ambiguity resolution
Still collecting data, expect to have ≈ 2 times more by the end of
2011
-1
Luminosity (pb )
01/04
01/05
01/06
01/07
01/08
01/09
01/10
2000
CDF Acquired Luminosity (pb-1)
01/03
1750
8000
1500
2010
1250
6000
2009
1000
4000
2000
Delivered
Acquired
750
2005
500
2006
2004
250
0
1000
2000
3000
4000
5000
6000
7000
8000
store number
32 18 March 2011
2008
2007
0
0
50
2003
2002
2001
100 150 200 250 300 350
Day
Michal Kreps – Measurement of CP Violation in Bs →J/ψφ at CDF