1. CP VIOLATION (B-factories)
P. Pakhlov (ITEP)

2. Summary of CP violation measurements (discussed yesterday)
Previous lecture
10 years of running of two B-factories provided high statistics (109 B0 ~ one year of operation of LHCb). We have measured CP violation in B0  J/ K0 quite precisely.
Summary of CP violation measurements (discussed yesterday)
sin 2β
cos 2β εK
Do allowed areas have intersection?
Does this mean that KM ansatz is checked?

3. The UT constrain
- One way to test the Standard Model is to measure 3 angles and check if the triangles closes.
- This is not yet all possibilities. We can measure 3 sides and check the consistency with angle measurements.
VudV*ub
VcdV*cb
VtdV*tb β α γ
experimentally
easy
sin2β:
sin2α:
sin2γ:
hard

4. Combine all measurements together
It is done now at professional level: few competing averaging groups make fits of all available data.
They publish report and even papers. In the nearest future averaging groups, rather experimentalists will make new discoveries, manipulating with experimental measurements.
However, they do useful job:
Somebody needs to read ~300 papers by Belle and BaBar and summarizes the results.
They calculate WA, taking into account common and individual errors of experiments.
They check the consistency.
They produce good pictures, representing the results.

5. Angle α

6. B0  π π π– b u π+ d b π– t u π+ d Vub V*td
In this case the penguin diagram is not small and has different weak phase:
The indirect CP violation
~ S sin(Δm t), where S≠ sin 2α, but sin(2α + some not-negligible phase).
There will be direct CP asymmetry ~ A cos(Δm t),
How to take into account this?

7. B0  π π
The decay amplitudes B → π+π– (ρ+ρ–) are characterized by two different CKM terms:
a tree term (T) ~ Vub* Vud (dominant)
a penguin term (P) ~ Vtb* Vtd, (suppressed, but not small)
Parameter S of indirect CPV:
δ – the relative strong phase between T and P amplitudes.
r < 1 – ratio of P to T amplitude
We can measure effective α (αeff) shifted by extra angle
But we want α!
Additional inputs required.

8. Gronau-London idea
The cleanest method now available is the isospin analysis, proposed by M. Gronau and D. London. We need to measure all 6 BR’s of B0 and B+ to ππ decays: π+π–, π0π0, π+π0.
To extract θ build two triangles:
2αeff 2α
Isospin triangles

9. B0  π+ π–: experimental results
Phys.Rev.Lett., 98, (2007)
B0 tag _
S = – 0.61 ± 0.10 ± 0.04
A = ± 0.08 ± 0.05
S = – 0.68 ± 0.10 ± 0.03
A = ± 0.08 ± 0.02

10. B0  ρ+ρ–: experimental results
r+ r-
Angular analysis: purely CP=+1 final state
Small Br(B0  ρ0ρ0 ): small penguin contribution
S = –0.17 ± 0.20 ± 0.06
A = –0.01 ± 0.15 ± 0.06
S = ± 0.30 ± 0.07
A = 0.16 ± 0.21 ± 0.07

11. Fit results
Add also B0  ρ±π±: (not CP eigenstate, but B0 can decay to both ρ+π– and ρ– π+)
r(π+π– )> r(ρ+π– )~r(ρ– π+)>r(ρ– ρ+ )

12. Angle γ

13.  Direct CPV and γ u s b c K – D0 u s b c D0 K– B→DK V*ub V*cb VudV*ub  
VudV*ub
VtdV*tb
VcdV*cb
Aλ3
V*ub u s b c
K – D0 u s b c D0 K–
Aλ3(ρ+iη)
V*cb
Color suppressed
Color allowed

14. The angle between two amplitudes is really γ, but the final states are different D0≠D0 , however …
D0 decays into CP eigenstate (rarely – Cabibbo suppressed modes, e.g. K+K–, KSπ0)
GLW method. Phys. Lett. B253, 483 (1991)
D0 decays into final state typical for D0 (very rarely – Doubly Cabibbo suppressed modes, e.g. K+ π–). Enhance CP asymmetry by suppression (in D-decay) of allowed (in B-decays)
ADS method. Phys. Rev. Lett. 78, 3357 (1997)
D0 decays into three body state (e.g. KSπ+ π–): mixture of opposite CP eigenvalues +1/–1, also contain DCSD. Resolve by Dalitz analysis.
GGSZ method. Phys. Rev. D (2003) (Used by experimentalists (A.Bondar) before suggested by theoreticians)

15. γ from GLS and ADS methods

16. Mirror symmetry between D0 and D0 Dalitz plots
γ from GGSZ method
Measure B+/B– asymmetry across Dalitz plot
Mirror symmetry between D0 and D0 Dalitz plots
Determine f in flavor-tagged D*+→D0π+ decays
x± = rB cos( δ ± γ ) , y± = rB sin( δ ± γ ) 2γ

17. Fit to all measurements
The accuracy of present measurements are limited by statistics (we really study VERY rare decay). The systematics and model uncertainties are much smaller.

18. Sides of UT 2 3 1 Vtd Vtb * Vud Vub * (a) (g) (b) Vcd Vcb * Vcd Vcb
(ρ,η)
Vtd Vtb *
Vud Vub * 2
(a)
phase of Vtd 3
(g) 1
(b)
phase of Vub
Vcd Vcb *
Vcd Vcb * 1

20. Testing loops! b φ t s K0 d b φ ? s K0 d V*ts ?*
CP asymmetry should be ~ sin2β
No tree contribution!
Theoretical uncertainty ~ much smaller than the current exp error!
All our previous measurements test new physics contribution to the box diagram and check the consistency with pure tree (where no big contribution from NP expected)
This one really give access to the loop. If any (heavy) particles (with extra to KM phases) are involved in the loop we can see the effect! ?* d s b ? φ K0

21. Sin 2β from penguin decays
2005 intrigue: penguin CP violation parameter was ~3σ smaller than sin2β
1.9 σ difference
Precision of measurement (10%) is dominated by statistics
To obtain sensitivity ~ 1-2%, need few years of LHCb or SuperB-factory data taking.

22. Test of V-A in the loop γ d s b t K*0 Indirect CP violation:
No indirect CP asymmetry expected in SM: different γ polarizations for B0 and B0
BK*(KS0) : use KS secondary tracks to reconstruct B vertex
The present measurements (accuracy ~ 0.2) are far from the real test of V-A in the penguin loop. Good task for SuperB factory with L ~ 100 times higher than at B-factories

23. Electroweak penguin: FB asymmetry
Bl-
K(*) – –
ℓ ℓ
Bl-
Wilson coefficients

24. Br(B → Xs γ) γ d s b t Xs W–, H–
To reduce model uncertainty need to measure at as smaller E as posible d s b t γ Xs
W–, H–
S/B~1
S/B~200
S/B~20

25. Purely leptonic decay H– b τ W– b τ υ υ u u
~mb tanβ
~mτ
Reconstruct B fully, see one track from decay, check that there is no extra energy deposition in the event

26. Compare with SM & constrain on charged Higgs
Theoretical uncertainty due to fB and Vub are reduced by using prices measurement of Δmd
WA experiment – expectation ~ 2.4 σ difference!

27. Loops in B vs direct searches
Atlas 30 fb–1
Atlas 1fb–1
95% excluded by CDF

28. Two super B-factory projects
KEKB/Belle
are prolongation of the successful B-factories
PEP-II/BaBar
2.1 × 1034
1.2 × 1034
8 × 1035
10 × 1035
SuperB
SuperKEKB/Belle2 28

29. Physics reach with 50 ab–1 (~ 5 years with 8×1035/cm2/s)
Which physics will we do at Super B-factories?
Basically the same we did at B-factories:
Measure UT (angles & sides) with much better precision. If new phases contribute to any measurable  inconsistency of UT.
CPV in b → sqq vs b → ccs: Extra new phases in the penguin loop makes CPV parameters different. Typical accuracy in ΔS σ ≈ 0.02–0.03 for B → K0  (K0 η').
search for CPV in radiative decays B → K*0(KS0 π0) γ is a test of right-handed current in the penguin loop (CPV ≠ 0).
Rare decays b → sg(γ), B → τν. Even Br’s constrain mass of NP (provided CKM matrix elements and FF are known precisely).
Electro-weak penguins b → sμμ, see, sνν: Br’s, Q2 -distribution, FB asymmetry are sensitive to NP
+ many new decay channels hardly / not seen with the present statistics.
+ New ideas.
50ab-1
B0→ K0
ΔS=0.23
B0→J/ψK0
Not technical updates of the previous analyses:
need to reduce model dependence and systematic uncertainties