1. future CP violation Experiment
Prospects for
future CP violation Experiment
in the B-meson system
Parallel Session 6
ICHEP
Vancouver, July 1998
Tatsuya Nakada
CERN

2. -CP violation has been seen only in the neutral kaon system.
-Experimental attempt in the B-meson system:
Bd0(t= 0)  J/y KS(t) vs. Bd0(t= 0)  J/y KS(t)
OPAL: sin 2bJ/y KS =  0.5
CDF: sin 2bJ/y KS = 1.8  1.1  0.3
where GB0  J/y KS(t) - GB0  J/y KS(t)
GB0  J/y KS(t) + GB0  J/y KS(t)
+ 1.8
- 2.0
= sin 2bJ/yKS sin Dmdt

3. The next steps are 1) To observe CP violation in B-meson decays
2) To test whether CP violation is largely generated by the
Standard Model
If the standard model is the main source of CP violation,
CP violation in Bd0 J/y KS will be discovered by
BaBar, BELLE
HERA-B starting 1999~2000
CDF, D0
Expected to be large: 0.3<sin2b<0.8

4. CKM Unitarity Triangles
Vtd Vtb + Vcd Vcb + Vud Vub = 0
Vtd Vud + Vts Vus + Vtb Vub = 0
Bd  p+p- rp
D*p  
Vub
Vtd
Vtd
Vub 
Vts  

Vcb
 = l2h
Bs  DSK
Bd  DK*
Bd  J/yKS
J/yKL
Bs  J/yf
(Theoretically clean channels)

5. “Golden” channels
b measurements:
Bd  J/yKS + theoretically clean (little penguin)
+ experimentally easy
“g” measurements:
Bs  DsK + theoretically very clean (no penguin)
- need time development of Bs decays
Bd  DK* + theoretically very clean (no penguin)
- very small visible branching fractions
“a” measurements:
Bd  D*p + theoretically very clean (no penguin)
- very small asymmetry (~10-2)
“dg” measurements:
Bs  J/yf + theoretically very clean (no penguin)
- CP = +1/CP = -1 has to be measured

6. Penguin and “a” measurements
Bd  p+p-
time dependent studies,
- penguin/tree must be known,
Bd  p+p-, p0p0, Bu  p+p0
isospin analysis using branching fractions
- small branching fractions (p0p0: ~10-6)
Bd  r+p-, r0p0, r-p+
time dependent p+p-p0 Dalitz plot studies
- small branching fractions (r0p0: ~10-6 )
- possible contributions from non-resonance, re-scattering etc.

7. Experiment Now In preparation R&D
(19982003) (2003 ?)
sym.
CLEO II CLEO III
sbb ~1 nb
L 4  1034
sbb/shadronic ~210-1
B-hadron Bu, Bd
Detector central
Trigger all
st(B) very modest
Particle ID e/m/hadron e/m/p/K/p
limited p/K/p
few107 B’s by ~2000: Rare decays, direct CP but not J/yKS

8. Experiments in near future(~2000)
asym. e+e hadron
(4S)
BaBar/BELLE HERA-B CDF/D0
sbb ~1 nb ~760 nb ~60 mb
BB/sec 3/
sbb/shadronic ~210-1 ~10-6 ~10-3
B-hadron Bu, Bd Bu,Bd,Bs,Bc Bu,Bd,Bs,Bc
Detector slightly forward forward central
Trigger all J/y high pt m
st modest good good
Particle ID e/m/p/K/p e/m/p/K/p e/m/hadron

9. Around 2005, we will have all combined results of:
sb: ~ 0.02 [rad]
sa: depends on how well we understand strong interactions
penguin, re-scattering, SU(3), resonance etc.
xs: depends on the value, measured if xs<~20
sdg: depends on xs
Physics with “108” B’s
a, g, dg, xs would remain to be still open questions
For a significant improvement (>109 B’s physics)
 new generation of experiments
Which is needed to discover New Physics.

10. New physics can appear in
Db = 1 process
through penguin
Db = 2 process
through box
through tree
new particles b
b, s b
b, s
new particles
d,s d b
d, s
new particles
d,s b

11. CP violation must be studied in
Bd decays via Oscillations  bc+W and bu+W
Bs decays via Oscillations  bc+W and bu+W
Bd,s,u decays via penguins
Bd,s decays via box
Experimental conditions are
Small branching fractions  many Bd,s,u’s
Rapid Bs oscillations  decay time resolution
Including multi-body hadronic final states  particle ID
mass resolution

12. approved recommended proposed sbb ~500 mb ~500 mb ~60 mb
Experiments >~2005
ATLAS/CMS* LHCb& BTeV
approved recommended proposed
for approval
sbb ~500 mb ~500 mb ~60 mb
BB/sec 500k 100k k+
sbb/shadronic ~510-3 ~510-3 ~10-3
B-hadron Bu,Bd,Bs,Bc Bu,Bd,Bs,Bc Bu,Bd,Bs,Bc
Detector central forward double forward
Early trigger high pt m medium pt e/m/h vertex
(reduction >100) vertex
st good very good very good
Particle ID e/m/hadron e/m/p/K/p e/m/p/K/p
*L=1033 for the first few years, &L=21032 for many years, +L=1-101032

13. New generation of experiments could give sb: < 0.01 sdg: < 0.01
>2005
New generation of experiments could give
sb: < 0.01
sdg: < 0.01
xs: up to xs~40 (ATLAS/CMS), ~80 (LHCb/BTeV)
In addition, due to the particle identification capability and efficient trigger, dedicated experiments could give
sg: < 0.1
sa: < 0.1
using various decay modes.
Also:
Bs  K*l+l-, K*g, m+m-, Bd  fKS, rare D and tau decays etc.
essential for discovering new physics

14. We all hope to discover New Physics!
Conclusions
CP violation studies in B-meson decays have just started. Exploratory works will be done by (<2005) BaBar, BELLE: asymmetric e+e- machine at (4S) CLEO III: symmetric e+e- machine at (4S) HERA-B: fixed target experiment with the HERA proton beam CDF, D0: general purpose central detector at Tevatron
Thorough work will be done by (>2005) at LHC ATLAS and CMS (approved general purpose experiments) and LHCb (recommended special purpose experiment) at Tevatron BTeV (proposed special purpose experiment)
We all hope to discover New Physics!