Transcript No Slide Title

Prospects for
future CP violation Experiment
in the B-meson system
Parallel Session 6
ICHEP
Vancouver, 23-29 July 1998
Tatsuya Nakada
CERN
-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)
+ 1.8
OPAL: sin 2bJ/y KS = 3.2 - 2.0  0.5
CDF:
where
sin 2bJ/y KS = 1.8  1.1  0.3
GB0  J/y KS(t) - GB0  J/y KS(t)
GB0  J/y KS(t) + GB0  J/y KS(t) = sin 2bJ/yKS sin Dmdt
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
CKM Unitarity Triangles
Vtd Vtb + Vcd Vcb + Vud Vub = 0
Vtd Vud + Vts Vus + Vtb Vub = 0
Bd  p+pp
Dp
Vub

Bs  DSK
Bd  DK


Vcb
Vtd
Vub
b

h
Vtd
Vts
 =l2h
Bd  J/yKS
J/yKL
(Theoretically clean channels)
Bs  J/yf
“Golden” channels
b measurements:
Bd  J/yKS + theoretically clean (little penguin)
+ experimentally easy
“” 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
“” measurements:
Bd  Dp
+ theoretically very clean (no penguin)
- very small asymmetry (~10-2)
“” measurements:
Bs  J/yf
+ theoretically very clean (no penguin)
- need time development of Bs decays
- CP =+1/CP =-1 has to be measured
Penguin and “” measurements
Bd  p+ptime 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  +p-, 0p0, -p+
time dependent p+p-p0 Dalitz plot studies
- small branching fractions (0p0: ~10-6)
- possible contributions from non-resonance, re-scattering
etc.
sbb
L
sbb/shadronic
B-hadron
Detector
Trigger
st(B)
Particle ID
Experiment Now In preparation
(19982003)
sym. e+e-@(4S)
CLEO II
CLEO III
~1 nb
41032
1.71033
~210-1
Bu, Bd
central
all
very modest
e/m/hadron
e/m/p/K/p
limited p/K/p
R&D
(2003?)
31034
few107 B’s by ~2000: Rare decays, direct CP but not J/yKS
sbb
BB/sec
sbb/shadronic
B-hadron
Detector
Trigger
st
Particle ID
Experiments in near future(~2000)
asym. e+ehadron
(4S)
p+metal@40GeV pp@2TeV
BaBar/BELLE
HERA-B
CDF/D0
~1 nb
~760 nb
~60 mb
3/10
38
6000
~210-1
~10-6
~10-3
Bu, Bd
Bu,Bd,Bs,Bc
Bu,Bd,Bs,Bc
slightly forward
forward
central
all
J/y
high pt m
modest
good
good
e/m/p/K/p
e/m/p/K/p
e/m/hadron
Around 2005, we will have all combined results of:
sb: ~ 0.02
[rad]
s: depends on how well we understand strong interactions
penguin, re-scattering, SU(3), resonance etc.
xs: depends on the value, measured if xs<~20
s: depends on xs
Physics with “108” B’s
, , , 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.
New physics can appear in
Db = 1
process
through penguin
Db = 2 process
through box
b
b
d,s
through tree
b
d,s
new
particles
b, s
new
particles
b, s
new
particles
d, s
d
b
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
Experiments >~2005
sbb
BB/sec
sbb/shadronic
B-hadron
Detector
Early trigger
pp@14TeV
pp@14TeV
pp@2TeV
ATLAS/CMS
LHCb&
BTeV
approved
recommended
for approval
proposed
~500 mb
500k
~510-3
Bu,Bd,Bs,Bc
central
high pt m
(reduction >100)
st
Particle ID
L=1033
good
e/m/hadron
~500 mb
~60 mb
100k
6-60k+
~510-3
~10-3
Bu,Bd,Bs,Bc
Bu,Bd,Bs,Bc
forward
double forward
medium pt e/m/h
vertex
vertex
very good
very good
e/m/p/K/p
e/m/p/K/p
for the first few years, &L=21032 for many years, +L=1-101032
>2005
New generation of experiments could give
sb: < 0.01
s: < 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
s: < 0.1
essential for discovering new physics
s: < 0.1
using various decay modes.
Also:
Bs  Kl+l-, K, m+m-, Bd  fKS, rare D and tau decays etc.
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!