Prospects for future CP violation Experiment

in the B-meson system

Parallel Session 6ICHEP

Vancouver, 23-29 July 1998

Tatsuya NakadaCERN

-CP violation has been seen only in the neutral kaon system.

-Experimental attempt in the B-meson system:Bd

0(t= 0) J/ KS(t) vs. Bd0(t= 0) J/ KS(t)

OPAL: sin 2J/ KS = 3.2 0.5

CDF: sin 2J/ KS = 1.8 1.1 0.3

where B0 J/ KS(t) B0 J/ KS

(t)

B0 J/ KS(t) B0 J/ KS

(t)

1.8 2.0

= sin 2J/KS sin mdt

The next steps are

1) To observe CP violation in B-meson decays

2) To test whether CP violation is largely generated by theStandard Model

If the standard model is the main source of CP violation,CP violation in Bd

0 J/ KS will be discovered by BaBar, BELLEHERA-B starting 1999~2000CDF, D0

Expected to be large: 0.3<sin2<0.8

CKM Unitarity Triangles

Vtd Vtb + Vcd Vcb

+ Vud Vub = 0 Vtd Vud

+ Vts Vus + Vtb Vub

= 0

Vub

Vcb

Vtd

Vub Vtd

Vts

Bd

D

Bs DSKBd DK

Bd J/KS

J/KLBs J/

(Theoretically clean channels)

“Golden” channels measurements:

Bd J/KS + theoretically clean (little penguin)+ experimentally easy

“” measurements: Bs DsK theoretically very clean (no penguin)

need time development of Bs decaysBd DK + theoretically very clean (no penguin)

very small visible branching fractions“” measurements:

Bd D theoretically very clean (no penguin) very small asymmetry (~)

“” measurements:Bs J/ theoretically very clean (no penguin)

need time development of Bs decays CP /CP has to be measured

Penguin and “” measurementsBd

time dependent studies, penguin/tree must be known,

Bd , , Bu

isospin analysis using branching fractions small branching fractions (: ~)

Bd , ,

time dependent Dalitz plot studies small branching fractions (: ~) possible contributions from non-resonance, re-scattering

etc.

Experiment Now In preparation R&D(1998

sym. ee@(4S)CLEO II CLEO III

bb ~1 nbLbb/hadronic ~

B-hadron Bu, Bd

Detector centralTrigger allt(B) very modestParticle ID e//hadron e///K/p

limited /K/p

few107 B’s by ~2000: Rare decays, direct CP but not J/KS

Experiments in near future(~2000)asym. ee hadron(4S) p+metal@40GeV pp@2TeV

BaBar/BELLE HERA-B CDF/D0bb ~1 nb ~760 nb ~60 bBB/secbb/hadronic ~~~

B-hadron Bu, Bd Bu,Bd,Bs,Bc Bu,Bd,Bs,Bc

Detector slightly forward forward centralTrigger all J/ high pt t modest good goodParticle ID e///K/p e///K/p e//hadron

Around 2005, we will have all combined results of:: ~ 0.02 [rad]: depends on how well we understand strong interactions

penguin, re-scattering, SU(3), resonance etc.xs: depends on the value, measured if xs<~20: depends on xs

Physics with “108” B’s

, , , xs would remain to be still open questionsFor a significant improvement (>109 B’s physics)

new generation of experiments

Which is needed to discover New Physics.

newparticles

newparticles

New physics can appear inb = 1 process

through penguin

b = 2 processthrough box

through tree

b b, s

b b, snewparticles

d,s d

b d, s

d,s b

CP violation must be studied inBd decays via Oscillations bc+W and bu+WBs decays via Oscillations bc+W and bu+WBd,s,u decays via penguinsBd,s decays via box

Experimental conditions areSmall branching fractions many Bd,s,u’sRapid Bs oscillations decay time resolutionIncluding multi-body hadronic final states particle ID

mass resolution

Experiments >~2005 pp@14TeV pp@14TeV pp@2TeV

ATLAS/CMS LHCb& BTeVapproved recommended proposed

for approvalbb ~500 b ~500 b ~60 bBB/seckk-k+

bb/hadronic ~~~

B-hadron Bu,Bd,Bs,Bc Bu,Bd,Bs,Bc Bu,Bd,Bs,Bc

Detector central forward double forwardEarly trigger high pt medium pt e//h vertex(reduction >100) vertext good very good very goodParticle ID e//hadron e///K/p e///K/pL=1033 for the first few years, &L=21032 for many years, +L=1-101032

>2005New generation of experiments could give

: < 0.01: < 0.01xs: up to xs~40 (ATLAS/CMS), ~80 (LHCb/BTeV)

In addition, due to the particle identification capability and efficient trigger, dedicated experiments could give: < 0.1: < 0.1

using various decay modes.Also:Bs Kll, K, , Bd KS, rare D and tau decays etc.

essential for discovering new physics

ConclusionsCP 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 ee machine at (4S)HERA-B: fixed target experiment with the HERA proton beamCDF, 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!