future CP violation Experiment 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) OPAL: sin 2bJ/y KS = 3.2  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

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- 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)

“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

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.

Experiment Now In preparation R&D (19982003) (2003 ?) sym. e+e-@(4S) CLEO II CLEO III sbb ~1 nb L 41032 1.71033 3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

Experiments in near future(~2000) asym. e+e- hadron (4S) p+metal@40GeV pp@2TeV BaBar/BELLE HERA-B CDF/D0 sbb ~1 nb ~760 nb ~60 mb BB/sec 3/10 38 6000 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

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.

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

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

approved recommended proposed sbb ~500 mb ~500 mb ~60 mb Experiments >~2005 pp@14TeV pp@14TeV pp@2TeV ATLAS/CMS* LHCb& BTeV approved recommended proposed for approval sbb ~500 mb ~500 mb ~60 mb BB/sec 500k 100k 6-60k+ 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

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

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!