Search for CP Violating Decays of theU(4S) O. Tajima (KEK) for Belle collaboration EPS-HEP`07 , Manchester

Introduction CP violation !! f1 B0 Y(4S) _ B0 f2 x1 x2 xY(4S)= +1 xCP = - x1 x x2 In case of x1 = x2 xCP = -1 CP violation !!

Examples of CP-violating decays J/yKS x1=-1 J/yKL x1=+1 x2=+1 xCP=-1 J/yKS x1=-1 hCKS cC1KS y(2S)KS x2=-1 xCP=-1 Y(4S) xCP=+1 B0 _ B0 J/yKS x2=-1 xCP=+1 xCP=-1 CP violation !!

Y(4S) CPV is well described by the SM Br( Y(4S)  B0B0bar  f1 f2 ; x1=x2 ) = F * Br(Y(4S)  B0B0bar) * Br(B0f1) * Br(B0f2) Suppression factor due to CP violation F = x2/(1+x2) * (2 sin2f1)2 x = 0.776 +/- 0.008 sin2f1 = 0.675 +/- 0.026 = 0.68 +/- 0.05 DCPV effect is neglected This is an another method to measure Mixing induced CPV Details are described in Text-books etc. I.Bigi, V.Khoze, N.Uraltsev and A.Sanda, “CP Violation” (ed. Jarlskog), p175; L.Wolfenstein, Nucl. Phys. B246, 45 (1984); M.B.Gavela et. al., Phys. Lett. B162, 197 (1985); I.Bigi and A.Sanda, Phys. Lett. B194, 307 (1987).

Fully reconstruct both B0B0 decays Brute Force method Fully reconstruct both B0B0 decays _ m+ J/y m- B0 Y(4S) Far from the 5s observation even if we have Super-B factory, 50billion Y(4S) (~50ab-1) p+ KS p- Full reconstruction _ B0 e+ J/y e- p+ KS p- Full reconstruction Only ~0.04 events/(0.5billion Y(4S)) are expected … ( 1billion Y(4S)  1ab-1 data at a B-factory)

An Idea to Hunt for Such Decays Full reconstruction m+ J/y m- B0 Y(4S) p+ KS p- _ B0 Signal MC J/y(l+l-)KS J/y(any)KS p+ KS p- J/y, hc Partial reconstruction About 40 times higher eff. than “brute force method” 1.1(0.6) inclusive-J/y(hc) events in 535 million Y(4S) decays

This technique can be demonstrated with B+B- data Full reconstruction: B- J/y(l+l-)K-, D0(K-p+, K-p+p-p+)p- Partial reconstruction: B+ hc K+ and J/y K+ Nsig = 206  57 events 532M Y(4S) decays

Generic B0 decays are background Large recoil mass region (>3.3GeV) is not used because of large BG and CP conserving BG (cc0, cc2 …) MC samples ( 36billion Y(4S) ) scaled to 535million Y(4S) y(2S) ccbar KS + BG Generic B0 decays cc1 Events/(0.04GeV/c2) J/y hc recoil mass (GeV/c2) We do not have any peaking BG contribution in MC samples, Mbc sideband data

Additional BG suppression CP violating modes (CP eigenstate) are flavor non-specific flavor tagging quality (r) for signal MC (J/yKS , hcKS ) r No flavor discrimination Perfect flavor flavor tagging quality (r) for BG MC r No flavor discrimination Perfect flavor discrimination Generic B0 decays (BG) contain flavor specific decays, such as B0D(*)ln , D*pslow …

Demonstration with a control sample Full reconstruction: B0 D(*)-p+ and D*-r+ Partial reconstruction: B0 hc KS and J/y KS Signal extraction by 2-D fitting Nsig = 35  16 events 532 million Y(4S) decays

Preliminary Results with 535 million Y(4S) decays for Y(4S)  B0B0  J/yKS+J/y(hc)KS Nsig = -1.5 -2.8 events (consistent with ZERO) +3.6 With 30 billion Y(4S) (30ab-1), such decays will be observed with 5s significance Br(Y(4S)B0B0J/yKS+J/y(hc)KS) < 4x10-7 (90%C.L.) SM prediction : 1.4x10-7

Super B Factory at KEK L = 8x1035 cm-2s-1 x±y I± L a b*±y q=30mrad. b*y=3mm L = 8x1035 cm-2s-1 L a I± x±y b*±y More beam currents 4x higher than KEKB More RF power New IR design b*±y x1/2 (63mm) New Beam pipe Crab crossing Beam-beam para. x6 0.057 (KEKB)  0.19 (sKEKB) Damping ring Linac upgrade

Prospects of Super-KEB Observation of CP violation in Y(4S) decay Now, we are here

Physics in Super-KEKB Discovery of Lepton Flavor Violation in tmg decays# Search for New CP-Violating Phase in b g s with 1 degree precision CKM Angle Measurements with 1 degree precision Discovery of B g Knn Discovery of New Right handed currents in bs transition# Discovery of New Subatomic Particles sin2qW with O(10-4) precision SfKs < SJ/yKs is established# New results with U(5S), U(3S) etc. |Vub| with 5% Precision Discovery of B g Dtn Discovery of B g mn # SUSY GUT with gluino mass = 600GeV, tanb = 30 “Discovery” with significance > 5s

Summary A new method to hunt for CP violation in Y(4S) decay Y(4S)B0B0barJ/yKS+J/y(hc)KS Partial (with Full) reconstruction technique Using 535 million Y(4S) decays in Belle experiment, we obtain an U.L. of 4x10-7 (90%CL) for Br of such decays (SM prediction 1.4x10-7) A Super-B factory has sufficient potential for observation of such CP-violating decays Preliminary

Systematic uncertainty for Br(Y(4S)B0B0J/yKS+J/y(hc)KS) Source (%) Recoil mass distribution 20.5 r distribution 4.2 Reconstruction efficiency 5.7 Number of BBbar 1.3 Branching fraction of sub decays 10.9 Total 24.3 Obtained from B+B- control samples Dominated by statistical fluctuation  to be reduced with increasing stat. Dominated with uncertainty of Br(B0  hc KS)