Direct CP violation in    decays at Belle Yuuj ｉ Unno Hanyang university (For the Belle Collaboration) June 16 th -21 st, Seoul, Korea

17 June, 2008 Y.Unno 2 Introduction (Direct CP violation) Decay amplitudes: CP violating asymmetry (A CP ) is defined as: A non-zero A CP requires the following 3 conditions: more than 2 amplitudes non-zero strong phase difference :  I -  j =  ≠ 0 non-zero weak phase difference : Á i - Á j =  Á ≠ 0 DCPV measurement plays important roles: Test KM model Help to understand B decay mechanism Search for new physics beyond SM In ratios of BFs, systematic uncertainties cancel

17 June, 2008 Y.Unno 3 DCPV through interference of T & P  3 through b  u transition (but theoretically challenging…) Naïve expectation Acp(     ) ~ Acp(     ) A CP (     ) ≠ A CP (     )  might indicate new physics Introduction (    )         (T+P)        (T+P) New physics ? Á3Á3

17 June, 2008 Y.Unno 4 Introduction (    )        (P)        (P) A CP ~0 in SM S~sin2  1 (  ) in SM (  S~O(0.1)) help to test  S puzzle: sin2  1 from b  sqq differs from J/           (T) A CP ~0 in SM No P due to Isospin symmetry        (P)        (P) b  d Penguin Br ~0.05 x Br(        ) Sizable A CP in SM (J.-M. Gerard, W.-S. Hou, PLB253,478)

17 June, 2008 Y.Unno 5 Integrated luminosity (/fb) 8.0 GeV e – KEKB & Belle detector Two separate rings for e + and e – Energy in CM is 10.58GeV   (4S) Ring circumference is ~3Km Two separate rings for e + and e – Energy in CM is 10.58GeV   (4S) Ring circumference is ~3Km Total ∫L dt = 842/fb Peak L = 17.1 /nb/sec Results are based on 449 or 535 MBB pairs 3.5 GeV e +

17 June, 2008 Y.Unno 6 Kinematic reconstruction     S          B reconstruction Main background e + e –  qq(q=u,d,s,c)  event topology  / K separation  PID Signal extraction Unbinned ML fit to  E, m bc for B & B Analysis Overview Jet-likeSpherical

17 June, 2008 Y.Unno 7 A CP (        ) w/ 535MBB   Signal  reflection continuum charmless B # of signal, continuum, charmless B bkg are floated  yields are fixed to the expectation using BFs and KID eff./fake small KID charge asymmetry is corrected Nature 452, (2008) N(     ) = 1856±52 N(     ) = 2241±57 Observation of DCPV in     A CP (     ) = –0.094±0.018±0.008 with 4.8  Consistent with BABAR :

17 June, 2008 Y.Unno 8 A CP (        ) & A CP (        ) w/ 535MBB     simultaneous fit to    0 and     A CP (     ) = ±0.03±0.01A CP (     ) = +0.07±0.06±0.01        : (T)        : (T & P) Nature 452, (2008)  Both     and     are (T & P) dominant modes Naïve expectation is A CP (     ) ~ A CP (     )  A CP puzzle is established with 4.4 significance  A CP = A CP (     ) - A CP (     ) = ±0.037 A CP (     ) = – 0.094±0.018±0.008 ≠

17 June, 2008 Y.Unno 9 A CP (        ) & A CP (        ) w/ 449MBB PRL 98, (2007) simultaneous fit to    + and            A CP (     ) = +0.03±0.03±0.01 No significant asymmetry in either mode        : (b  s P)    ± feed across        : (b  d P)

17 June, 2008 Y.Unno 10 A CP (        ) w/ 535MBB PRD 76, (2007) A CP (     ) = –0.05±0.14±0.05 “sin2  1 ” = +0.33±0.35±0.08 consistent with HFAG Ave: sin2  1 = ±0.026 A CP (     ) and S(     ) with time-dependent CP analysis b flavor tagging efficiency =~30%  vertex from  S trajectory and IP : efficiency =~ 30%  

17 June, 2008 Y.Unno 11  A CP = A CP (     ) – A CP (     ) = 4.4   A CP puzzle Published in Nature Discussion on ΔA CP puzzle What is happening with A CP (     ) and A CP (     ) ?

17 June, 2008 Y.Unno 12 Discussion on ΔA CP puzzle  A CP ~ 0 is expected if C and P EW are neglected Enhancement of C ?  C ＞ T is needed (C/T = 0.3–0.6 in SM)  breakdown of theoretical understanding Enhancement of P EW ?  Would indicate new physics. Due to poor understanding of strong interactions? C.-W.Chaing, et al., PRD 70, Y.-Y.Charng, et al., PRD 71, W.-S.Hou, et al., PRL 95, S.Baek, et al., PRD 71, S.Baek, et al., PLB 653, 249 H.-n.Li,et al., PRD 72, etc… C.-W.Chaing, et al., PRD 70, Y.-Y.Charng, et al., PRD 71, W.-S.Hou, et al., PRL 95, S.Baek, et al., PRD 71, S.Baek, et al., PLB 653, 249 H.-n.Li,et al., PRD 72, etc…

17 June, 2008 Y.Unno 13 Isospin sum rule among    CP asymmetries ( M. Gronau, PLB 672, ) A violation of the sum rule would be an unambiguous evidence of new physics Discussion on ΔA CP puzzle The sum rule predicts A CP (     ) = –0.15±0.06  –15% DCPV in     ???   A CP (     ) is still too large to claim a discrepancy.  Have to examine this with larger statistics

17 June, 2008 Y.Unno 14  A CP = A CP (     ) – A CP (     ) = 4.4   A CP puzzle Published in Nature Discussion on ΔA CP puzzle What is happening with A CP (     ) and A CP (     ) ?

17 June, 2008 Y.Unno 15 Summary A CP measurements in all    decays DCPV observation in        decay  A CP puzzle is established w/ 4.4  ΔA CP = A CP (     ) – A CP (     ) = ±0.037 Published in Nature 452, (2008) No significant A CP in                 To test “isospin sum rule” more statistics are needed Stay tuned for update results in summer !

17 June, 2008 Y.Unno 16 Systematics of A CP detector bias of       from qq bkg in (  E, m bc ) detector bias of     from D* +  D 0 (   )  

17 June, 2008 Y.Unno 17 Systematic Errors  S  A Vertexing Flavor tagging Resolution Physics Possible Fit bias BG fraction BG dt shape Tag-side interference Total

17 June, 2008 Y.Unno 18 NIM A 533, 516 (2004) Flavor tagging b flavor information is needed for non-flavor-specific B 0 modes Judge tag side b flavor with flavor specific processes: sign of lepton / Kaon / slow-pion. Tagging efficiency is  30 %

17 June, 2008 Y.Unno 19 Analysis Kπ separation Analysis (Kπ separation) Cherenkov light yield Ionization energy loss Charged particle emit cherenkov light (transition radiation) if velocity is faster than that of light in material

17 June, 2008 Y.Unno 20 Analysis Kπ separation Analysis (Kπ separation) EfficiencyFake rate K~90%~7% π~89%~12% ex) B  K + π - selection Before cut After cut

17 June, 2008 Y.Unno 21 Analysis Analysis (KID correction: ex. B 0  K    ) Belle KID has high performance BUT NOT PERFECT Existence of KID charge asymmetry smears true Acp Finite KID fake dilutes true Acp : K ＋    K    To obtain true Acp, introduce KID correction B 0  K    :  1% correction is applied

17 June, 2008 Y.Unno GeV e ＋ 8.0 GeV e — Introduction (Belle detector) Aerogel Cherenkov Counter Kπ separation Central Drift Chamber Charged track momentum Kπ separation K L Muon Detector K L, μ detection Silicon Vertex Detector B vertex TOF Counter Kπ separation Electromagnetic Calorimeter γ, π 0 reconstruction e ＋－, K L identification

17 June, 2008 Y.Unno countries 55 institutes ~400 collaborators IHEP, Vienna ITEP Kanagawa U. KEK Korea U. Krakow Inst. of Nucl. Phys. Kyoto U. Kyungpook Nat’l U. EPF Lausanne Jozef Stefan Inst. / U. of Ljubljana / U. of Maribor U. of Melbourne BINP Chiba U. U. of Cincinnati Ewha Womans U. Fu-Jen Catholic U. U. of Giessen Gyeongsang Nat’l U. Hanyang U. U. of Hawaii Hiroshima Tech. IHEP, Beijing IHEP, Moscow Nagoya U. Nara Women’s U. National Central U. National Taiwan U. National United U. Nihon Dental College Niigata U. Nova Gorica Osaka U. Osaka City U. Panjab U. Peking U. Princeton U. Riken Saga U. USTC Seoul National U. Shinshu U. Sungkyunkwan U. U. of Sydney Tata Institute Toho U. Tohoku U. Tohuku Gakuin U. U. of Tokyo Tokyo Inst. of Tech. Tokyo Metropolitan U. Tokyo U. of Agri. and Tech. INFN Torino Toyama Nat’l College VPI Yonsei U. Introduction (Belle Collaboration)

17 June, 2008 Y.Unno 24 Introduction (    )

17 June, 2008 Y.Unno 25 ΔA CP puzzle Belle A CP (    - ) = –0.094±0.018±0.008 A CP (     ) = +0.07±0.03±0.01  A CP = A CP (     ) – A CP (     ) = ±0.037 (4.4  ) Probability for no difference is ＜ 9.3x10 -6 BABAR A CP (     ) = –0.107± (PLR99,021603(2007)) A CP (     ) = ±0.039±0.010 (PRD76,091102(2007))  A CP = (3.0  ) Belle + BABAR  A CP = ±0.029  5.2  Belle A CP (    - ) = –0.094±0.018±0.008 A CP (     ) = +0.07±0.03±0.01  A CP = A CP (     ) – A CP (     ) = ±0.037 (4.4  ) Probability for no difference is ＜ 9.3x10 -6 BABAR A CP (     ) = –0.107± (PLR99,021603(2007)) A CP (     ) = ±0.039±0.010 (PRD76,091102(2007))  A CP = (3.0  ) Belle + BABAR  A CP = ±0.029  5.2 