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Direct CP violation in B Kp decays at Belle

Direct CP violation in B Kp decays at Belle. Yuuj ｉ Unno Hanyang university (For the Belle Collaboration) June 16 th -21 st , SUSY2008 @ Seoul, Korea. Introduction (Direct CP violation). Decay amplitudes: CP violating asymmetry (A CP ) is defined as:

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Direct CP violation in B Kp decays at Belle

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  1. Direct CP violation in BKp decays at Belle Yuujｉ Unno Hanyang university (For the Belle Collaboration) June 16th-21st, SUSY2008 @ Seoul, Korea

  2. Introduction (Direct CP violation) • Decay amplitudes: • CP violating asymmetry (ACP) is defined as: • A non-zero ACP requires the following 3 conditions: • more than 2 amplitudes • non-zero strong phase difference :I - j= ≠ 0 • non-zero weak phase difference : Ái - Áj = 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 Y.Unno

  3. Introduction (BKp) • B0K+p- (T+P) • B+K+p0 (T+P) Á3 New physics ? DCPV through interference of T & P f3 through bu transition (but theoretically challenging…) Naïve expectation Acp(K+p-) ~ Acp(K+p0) ACP(K+p-)≠ ACP(K+p0)  might indicate new physics Y.Unno

  4. Introduction (BKp) B+K0p+ (P) B0K0p0 (P) • ACP~0 in SM • S~sin2f1(b) in SM (DS~O(0.1)) • help to test DS puzzle: • sin2f1 from bsqq differs from J/yK0 • ACP~0 in SM • B0K0K+ (P) • bd Penguin • Br ~0.05 x Br( B+K0p+ ) • Sizable ACP in SM • (J.-M. Gerard, W.-S. Hou, PLB253,478) • B+p+p0 (T) • ACP~0 in SM • No P due to Isospin symmetry Y.Unno

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

  6. Analysis Overview • Kinematic reconstruction • K0  KS  p+p- • p0  g g • B reconstruction • Main background • e+e– qq(q=u,d,s,c)  event topology • p / K separation  PID • Signal extraction • Unbinned ML fit to DE, mbc for B & B Spherical Jet-like Y.Unno

  7. Observation of DCPV in K+p- • ACP(K+p-) = –0.094±0.018±0.008 with 4.8s • Consistent with BABAR : ACP(B0K+p-) w/ 535MBB Nature 452, 332-335(2008) • # of signal, continuum, charmless B bkg are floated • pp yields are fixed to the expectation using BFs and KID eff./fake • small KID charge asymmetry is corrected K-p+ K+p- Signal pp reflection continuum charmless B N(K+p-) = 2241±57 N(K-p+) = 1856±52 Y.Unno

  8. ≠ ACP(K+p-) = – 0.094±0.018±0.008 • Both K+p- and K+p0 are (T & P) dominant modes • Naïve expectation is ACP(K+p0) ~ ACP(K+p-) • DACP puzzle is established with 4.4 significance • DACP = ACP(K+p0) - ACP(K+p-) = +0.164±0.037 ACP(B+K+p0) & ACP(B+p+p0) w/ 535MBB simultaneous fit to K+p0 and p+p0 Nature 452, 332-335(2008) B+K+p0 : (T & P) B+p+p0 : (T) K-p0 K+p0 p-p0 p+p0 ACP(K+p0) = + 0.07±0.03±0.01 ACP(p+p0) = +0.07±0.06±0.01 Y.Unno

  9. ACP(B+K0p+) & ACP(B+K0K+) w/ 449MBB simultaneous fit to K0p+ and K0K+ PRL 98, 181804(2007) B+K0K+ : (bd P) B+K0p+ : (bs P) K0p - K0K- K0K+ K0p+ K0p± feed across ACP(K0p+) = +0.03±0.03±0.01 No significant asymmetry in either mode Y.Unno

  10. ACP(B0K0p0) w/ 535MBB PRD 76, 091103(2007) • ACP(K0p0) and S(K0p0) with time-dependent CP analysis • b flavor tagging efficiency =~30% • B vertex from KS trajectory and IP : efficiency =~ 30% B 0 B 0 • ACP(K0p0) = –0.05±0.14±0.05 • “sin2f1”= +0.33±0.35±0.08 • consistent with HFAG Ave: sin2f1 = +0.668±0.026 Y.Unno

  11. DACP puzzle Published in Nature Discussion on ΔACP puzzle DACP = ACP(K+p0) – ACP(K+p-) = +0.164±0.037 @ 4.4s What is happening with ACP(K+p-) and ACP(K+p0) ? Y.Unno

  12. Enhancement of C ? •  C＞T is needed (C/T = 0.3–0.6 in SM) •  breakdown of theoretical understanding • Enhancement of PEW ? •  Would indicate new physics. • Due to poor understanding of strong interactions? • C.-W.Chaing, et al., PRD 70, 034020 • Y.-Y.Charng, et al., PRD 71, 014036 • W.-S.Hou, et al., PRL 95, 141601 • S.Baek, et al., PRD 71, 057502 • S.Baek, et al., PLB 653, 249 • H.-n.Li,et al., PRD 72, 114005 • etc… Discussion on ΔACP puzzle DACP~ 0 is expected if C and PEW are neglected Y.Unno

  13. Discussion on ΔACP puzzle • Isospin sum rule among BKp CP asymmetries(M. Gronau, PLB 672, 82-88) • A violation of the sum rule would be an unambiguous evidence of new physics • The sum rule predicts ACP(K0p0) = –0.15±0.06 • –15% DCPV in K0p0 ??? • dACP(K0p0) is still too large to claim a discrepancy.  Have to examine this with larger statistics Y.Unno

  14. DACP puzzle Published in Nature Discussion on ΔACP puzzle DACP = ACP(K+p0) – ACP(K+p-) = +0.164±0.037 @ 4.4s What is happening with ACP(K+p-) and ACP(K+p0) ? Y.Unno

  15. Summary • ACP measurements in all BKp decays • DCPV observation in B0K+p- decay • DACP puzzle is established w/ 4.4s • ΔACP = ACP(K+p0) – ACP(K+p-) = +0.164±0.037 • Published in Nature 452, 332-335(2008) • No significant ACP in K0p+, K0p0, p+p0, K0K+ • To test “isospin sum rule” more statistics are needed • Stay tuned for update results in summer ! Y.Unno

  16. Systematics of ACP • detector bias of K+p0,p+p0from qq bkg in (DE, mbc) • detector bias of K+p-from D*+D0(Kp)p+ Y.Unno

  17. Systematic Errors dS dA Vertexing 0.011 0.020 Flavor tagging 0.008 0.005 Resolution 0.066 0.010 Physics 0.007 0.001 Possible Fit bias 0.009 0.004 BG fraction 0.009 0.001 BG dt shape 0.046 0.019 Tag-side interference 0.001 0.043 -------------------------------------------------- Total 0.082 0.053 Y.Unno

  18. Flavor tagging b flavor information is needed for non-flavor-specific B0 modes Judge tag side b flavor with flavor specific processes: sign of lepton / Kaon / slow-pion. NIM A 533, 516 (2004) Tagging efficiency is ~ 30 % Y.Unno

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

  20. Analysis (Kπ separation) ex) BK+π- selection Before cut After cut Y.Unno

  21. Analysis (KID correction: ex. B0K+p-) Belle KID has high performance BUT NOT PERFECT • Existence of KID charge asymmetry smears true Acp • Finite KID fake dilutes true Acp : K＋p- K-p+ To obtain true Acp, introduce KID correction B0K+p- : ~ -1% correction is applied Y.Unno

  22. Introduction (Belle detector) Aerogel Cherenkov Counter Kπ separation Electromagnetic Calorimeter γ, π0 reconstruction e＋－, KL identification 3.5 GeV e＋ TOF Counter Kπ separation 8.0 GeV e — KLMuon Detector KL, μ detection Central Drift Chamber Charged track momentum Kπ separation Silicon Vertex Detector B vertex Y.Unno

  23. 14 countries 55 institutes ~400 collaborators Introduction (Belle Collaboration) 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. 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 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 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 Y.Unno

  24. Introduction (BKp) Y.Unno

  25. ΔACP puzzle • Belle • ACP(K+p-) = –0.094±0.018±0.008 • ACP(K+p0) = +0.07±0.03±0.01 • DACP = ACP(K+p0) – ACP(K+p-) = +0.164±0.037 (4.4s) • Probability for no difference is ＜ 9.3x10-6 • BABAR • ACP(K+p-) = –0.107±0.018+0.007-0.004(PLR99,021603(2007)) • ACP(K+p0) = +0.030±0.039±0.010 (PRD76,091102(2007)) • DACP = +0.137+0.045-0.044(3.0s) • Belle + BABAR • DACP = +0.152±0.029 5.2s Y.Unno

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