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Belle 実験における B 0 g a 1  p  分岐比の測定

Belle 実験における B 0 g a 1  p  分岐比の測定. 樹林敦子 石野宏和 東工大理 他　 Belle Collaboration. Outline. Introduction Procedure Fitting Results Summary. Preliminary!. KEKB Collider. Belle Detector. KEKB Tsukuba, Japan. 3km. World Record !. Asymmetric e + (3.5GeV) e - (8GeV) Collider

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Belle 実験における B 0 g a 1  p  分岐比の測定

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  1. Belle実験におけるB0ga1p分岐比の測定 樹林敦子 石野宏和 東工大理 他　Belle Collaboration

  2. Outline • Introduction • Procedure • Fitting • Results • Summary Preliminary!

  3. KEKB Collider Belle Detector KEKB Tsukuba, Japan 3km World Record ! Asymmetric e+(3.5GeV) e-(8GeV) Collider Lpeak = 1.71  x 1034 /cm2 /s  (Nov 2006) ∫Ldt = 710.3 /fb (~Dec25,2006)

  4. Introduction • B0→a1±p∓ decays (bgu) are sensitive to f2 • BaBar measured the B.F. and tCPV parameters • PRL 97, 051802 (2006) • observation of a1pi signal • B.R. = (33.23.83.0) x 10-6 • hep-ex/0612050 • tCPV analysis • effective f2 (NOT f2!) is measured.

  5. Event Selection • B0ga1p, a1gppp • 2.2<pbach<2.7 GeV/c • 0.8 < M(a1)< 1.8GeV/c2 • 0.55< M(p+p−) <1.15 GeV/c2 at least one combination of the three pions from the a1 decay • |Dt|<70ps • Charm vetos • 1.86 < M(K−p+p+)<1.88 GeV/c2 for D+p− decays • 3.05< M(p+p−)<3.15 GeV/c2 for J/y K*0 decays • 2.00< M(K−p+p+)<2.05 GeV/c2 for D*+p- decays • |DE|<0.12 GeV, Mbc>5.20 GeV/c2

  6. a2p Analysis Procedure a1p • the signal yields from a 3D fit to DE, Mbc and cosq distribution. • DE = E*B-E*beam, Mbc2= (E*beam)2-|p*B|2, where E*beam = CMS beam energy, E*B and p*B are CMS energy and momentum of the reconstructed B meson, cosq (=helicity angle) • cosq for discriminating a1p and a2p . • helicity angle definition: the angle between the normal of the a1 decay plane and B direction in the a1 rest frame. a1g3pions L=1 assuming s-wave decay: prim. pion q B

  7. Likelihood Function TM = 4 pions at a final state are truely different pions SCF = some of the four pions at a final state are replaced by the pions from theother B decay, fraction of these are estimated from MC and fixed in the fit. c0 & c1 = shape parameters of the continuum DE a = shape parameter of the continuum Mbc

  8. Fitting Results a1p TM a1p SCF a2pTM a2p SCF bgc bgu Continuum Signal region (|DE|<0.05 GeV, 5.27< Mbc < 5.30 GeV/c2 ) enhanced

  9. Preliminary! Branching Fraction eg no. falls into our analysis region/no. signal MC generated) Brsubgassume 1/2 a1 decay to r0p+, 1/2 r+p0 ePIDgfor 4 pion final state

  10. Cut : -0.15 < DE < -0.05 GeV, Mbc>5.27 GeV/c2 Efficiency from MC = 3.3% N(BB)=449x106 B.R. = (2.42  0.05) x10-4 PDG (2.54  0.28) x10-4 Validity Check with B0gD-p+, D-gK+p-p-

  11. 2D (DE-Mbc) fit separately in each helicity angle bin apply correct SCF fraction fix for the fit sig. yield x (1-SCF frac.) to get TM compare w/ PDF Validity Checka1p helicity shape a1p TM helicity shape Matches w/ a1p hel. shape a2p TM helicity shape

  12. Preliminary! Systematic Errors

  13. make 1,000 ToyMC experiments w/ D-wave PDF fit with the 3D fitter, made w/ purely S-wave PDF Obtain sig. yield Use D-wave reconstruction efficiency, 9.77%  Sys. error in B.F. = +4.7% Systematic Error for assuming purely S-wave a1

  14. Fit to a1 mass • Motivation • determination of a1 properties • mass and width • non-resonant (NR) contributions • B grpp and 4p • Functions used • signal: relativistic Breit-Wigner function • B.G: MC for b g c and b g u, sideband for continuum • NR from MC • rpp and 4p are combined to a single function

  15. a1 mass fit results event fractions are fixed with DE-Mbc-helicity fit, NR not included fit with NR floated B.G. a1 a2

  16. Preliminary! Summary • B.F. of B0ga1p obtained using 535MBBbars collected at Belle detector: BaBar: (33.2  3.8  3.0)x10-6 • Mass and width of a1 obtained: BaBar: M(a1) = 1229  21 MeV/c2,G(a1) = 393  62 MeV/c2

  17. Backups

  18. 3D (DE-Mbc-cosq) fit separately in each mass angle bin obtain a1 and also a2 mass apply correct SCF fraction plot a1 & a2 mass yield distributions Validity Checkw/ a1mass a1 mass distribution in signal region MC M(a1) = 1.23 GeV/c2, G(a1)=0.460 GeV/c2 M(a2) = 1.3183 GeV/c2, G(a2)=0.107 GeV/c2

  19. Signal Yield

  20. Physics Motivation 8GeV electron 3.5GeV positron CP eigenstate B0 or B0 (flavor tag side) U(4s) Dz ~ 200mm Measurement of time dependent CP violation B mesons: ct = 460 mm boost: bg = 0.42 decay distance~ 200 mm _ Requires vertex resolution ~ 100 mm

  21. Charm Veto efficiency loss: BgDp 1.2% BgD*p 1.7% BgJ/yK* 1.1%

  22. charmless B decay peaking B.G. rare decay MC corresponding to (exp.7-41) x 25 luminosity after removing the peaking B.G. vary ±100% and see the signal yield fluctuation: assigned as systematic errors DE with Mbc>5.27GeV/c2 13% error on K*±p∓ 6.6% error on K0p+p− well known B.R. a1 mass is used to estimate r0p+p-

  23. Projection Plots in Global Analysis Region

  24. Sys. error : Fit Bias GeantMC: from linear fit Sig. in = 653.4 Sig. expected = 628.8 error = 3.8 % ToyMC: Sig. in = 604.7 Sig. out = 604.2 error = 0.1 % total. 3.8 %

  25. Sys. error : dwave • TM helicities differ swave dwave

  26. Sys. error : dwave cont'd • scf DE-Mbc shapes differ dwave swave

  27. 2D (DE-Mbc) PDF taken from 'smooth' function in PAW 15 x 15 bin histogram for sys. error study 7 x 7 bin histogram 30 x 30 bin histogram for helicity, vary each parameter by 1s shifts from mean 30x30bin 13.39 7x7bin 27.00 GENEHELCHB02 minus 0.53 GENEHELCHB02 plus 0.77 GENEHELCHB04 minus 0.16 GENEHELCHB04 plus 1.17 square sum -0.00 +30.18 -0.00% +4.61% Systematic Errorgeneric background shapes 2D PDF, Generic MC

  28. 2D (DE-Mbc) PDF taken from 'smooth' function in PAW 15 x 15 bin histogram for sys. error study increase/decrease binning for helicity, vary each parameter by 1s Systematic Errorrare decay background 2D PDF, rare decay MC -7.39% +3.93%

  29. a1 Massother measurements • This analysis M(a1) = 1205 + 80 - 47 MeV/c2 G(a1) = 592 + 377 - 140 MeV/c2 • BaBar M(a1) = 1229  21 MeV/c2 G(a1) = 393  62 MeV/c2 • BaBar PhD thesis M(a1) = 1209  8 MeV/c2 G(a1) = 448  35 MeV/c2

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