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a and g at Babar Malcolm John LPNHE – Université s Paris 6&7

a and g at Babar Malcolm John LPNHE – Université s Paris 6&7 On behalf of the B A B AR collaboration. Conclusions (for those who can't wait…). PEP-II and B A B AR have performed beyond expectation CP violation in the B system is well established

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a and g at Babar Malcolm John LPNHE – Université s Paris 6&7

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  1. aand g at Babar Malcolm John LPNHE – Universités Paris 6&7 On behalf of the BABAR collaboration

  2. Conclusions (for those who can't wait…) • PEP-II and BABAR have performed beyond expectation • CP violation in the B system is well established • sin(2b) fast becoming a precision measurement • As for the other two angles (the subject of this presentation) : • Many analysis strategies in progress • The CKM angle a is measured but greater precision will come • First experimental results on g are available • First experimental results on 2b+g are available • Results presented here are based on datasets up-to 227 MBB • BABARand PEP-II aim to achieve 550 MBB (500 fb-1) by summer 2006

  3. * Vtd Vtb * Vub Vud * Vcd Vcb Vcd Vcb (r,h) a g b (0,0) (0,1)

  4. BABAR : where? what? who? • BABARcollaboration consists 11 countries and ~590 physicists ! • At the PEP-II B-factory at SLAC 1.5T solenoid ElectroMagnetic Calorimeter 6580 CsI(Tl) crystals e+ (3.1 GeV) DIRC (PID) 144 quartz bars 11000 PMs Silicon Vertex Tracker 5 layers, double sided strips (9.0 GeV) e- Drift Chamber 40 layers Instrumented Flux Return iron / RPCs [ → LSTs ]

  5. PEP-II : performance • Beams circulating in PEP-II again this month for the beginning of the 2005-2006 run. • Aim for 500 fb-1 by summer 2006 • Belle and KEKB are running well • Their dataset could be 600 fb-1 in the same time period PEP-II / BABAR: August 2004 Lpeak = 9.2×1033 cm-2 s-1 (3 times design luminosity !) PEP-II delivered 253 fb-1 BABARrecorded 244 fb-1 At (4S) resonance 221 fb-1 Analysis dataset 211 fb-1

  6. Variables that distinguish spherical B events from jet-like continuum. Variables that distinguish (4S)→bbfrom e+e-→qq Other variables, like qH(D0) bb signal bb background qq continuum Analysis techniques : Continuum suppression • For every pair-production, expect three • Many techniques available it fight this background. • They can be amalgamated in linear discriminators or neural networks.

  7. Analysis techniques : mES and DE • Precise kinematics, unique to machines operating at a threshold • The initial energy of the system is well known from the precise tuning of the beam

  8. Large data sample feeds a plethora of analyses New particle searches : Pentaquarks, exotic baryons, DsJ Precision measurement of SM CP violation : sin(2b) Precision measurement of SM CP violation : sin(2b) New physics searches in s-penguin decays SM CP violation : measurement of CKM angle a SM CP violation : measurement of CKM angle a SM CP violation : measurement of CKM angle g SM CP violation : measurement of CKM angle g SM CP violation : measurement of CKM angles 2b+g SM CP violation : measurement of CKM angles 2b+g Semileptonic B decays and the determination of |Vub| and |Vcb| Radiative penguin B decays Search for rare leptonic B decays Charm physics : D0 mixing, precision D0 measurements Tau physics : lifetime measurements, rare decay searches

  9. t =0 Dz = Dt gbc bg =0.56 l - (e-, m -) The two mesons oscillate coherently : at any given time, if one is a B0 the other is necessarily a B0 Dt picoseconds later, the B 0 (or perhaps its now a B 0) decays. In this example, the tag-side meson decays first. It decays semi-leptonically and the charge of the lepton gives the flavour of the tag-side meson : l -= B 0l+ = B 0. Kaon tags also used. (4S) Time-dependent analysis requires B0 flavour tagging • We need to know the flavour of the B at a reference t=0. At t=0 we know this meson is B0 B 0 rec B 0 B 0 tag

  10. Final State Amplitudes Formalism of CP violation with B mesons Time evolution of a S 0 : Indirect CP violation C 0 : Direct CP violation from mixing Time-dependent asymmetry

  11. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g (0,0) (0,1) B→ J/yKS b

  12. Limit on direct CPV = sin(2b) = 0 (1-2w) sin(2b) = ±1 from B0/B0 mixing w = mis-tag fraction sin(2b) measurement with charmonium (214 MBB) 7730 events Time-dependent asymmetry with an amplitude  sin(2b)

  13. (r,h) * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g b (0,0) (0,1) B→ p p B→ r r B→ r p a

  14. Tree decay B0B0mixing Penguin decay  The route to sin(2a) • Access to a from the interference of a b→u decay (g) with B0B0 mixing (b) g Inc. penguin contribution How can we obtain α from αeff ? Time-dep. asymmetry : NB : T = "tree" amplitude P = "penguin" amplitude

  15. How to estimate |a-aeff| : Isospin analysis • Use SU(2) to relate decay rates of different hh final states (h  {p,r}) • Need to measure several related B.F.s 2|-eff| Difficult to reconstruct. Limiting factor in analysis Gronau, London : PRL65, 3381 (1990)

  16. Time-dependent ACP of B0→p+p- • Good p/K separation up to 4.5 GeV/c Blue : Fit projection Red : qq background + B0→Kp cross-feed BR result in fact obtained from 97MBB

  17. Now we need B+→p+p0 • Analysis method reconstructs and fits B+→p+p0 and B+→K+p0 together B+→h+p0 B+→K+p0 B+→p+p0 Inserts show background components

  18. Using isospin relations and • 3 B.F.s • B0→p+p- • B+→p+p0 • B0→p0p0 • 2 asymmetries • Cp+p- • Cp0p0 |a-aeff |< 35° • Large penguin pollution ( P/T ) • Isospin analysis not currently viable in the B→ppsystem …and B0→p0p0 • 61±17 events in signal peak (227MBB) • Signal significance = 5.0s • Detection efficiency 25% B±→r±p0 • Time-integrated result gives :

  19. Isospin analysis using B→rr • Extraction of  follows the same logic as for the B→ppsystem • Except rr is a vector-vector state • r+r- is not generally a CP eigenstate • Angular analysis needed Transverse Helicity state h=±1 non-CP eigenstate Longitudinal Helicity state h=0 CP+1 eigenstate • However, is measured to be 1 in B→rr • Transverse component taken as zero in analysis

  20. very clean tags Time dependent analysis of B→r+r- • Maximum likelihood fit in 8-D variable space 32133 events in fit sample

  21. Searching for B→r0r0 • Similar analysis used to search for r0r0 • Dominant systematic stems from the potential interference from B→a1±p± (~22%) c.f. B→p+p- B.F.= 4.7 x 10-6 and B→p0p0 B.F.= 1.2 x 10-6 B (B→r+r-) = 33 x 10-6

  22. Isospin analysis using B→rr • Taking the world average and thanks to we apply the isospin analysis to B→rr • The small rate of means • |a-aeff | is small[er] • P/T is small in theB→rrsystem (…Relative to B→ppsystem) |a-aeff |< 11°

  23. +– 00 –+ Another approach : B→(rp)0 • Unlike p+p-and r+r-, r+p- is not a CP eigenstate • Must consider 4 (flavour/charge) configurations • Equivalent "isospin analysis" not viable (triangles→pentagons, 6→12 unknowns…) • However, a full time-dependent Dalitz plot analysis of can work! • Enough information to constrain a Interference at equal masses-squared gives information on strong phases between resonances r0 p- p0 p+  p- p0 r- p+ Snyder, Quinn : PRD 48, 2139 (1993)

  24. Time-dependent Dalitz fit • Extract  and strong phases using interferences between amplitudes • Time evolution of can be written as : • Assuming amplitude is dominated by r+,r- and r0, we write script {+,-,0} refers to {r+,r-,r0} • The "f"sare functions of the Dalitz-plot and describe the kinematics of B→rp (S→VS) • The "A"s are the complex amplitudes containing weak and strong phases. They are independent of the Dalitz variables • Complicated stuff! • At least 17 parameters to fit-for in a 6-D variable space • Large backgrounds. Over 80% of selected events are continuum

  25. B→p+p-p0 : data/MC, 213MBB • Fit finds 1184 ± 58 mES E’ NN t m’ (DP variable) ’ (DP variable) Signal B-background Self-crossfeed Continuum-background

  26. Fit result → Physics results : B→(rp)0213MBB • Hint of direct CP-violation • Likelihood scan of a using : k {+,-,0} T =tree amp. P =penguin - - 2.9  Mirror solution not shown Weak constraint at C.L.<5%

  27. Combining results on  • Combining results in a global CKM fit • Mirror solutions are clearly disfavoured • a is measured. • Although improve-ments will come

  28. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb b (0,0) (0,1) B±→ D(*)K(*) GLW, ADS and D0-Dalitz methods g

  29. GLW method → fCP → fCP Colourfavoured bcamplitude Colour suppressed bu amplitude How to access g? • Decays where interferes with • charged Bs only (time-independent, direct CPV) • no penguins pollution • Need same final state Strong phase between diagrams Crucial parameter : (not well measured)

  30. GLW method : B→D0K (214 MBB) • Main background from kinematically similar B→D0p which has B.F. 12x larger • So the signal and this main background are fitted together • 2D fit to DE and the Čerenkov angle of the prompt track A 2s cut on qC in these plots RCP-= 0.80±0.14(stat.) ±0.08(syst.) RCP+ = 0.87±0.14(stat.) ±0.06(syst.) ACP+ = 0.40±0.15(stat.) ±0.08(syst.) ACP-= 0.21±0.17(stat.) ±0.07(syst.) RCP-= 0.64±0.25(stat.) ±0.07(syst.) RCP+ = 1.73±0.36(stat.) ±0.11(syst.) B±→D0K*± ACP-= -0.35±0.38(stat.) ±0.10(syst.) ACP+ = -0.08±0.20(stat.) ±0.06(syst.) Only a loose bound on rB with current statistics: (rB)2 = 0.19±0.23

  31. ADS method → K-p + → K-p +   Cabibbo suppressedcd amplitude Cabibbo favoured cs amplitude Accessing g without using CP states • Using CP final states of the D0 yields an expected ACP of only ~10% • We can potentially do better using "wrong-sign" final states Colour favoured bcamplitude Colour suppressed bu amplitude D0→Kpsuppression factor: rD = 0.060±0.003 Phys.Rev.Lett. 91:17 1801 • And with enough events (i.e. large rB), expect large asymmetry

  32. Any d Any g DK : rB < 0.23 (90% C.L.) D*K : (rB)2 < (0.16)2 The smallness of rB makes the extraction of g with the GLW/ADS methods difficult ADS method : B→D(*)0K (227 MBB) • The number of events depends foremost on the value of

  33. Colourfavoured bcamplitude Colour suppressed bu amplitude r (770) K*DCS Sensitivity to g g=75°, d=180°, rB =0.125 b→u sensitivity with an unsuppressed D0 decay • Consider once again B→D(*)0K decays, this time the with D0→KSpp. • Obtain dD information from a fit to the D0 Dalitz plot → KSp-p+ → KSp+p- • D0 Dalitz model

  34. K*(892) r (770) K*DCS The D0→KSp+p-Dalitz model • Determine on clean, high statistics sample of 81500 D*+→D0p+ events • ASSUME no D-mixing or CP violation in D decays • Build model from 15 known resonances (+2 unidentified scalar pp resonances) c2/ d.o.f. = 3824/(3054-32) = 1.27

  35. B- B+ B- B+ B+ B- K* DCS D0 Dalitz method : B→D(*)0K (227 MBB) • Maximum likelihood fit extracts rB(*),g, d(*) from a fit to mES, DE, Fisher and the D0→KSp+p- Dalitz model. 282 ± 20 89 ± 11 44 ± 8

  36. 180° g 0° DK -180° 180° g 0° D*K -180° 0.1 0.3 rB D0 Dalitz method : B→D(*)0K : result • Measurement of gamma • Twofold ambiguity in g extraction Bayesian C.L.s 68% 95% g = 70°±26°±10°±10° (+np) (90% C.L.) D*K : rB = 0.155 +0.070 ± 0.040 ± 0.020 DK : rB < 0.19 -0.077 dB = 114°±41°±8°±10° (+np) dB = 303°±34°±14°±10° (+np) 3rd error is due attributed to the Dalitz model

  37. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb (0,0) (0,1) B0→ D(*)K(*) B0→ D±KSp B0→ D(*) p b 2b+g g

  38. mixing self taggingbcamplitude self tagging bu amplitude Other ways to access b→u • So, what happens if we start with a neutral B0? → fCP → fCP bcamplitude bu amplitude • Eventually this will be a time-dependent analysis • Early days yet though. Using non-CP modes of the D0, we search for : AND AND

  39. D0 mass sideband bc bu bc bu bcamplitude ( ) buamplitude B0→D(*)0K(*)0 (124 MBB) • Very challenging for 2b+g

  40. mixing D±K*± → Avoiding colour suppression : B0→D±KSp±(88 MBB) • Method has two advantages : • Avoids colour suppression in b→u • Integrating over Dalitz plane removes ambiguities in eventual g extraction • First experimental step complete : • Branching fraction measurement • Currently, Too few events for TD analysis • 1/3 of events are NOT in the K* region bcamplitude bu amplitude

  41. mixing Input is estimated from • SU(3) symmetry used Another way to sin(2b+g) : B0→D*-p+ • Both and decay to , neither with a colour-suppressed diagram ~l2 ~l4 favoured bc amplitude suppressed bu amplitude but there's is not enough information to solve the system… The suppression factor, rB must be taken from elsewhere.

  42. B0→D*-p+: very small ACP offset by copious statistics Full reconstruction (110MBB) Partial reconstruction (178 MBB) Find events with two pions and examine the missing mass X D*r Combinat. BB Peaking BB Continuum Total yields (all tags) yields

  43. sin(2b+g)results Full reconstruction (110MBB) L L L Partial reconstruction (178 MBB) L L : result uses lepton tags only

  44. Conclusions • PEP-II and BABARhave performed beyond expectation • CP violation in the B system is well established • sin(2b) fast becoming a precision measurement • As for the other two angles (the subject of this presentation) : • Many analysis strategies in progress • The CKM angle a is measured but greater precision will come • First experimental results on g are available • First experimental results on 2b+g are available • Results presented here are based on datasets up-to 227 MBB • BABARand PEP-II aim to achieve 550 MBB (500 fb-1) by summer 2006

  45. (r,h) a * * Vub Vud Vtd Vtb * * Vcd Vcb Vcd Vcb g b (0,0) (0,1) BACK-UP

  46. Before implementation of trickle injection Trickle injection in the 3.1GeV beam Trickle injection in both beams Luminosity LER current HER current PEP-II : performance • 5Hz "trickle" injection used in 2004

  47. 3.2s 5.2s Comparison with Belle : CPV in B0 +- Belle report observation of CPV in B0 +- >3s discrepancy between BABAR& Belle Belle 3.2s evidence for Direct CP violation not supported by BABARmeasurements

  48. GLW method : B→D0K* (227 MBB) • Recontruct K*→KSp. • Clean, no kinematically similar background • Lower B.F. and lower efficiency : Fewer events than D0K analysis RCP-= 0.64±0.25(stat.) ±0.07(syst.) RCP+ = 1.73±0.36(stat.) ±0.11(syst.) ACP-= -0.35±0.38(stat.) ±0.10(syst.) ACP+ = -0.08±0.20(stat.) ±0.06(syst.) (rB)2 = 0.19±0.23 RCP+ = 1.09±0.26(stat.) ±0.09(syst.) ACP+ = -0.02±0.24(stat.) ±0.05(syst.) Similar analysis, 121 MBB

  49. g from B→DK • Combining results from GLW, ADS and D0-Dalitz methods • UTFit collaboration • hep-ph/0501199 g = 60°±28° (+np)

  50. g from Belle

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