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Princeton University, Department of Physics Jadwin Hall, Washington Rd.

Measurements of the CP angle  with the BaBar experiment. Alexandre V. Telnov Princeton University for the BaBar Collaboration. XXXIII International Conference on High Energy Physics Moscow, Russia Session 8: CP violation, Rare decays, CKM Friday, July 28, 2006, 10:06.

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Princeton University, Department of Physics Jadwin Hall, Washington Rd.

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  1. Measurements of the CP angle  with the BaBar experiment Alexandre V. Telnov Princeton University for the BaBar Collaboration XXXIII International Conference on High Energy Physics Moscow, Russia Session 8: CP violation, Rare decays, CKM Friday, July 28, 2006, 10:06 Princeton University, Department of Physics Jadwin Hall, Washington Rd. Princeton, NJ 08542-0708, U.S.A. E-mail: AVTELNOV@PRINCETON.EDU

  2. _ Current BaBar dataset: 347 million BB pairs (±1.1%) Outline Theoretical and experimental introduction to the CKM angle  New BaBar results; their interpretation and implications for: B → +−, ±0, 00 B → 00, ±0, +− B0 → ()0 Summary and outlook Measurements of the CP angle  with the BaBar experiment

  3. Penguin Tree Measuring  ACP(t) in decay to a CP eigenstateat the tree level : Measure Penguins: ACP (t)  sin(2aeff); aeff = a-Δ; direct ACP ≠ 0 Measurements of the CP angle  with the BaBar experiment

  4. Isospin analysis in B →  , ρρ M. Gronau, D. London, Phys. Rev. Lett. 65, 3381 (1990) In B → ρρ, there are 3 such relations (one for each polarization) 6 unknowns, 6 observables in  (there is no vertex to measure S00) 5 observables in  (or 7, when both C00 and S00 are measured) 4-fold ambiguity in 2Δ: either triangle can flip up or down Neglecting EW penguins, ±0 is a pure tree mode, and so the two triangles share a common side: Measurements of the CP angle  with the BaBar experiment

  5. TheB0→ +−analysis Simultaneous ML fit toB0 →+−,K+−, +K−,K+K− Using DIRC Cherenkov angle to separate pions and kaons Additional /K/KKseparation fromΔE Also measureAK+−: see talk by Emanuele Di Marco at 12:12 today DIRC:144 quartz bars 0.84 x 4π coverage; 97% eff. @ 3 GeV/c 12σ/Kseparation at 1.5 GeV/c, 2σat 4.5 GeV/c Calibration sample:B−→−D0, D0→+K− Measurements of the CP angle  with the BaBar experiment

  6. background signal mES _ B0 tags mES Δt Δt New BaBar results: B0→ +−(1) BaBar-CONF-06/039 N+− = 675 ±42 B0 tags asymmetry Builds a histogram of x excluding it from the Maximum-Likelihood fit, assigning a weight to each event,keeping all signal events,getting rid of all background events, and keeping track of the statistical errors in each x bin M. Pivk and F. R. Le Diberder, “sPlot: a statistical tool to unfold data distributions,” Nucl. Instrum. Meth. A 555, 356 (2005) [arXiv:physics/0402083]. sPlot: Measurements of the CP angle  with the BaBar experiment

  7. New BaBar results: B0→ +−(2) BaBar-CONF-06/039 BaBar has observed a 3.6σevidence for CP violation in B0→ +− S = −0.53 ±0.14 ±0.02 C = −0.16 ±0.11 ±0.03 (S,C) = (0.0, 0.0) is excluded at a confidence level of 0.99970 (3.6σ) Measurements of the CP angle  with the BaBar experiment

  8. TheB → ±0, 00analysis Simultaneous fit toB0 →+0,K+0(using DIRC Cherenkov angle to separate pions and kaons) B0 →00:branching fraction and time-integrated direct CP asymmetry new:in addition to 0 →, we use merged 0and →e+e−conversions  10% efficiency increase per 0(4% from merged 0, 6% from conversions) merged 0:  →e+e−conversions: result from interactions with detector elements the two photons are too close to one another in the EMC to be reconstructed individually; can be recovered using , where S is the second EMC moment of the merged 0 → SVT outer layers beam pipe inner SVT layers DCH inner wall The control sample: →  Measurements of the CP angle  with the BaBar experiment

  9. New BaBar results: B → ±0, 00 BaBar-CONF-06/039 N±0 = 572 ±53 N00 = 140 ±25 ±0 mES 00 mES sPlot B±→ ±0 background Br00= (1.48 ±0.26 ±0.12)  10−6 Br±0= (5.12 ±0.47 ±0.29)  10−6 C00 = −0.33 ±0.36 ±0.08 Measurements of the CP angle  with the BaBar experiment

  10. An interpretation of the new B → results BaBar-CONF-06/039 Δ  |Δ|<41º at 90% C.L. near0 can be disfavored by additional experimental information =0 excluded at 1−C.L. = 4.4 10−5 This is a frequentist interpretation: we use only the B→ isospin-triangle relations in arriving at these constraints on Δ=−eff and on itself Here is one of the possible solutions totheGronau-London isospin triangle in B→ according to the central values of the latest BaBar results: Measurements of the CP angle  with the BaBar experiment

  11. “helicity frame” fL(B0→ +−)WA= 0.967+0.023 −0.028 B → angular analysis B → is a vector-vector state; angular analysis is required to determine CP content: pure CP = +1 transverse is not a CP eigenstate Fortunately, the fraction fL of the helicity-zero state in B→  decays is very close to 1: fL(B±→ ±0)WA= 0.96 ± 0.06 Heavy Flavor Averaging Group, April 2006 update: http://www.slac.stanford.edu/xorg/hfag/rare/winter06/polar/index.html Measurements of the CP angle  with the BaBar experiment

  12. N00 = 98+32±22 −31 00 ΔΕ 0f0 mES Br00 = (1.16+0.37±0.27)  10−6 −0.36 fL(B0→ 00)= 0.86+0.11± 0.05 −0.13 The systematic error is dominated by interference with B0→ a± (1260) and by PDF parameter uncertainties 1 Br (B0→ a± (1260)) Br (a± (1260) →±±) = (16.6 ±1.9 ±1.5)  10−6 1 1 New BaBar results: 3.0evidence forB0→ 00 BaBar-CONF-06/027 Incremental improvements in the event selection and the analysis technique Results are statistically consistent with the previous BaBar analyses hep-ex/0603050, accepted by PRL Br (B0→ 0f0) Br (f0→+−) < 0.68  10−6 (at 90% C.L.) Also measure: Br (B0→ f0f0) Br2(f0→+−) < 0.33  10−6 (at 90% C.L.) Measurements of the CP angle  with the BaBar experiment

  13. _ Based on 232 million BB pairs; BaBar-PUB-06/052 N±0 = 390 ±49 BABAR preliminary continuum + BB backgrounds ΔΕ mES fL(B±→ ±0)= 0.905 ± 0.042+0.023 −0.027 isospin prediction “before”: PDG 2004: (26 ± 6)  10−6 Belle: (31.7 ± 7.1+3.8)  10−6 Previous BaBar : (22.5+5.7 ± 5.8 )  10−6 00 +−/√2 old±0WA −6.7 +0 −5.4 New BaBar results: B±→ ±0 BABAR preliminary Br±0 = (16.8 ±2.2 ±2.3)  10−6 The systematic error is dominated by modeling of backgrounds, signal misreconstruction, and by statistical PDF uncertainties The new BaBar measurement inB±→ ±0allows the isospin triangle to close } Phys. Rev. Lett. 91, 221801 (2003) Phys. Rev. Lett. 91, 171802 (2003) Measurements of the CP angle  with the BaBar experiment

  14. New BaBar results:B0→ +− Br (B0→ a±) Br (a±→+−±) < 30  10−6 (90% C.L.) 1 1 _ B0 tags Slong = −0.19 ±0.21+0.05 −0.07 fL(B0→ +−)= 0.977 ± 0.024+0.015 −0.013 reduced systematics thanks to hep-ex/0605024, accepted by PRD distributions for the highest-purity tagged events B0 tags ΔΕ mES sum ofbackgrounds BABAR preliminary helicity m±0 asymmetry N+− = 615 ±57 Δt (ps) dominated by self-crossfeed BaBar-CONF-06/016 Br +− = (23.5 ±2.2 ±4.1)  10−6 Clong = −0.07 ±0.15 ± 0.06 Measurements of the CP angle  with the BaBar experiment

  15. [74, 117]º at 68.3% C.L. BABAR preliminary BABAR preliminary Δ  |Δ|<18º at 68% C.L. |Δ|<21º at 90% C.L. An interpretation of the new B → results BaBar-CONF-06/27, BaBar-CONF-06/016 Due to the newB0→00BF result, the constraint onfromB→has become less stringent This is a frequentist interpretation: we use only the B→ branching fractions, polarization fractions and isospin-triangle relations in arriving at these constraints on Δ=−eff and  As datasets increase, determination of both CandS will become possible inB0→00, leading to an improvement in the precision of the the isospin analysis Measurements of the CP angle  with the BaBar experiment

  16. p- r- p- r0 p0 p0  p+ p+ B0→ ()0: Dalitz-plot analysis BaBar-CONF-06/037 and references therein rpis not a CP eigenstate An isospin-pentagon analysis method exists but is not fruitful Time-dependent Dalitz-plot analysis assuming isospin symmetry, measuring 26 coefficients of the bilinear form factors A. Snyder and H. Quinn, Phys. Rev. D, 48, 2139 (1993) Monte Carlo r0p0 Interference in the corners of the Dalitz plot provides information on strong phases between resonances r+p− r−p+ The(1450)and(1700)resonances are also included in this analysis Measurements of the CP angle  with the BaBar experiment

  17. New BaBar results: B0→ ()0(1) BaBar-CONF-06/037 ΔΕ mES minimum of the three di-pion invariant masses data projection of the fit result NN output signal misreconstruction expected B background continuum background Δt/(Δt) m' ' Measurements of the CP angle  with the BaBar experiment

  18. A = 0.03 ±0.07 ±0.03 +− A = −0.38+0.15±0.07 −+ −0.16 New BaBar results: B0→ ()0(2) BaBar-CONF-06/037 S = 0.01 ±0.12 ±0.028 C = 0.154 ±0.090 ±0.037 A = −0.142 ±0.041 ±0.015 a more physically intuitive way to represent direct-CP quantities: parameters from the quasi-two-body description ofB → : ΔS = 0.06 ±0.13 ±0.029 ΔC = 0.377 ±0.091 ±0.021 For results on Direct CP Violation, attend talk by Emanuele Di Marco at 12:12 today Measurements of the CP angle  with the BaBar experiment

  19. +− [75, 152]º at 68.3% C.L.  [5, 63]º at 68.3% C.L. An interpretation of the new B0→ ()0results BaBar-CONF-06/037 the relative phase between the amplitudes of + − = arg(A+*A−) : B0→ −+andB0→ +− no constraint at 2σ level The constraint onfromB0→ ()0is relatively weak – but free from ambiguities! Measurements of the CP angle  with the BaBar experiment

  20. Br (B0→ a±) Br (a±→+−±) < 30  10−6 (90% C.L.) 1 1  fL(B0→ 00)= 0.86+0.11± 0.05 −0.13  Clong = −0.07 ±0.15 ± 0.06 Br (B0→ a± (1260)) Br (a± (1260) →±±) = (16.6 ±1.9 ±1.5)  10−6 1 Slong = −0.19 ±0.21+0.05 fL(B±→ ±0)= 0.905 ± 0.042+0.023 1 −0.027 −0.07 fL(B0→ +−)= 0.977 ± 0.024+0.015 −0.013 Recap of new results B0→ ()0:see page 18 S = −0.53 ±0.14 ±0.02 C = −0.16 ±0.11 ±0.03 CP violation at 3.6 Br±0 = (5.12 ±0.47 ±0.29)  10−6 Br00 = (1.48 ±0.26 ±0.12)  10−6 C00 = −0.33 ±0.36 ±0.08 Br00 = (1.16 +0.37±0.27)  10−6 First evidence, at 3.0 −0.36 Br±0 = (16.8 ±2.2 ±2.3)  10−6 Br +− = (23.5 ±2.2 ±4.1)  10−6 Measurements of the CP angle  with the BaBar experiment

  21. 169.7° CKM fit no  in fit [164, 176]º at 68.3% C.L. Global fits for the value of Please see talks by S. T'Jampens (CKMfitter) and V. Vagnoni (UTfit) for details Two interpretations currently exist that convert theB→ , , measurements to constraints on: 97.5° [86, 114]º at 68.3% C.L. CKMfitter talk: 17:30 tomorrow UTfit talk: 17:48 tomorrow CKMfitter Group (J. Charles et al.), Eur. Phys. J. C41, 1-131 (2005), [hep-ph/0406184], updated results and plots available at http://ckmfitter.in2p3.fr M. Ciuchini, G. D'Agostini, E. Franco, V. Lubicz, G. Martinelli, F. Parodi, P. Roudeau, A. Stocchi, JHEP 0107 (2001) 013 [hep-ph/0012308], updated results and plots available at http://utfit.roma1.infn.it Measurements of the CP angle  with the BaBar experiment

  22. Summary and outlook • The BaBar experiment has observed evidence of • Time-dependent CP violation inB0 → +− • The decay processB0 → 00 • and improved the precision of other measurements related to the extraction of . The ability of existing B-meson factories to measure the angle  with a precision of a few degrees cruciallydepends on the developments in measuring the branching fractions and CP parameters in B0 → 00 and B0 → 00 The extraction of depends significantly on the statistical and theoretical treatment; The larger of the CKMfitter and UTfit68.3% C.L. intervals is  [86, 114]º(CKMfitter) Measurements of the CP angle  with the BaBar experiment

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