Measurements of  and future projections Fabrizio Bianchi University of Torino and INFN-Torino Beauty 2006 The XI International Conference on B-Physics at Hadron Machines

2 Outline Introduction to the measurement of  Results from the B-factories: B      ±            ±           Summary and outlook Will not cover expectations at LHC and Super B-Factories See talks of P. Robbe and A. Bevan

3 Measuring  Access to  from the interference of a b → u decay (  ) with B 0 B 0 mixing (  ) Inc. penguin contribution

4 From  eff to  : Isospin Analysis Gronau and London, Phys. Rev. Lett. 65, 3381 (1990) Neglecting EW Penguins: is a pure tree mode. The triangles share a common side. Assume SU(2) symmetry among amplitudes

5 Time Dependent Analysis Outline  Fully reconstruct the B decaying to a CP eigenstate.  Tag the flavor of the other B.  Mis-tag probability measured in B flav sample.  Measure  t.  Extract S and C with a ML fit on a signal enriched sample.  Signal PDF from MC.  Background PDF from MC or sidebands

6 Variables used in the ML fit signal background Event Topology Combine variables in F or N  PID info:  DIRC + dE/dX (BaBar)  Aerogel + dE/dX (Belle)   t

7 :results (preliminary) Background Signal m ES EE EE 347 million BB sPlot N  = 675±42 hep-ex/ B 0 tag

8 :results (preliminary) 535 million BB N  = 1464±65 hep-ex/

9 :results (preliminary) C  = ± 0.08 ± 0.05 S   = ± 0.10 ± 0.04 C  = ± 0.11 ± 0.03 S  = ± 0.14 ± 0.02 (S , C  ) = (0.0, 0.0) excluded at 3.6  Observation of Direct CPV at 5.5  Observation of mixing-induced CPV at 5.6  347 million BB 535 million BB 2.3  discrepancy C =−A Belle BaBar Average

10 (preliminary) 347 million BBhep-ex/ N     = 140 ± 25N  ±   = 572 ± 53

11  constraint from No stringent constraint from  system alone  need  and     |  | < 41 o at 90% C.L. Frequentist interpretation: use only the B →  branching fractions and isospin-triangle relations.  eff 1- C.L.

12 The analysis Worse than  at first sight: V V final state. Mixture of CP = +1 and  1: need to know each fraction However: ~100% longitudinally polarized (~pure CP-even state) no need for elaborate angular analysis Branching fraction for B 0      is larger than     Branching fraction for B 0      is small (~1.1x10 -6 ) small penguin pollution

13 results (preliminary) 347 million BBhep-ex/

14 results 275 million BBPRL 96, (2006) N  = 194±32

15 results (preliminary)

16 results (preliminary) 232 million BBhep-ex/ N     =390 ± 49

17 results (preliminary) 347 million BBhep-ex/ N     = 98 ± 32 ±  evidence

18  constraint from [71, 105] o at 68.3% C.L. Frequentist interpretation: use only the B → ρρ branching fractions, polarization fractions and isospin-triangle relations. First evidence of B →  0  0 Constraint on  is less stringent PRL 96, (2006)hep-ex/  Use BR(B->  0  0 )<1.1 X 10 -6

19 The Dalitz analysis A. Snyder and H. Quinn, Phys. Rev. D, 48, 2139 (1993)   B0B0 B0B0 Monte Carlo  (1450) and  (1700) are included Interference provides information on strong phase difference  Time-dependent Dalitz-plot analysis assuming isospin simmetry.  26 coefficients of the bilinear form factor terms occurring in the decay rate are measured with a UML fit.  Physically relevant quantities are derived from subsequent fits to these coefficients.

20 analysis (preliminary) hep-ex/ million BB m’ and  ’ are the transformed Dalitz variables

21 analysis (preliminary) hep-ex/ million BB             mass helicity Dalitz + Isospin (pentagon) analysis 26(Dalitz) + 5(Br(     ), Br(  +  0 ), Br(  0  + ), A(  +  0 ), and A(  0  + )) Signal SCF BB bkg continuum

22  constraint from (preliminary) [0,8] o U [60,95] o U[129,180] o at 68.3% C.L.  (deg) 1- C.L.

23  constraints  B-Factories = [ 93 ] º  Global Fit = [ 98 ] º Belle  result is not included. It will weakens the suppression of solutions around 0 o and 180 o. Nice agreement  B-Factories = [92 ± 7] o ( SM Solution)  Global Fit = [93 ± 6] o CKMfitter UTfit B-Factories Global Fit

24 Pending Issues Discrepancy on C  Solutions at 0 o and 180 o should be (more) suppressed. Using  nice suppression from BaBar, not from Belle. Background modeling. Interference with other resonances or non-resonant component in ,  modes. Subtleties on statistical analysis with small statistics. C  = ± 0.11 ± 0.03 C  = ± 0.08 ± 0.05

25 Uncertainties on  extraction Possible contribution of EW penguin and isospin breaking effect. EW penguin effect seems to be small (~2°). Other isospin breaking effect ~ O(1°). [M.Gronau and J.Zupan PRD 71, (2005)] I=1 contribution due to finite width of  mass (  mode). [A.Falk et al. PRD 69, (R)] Too small to be an issue at B-factories

26 Summary and Outlook The three modes are complementary. Need to study them all. Good agreement between the CKM fit (  determined by others) and direct measurements. Still a lot to do. Refine previous analysis and exploit new ideas:  from B->a 1  ? Constraint on  from B 0 ->  +  - and B + ->K *0  + [M. Beneke et al., Phys. Lett. B638, 68(2006)] Doubling of statistics at the B-factories is much needed. Looking forward to LHC and to a Super B-Factory.

Backup Slides

28 CP mixing decay CP eigenvalue Amplitude ratio Time Dependent CP Asymmetry

29 B A B AR Detector

30 DIRC: Control samples for  and K K  Projection for 2.5 < p < 3 GeV/c

31

32 :results (preliminary) C  = ± 0.11 ± 0.03 S  = ± 0.14 ± 0.02 (S , C  ) = (0.0, 0.0) excluded at 3.6 

33 :results (preliminary) A  = ± 0.08 ± 0.05 S   = ± 0.10 ± 0.04 Observation of Direct CPV at 5.5  Observation of mixing-induced CPV at 5.6 

34  constraint from

35  constraint from

36 formalism Direct CP Violation CP violation in the interference with and without B mixing.

37 parameters (prelim)

38 Direct CP violation in Significance for non-zero DCPV: BaBar: 3.0  Belle: 2.4 

39 Differences in peak height Courtesy of Marcella Bona