1. 11 th July 2003Daniel Bowerman1 2-Body Charmless B-Decays at B A B AR and BELLE Physics at LHC Prague Daniel Bowerman Imperial College 11 th July 2003

2. Daniel Bowerman2 Overview Measuring sin2α (sin2φ 2 ) through B  ππ General analyses overview CP results from B  π + π -, B  K + π - –How compatible are Belle and BaBar? Isospin analyses: Adding in B +  π + π 0 and B  π 0 π 0 Results overview and prospects What does this mean for LHCb?

3. 11 th July 2003Daniel Bowerman3 Measuring CP Asymmetries Three observable interference effects: –CP violation in mixing (|q/p| ≠ 1) –(direct) CP violation in decay (|A/A| ≠ 1) –(indirect) CP violation in mixing and decay (Im ≠ 0) Observable in time evolution of B  B  system (assume  ) direct CP violation  C ≠ 0 indirect CP violation → S ≠ 0 -A f =

4. 11 th July 2003Daniel Bowerman4 Measuring α with B  ππ With Penguins (P): mixing decay Tree (T) Level: Need branching fractions for    ,    , and     to get  from  eff : isospin analysis e -i2β e -i2γ sin(2(π-β-γ))

5. 11 th July 2003Daniel Bowerman5 α eff  α :Isospin Analysis The decays B    ,    ,     are related by isospin Central observation is that  states can have I = 2 or 0 –(gluonic) penguins only contribute to I = 0  I = 1/2) –     is pure I = 2  I = 3/2) so has only tree amplitude  (|A     A   ) Triangle relations allow determination of penguin-induced shift in  Gronau and London, Phys. Rev. Lett. 65, 3381 (1991) Need branching fractions for all three decay modes, and for B 0 and B 0 separately, even for π 0 π 0

6. 11 th July 2003Daniel Bowerman6 Analysis Overview for B  ππ Analysis issues: charmless B decays –Low branching ratios - BR ~ 10  -10  –Backgrounds: Large background from e  e   qq  need background suppression Modes with   suffer backgrounds from other B decays –Ambiguity between  and K - need excellent particle ID Time-dependent CP analysis issues: –Need to determine vertex position of both B mesons –Need to know the flavor of “other” B - particle ID Use maximum likelihood (ML) fits to extract signal yields and CP- violating asymmetries –Use as much information as possible The data sample corresponds to –88 million BB pairs (BaBar) –85 million BB pairs (Belle)

7. 11 th July 2003Daniel Bowerman7 Analysis Procedure B  ππ Kinematically select B candidates with m ES,  E Suppress/separate qq background with Event-Shape discriminant Linear Fisher (BaBar), Likelihood selector (Belle) BaBar –Loose cut on event shape |cos(  S )| –Fit for ππ, Kπ, and KK using m ES,  E, Fisher,  C –Add tagging and  t, fit for S and C Belle –Optimize cut on event-shape –Select pions –Cut ~3  in m ES and  E –Fit S and C using m ES,  E, and  t

8. 11 th July 2003Daniel Bowerman8 Branching Fraction Results Projections in  E Mode BelleBaBar YieldBR (10 -6 ) A CP (K  ) YieldBR (10 -6 ) A CP (K  ) B  →     133 ± 194.4 ± 0.6 ± 0.3157 ±194.7 ± 0.6 ± 0.2 B  → K    596 ± 3318.5 ± 1.0 ± 0.7 -0.07 ± 0.06 ± 0.01 589 ± 3017.9 ± 0.9 ± 0.7 -0.10 ± 0.05 ± 0.02 B  → K  K  -1 ± 7< 0.7 (90%) CL1 ± 8<0.6 (90%) CL BELLE Branching fractions are consistent 2σ direct CP effect in K   

9. 11 th July 2003Daniel Bowerman9 Reconstructed Vertex and Flavour tagging Exclusive B rec reconsctuction Beam spot Interaction Point B REC Vertex B REC daughters B TAG direction TAG tracks, V 0 s z B TAG Vertex Example in B →  B →  e  e  → qq  z resolution dominated by tag side Same resolution function as charmonium (sin2  ) sample Resolution functions determined in data Same Tagging algorithms as with sin2  analysis Primarily use Lepton and Kaon tags, and more complex NN based approach Event shape and Δt resolution functions are dependent on tagging category

10. 11 th July 2003Daniel Bowerman10 qq + K  Time Dependent CP Results With no penguins expect: BaBarBelle

11. 11 th July 2003Daniel Bowerman11 Time Dependent CP Results Very crudely put both asymmetries on the same scale BaBarBelle Highlights how different the measurements are!

12. 11 th July 2003Daniel Bowerman12 Compatibility of the CP results SC Belle inconsistent with (C=S=0) at 99.93% C.L. BaBar is still consistent with C=S=0

13. 11 th July 2003Daniel Bowerman13 Compatibility of the CP results Belle results and contour plot Note the y-axis scale change (-C = A) Physical boundary at C 2 + S 2 = 1 Inconsistent with (C = S = 0) at the 99.93% CL (3.4  ) BaBar and Belle are compatible at the 2- 2.5  level -C ππ Belle Result BaBar Result

14. 11 th July 2003Daniel Bowerman14 Completing the Triangle: B +  π + π 0 BaBar Belle 3-body feedthrough M ES ΔEΔE 72.4 ± 17.4 (4.5σ) 125 ± 22 (7.7σ) No direct CP violation seen here!

15. 11 th July 2003Daniel Bowerman15 Completing the Triangle: B  π 0 π 0 N=12 ± 9 (1.9σ) BaBar Belle M ES ΔEΔE N=23 ± 10 (2.5σ) Most challenging of the modes – lower efficiency, poor resolutions, 3-body background, correlations Hints of a signal at : BR(B  π 0 π 0 ) ~ 1.7 * 10 -6 At the very top end of expectations Have to measure both B 0 and B 0 rates Would have big impact on measuring α

16. 11 th July 2003Daniel Bowerman16 Summary of the results Branching ratio’s show that Penguin contribution is not negligible!

17. 11 th July 2003Daniel Bowerman17 B  ππ conclusions BelleBaBar Currently an Isospin analysis provides no new information

18. 11 th July 2003Daniel Bowerman18 The need for an Isopsin Analysis If the Branching fraction for B  π 0 π 0 holds up - Isospin analysis is necessary! Can still get information on  with only an upper bound on     : –For example: Grossman-Quinn bound (assume only isospin) BaBar

19. 11 th July 2003Daniel Bowerman19 Prospects at the B-factories Belle collecting average 450pb -1 /day, BaBar collecting 300pb -1 /day Next set of results should fully test B  ππ compatibility Both experiments expect ~500fb -1 by 2006 May go much higher with ‘Super’ B-factories What does this mean for α through B  ππ ? Belle BaBar

20. 11 th July 2003Daniel Bowerman20 Prospects at the B-factories Isospin Analysis Using present BaBar branching fractions extrapolated to 500fb -1 Need much more data!

21. 11 th July 2003Daniel Bowerman21 Prospects for B-factories and LHC If the branching ratio for B  π 0 π 0 holds at (~1.7 *10 -6 ) then: Will need an Isospin analysis to extract α Probably not possible at LHC Only possible at Super B-factory (maybe) We should hope that B  π 0 π 0 disappears! That α through ρπ is feasible at the LHC Still much to be learnt from the 2-body modes! Perhaps measure γ through Kπ Direct CP violation in Kπ

22. 11 th July 2003Daniel Bowerman22 Conclusions 2-body results have provided many highlights for the B- factory programmes Belle results are inconsistent with C = S = 0 in B  ππ at the 3.4σ level BaBar and Belle results disagree at the 2σ level Results indicate large Penguin contributions B  π 0 π 0 results indicate that Isospin analysis will be necessary - but very difficult at B-factories Probably not possible to measure α through B  ππ at LHC (hopefully through ρπ) Thanks to Jim Olsen, Belle and Babar 2-body groups and the CKM fitters : http://ckmfitter.in2p3.fr

23. 11 th July 2003Daniel Bowerman23 Back up Slides

24. 11 th July 2003Daniel Bowerman24 CP Violation in the SM CP violation arises in Standard Model through a single phase in the CKM matrix CP violating asymmetries A(  t) in B 0 decays measure  Unitarity of V requires e.g. Can be represented as “unitarity” triangle in the complex plane

25. 11 th July 2003Daniel Bowerman25 CP violation in the SM World Average sin2  = 0.734  0.055 http://ckmfitter.in2p3.fr

26. 11 th July 2003Daniel Bowerman26 BaBar and Belle crosschecks Both BaBar and Belle have undertaken many cross-checks: Fitting sideband and B  → K    samples Lifetime and mixing validation with B  → K    sample More stringent cuts to select signal events Repeat analysis on previous published data samples Toy MC validation of errors Belle Interesting one event effect in Belle dataset, but overall things seem fine BaBar

27. 11 th July 2003Daniel Bowerman27 Conclusions: Penguins Use data –P from K 0  + –Two-body BFs –S  and C  –CKM indirect constraint on  BaBar prefers: –0.1 < |P/T| < 0.4 –-170 < arg(P/T) < -40 Belle prefers: –0.5 < |P/T| < 1.1 –-70 < arg(P/T) < -30 P/T Arg(P/T) BELLE BABAR P/T Constraints on P/T Penguins not negligible!