1 Multi-body B-decays studies in BaBar Ben Lau (Princeton University) On behalf of the B A B AR collaboration The XLIrst Rencontres de Moriond QCD and high energy hadronic interactions

2 Multi-body decay and CP violation Sides are determined from the rates for various processes involving b quarks Angles are determined from CP-violating asymmetries Area is proportional to the amount of CP violation   “The” Unitarity Triangle Surprising, the best  and  estimation are coming from multi-body decay! B 0   B +  D  dalitz

3 Introduction to analysis technique  (m ES )  3 MeV e - (9 GeV) e + (3.1 GeV)  (4S) B background signal Event selection: Quality cuts for tracks and showers Continuum rejection using event shape variables Kinematic signal identification with m ES and  E: Maximum Likelihood Fit to determine yields and asymmetries

4 Measuring  in b → uud WW WW      a 1 +    , a 1 - (direct CPV) Goal: Measure time dependent A CP B 0     large penguin B 0    need time-dependent dalitz plot B 0     small penguin, mostly longitudinal polarization If tree dominated: Unfortunately, there is penguin pollution “effective” value of 

5 CKM  and Isospin Analysis Isospin Analysis disentangles penguin contributions to S=sin2α eff using SU(2) symmetry relations between the B →  modes (analogous to B → ππ system) We need branching fraction measurements:  B (B ± → ρ ± ρ 0 ), B (B 0 → ρ + ρ - ), B (B 0 → ρ + ρ - ), B (B 0 → ρ 0 ρ 0 ), B (B 0 → ρ 0 ρ 0 ) BaBar has an improved measurement on Bf(B ± →ρ ± ρ 0 ) Gronau-London Method (PRL 65, 3381) In this construction κ = 2(α eff -α) S and C are parameters relating to the CP asymmetry of the ρ+ρ- mode. κ

6 BaBar Updated Results (230M BB) Branching Fractions: Previous measurement: Consistent with hypothesis that EW penguin pollution is small Differential decay rate: Charge Asymmetry: The new measurement is in better agreement with the isospin symmetry

7 Motivation: Can be used to give a new measurement of  by time-dependent A CP analysis Observation of B 0  a 1 (1260) +    ±  events Branching Fractions: Fitted a 1 (1260) resonance parameters: Next step: Measure  using time-dependent CP analysis

8 Motivated by B  , with sufficient statistics one can measure  Little is known about these 5-body states Theory prediction for Branching Fraction (from 1987): BR(B 0  a 1  )=43x10 -6 Search for B 0  a 1  Place an upper Limit < 30 × (90% C.L.)  extraction will be difficult due to small statistics BaBar performed a search using 110M BB events BaBar Preliminary Fit results: 68 ± 34 events

9 sin(2  +  ) in B 0  D (*) ,D  Favored b  c transition Doubly-Cabibbo suppressed b  u transition u,c,t V * ub Interference between:  = strong phase difference V cd V cb V * ud - CP asymmetry proportional to ratio r of amplitudes r~0.02 (from CKM elements) small CP asymmetry

10 B 0  D s *  and SU(3) Such an important parameter |r D  | cannot be calculated accurately… need measurement.. Need D s mode. Because |r D  | is extremely difficult to measure (background too huge) Measurement of B ( B 0  D s +  - ) would help measure |r D  | using SU(3)* s b d d u c B0B0 -- Ds+Ds+ W b d d u c B0B0  D+D+ W d flavor SU(3) SU(3) first order corrections *W exchange amplitude assumed to be small and neglected in this SU(3) analysis

11 B 0  D s *  /K results 6 sigma 5 sigma First observation of B 0  D s *+  - /D s *+ K - ! D modeD* mode r D    

12 Direct CP Violation and Polarization in B  K*  An interesting mode: B → K* ρ are charmless hadronic B decays. Proceed through the dominant gluonic penguin and Cabibbo-suppressed tree level diagram B  uus Goal:Measure the polarization: Will f L ~ 100% like tree dominated  Or f L ~ 50% like penguin dominated  K* ? It is interesting to look for the connection

13 Results for B +  f 0 (980)K* + Branching Fractions Direct CP violation: B +  f 0 (980)K* + 5 sigma B +   0 K* sigma Upper Limit: <5.9 x (90% C.L.) Branching Fraction:  K* is a vector-vector decay efficiency depends on polarization need to extract f L from the fit: Results for B +    K* +

14 Summary Multibody B decays are playing a critical role in the study of CP violation at the B Factories  Currently, the best measurements of  and  are coming from multibody decays BaBar measurements of  :  Updated measurement of      Expanding into a 1 X modes: First observation of B 0 → a 1 (1260) +   search for B 0 → a 1 +   Measurement of  /direct CP violation  First observation of D s (*)  /K, useful in getting sin(2  +  ) in D*   Searching for direct CP violation in B   K*