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Multi-body B-decays studies in BaBar

The XLIrst Rencontres de Moriond. QCD and high energy hadronic interactions. Multi-body B-decays studies in BaBar. Ben Lau (Princeton University) On behalf of the B A B AR collaboration. “The” Unitarity Triangle. . . Multi-body decay and CP violation.

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Multi-body B-decays studies in BaBar

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

  2. “The” Unitarity Triangle   Multi-body decay and CP violation Sidesare determined from the rates for various processes involving b quarks Anglesare determined from CP-violating asymmetries B0rr Area is proportional to the amount of CP violation B+DKdalitz Surprising, the best a and g estimation are coming from multi-body decay!

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

  4. p+,r+,a1+ p-,r- ,a1- W+ W- (direct CPV) Measuring a in b → uud If tree dominated: Goal: Measure time dependent ACP Unfortunately, there is penguin pollution “effective” value of a B0pp  large penguin B0rp  need time-dependent dalitz plot B0rr  small penguin, mostly longitudinal polarization

  5. CKM a and Isospin Analysis • Isospin Analysis disentangles penguin contributions to S=sin2αeffusing SU(2) symmetry relations between the B→ρρ modes (analogous to B →ππ system) • We need branching fraction measurements: • B(B±→ρ±ρ0),B(B0→ρ+ρ-), B(B0→ρ+ρ-), B(B0→ρ0ρ0), B(B0→ρ0ρ0) • BaBar has an improved measurement on Bf(B±→ρ±ρ0) • Gronau-London Method (PRL 65, 3381) • In this construction κ = 2(αeff-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: The new measurement is in better agreementwith the isospin symmetry Differential decay rate: Charge Asymmetry: Consistent with hypothesis thatEW penguin pollution is small

  7. Observation of B0a1(1260)+p- 867±85 events Motivation: Can be used to give a new measurementof a by time-dependent ACP analysis Branching Fractions: Fitted a1(1260) resonance parameters: Next step: Measure a using time-dependent CP analysis

  8. Search for B0a1r • Motivated by Brr, with sufficient statistics one can measure  • Little is known about these 5-body states • Theory prediction for Branching Fraction (from 1987): • BR(B0a1)=43x10-6 BaBar performed a search using 110M BB events Fit results: 68 ± 34 events BaBar Preliminary Place an upper Limit < 30 × 10-6 (90% C.L.) a extraction will be difficult due to smallstatistics

  9. Interference between: Doubly-Cabibbo suppressed b  u transition Vcd Favored b  c transition V*ub V*ud u,c,t Vcb u,c,t = strong phase difference - CP asymmetry proportional to ratio r of amplitudes r~0.02 (from CKM elements) small CP asymmetry sin(2+) in B0D(*),D

  10. s d Ds+ D+ W W c c u b u b p- p B0 B0 d d d d B0Ds*p/K and SU(3) • Such an important parameter |rDp|cannot be calculated accurately…need measurement.. • Need Ds mode. Because |rDp|is extremely difficult to measure (background too huge) • Measurement of B(B0Ds+p -) would help measure |rDp| using SU(3)* flavor SU(3) SU(3) first order corrections *W exchange amplitude assumed to be small and neglected in this SU(3) analysis

  11. 5 sigma 6 sigma B0Ds*p/K results D mode D* mode rDp(10-2) First observationof B0Ds*+p- /Ds*+K- !

  12. Direct CP Violationand Polarization in BK*r • 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 fL ~ 100% like tree dominatedrr ? Or fL ~ 50% like penguin dominatedjK* ? It is interesting to look for the connection

  13. Results for B+f0(980)K*+ B+f0(980)K*+ 5 sigma Branching Fractions Direct CP violation: Results for B+r0K*+ • rK* is a vector-vector decay • efficiency depends on polarization • need to extract fL from the fit: B+r0K*+ 2.6 sigma Branching Fraction: Upper Limit: <5.9 x 10-6 (90% C.L.)

  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 a and g are coming from multibody decays • BaBar measurements of a: • Updated measurement of r+r0 • Expanding into a1X modes: • First observation of B0→ a1(1260)+p- • search for B0→ a1+r- • Measurement of g/direct CP violation • First observation of Ds(*)p/K, useful in getting sin(2b+g) in D*p • Searching for direct CP violation in B rK*

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