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Constraints on α from B  Decays at BaBar

32 nd International Conference on High Energy Physics Beijing, China. Constraints on α from B  Decays at BaBar. Carlo Dallapiccola University of Massachusetts, Amherst For the BaBar Collaboration. Outline. Introduction and Motivation History of Measurements

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Constraints on α from B  Decays at BaBar

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  1. 32nd International Conference on High Energy Physics Beijing, China Constraints on α from B Decays at BaBar Carlo Dallapiccola University of Massachusetts, Amherst For the BaBar Collaboration C. Dallapiccola, ICHEP 2004

  2. Outline • Introduction and Motivation • History of Measurements • Time dependent CP Asymmetry in • Update of • Constraint on Unitarity Triangle angle a NEW! C. Dallapiccola, ICHEP 2004

  3. Measure Tree Motivation: Measuring a ACP(t) in decay to CP eigenstate: If dominates C. Dallapiccola, ICHEP 2004

  4. Penguin Motivation: Measuring a But...contribution from Interferes with Tree: ACP(t)  sin(2aeff) aeff = a+dapeng direct ACP ≠ 0 But can measure dapeng using isospin relations… C. Dallapiccola, ICHEP 2004

  5. Much smaller in rr system dapeng much smaller!! Motivation: Isospin and rr Gronau&London, PRL 65, 3381 (1990) Relative to experimentally simpler B  pp: 3 such relations (one for each polarization) C. Dallapiccola, ICHEP 2004

  6. Non-CP eigenstates CP eigenstate • * Observation of PRD 69, 031102 (2004) * • Run1-2 data (89M ) • Measure BF:  5 times larger than p+p- • Measure Polarization History: r+r-Observation But r is a vectorr+r-not a CP eigenstate? Transverse (h=±1) and longitudinal (h=0) helicity states It is almost a pure CP eigenstate (CP =+1) C. Dallapiccola, ICHEP 2004

  7. 89M History: r+r0and r0r0 • and measurements: • Update of in this talk * PRL 91, 171802 (2003)  hep-ex/0404029, submitted to PRL C. Dallapiccola, ICHEP 2004

  8. Fit params Set to 0 since fL1 ACP(t) in B0r+r- Decays • Reconstruct candidates  combine  • Find vertex positions of and otherB meson  • Tag flavor of • Compute Dt=tCP-ttag C. Dallapiccola, ICHEP 2004

  9. mESDE NN MV1,2 cos(qH)1,2Dt r helicities B kinematics Event shape r masses ACP(t) in B0r+r- Decays • Run1-3 data (122M ) • Max. Likelihood fit in 8 dimensional space • Fit for signal yield, polarization, Slongand Clong • Model: true signal, misreco. signal, continuum and 17 backgrounds 32133 events in fit sample: • 87% of background is continuum, 13% B backgrounds C. Dallapiccola, ICHEP 2004

  10. Fit: total mES DE Fit: bkgd Events with cleanest tags ACP(t) in B0r+r- Decays • Run1-3 data (122M )  Preliminary 314±34 Signal Events (205 tagged) fL=1.00±0.02 After cuts on likelihood ratio BaBar prelim BaBar prelim C. Dallapiccola, ICHEP 2004

  11. ACP ACP(t) in B0r+r- Decays • Run1-3 data (122M ) BaBar prelim • BaBar Run1-2 (89M ) Hep-ex/0404029, to PRL Dt (ps) C. Dallapiccola, ICHEP 2004

  12. Prelim studies show it’s not large ACP(t) in B0r+r- Decays: Run4 • Run1-4 data (226.6M )  Analysis in progress! • Add 86% more statistics • Comprehensive study of systematics due to interference of signal mode with other decays to p+p-p0p0 final states C. Dallapiccola, ICHEP 2004

  13. Search for B0r0r0 • Analysis description similar to that of B0r+r- • First result from Run1-2 (89M ) • Updated with Run1-4 data (226.6M ) • signal observed PRL 91, 171802 (2003) NEW! mES DE • Dominant Syst • a1p interfer: ±7.5 events • PDF variations: ±6 events • B bkgd: ±5.8 events BaBar prelim BaBar prelim C. Dallapiccola, ICHEP 2004

  14. Run1-2 result: Constraint on a • Preliminary update on a constraint: • BaBar BF(r+r-), BF(r0r0) and Slong and Clong • World average BF(r+r0)= (HFAG) prelim From r0r0 measurement a C. Dallapiccola, ICHEP 2004

  15. http://ckmfitter.in2p3.fr/ a from rr, rp, pp only • from full CKM fit (eK, Vub, Dmd,s, sin(2b)) Constraints on a Using BaBarrr, rp, and pp Measurements • Mirror solutions being disfavored! • From full CKM fit: C. Dallapiccola, ICHEP 2004

  16. Conclusion • First measurement of ACP(t) in B0r+r- decays • Updated (2004) with Run1-3 data (122M ) • Limit on • Updated with full Run1-4 sample (226.6M ) • Low BF allows for relatively clean measurement of a via isospin relations! • Important milestone for B-Factories! • Coming soon  update of ACP(t) in B0r+r- with full Run1-4 data sample and improved analysis C. Dallapiccola, ICHEP 2004

  17. Use Backup Slide • A00 small  Grossman-Quinn bound PRD 58, 017504 (1998). Gives same bound on dapeng C. Dallapiccola, ICHEP 2004

  18. Backup Slide • Distribution of r± helicity distributions for data • Clear demonstration of strong longitudinal polarization C. Dallapiccola, ICHEP 2004

  19. Backup Slide • Constraints in the r-h plane: C. Dallapiccola, ICHEP 2004

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