Constraints on α from B Decays at BaBar 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 17 August, 2004 C. Dallapiccola, ICHEP 2004

Outline Introduction and Motivation History of Measurements Time dependent CP Asymmetry in Update of Constraint on Unitarity Triangle angle a NEW! 17 August, 2004 C. Dallapiccola, ICHEP 2004

Motivation: Measuring a ACP(t) in decay to CP eigenstate: Measure Tree If dominates 17 August, 2004 C. Dallapiccola, ICHEP 2004

Motivation: Measuring a Penguin But...contribution from Interferes with Tree: ACP(t)  sin(2aeff) aeff = a+dapeng direct ACP ≠ 0 But can measure dapeng using isospin relations… 17 August, 2004 C. Dallapiccola, ICHEP 2004

Motivation: Isospin and rr Gronau&London, PRL 65, 3381 (1990) 3 such relations (one for each polarization) Relative to experimentally simpler B  pp: Much smaller in rr system dapeng much smaller!! 17 August, 2004 C. Dallapiccola, ICHEP 2004

History: r+r- Observation But r is a vector r+r- not a CP eigenstate? Transverse (h=±1) and longitudinal (h=0) helicity states 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 It is almost a pure CP eigenstate (CP =+1) 17 August, 2004 C. Dallapiccola, ICHEP 2004

History: r+r0 and r0r0 and measurements: Update of in this talk Mode BF (10-6) fL * B+r+r0 * B0r0r0  B0r+r- * PRL 91, 171802 (2003)  hep-ex/0404029, submitted to PRL 89M 17 August, 2004 C. Dallapiccola, ICHEP 2004

ACP(t) in B0r+r- Decays Reconstruct candidates  combine  Find vertex positions of and other B meson  Tag flavor of Compute Dt=tCP-ttag Fit params Set to 0 since fL1 17 August, 2004 C. Dallapiccola, ICHEP 2004

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

ACP(t) in B0r+r- Decays Run1-3 data (122M )  Preliminary 314±34 Signal Events (205 tagged) fL=1.00±0.02 Events with cleanest tags mES DE Fit: total Fit: bkgd After cuts on likelihood ratio BaBar prelim BaBar prelim 17 August, 2004 C. Dallapiccola, ICHEP 2004

ACP(t) in B0r+r- Decays Run1-3 data (122M ) ACP BaBar prelim BaBar Run1-2 (89M ) Hep-ex/0404029, to PRL Dt (ps) 17 August, 2004 C. Dallapiccola, ICHEP 2004

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 Prelim studies show it’s not large 17 August, 2004 C. Dallapiccola, ICHEP 2004

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 17 August, 2004 C. Dallapiccola, ICHEP 2004

Constraint on a 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 Run1-2 result: a 17 August, 2004 C. Dallapiccola, ICHEP 2004

Constraints on a Using BaBar rr, rp, and pp Measurements http://ckmfitter.in2p3.fr/ a from rr, rp, pp only from full CKM fit (eK, Vub, Dmd,s, sin(2b)) Mirror solutions being disfavored! From full CKM fit: 17 August, 2004 C. Dallapiccola, ICHEP 2004

Conclusion First measurement of ACP(t) in B0r+r- decays Limit on 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 17 August, 2004 C. Dallapiccola, ICHEP 2004

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

Backup Slide Distribution of r± helicity distributions for data Clear demonstration of strong longitudinal polarization 17 August, 2004 C. Dallapiccola, ICHEP 2004

Backup Slide Constraints in the r-h plane: 17 August, 2004 C. Dallapiccola, ICHEP 2004