We report on a precision measurement of the ratio R_{τμ}^{ϒ(3S)}=B(ϒ(3S)→τ^{+}τ^{-})/B(ϒ(3S)→μ^{+}μ^{-}) using data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider. The measurement is based on a 28  fb^{-1} data sample collected at a center-of-mass energy of 10.355 GeV corresponding to a sample of 122 million ϒ(3S) mesons. The ratio is measured to be R_{τμ}^{ϒ(3S)}=0.966±0.008_{stat}±0.014_{syst} and is in agreement with the standard model prediction of 0.9948 within 2 standard deviations. The uncertainty in R_{τμ}^{ϒ(3S)} is almost an order of magnitude smaller than the only previous measurement.

Searches for B mesons decaying to final states containing a baryon and a lepton are performed, where the baryon is either Λc or Λ and the lepton is a muon or an electron. These decays violate both baryon and lepton number and would be a signature of physics beyond the standard model. No significant signal is observed in any of the decay modes, and upper limits in the range (3.2-520)×10-8 are set on the branching fractions at the 90% confidence level. © 2011 American Physical Society.

The decay width and mass of the Ds1(2536)+ meson are measured via the decay channel Ds1+→D*+KS0 using 385fb-1 of data recorded with the BABAR detector in the vicinity of the Υ(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is Γ(Ds1+)=0.92±0.03(stat.)±0.04(syst.)MeV. For the mass, a value of m(Ds1+)=2535.08±0.01(stat.)±0.15(syst.)MeV/c2 is obtained. The mass difference between the Ds1+ and the D*+ is measured to be m(Ds1+)-m(D*+)=524. 83±0.01(stat.)±0.04(syst.)MeV/c2, representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the Ds1+ meson is confirmed. © 2011 American Physical Society.

We present measurements of partial branching fractions of B→K +X, B→K0X, and B→π+X, where X denotes any accessible final state above the endpoint for B decays to charmed mesons, specifically for momenta of the candidate hadron greater than 2.34 (2.36) GeV for kaons (pions) in the B rest frame. These measurements are sensitive to potential new-physics particles which could enter the b→s(d) loop transitions. The analysis is performed on a data sample consisting of 383×106BB̄ pairs collected with the BABAR detector at the PEP-II e+e- asymmetric energy collider. We observe the inclusive B→π+X process, and we set upper limits for B→K +X and B→K0X. Our results for these inclusive branching fractions are consistent with those of known exclusive modes, and exclude large enhancements due to sources of new physics. © 2011 American Physical Society.

We search for the rare decay of the D0 meson to two photons, D0→γγ, and present a measurement of the branching fraction for a D0 meson decaying to two neutral pions, B(D0→π0π0). The data sample analyzed corresponds to an integrated luminosity of 470.5fb -1 collected by the BABAR detector at the PEP-II asymmetric-energy e +e - collider at SLAC. We place an upper limit on the branching fraction, B(D0→γγ)<2.2×10 -6, at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B(D0→π0π0)=(8.4±0.1±0. 4±0.3)×10 -4. © 2012 American Physical Society.

We report on a search for CP violation in the decay D ±→KS0π± using a data set corresponding to an integrated luminosity of 469fb-1 collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The CP-violating decay rate asymmetry ACP is determined to be (-0.44±0.13(stat)±0.10(syst))%, consistent with zero at 2.7σ and with the standard model prediction of (-0.332±0.006)%. This is currently the most precise measurement of this parameter. © 2011 American Physical Society.

We study the reactions e+e-→e+e -η(′) in the single-tag mode and measure the γγ*→η(′) transition form factors in the momentum-transfer range from 4 to 40GeV2. The analysis is based on 469fb-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV. © 2011 American Physical Society.

We present a study of the decays B±→DK ± with D mesons reconstructed in the K+π -π0 or K-π+π0 final states, where D indicates a D0 or a D̄0 meson. Using a sample of 474×106 BB̄ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we measure the ratios R ±Γ(B±→[K±π ±π0]DK±)Γ(B ±→[K±π±π0] DK±). We obtain R+=(5-10+12(stat)- 4+2(syst))×10-3 and R-=(12-10+12(stat)-5+3(syst)) ×10-3, from which we extract the upper limits at 90% probability: R+<23×10-3 and R -<29×10-3. Using these measurements, we obtain an upper limit for the ratio rB of the magnitudes of the b→u and b→c amplitudes rB<0.13 at 90% probability. © 2011 American Physical Society.