BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2011). Observation of the Decay B- -> D_s(*) K- l- nu(bar). Phys. Rev. Lett., 107(4), 041804–8pp.
Abstract: We report the observation of the decay B(-) -> D(s)(()*()+)K(-)l(-)(nu) over bar (l) based on 342 fb(-1) of data collected at the Y(4S) resonance with the BABAR detector at the PEP-II e(+)e(-) storage rings at SLAC. A simultaneous fit to three D(s)(+) decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B(-) -> D(s)(()*()+)K(-)l(-)(nu) over bar (l) with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be B(B(-) -> D(s)(()*())K(-)l(-)(nu) over bar (l) = [6.13(-1.03)(+1.04)(stat) +/- 0.43(syst) +/- 0.51 (B(D(s)))] X 10(-4), where the last error reflects the limited knowledge of the D(s) branching fractions.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Search for Production of Invisible Final States in Single-Photon Decays of Gamma(1S). Phys. Rev. Lett., 107(2), 021804–7pp.
Abstract: We search for single-photon decays of the Gamma(1S) resonance, Gamma -> gamma + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A(0), or a pair of dark matter particles, chi(chi) over bar. Both A(0) and chi are assumed to have zero spin. We tag Gamma(1S) decays with a dipion transition Gamma(1S) -> pi(+)pi(-)Y(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A0) <= 9.2 GeV and m(chi) <= 4.5 GeV in the sample of 98 x 10(6) Gamma(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2011). Observation of eta(c) (1S) and eta(c) (2S) decays to K(+)K(-) pi(+) pi(-) pi(0) in two-photon interactions. Phys. Rev. D, 84(1), 012004–9pp.
Abstract: We study the processes gamma gamma -> K(S)(0) K(-+) pi(-+) and gamma gamma -> K(+)K(-) pi(+)pi(-)pi(0) using a data sample of 519: 2fb(-1) recorded by the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies near the Y(nS) (n = 2, 3, 4) resonances. We observe the eta(c) (1S), chi(c0) (1P) and eta(c) (2S) resonances produced in two-photon interactions and decaying to K(+)K(-) pi(+)pi(-)pi(0), with significances of 18.1, 5.4 and 5.3 standard deviations (including systematic errors), respectively, and report 4.0 sigma evidence of the X(c2)(1P) decay to this final state. We measure the eta(c)(2S) mass and width in K(S)(0) K(+-) pi(+-) decays, and obtain the values m(eta(c)(2S)) = 3638: 5 +/- 1.5 +/- 0.8 MeV/c(2) and Gamma(eta(c)(2S)) = 13.4 +/- 4: 6 +/- 3.2 MeV, where the first uncertainty is statistical and the second is systematic. We measure the two-photon width times branching fraction for the reported resonance signals, and search for the X(c2) (2P) resonance, but no significant signal is observed.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Measurement of the gamma gamma* -> eta and gamma gamma* -> eta ' transition form factors. Phys. Rev. D, 84(5), 052001–19pp.
Abstract: We study the reactions e(+)e(-) --> e(+)e(-) eta((')) in the single-tag mode and measure the gamma gamma* --> eta((')) transition form factors in the momentum-transfer range from 4 to 40 GeV(2). The analysis is based on 469 fb(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Measurement of CP observables in B-+/- -> DCPK +/- decays and constraints on the CKM angle gamma. Phys. Rev. D, 82(7), 072004–20pp.
Abstract: Using the entire sample of 467 x 10(6) Y(4S) -> B (B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, we perform an analysis of B-+/- -> DK +/- decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A(CP+) = 0.25 +/- 0.06 +/- 0.02 and A(CP-) = 0.09 +/- 0.07 +/- 0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A(CP+) is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, RCP+ 1.18 +/- 0.09 +/- 0.05 and RCP- = 1.07 +/- 0.08 +/- 0.04. We infer frequentist confidence intervals for the angle gamma of the unitarity triangle, for the strong phase difference delta(B), and for the amplitude ratio r(B), which are related to the B- -> DK- decay amplitude by r(B)e(i(delta B-gamma)) = A(B- -> (D) over bar K-0(-)) = A(B- -> (D) over bar K-0(-))/A(B- -> (DK-)-K-0). Including statistical and systematic uncertainties, we obtain 0: 24 < rB < 0: 45 ( 0: 06 < rB < 0: 51) and, modulo 180 degrees, 11.3 degrees < gamma < 22.7 degrees or 80.8 degrees < gamma < 99.2 degrees or 157.3 degrees < gamma < 168.7 degrees (7.0 degrees < gamma < 173.0 degrees) at the 68% ( 95%) confidence level.
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