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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Measurement of B (B -> Xs gamma), the B -> Xs gamma photon energy spectrum, and the direct CP asymmetry in B -> Xs+d gamma decays. Phys. Rev. D, 86(11), 112008–33pp.
Abstract: The photon spectrum in B -> X-s gamma decay, where X-s is any strange hadronic state, is studied using a data sample of (382.8 +/- 4.2) x 10(6) e(+)e(-) -> Upsilon(4S) -> B (B) over bar events collected by the BABAR experiment at the PEP-II collider. The spectrum is used to measure the branching fraction B(B -> X-s gamma) (3.21 +/- 0.15 +/- 0.29 +/- 0.08) x 10(-4) and the first, second, and third moments < E-gamma > = 2.267 +/- 0.019 +/- 0.032 +/- 0.003 GeV, <(E-gamma – < E-gamma >)(2)> = 0.0484 +/- 0.0053 +/- 0.0077 +/- 0.0005 GeV2, and <(E-gamma – < E-gamma)(3)> = -0.0048 +/- 0.0011 +/- 0.0011 +/- 0.0004 GeV3, for the range E-gamma > 1.8 GeV, where E-gamma is the photon energy in the B-meson rest frame. Results are also presented for narrower E-gamma ranges. In addition, the direct CP asymmetry A(CP)(B -> Xs+d gamma) is measured to be 0.057 +/- 0.063. The spectrum itself is also unfolded to the B-meson rest frame; that is the frame in which theoretical predictions for its shape are made.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2013). Branching fraction measurement of B+ -> omega l(+)nu decays. Phys. Rev. D, 87(3), 032004–11pp.
Abstract: We present a measurement of the B+ -> omega l(+)nu branching fraction based on a sample of 467 million B (B) over bar pairs recorded by the BABAR detector at the SLAC PEP-II e(+)e(-) collider. We observe 1125 +/- 131 signal decays, corresponding to a branching fraction of B(B+ -> omega l(+)nu) = (1.21 +/- 0.14 +/- 0.08) x 10(-4), where the first error is statistical and the second is systematic. The dependence of the decay rate on q(2), the invariant mass squared of the leptons, is compared to QCD predictions of the form factors based on a quark model and light-cone sum rules.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2013). Evidence of B+ -> tau(+)nu decays with hadronic B tags. Phys. Rev. D, 88(3), 031102–9pp.
Abstract: We present a search for the decay B+ -> tau(+)nu using 467.8 x 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with one completely reconstructed B- in the hadronic decay mode (B- -> D-(*X-)0(-) and B- -> J/psi X-). We examine the rest of the event to search for a B+ -> tau(+)nu decay. We identify the tau(+) lepton in the following modes: tau(+) -> e(+)nu(nu) over bar, tau(+) -> mu(+)nu(nu) over bar, tau(+) -> pi(+)(nu) over bar and tau(+) -> rho(+)(nu) over bar. We find an excess of events with respect to the expected background, which excludes the null signal hypothesis at the level of 3.8 sigma (including systematic uncertainties) and corresponds to a branching fraction value of B(B+ -> tau(+)nu) = (1.83(-0.49)(+0.53)(stat) +/- 0.24(syst)) x 10(-4).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2014). Dalitz plot analysis of eta(c) -> K+K-eta and eta(c) -> K+K-pi(0) in two-photon interactions. Phys. Rev. D, 89(11), 112004–16pp.
Abstract: We study the processes gamma gamma -> K+K-eta and gamma gamma -> K+K-pi(0) using a data sample of 519 fb(-1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies at and near the Upsilon(nS) (n = 2, 3, 4) resonances. We observe eta(c) -> K+K-pi(0) and eta(c) -> K+K-eta decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K*(0)(1430) -> K eta decay and measure its branching fraction relative to the K pi decay mode to be R(K*(0)(1430)) = B(K*(0)(1430)-> K eta)/B(K*(0)(1430)-> K pi) = 0.092 +/- 0.025(- 0.025)(+0.010). The eta(c) -> K+K-eta and K*(0)(1430) -> K eta results correspond to the first observations of these channels. The data also show evidence for eta(c)(2S) -> K+K-pi(0) and first evidence for eta(c)(2S) -> K+K-eta.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Measurement of the I=1/2 K pi S-wave amplitude from Dalitz plot analyses of eta(c) -> K(K)over-bar pi in two-photon interactions. Phys. Rev. D, 93(1), 012005–16pp.
Abstract: We study the processes gamma gamma -> (KSK +/-)-K-0 pi(-/+) and gamma gamma -> K+K-pi(0) using a data sample of 519 fb(-1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies at and near the Upsilon(nS) (n = 2, 3, 4) resonances. We observe eta(c) decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I = 1/2 K pi S-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c(2). In contrast, the amplitudes show very marked differences. The data require the presence of a new a(0)(1950) resonance with parameters m = 1931 +/- 14 +/- 22 MeV/c(2) and Gamma = 271 +/- 22 +/- 29 MeV.
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