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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Measurement of angular asymmetries in the decays B -> K*l(+) l(+). Phys. Rev. D, 93(5), 052015–16pp.
Abstract: We study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization F-L, as well as an observable P-2 derived from them, in the rare decays B -> K*l(+)l(-), where l(+)l(-) is either e(+)e(-) or mu(+)mu(-), using the full sample of 471 million B (B) over bar events collected at the Upsilon(4S) resonance with the BABAR, detector at the PEP-II e(+)e(-) collider. We separately fit and report results for the K*(0)(892)l(+)l(-) and K*(+)(892) l(+)l(-) final states, as well as their combination K*l(+)l(-), in five disjoint dilepton mass-squared bins. An angular analysis of B+ -> K*(+)l(+)l(-) decays is presented here for the first time.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Measurement of the neutral D meson mixing parameters in a time-dependent amplitude analysis of the D-0 -> pi(+)pi(-)pi(0) decay. Phys. Rev. D, 93(11), 112014–10pp.
Abstract: We perform the first measurement on the D-0 – (D) over bar (0) mixing parameters using a time-dependent amplitude analysis of the decay D-0 -> pi(+)pi(-)pi(0). The data were recorded with the BABAR detector at center-of-mass energies at and near the Upsilon(4S) resonance, and correspond to an integrated luminosity of approximately 468.1 fb(-1). The neutral D meson candidates are selected from D*(2010)(+) -> D-0 pi(+)(s) decays where the flavor at the production is identified by the charge of the low-momentum pion, pi(+)(s). The measured mixing parameters are x = (1.5 +/- 1.2 +/- 0.6)% and y = (0.2 +/- 0.9 +/- 0.5)%, where the quoted uncertainties are statistical and systematic, respectively.
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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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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Search for a muonic dark force at BABAR. Phys. Rev. D, 94(1), 011102–7pp.
Abstract: Many models of physics beyond the standard model predict the existence of new Abelian forces with new gauge bosons mediating interactions between “dark sectors” and the standard model. We report a search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e(+)e(-) -> mu(+)mu(-) Z', Z' -> mu(+)mu(-) using 514 fb(-1) of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212-10 GeV. Limits on the coupling parameter g' as low as 7 x 10(-4) are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Observation of (B)over-bar -> D-(*()) pi(+)pi(-)l(-)(nu)over-bar Decays in e(+)e(-) Collisions at the Upsilon(4S) Resonance. Phys. Rev. Lett., 116(4), 041801–7pp.
Abstract: We report on measurements of the decays of (B) over bar mesons into the semileptonic final states (B) over bar -> D-(*())pi(+)pi(-)l(-)(nu) over bar, where D-(*()) represents a D or D* meson and l(-) is an electron or a muon. These measurements are based on 471 x 10(6) B (B) over bar pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R-pi+pi-(()*()) = B((B) over bar -> D-(*())pi(+)pi(-)l(-)(nu) over bar /B (B) over bar -> D-(*())l(-)(nu) over bar) using events in which the second B meson is fully reconstructed. We find R pi+pi- = 0.067 +/- 0.010 +/- 0.008 and R pi+pi-* = 0.019 +/- 0.005 +/- 0.004, where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that (B) over bar -> D-(*())pi pi l (nu) over bar decays, where pi denotes either a pi(+/-) and pi(0) meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.
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