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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2017). Search for Invisible Decays of a Dark Photon Produced in e(+)e(-) Collisions at BABAR. Phys. Rev. Lett., 119(13), 131804–7pp.
Abstract: We search for single-photon events in 53 fb(-1) of e(+)e(-) collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A' through the process e(+)e(-) -> gamma A'; A' -> invisible. Such particles, referred to as “dark photons,” are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A' to e(+)e(-) in the mass range m(A') <= 8 GeV. In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g – 2)(mu) anomaly, as well as a broad range of parameters for the dark-sector models.
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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 mixing-induced CP violation using partial reconstruction of (B)over-bar(0) -> D*(+)Xl(-)(nu)over-bar(l) and kaon tagging. Phys. Rev. D, 93(3), 032001–13pp.
Abstract: We describe in detail a previously published measurement of CP violation in B-0-(B) over bar (0) oscillations, based on an integrated luminosity of 425.7 fb(-1) collected by the BABAR experiment at the PEPII collider. We apply a novel technique to a sample of about 6 million (B) over bar (0) -> D*(+)l(-)(nu) over bar (l) decays selected with partial reconstruction of the D*(+) meson. The charged lepton identifies the flavor of one B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine a CP violating asymmetry A(CP) = (N((BB0)-B-0) – N((B) over bar (0)(B) over bar (0)))/(N((BB0)-B-0) + N((B) over bar (0)(B) over bar (0))) = (0.06 +/- 0.17(-0.32)(+0.38))% corresponding to Delta(CP) = 1-vertical bar q/p vertical bar = (0.29 +/- 0.84(-1.61)(+1.88)) x 10(-3). This measurement is consistent and competitive with those obtained at the B factories with dilepton events.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Tests of CPT symmetry in B-0-(B)over-bar(0) mixing and in B-0 -> c(c)over-barK(0) decays. Phys. Rev. D, 94(1), 011101–7pp.
Abstract: Using the eight time dependences e(-Gamma t)(1+C(i)cos Delta mt+S(i)sin Delta mt) for the decays Upsilon (4S) -> B-0(B) over bar (0) -> f(j)f(k), with the decay into a flavor-specific state f(j) = l(+/-)X before or after the decay into a CP eigenstate f(k) = c (c) over barK(S,L), as measured by the BABAR experiment, we determine the three CPT-sensitive parameters Re(z) and Im(z) in B-0-(B) over bar (0) mixing and vertical bar(A) over bar /A vertical bar in B-0 -> c (c) over barK(0) decays. We find Im(z) = 0.010 +/- 0.030 +/- 0.013, Re(z) = -0.065 +/- 0.028 +/- 0.014, and vertical bar(A) over bar /A vertical bar = 0.999 +/- 0.023 +/- 0.017, in agreement with CPT symmetry.
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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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