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 super(+) e super(?)arrowrightmu super(+)mu super(?)Z',Z'arrowrightmu super(+) mu? using 514fb super(?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 7x10 super(?4) are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.
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^{-}→γA^{'}; 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)_{μ} anomaly, as well as a broad range of parameters for the dark-sector models.
Based on the full BABAR data sample, we report improved measurements of the ratios R(D(*))=B(B̄→D(*)τ⁻ν¯τ)/B(B̄→D(*)ll¯ν¯l), where l is either e or μ. These ratios are sensitive to new physics ...contributions in the form of a charged Higgs boson. We measure R(D)=0.440±0.058±0.042 and R(D*)=0.332±0.024±0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.
Dark sectors charged under a new Abelian interaction have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon ...(A^{'}), connecting the dark sector to the standard model. We present a search for a dark photon in the reaction e^{+}e^{-}→γA^{'}, A^{'}→e^{+}e^{-}, μ^{+}μ^{-} using 514 fb^{-1} of data collected with the BABAR detector. We observe no statistically significant deviations from the standard model predictions, and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^{-4}-10^{-3} for dark photon masses in the range 0.02-10.2 GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon.
We study the processes γγ→KS0K±πℓ and γγ→K+K-π0 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 Υ(nS) (n=2, 3, 4) resonances. We observe ηc 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 Kπ 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/c2. In contrast, the amplitudes show very marked differences. The data require the presence of a new a0(1950) resonance with parameters m=1931±14±22 MeV/c2 and Γ=271±22±29 MeV.
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