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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Time-integrated luminosity recorded by the BABAR detector at the PEP-II e(+)e(-) collider. Nucl. Instrum. Methods Phys. Res. A, 726, 203–213.
Abstract: We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e(+)e(-) collider at the Upsilon(4S), Upsilon(3S), and Upsilon(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e(+)e(-)-> e(+)e(-) and (for the Upsilon(4S) only) e(+)e(-)->mu(+)mu(-) candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e(+)e(-)-> e(+)e(-) and e(+)e(-)->mu(+)mu(-), the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the Upsilon(3S) and Upsilon(2S) resonances, an additional uncertainty arises due to Upsilon -> e(+)e(-)X background. For data collected off the Upsilon resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the Upsilon(4S), 0.58% (0.72%) for the Upsilon(3S), and 0.68% (0.88%) for the Upsilon(2S).
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BABAR Collaboration(Lees, J. P. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Search for Charged Lepton Flavor Violation in Narrow Gamma Decays. Phys. Rev. Lett., 104(15), 151802–7pp.
Abstract: Charged-lepton flavor-violating processes are unobservable in the standard model, but they are predicted to be enhanced in several extensions to the standard model, including supersymmetry and models with leptoquarks or compositeness. We present a search for such processes in a sample of 99 x 10(6)Gamma(2S) decays and 117 x 10(6)Gamma(3S) decays collected with the BABAR detector. We place upper limits on the branching fractions B(Gamma(nS) --> e(+/-)tau(-/+)) and B(Gamma(n(S) --> mu(+/-)tau(-/+)) (n = 2, 3) at the 10(-6) level and use these results to place lower limits of order 1 TeV on the mass scale of charged-lepton flavor-violating effective operators.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2011). Search for Hadronic Decays of a Light Higgs Boson in the Radiative Decay Gamma -> gamma A(0). Phys. Rev. Lett., 107(22), 221803–7pp.
Abstract: We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Gamma(2S) or Gamma(3S) meson, Gamma -> gamma A(0). The data have been recorded by the BABAR experiment at the Gamma(3S) and Gamma(2S) center-of-mass energies and include (121.3 +/- 1.2) x 10(6) Gamma(3S) and (98.3 +/- 0.9) x 10(6) Gamma(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Gamma(nS) -> gamma A(0))B(A(0) -> hadrons) (n = 2 or 3) that range from 1 x 10(-6) for an A(0) mass of 0: 3 GeV/c(2) to 8 x 10(-5) at 7 GeV/c(2).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Search for Low-Mass Dark-Sector Higgs Bosons. Phys. Rev. Lett., 108(21), 211801–7pp.
Abstract: Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb(-1) of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the standard model-dark-sector mixing angle and the dark-sector coupling constant.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Evidence for an Excess of (B)over-bar -> D-(*()) tau(-)(nu)over-bar(tau) Decays. Phys. Rev. Lett., 109(10), 101802–8pp.
Abstract: Based on the full BABAR data sample, we report improved measurements of the ratios R(D-(*())) = B((B) over bar -> D-(*()) tau(-)(nu) over bar (tau))/B((B) over bar -> D-(*()) l(l)(-)(nu) over bar (l), where l is either e or mu. 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 2.0 sigma and 2.7 sigma, respectively. Taken together, our results disagree with these expectations at the 3.4 sigma level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.
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