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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. (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), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Production of charged pions, kaons, and protons in e(+)e(-) annihilations into hadrons at root s=10.54 GeV. Phys. Rev. D, 88(3), 032011–26pp.
Abstract: Inclusive production cross sections of pi(+/-), K-+/- and p/(p) over bar per hadronic e(+)e(-) annihilation event are measured at a center-of-mass energy of 10.54 GeV, using a relatively small sample of very high quality data from the BABAR experiment at the PEP-II B-factory at the SLAC National Accelerator Laboratory. The drift chamber and Cherenkov detector provide clean samples of identified pi(+/-), K-+/-, and p/(p) over bar over a wide range of momenta. Since the center-of-mass energy is below the threshold to produce a B (B) over bar pair, with B a bottom-quark meson, these data represent a pure e(+)e(-) -> q (q) over bar sample with four quark flavors, and are used to test QCD predictions and hadronization models. Combined with measurements at other energies, in particular at the Z(0) resonance, they also provide precise constraints on the scaling properties of the hadronization process over a wide energy range.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Search for the rare decays B -> pi l(+)l(-) and B-0 -> eta l(+)l(-). Phys. Rev. D, 88(3), 032012–16pp.
Abstract: We present the results of a search for the rare flavor-changing neutral-current decays B -> pi l(+)l(-) (pi = pi(+), pi(0) and l = e, mu) and B-0 -> eta l(+)l(-) using a sample of e(+)e(-) -> Upsilon(4S) -> B (B) over bar decays corresponding to 428 fb(-1) of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of B(B -> pi l(+)l(-)) < 5.9 x 10(-8) and a lepton-flavor averaged upper limit of B(B-0 -> eta l(+)l(-)) < 6.4 x 10(-8), both at the 90% confidence level. We also report 90% confidence level branching fraction upper limits for the individual modes B+ -> pi(+)e(+)e(-), B-0 -> pi(0)e(+)e(-), B-0 -> pi(+)mu(+)mu(-), B-0 -> pi(+)mu(+)mu(-), B-0 -> pi(0)mu(+)mu(-), B-0 -> eta e(+)e(-), and B-0 ->eta mu(+)mu(-).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Precision measurement of the e(+)e(-) -> K+K-(gamma) cross section with the initial-state radiation method at BABAR. Phys. Rev. D, 88(3), 032013–28pp.
Abstract: A precise measurement of the cross section for the process e(+)e(-) -> K+K-(gamma) from threshold to an energy of 5 GeV is obtained with the initial-state radiation (ISR) method using 232 fb(-1) of data collected with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV. The measurement uses the effective ISR luminosity determined from the e(+)e(-) -> mu(+)mu(-)(gamma)gamma(ISR) process with the same data set. The corresponding lowest-order contribution to the hadronic vacuum polarization term in the muon magnetic anomaly is found to be a(mu)(KK,LO) = (22.93 +/- 0.18(stat) +/- 0.22(syst)) x 10(-10). The charged kaon form factor is extracted and compared to previous results. Its magnitude at large energy significantly exceeds the asymptotic QCD prediction, while the measured slope is consistent with the prediction.
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