We present a search for a neutral, long-lived particle L that is produced in e+ e- collisions and decays at a significant distance from the e+ e- interaction point into various flavor combinations of ...two oppositely charged tracks. The analysis uses an e+ e- data sample with a luminosity of 489.1 fb(-1) collected by the BABAR detector at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and just below the ϒ(4S). Fitting the two-track mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible two-body L decay modes as a function of the L mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction B(B→XsL), where Xs is a strange hadronic system.
We study the process $e^+e^-\to\psi(2S)\pi^{+}\pi^{-}$ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the \BaBar detector at ...center-of-mass energies at and near the $\Upsilon(\mathrm{nS})$ (n = 2, 3, 4) resonances and correspond to an integrated luminosity of 520$fb^{-}$. We investigate the $\psi(2S)\pi^{+}\pi^{-}$ mass distribution from 3.95 to 5.95 $GeV/c^{2}$, and measure the center-of-mass energy dependence of the associated $e^+e^-\to \psi(2S)\pi^{+}\pi^{-}$ cross section. The mass distribution exhibits evidence of two resonant structures. A fit to the $\psi(2S)\pi^{+}\pi^{-}$ mass distribution corresponding to the decay mode $\psi(2S)\to J/\psi \pi^{+}\pi^{-}$ yields a mass value of $4340 \pm16$ (stat) $\pm 9$ (syst) ${\mathrm {MeV/c^{2}}}and a width of $94 \pm 32$ (stat) $\pm 13$ (syst) MeV for the first resonance, and for the second a mass value of $4669 \pm 21$ (stat) $\pm 3$ (syst) ${\mathrm {MeV/c^{2}}}$ and a width of $104 \pm 48$ (stat) $\pm 10$ (syst) MeV. In addition, we show the $pi^{+}\pi^{-}$ mass distributions for these resonant regions.
We report on measurements of the decays of B¯ mesons into the semileptonic final states B¯→D^(*)π^(+)π^(-)ℓ^(-)ν¯, where D^(*) represents a D or D^(*) meson and ℓ^(-) is an electron or a muon. These ...measurements are based on 471×10^(6) BB ¯ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R_{π^{+}π^{-}}^{(*)}=B(Bover ¯→D^{(*)}π^{+}π^{-}ℓ^{-}νover ¯)/B(Bover ¯→D^{(*)}ℓ^{-}νover ¯) using events in which the second B meson is fully reconstructed. We find R_{π^{+}π^{-}}=0.067±0.010±0.008 and R_{π^{+}π^{-}}^{*}=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 Bover ¯→D^{(*)}ππℓ^{-}νover ¯ decays, where π denotes either a π^{±} and π^{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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