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Search for mixing-induced CP violation using partial reconstruction of B¯0→D*+Xℓ−ν¯ℓ and kaon tagging

  • Graugés Pous, Eugeni
  • BABAR Collaboration
We describe in detail a previously published measurement of C P violation in B 0 - ¯ B 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 0 → D * + ℓ − ¯ ν 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 C P violating asymmetry A C P = ( N ( B 0 B 0 ) − N ( ¯ B 0 ¯ B 0 ) ) / ( N ( B 0 B 0 ) + N ( ¯ B 0 ¯ B 0 ) ) = ( 0.06 ± 0.1 7 + 0.38 − 0.32 ) % corresponding to Δ C P = 1 − | q / p | = ( 0.29 ± 0.8 4 + 1.88 − 1.61 ) × 1 0 − 3 . This measurement is consistent and competitive with those obtained at the B factories with dilepton events.
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Tests of CPT symmetry in B0- B 0 mixing and in B0 →c c K0 decays

  • Graugés Pous, Eugeni
  • BABAR Collaboration
Using the eight time dependences e − Γ t ( 1 + C i cos Δ m t + S i sin Δ m t ) for the decays Υ ( 4 S ) → B 0 ¯ B 0 → f j f k , with the decay into a flavor-specific state f j = ℓ ± X before or after the decay into a C P eigenstate f k = c ¯ c K S , L , as measured by the BABAR experiment, we determine the three C P T -sensitive parameters Re ( z ) and Im ( z ) in B 0 − ¯ B 0 mixing and | ¯ A / A | in B 0 → c ¯ c K 0 decays. We find Im ( z ) = 0.010 ± 0.030 ± 0.013 , Re ( z ) = − 0.065 ± 0.028 ± 0.014 , and | ¯ A / A | = 0.999 ± 0.023 ± 0.017 , in agreement with C P T symmetry.
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Observation of inclusive D*+- production in the decay of Upsilon (1S)

  • Graugés Pous, Eugeni
  • Garra Ticó, Jordi
  • BABAR Collaboration
Bound states of heavy quarks provide a powerful testing ground for quantum chromodynamics (QCD). Experimental studies of charmonium and bottomonium spectroscopy have helped uncover some of the key aspects of the quarkonium potential. Studies of the decays of quarkonia and of their decay products can also reveal important information on QCD processes. The hadronic decays of the narrow quarkonia, states which are below the threshold for open flavor production, are dominated by couplings to gluons and the fragmentation process into light hadrons. The decay properties of charmonia, which have a relatively low multiplicity particle content, have been extensively studied. However, little is known about the final state contents of bottomonia. In particular, scarcely any experimental information exists on the decays of bottomonium to open charm. The CLEO Collaboration has observed charm production in the decays of the b states with branching fractions of the order of 10%. The ARGUS Collaboration searched for the decay Y(1S) -- D+-X and set a limit on its branching fraction of B < 1,9% at 90% confidence level.
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Measurement of the gamma gamma* --> eta_c transition form factor

  • Graugés Pous, Eugeni
  • Garra Ticó, Jordi
  • BABAR Collaboration
We study the reaction e+e- --> e+e- eta_c, eta_c --> K_S K+- pi-+ and obtain eta_c mass and width values 2982.2+-0.4+-1.6 MeV/c^2 and 31.7+-1.2+-0.8 MeV, respectively. We find Gamma(eta_c --> gamma gamma)B(eta_c --> K anti-K pi)=0.374+-0.009+-0.031 keV, and measure the gamma gamma* --> eta_c transition form factor in the momentum transfer range from 2 to 50 GeV^2. The analysis is based on 469 fb-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV.
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A Measurement of the Semileptonic Branching Fraction of the B_s Meson

  • Graugés Pous, Eugeni
  • Garra Ticó, Jordi
  • BABAR Collaboration
We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BaBar detector in the center-of-mass (CM) energy region above the Upsilon (4S) resonance. We use the inclusive yield of phi mesons and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of CM energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s to l nu X)=9.5 (+2.5/-2.0)(stat)(+1.1/-1.9)(syst)%, where l indicates the average of e and mu.
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Search for f_J(2220) in radiative J/psi decays

  • Graugés Pous, Eugeni
  • Garra Ticó, Jordi
  • BABAR Collaboration
We present a search for fJ(2220) production in radiative J/ψ→γfJ(2220) decays using 460fb-1 of data collected with the BABAR detector at the SLAC PEP-II e+e- collider. The fJ(2220) is searched for in the decays to K+K- and KS0KS0. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/ψ→γfJ(2220) and fJ(2220)→K+K-(KS0KS0) as a function of spin and helicity are set at the level of 10-5, below the central values reported by the Mark III experiment.
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Search for the Rare Decay B->K nu nubar

  • Garra Ticó, Jordi
  • Graugés Pous, Eugeni
  • BABAR Collaboration
We present a search for the rare decays B+ -> K+ nu nubar and B0 -> K0 nu nubar using 459 million BBbar pairs collected with the BaBar detector at the SLAC National Accelerator Laboratory. Flavor-changing neutral-current decays such as these are forbidden at tree level but can occur through one-loop diagrams in the Standard Model (SM), with possible contributions from new physics at the same order. The presence of two neutrinos in the final state makes identification of signal events challenging, so reconstruction in the semileptonic decay channels B -> D(*) l nu of the B meson recoiling from the signal B is used to suppress backgrounds. We set an upper limit at the 90% confidence level of 1.3 x 10^{-5} on the total branching fraction for B+ -> K+ nu nubar, and 5.6 x 10^{-5} for B0 -> K0 nu nubar. We additionally report partial branching fractions in two ranges of di-neutrino mass squared for B+ -> K+ nu nubar.
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Observation of new resonances decaying to Dπ and D∗π in inclusive e+e− collisions near sqrt{s}= 10.58 GeV

  • Garra Ticó, Jordi
  • Graugés Pous, Eugeni
  • BABAR Collaboration
We present a study of the D+π−, D0π+, and D∗+π− systems in inclusive e+e−→cc¯ interactions in a search for new excited D meson states. We use a dataset, consisting of ∼454 fb−1, collected at center-of-mass energies near 10.58 GeV by the BABAR detector at the SLAC PEP-II asymmetric-energy collider. We observe, for the first time, candidates for the radial excitations of the D0, D∗0, and D∗+, as well as the L=2 excited states of the D0 and D+, where L is the orbital angular momentum of the quarks.
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Test of lepton universality in Upsilon(1S) decays at BaBar

  • Garra Ticó, Jordi
  • Graugés Pous, Eugeni
  • BABAR Collaboration
The ratio Rtau mu(Υ(1S))=ΓΥ(1S)-->tau+tau-/GammaΥ(1S)-->mu+mu- is measured using a sample of (121.8±1.2)×10[superscript 6]Υ(3S) events recorded by the BABAR detector. This measurement is intended as a test of lepton universality and as a search for a possible light pseudoscalar Higgs boson. In the standard model (SM) this ratio is expected to be close to 1. Any significant deviations would violate lepton universality and could be introduced by the coupling to a light pseudoscalar Higgs boson. The analysis studies the decays Υ(3S)-->Υ(1S)pi+pi-, Υ(1S)→l+l-, where l=mu, tau. The result, Rtau mu(Υ(1S))=1.005±0.013(stat)±0.022(syst), shows no deviation from the expected SM value, while improving the precision with respect to previous measurements.
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Searches for lepton flavor violation in the decays tau+- --> e+- gamma and tau+- --> mu+- gamma

  • Garra Ticó, Jordi
  • Graugés Pous, Eugeni
  • BABAR Collaboration
Searches for lepton flavor violating decay of a tau lepton to a lighter mass lepton and a photon have been performed with the full dataset of (963 +- 7) x 10^6 tau decays collected by the BaBar detector near the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances. The searches yield no evidence of signals and we set upper limits on the branching fractions of BR(tau -> e gamma) < 3.3 x 10^-8 and BR(tau -> mu gamma) < 4.4 x 10^-8 at 90% confidence level.
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