5,002 research outputs found

    Measurement of the Inclusive Charm Cross Section at 4.03 GeV and 4.14 GeV

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    The cross section for charmed meson production at s=4.03\sqrt{s} = 4.03 and 4.14 GeV has been measured with the Beijing Spectrometer. The measurement was made using 22.3 pb‚ąí1pb^{-1} of e+e‚ąíe^+e^- data collected at 4.03 GeV and 1.5 pb‚ąí1pb^{-1} of e+e‚ąíe^+e^- data collected at 4.14 GeV. Inclusive observed cross sections for the production of charged and neutral D mesons and momentum spectra are presented. Observed cross sections were radiatively corrected to obtain tree level cross sections. Measurements of the total hadronic cross section are obtained from the charmed meson cross section and an extrapolation of results from below the charm threshold.Comment: 11 pages, 13 figures. The top level tex file is paper.tex. It builds the paper from other tex files in this .tar and the .eps file

    Evidence for the ő∑_b(1S) Meson in Radiative ő•(2S) Decay

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    We have performed a search for the ő∑_b(1S) meson in the radiative decay of the ő•(2S) resonance using a sample of 91.6 √ó 10^6 ő•(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_ő≥ = 609.3^(+4.6)_(-4.5)(stat)¬Ī1.9(syst) MeV, corresponding to an ő∑_b(1S) mass of 9394.2^(+4.8)_(-4.9)(stat) ¬Ī 2.0(syst) MeV/c^2. The branching fraction for the decay ő•(2S) ‚Üí ő≥ő∑_b(1S) is determined to be [3.9 ¬Ī 1.1(stat)^(+1.1)_(-0.9)(syst)] √ó 10^(-4). We find the ratio of branching fractions B[ő•(2S) ‚Üí ő≥ő∑_b(1S)]/B[ő•(3S) ‚Üí ő≥ő∑_b(1S)]= 0.82 ¬Ī 0.24(stat)^(+0.20)_(-0.19)(syst)

    Cross Sections for the Reactions e+e- --> K+ K- pi+pi-, K+ K- pi0pi0, and K+ K- K+ K- Measured Using Initial-State Radiation Events

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    We study the processes e+e- --> K+ K- pi+pi-gamma, K+ K- pi0pi0gamma, and K+ K- K+ K-gamma, where the photon is radiated from the initial state. About 84000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb-1 of BaBar data. The invariant mass of the hadronic final state defines the \epem center-of-mass energy, so that the K+ K- pi+pi- data can be compared with direct measurements of the e+e- --> K+ K- pi+pi- reaction. No direct measurements exist for the e+e- --> K+ K-pi0pi0 or e+e- --> K+ K-K+ K- reactions, and we present an update of our previous result with doubled statistics. Studying the structure of these events, we find contributions from a number of intermediate states, and extract their cross sections. In particular, we perform a more detailed study of the e+e- --> phi(1020)pipigamma reaction, and confirm the presence of the Y(2175) resonance in the phi(1020) f0(980) and K+K-f0(980) modes. In the charmonium region, we observe the J/psi in all three final states and in several intermediate states, as well as the psi(2S) in some modes, and measure the corresponding product of branching fraction and electron width.Comment: 35 pages, 42 figure

    Study of Upsilon(3S,2S) -> eta Upsilon(1S) and Upsilon(3S,2S) -> pi+pi- Upsilon(1S) hadronic trasitions

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    We study the Upsilon(3S,2S)->eta Upsilon(1S) and Upsilon(3S,2S)->pi+pi- Upsilon(1S) transitions with 122 million Upsilon(3S) and 100 million Upsilon(2S) mesons collected by the BaBar detector at the PEP-II asymmetric energy e+e- collider. We measure B[Upsilon(2S)->eta Upsilon(1S)]=(2.39+/-0.31(stat.)+/-0.14(syst.))10^-4 and Gamma[Upsilon(2S)->eta Upsilon(1S)]/Gamma[Upsilon(2S)-> pi+pi- Upsilon(1S)]=(1.35+/-0.17(stat.)+/-0.08(syst.))10^-3. We find no evidence for Upsilon(3S)->eta Upsilon(1S) and obtain B[Upsilon(3S)->eta Upsilon(1S)]<1.0 10^-4 and Gamma[Upsilon(3S)->eta Upsilon(1S)]/Gamma[Upsilon(3S)->pi+pi- Upsilon(1S)]<2.3 10^-3 as upper limits at the 90% confidence level. We also provide improved measurements of the Upsilon(2S) - Upsilon(1S) and Upsilon(3S) - Upsilon(1S) mass differences, 562.170+/-0.007(stat.)+/-0.088(syst.) MeV/c^2 and 893.813+/-0.015(stat.)+/-0.107(syst.) MeV/c^2 respectively.Comment: 8 pages, 16 encapsulated postscript figures, submitted to Phys.Rev.

    Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma

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    Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial and final state radiation. The asymmetry is determined as afunction of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e- --> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order FSR production is consistent with the QED expectation for e+ e- --> mu+ mu- gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.

    Measurement of the Branching Fraction for B- --> D0 K*-

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    We present a measurement of the branching fraction for the decay B- --> D0 K*- using a sample of approximately 86 million BBbar pairs collected by the BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the K*- through its decay to K0S pi-. We measure the branching fraction to be B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid Communications

    Observation of time-reversal violation in the B0 meson system

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    The individually named authors work collectively as The BABAR Collaboration. Copyright @ 2012 American Physical Society.Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B0 or B¬Į¬Į¬Į0), and J/ŌąK0L or cc¬ĮK0S final states (referred to as B+ or B‚ąí), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B¬Į¬Į¬Į0‚ÜíB‚ąí and B‚ąí‚ÜíB¬Į¬Į¬Į0, as a function of the time difference between the two B decays. Using 468√ó106 BB¬Į¬Į¬Į pairs produced in ő•(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding őĒS+T=‚ąí1.37¬Ī0.14(stat)¬Ī0.06(syst) and őĒS‚ąíT=1.17¬Ī0.18(stat)¬Ī0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG(Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MES (Russia), MINECO (Spain), STFC (United Kingdom). Individuals have received support from the Marie Curie EIF (European Union), the A. P. Sloan Foundation (USA) and the Binational Science Foundation (USA-Israel)

    Measurement of the quasi-elastic axial vector mass in neutrino-oxygen interactions