1,721,118 research outputs found
Study of the reaction e[superscript +]e[superscript -]→J/ψπ[superscript +]π[superscript -] via initial-state radiation at BABAR
No full textWe study the process e[superscript +]e[superscript -]→J/ψπ[superscript +]π[superscript -] 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 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 fb[superscript -1]. We investigate the J/ψπ[superscript +]π[superscript -] mass distribution in the region from 3.5 to 5.5 GeV/c[superscript 2]. Below 3.7 GeV/c[superscript 2] the ψ(2S) signal dominates, and above 4 GeV/c[superscript 2] there is a significant peak due to the Y(4260). A fit to the data in the range 3.74–5.50 GeV/c[superscript 2] yields a mass value 4245±5(stat)±4(syst) MeV/c[superscript 2] and a width value 114[subscript -15][superscript +16](stat)±7(syst) MeV for this state. We do not confirm the report from the Belle Collaboration of a broad structure at 4.01 GeV/c[superscript 2]. In addition, we investigate the π[superscript +]π[superscript -] system which results from Y(4260) decay.United States. Dept. of EnergyNational Science Foundation (U.S.
Search for lepton-number violating B[superscript +] → X[superscript −]ℓ[superscript +]ℓ[superscript ′+] decays
No full textWe report on a search for eleven lepton-number violating processes B[superscript +] → X[superscript −]ℓ[superscript +]ℓ[superscript '+] with X[superscript −] = K[superscript −], π[superscript −], ρ[superscript −], K[superscript *−], or D[superscript −] and ℓ[superscript +]/ℓ[superscript '+] = e[superscript +] or μ[superscript +], using a sample of 471±3 million B[¯ over B] events collected with the BABAR detector at the PEP-II e[superscript +]e[superscript −] collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range (1.5–26)×10[superscript −7].United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Observation of Time-Reversal Violation in the B[superscript 0] Meson System
No full textAlthough 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 (B[superscript 0] or B̅[superscript 0]), and J/ψK[subscript L][superscript 0] or cc̅ K[subscript S][superscript 0] final states (referred to as B+ or B-), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B̅[superscript 0]→B[subscript -] and B_→B̅[superscript 0], as a function of the time difference between the two B decays. Using 468×10[superscript 6] BB̅ pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS[subscript T]+=-1.37±0.14(stat)±0.06(syst) and ΔS[subscript T[superscript]]-=1.17±0.18(stat)±0.11(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
Search for b→u transitions in B±→[K∓π±π0]DK± decays
No full textWe present a study of the decays B[superscript ±]→DK[superscript ±] with D mesons reconstructed in the K[superscript +]π[superscript -]π[superscript 0] or K[superscript -]π[superscript +]π[superscript 0] final states, where D indicates a D[superscript 0] or a D̅[superscript 0] meson. Using a sample of 474×10[superscript 6] BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e[superscript +]e[superscript -] collider at SLAC, we measure the ratios R[superscript ±]≡Γ(B[superscript ±]→[K[superscript ∓]π[superscript ±π]0][subscript D]K[superscript ±])/Γ(B[superscript ±]→[K[superscript ±]π[superscript ∓]π[superscript 0]][subscript D]K[superscript ±]). We obtain R[superscript +]=(5[subscript -10][superscript +12](stat)-4[superscript +2](syst))×10[superscript -3] and R-=(12[subscript -10][[superscript +12](stat)[subscript -5][[superscript +3](syst))×10[superscript -3], from which we extract the upper limits at 90% probability: R[superscript +]<23×10[superscript -3] and R[superscript -]<29×10[superscript -3]. Using these measurements, we obtain an upper limit for the ratio r[subscript B] of the magnitudes of the b→u and b→c amplitudes r[subscript B]<0.13 at 90% probability.United States. Dept. of EnergyNational Science Foundation (U.S.)Natural Sciences and Engineering Research Council of Canada (NSERC)France. Commissariat à l'énergie atomiqueInstitut national de physique nucléaire et de physique des particulesGermany. Federal Ministry of Education and Research (BMBF)Deutsche Forschungsgemeinschaft (DFG)Istituto nazionale di fisica nucleare (INFN)Foundation for Fundamental Research on Matter (Netherlands)Research Council of NorwayMinistry of Education and Science of the Russian FederationSpain. Ministerio de Ciencia e Innovacio´n (MICINN)Science and Technology Facilities Council (Great Britain)Marie Curie International FellowshipAlfred P. Sloan Foundatio
Evidence for the Baryonic Decay [bar over B][superscript 0] → D[superscript 0]Λ[bar over Λ]
No full textEvidence is presented for the baryonic B meson decay [bar over B][superscript 0] → D[superscript 0]Λ[bar over Λ] based on a data sample of 471 × 10[superscript 6] B[bar over B] pairs collected with the BABAR detector at the PEP-II asymmetric e[superscript +]e[superscript −] collider located at the SLAC National Accelerator Laboratory. The branching fraction is determined to be B([bar over B][superscript 0] → D[superscript 0]Λ[bar over Λ]) = (9.8[+2.9 over −2.6] ± 1.9) × 10[superscript −6], corresponding to a significance of 3.4 standard deviations including additive systematic uncertainties. A search for the related baryonic B meson decay [bar over B][superscript 0] → D[superscript 0]Σ[superscript 0][bar over Λ] with Σ[superscript 0] → Λγ is performed and an upper limit B([bar over B][superscript 0] → D[superscript 0]Σ[superscript 0][bar over Λ] + [bar over B][superscript 0] → D[superscript 0]Λ[bar over Σ][superscript 0]) < 3.1 × 10[superscript −5] is determined at 90% confidence level.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Measurement of the γγ*→η and γγ*→η′ transition form factors
No full textWe study the reactions e[superscript +]e⁻-->e[superscript +]e⁻η(′) in the single-tag mode and measure the γγ*-->η(′) transition form factors in the momentum-transfer range from 4 to 40 GeV[superscript 2]. The analysis is based on 469 fb[superscript -1] of integrated luminosity collected at PEP-II with the BABAR detector at e[superscript ]e⁻ center-of-mass energies near 10.6 GeV.National Science Foundation (U.S.)United States. Dept. of EnergyAlfred P. Sloan Foundatio
Search for the Decay [bar over B][superscript 0] → Λ[+ over c][bar over p]p[bar over p]
No full textWe report a search for the decay [bar over B][superscript 0] → Λ[+ over c][bar over p]p[bar over p]. Using a data sample of 471 × 10[superscript 6] B[bar over B] pairs collected with the BABAR detector at the PEP-II2 storage ring at SLAC, we find no events and set an upper limit on the branching fraction B([bar over B][superscript 0] → Λ[+ over c][bar over p]p[bar over p]) × B(Λ[+ over c] → pK[superscript −]π[superscript +])/0.050 < 2.8 × 10[superscript −6] at 90% C.L., where we have normalized B(Λ[+ over c] → pK[superscript −]π[superscript +]) to the world average value.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
A prototype detector for directional measurement of the cosmogenic neutron flux
No full textThis paper describes a novel directional neutron detector. The low pressure time projection chamber uses a mix of helium and CF[subscript 4] gases. The detector reconstructs the energy and angular distribution of fast neutron recoils. This paper reports results of energy calibration using an α source and angular reconstruction studies using a collimated neutron source. The best performance is obtained with a 12.5% CF[subscript 4]–87.5% He gas mixture. At low energies the target for fast neutrons transitions is primarily helium, while at higher energies, the fluorine contributes as a target. The reconstruction efficiency is both energy and target dependent. For neutrons with energies less than 20 MeV, the reconstruction efficiency is ∼40% for fluorine recoils and ∼60% for helium recoils.National Science Foundation (U.S.)United States. Dept. of EnergyMassachusetts Institute of Technology (Lyons Fellowship)Massachusetts Institute of Technology. Institute for Soldier Nanotechnologie
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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