62 research outputs found
Track Finding Efficiency in BaBar
We describe several studies to measure the charged track reconstruction
efficiency and asymmetry of the BaBar detector. The first two studies measure
the tracking efficiency of a charged particle using and initial state
radiation decays. The third uses the decays to study the asymmetry in
tracking, the fourth measures the tracking efficiency for low momentum tracks,
and the last measures the reconstruction efficiency of particles. The
first section also examines the stability of the measurements vs BaBar running
periods.Comment: 20 pages, 30 figures, Submitted to Nuclear Instruments and Methods in
Physics Research
Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider
This article is the Preprint version of the final published artcile which can be accessed at the link below.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 Ï(4S), Ï(3S), and Ï(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-âe+e- and (for the Ï(4S) only) e+e-âÎŒ+ÎŒ- 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-âe+e- and e+e-âÎŒ+ÎŒ-, 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 Ï(3S) and Ï(2S) resonances, an additional uncertainty arises due to Ïâe+e-X background. For data collected off the Ï 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 Ï(4S), 0.58% (0.72%) for the Ï(3S), and 0.68% (0.88%) for the Ï(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat Ă lâEnergie Atomique and Institut National de Physique NuclĂ©aire et de Physiquedes Particules (France), the Bundesministerium fĂŒr Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e InnovaciĂłn (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)
Determination of the Form Factors for the Decay B0 --> D*-l+nu_l and of the CKM Matrix Element |Vcb|
We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element and of the parameters , , and , which fully characterize the form factors of the decay in the framework of HQET, based on a sample of about 52,800 decays recorded by the BABAR detector. The kinematical information of the fully reconstructed decay is used to extract the following values for the parameters (where the first errors are statistical and the second systematic): , , , . By combining these measurements with the previous BABAR measurements of the form factors which employs a different technique on a partial sample of the data, we improve the statistical accuracy of the measurement, obtaining: and Using the lattice calculations for the axial form factor , we extract , where the third error is due to the uncertainty in
Study of the Exclusive Initial-State Radiation Production of the System
A study of exclusive production of the system through initial-state r adiation is performed in a search for charmonium states, where or . The mesons are reconstructed in the , , and decay modes. The is reconstructed through the decay mode. The analysis makes use of an integrated luminosity of 288.5 fb collected by the BaBar experiment. The mass spectrum shows a clear signal. Further structures appear in the 3.9 and 4.1 GeV/ regions. No evidence is found for Y(4260) decays to , implying an up per limit \frac{\BR(Y(4260)\to D \bar D)}{\BR(Y(4260)\to J/\psi \pi^+ \pi^-)} < 7.6 (95 % confidence level)
Measurements of Branching Fractions, Polarizations, and Direct CP-Violation Asymmetries in BâÏKâ and Bâf0(980)Kâ Decays
We report searches for B -meson decays to the charmless final states Ï K â and f 0 ( 980 ) K â with a sample of 232 Ă 10 6 B ÂŻÂŻÂŻ B pairs collected with the BABAR detector at the PEP-II e + e â collider. We measure in units of 10 â 6 the following branching fractions, where the first error quoted is statistical and the second systematic, or upper limits are given at the 90% confidence level : B ( B + â Ï 0 K * + ) < 6.1 , B ( B + â Ï + K * 0 ) = 9.6 ± 1.7 ± 1.5 , B ( B 0 â Ï â K * + ) < 12.0 , B ( B 0 â Ï 0 K * 0 ) = 5.6 ± 0.9 ± 1.3 , B ( B + â f 0 ( 980 ) K * + ) = 5.2 ± 1.2 ± 0.5 , and B ( B 0 â f 0 ( 980 ) K * 0 ) < 4.3 . For the significant modes, we also measure the fraction of longitudinal polarization and the charge asymmetry: f L ( B + â Ï + K * 0 ) = 0.52 ± 0.10 ± 0.04 , f L ( B 0 â Ï 0 K * 0 ) = 0.57 ± 0.09 ± 0.08 , A C P ( B + â Ï + K * 0 ) = â 0.01 ± 0.16 ± 0.02 , A C P ( B 0 â Ï 0 K * 0 ) = 0.09 ± 0.19 ± 0.02 , and A C P ( B + â f 0 ( 980 ) K * + ) = â 0.34 ± 0.21 ± 0.03
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Variability of dayside high latitude convection associated with a sequence of auroral transients
10 second resolution ionospheric convection data covering the invariant latitude range from 71° to 76°, obtained by using the EISCAT UHF and VHF radars, are combined with optical data from Ny Ă
lesund during a sequence of auroral transients in the post-noon sector (⌠15 MLT). Satellite observations of polar cap convection patterns suggest negative BZ and BY components of the interplanetary magnetic field. Burst-like enhancements of westward (sunward) post-noon convection were accompanied by eastward moving auroral forms at higher latitudes, above the convection reversal boundary. In this case the background convection was weak, whereas the integrated potential drop across the radar field-of-view associated with the westward flow bursts was typically ⌠20-35 kV. The auroral phenomenon consists of a series of similar events with a mean repetition period of 8 min. A close correlation between the auroral activity and convection enhancements in the cleft ionosphere is demonstrated
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