6,656 research outputs found

    Impact of Saturn's rings on mission analysis for MJS 77

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    Mariner Jupiter-Saturn '77 mission objectives for Saturn are considered which affect the trajectory design and in particular the aim point at Saturn. These objectives include the following: (1) earth, sun occulation of Saturn, rings, and satellites; (2) close as possible to surface; (3) close as possible to rings; (4) close encounter with Titan (approximately 20,000 km); (5) close encounter with lapetus; (6) multiple satellite encounters; (7) post-Saturn trajectory to Uranus; and (8) post-Saturn trajectory toward solar apex

    First πK\pi K atom lifetime and πK\pi K scattering length measurements

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    The results of a search for hydrogen-like atoms consisting of πK±\pi^{\mp}K^{\pm} mesons are presented. Evidence for πK\pi K atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic πK\pi K pairs from their breakup in the same target (178±49178 \pm 49) and from Coulomb final state interaction (653±42653 \pm 42). Using these results the analysis yields a first value for the πK\pi K atom lifetime of τ=(2.51.8+3.0)\tau=(2.5_{-1.8}^{+3.0}) fs and a first model-independent measurement of the S-wave isospin-odd πK\pi K scattering length a0=13a1/2a3/2=(0.110.04+0.09)Mπ1\left|a_0^-\right|=\frac{1}{3}\left|a_{1/2}-a_{3/2}\right|= \left(0.11_{-0.04}^{+0.09} \right)M_{\pi}^{-1} (aIa_I for isospin II).Comment: 14 pages, 8 figure

    First Measurement of pi e -> pi e gamma Pion Virtual Compton Scattering

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    Pion Virtual Compton Scattering (VCS) via the reaction pi e --> pi e gamma was observed in the Fermilab E781 SELEX experiment. SELEX used a 600 GeV/c pi- beam incident on target atomic electrons, detecting the incident pi- and the final state pi-, electron and gamma. Theoretical predictions based on chiral perturbation theory are incorporated into a Monte Carlo simulation of the experiment and are compared to the data. The number of reconstructed events (9) and their distribution with respect to the kinematic variables (for the kinematic region studied) are in reasonable accord with the predictions. The corresponding pi- VCS experimental cross section is sigma=38.8+-13 nb, in agreement with the theoretical expectation sigma=34.7 nb.Comment: 10 pages, 12 figures, 4 tables, 25 references, SELEX home page is http://fn781a.fnal.gov/, revised July 21, 2002 in response to journal referee Comment

    First Observation of the Doubly Charmed Baryon Xi_cc^+

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    We observe a signal for the doubly charmed baryon Xi_cc^+ in the charged decay mode Xi_cc^+ --> Lambda_c^+ K- pi+ in data from SELEX, the charm hadro-production experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1 +/- 0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is (3519 +/- 1) MeV/c^2. The Gaussian mass width of this state is 3MeV/c^2, consistent with resolution; its lifetime is less than 33fsec at 90% confidence.Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letter

    First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+

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    We report the first observation of a charm-strange meson DsJ(2632) at a mass of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9 MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2 at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta) is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the Ds eta decay mode.Comment: 5 pages, 3 included eps figures. v2 as accepted for publication by PR

    Observation of the Cabibbo-suppressed decay Xi_c+ -> p K- pi+

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    We report the first observation of the Cabibbo-suppressed charm baryon decay Xi_c+ -> p K- pi+. We observe 150 +- 22 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Sigma- beam. The branching fractions of the decay relative to the Cabibbo-favored Xi_c+ -> Sigma+ K- pi+ and Xi_c+ -> X- pi+ pi+ are measured to be B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> Sigma+ K- pi+) = 0.22 +- 0.06 +- 0.03 and B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> X- pi+ pi+) = 0.20 +- 0.04 +- 0.02, respectively.Comment: 5 pages, RevTeX, 3 figures (postscript), Submitted to Phys. Rev. Let

    Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere

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    The dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy

    Measurement of Charged Pion Production Yields off the NuMI Target

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    The fixed-target MIPP experiment, Fermilab E907, was designed to measure the production of hadrons from the collisions of hadrons of momenta ranging from 5 to 120 GeV/c on a variety of nuclei. These data will generally improve the simulation of particle detectors and predictions of particle beam fluxes at accelerators. The spectrometer momentum resolution is between 3 and 4%, and particle identification is performed for particles ranging between 0.3 and 80 GeV/c using dE/dxdE/dx, time-of-flight and Cherenkov radiation measurements. MIPP collected 1.42×1061.42 \times10^6 events of 120 GeV Main Injector protons striking a target used in the NuMI facility at Fermilab. The data have been analyzed and we present here charged pion yields per proton-on-target determined in bins of longitudinal and transverse momentum between 0.5 and 80 GeV/c, with combined statistical and systematic relative uncertainties between 5 and 10%.Comment: 15 pages, 13 figure

    Determination of ππ\pi\pi scattering lengths from measurement of π+π\pi^+\pi^- atom lifetime

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    The DIRAC experiment at CERN has achieved a sizeable production of π+π\pi^+\pi^- atoms and has significantly improved the precision on its lifetime determination. From a sample of 21227 atomic pairs, a 4% measurement of the S-wave ππ\pi\pi scattering length difference a0a2=(.0.25330.0078+0.0080stat.0.0073+0.0078syst)Mπ+1|a_0-a_2| = (.0.2533^{+0.0080}_{-0.0078}|_\mathrm{stat}.{}^{+0.0078}_{-0.0073}|_\mathrm{syst})M_{\pi^+}^{-1} has been attained, providing an important test of Chiral Perturbation Theory.Comment: 6 pages, 6 figure
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