50,739 research outputs found

    Method and Apparatus for the Real-time Characterisation of Particles Suspended within a Fluid Medium.

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    This invention describes a method by which microparticles, typically in the size range from 0.3um to 100um, which are carried in a fluid suspension, may be rapidly detected and characterized. The method primarily relates to the measurement of atmospheric particles such as those in clouds or environmental aerosols, but it may be used to measure other forms of particulate suspension wherever the flow of suspension through a defined measurement space can be achieved. The method is based upon a rapid analysis of the spatial laser scattering profile (i.e., the complex manner in which individual particles scatter laser light) recorded from individual particles as they are carried in suspension through a measurement space. Using this method it is possible to differentiate various types of particles based on particle shape and structure, as manifest in characteristics of their individual spatial light scattering patterns. The sizes of spherical particles and the spherical equivalent sizes of non-spherical particles may also be determined, allowing size distribution for each particle type within the suspension to be determined. An implementation of the method for use in an aircraft mounted instrument is described

    Evidence for virtual Compton scattering from the proton

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    In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation

    Primakoff Physics for CERN COMPASS Hadron Beam: Hadron Polarizabilities, Hybrid Mesons, Chiral Anomaly, Meson Radiative Transitions

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    We describe a hadron physics program attainable with a partially instrumented CERN COMPASS spectrometer, involving tracking detectors and moderate-size ECAL2/HCAL2 calorimeters. COMPASS can realize a state-of-the-art hadron beam physics program based on hadron polarizability, hybrid mesons, chiral anomaly, and meson radiative transition studies. We review here the physics motivation for this hadron beam program. We describe the beam, detector, trigger requirements, and hardware/software requirements for this program. The triggers for all this physics can be implemented for simultaneous data taking. The program is based on using a hadron beam (positive/negative pion, kaon, proton) in COMPASS.Comment: Contribution to the Proceedings of the Charles U./JINR and International U. (Dubna) CERN COMPASS Summer School, Charles University, Prague, Czech Republic, August 1997, Eds. M. Chavleishvili and M. Finger Tel Aviv U. Preprint TAUP TAUP-2473-98. 26 pages, 11 figures, late

    Development of a bioaerosol single particle detector (BIO IN) for the fast ice nucleus chamber FINCH [Discussion paper]

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    In this work we present the setup and first tests of our new BIO IN detector. This detector is designed to classify atmospheric ice nuclei (IN) for their biological content. Biological material is identified via its auto-fluorescence (intrinsic fluorescence) after irradiation with UV radiation. Ice nuclei are key substances for precipitation development via the Bergeron–Findeisen process. The level of scientific knowledge regarding origin and climatology (temporal and spatial distribution) of IN is very low. Some biological material is known to be active as IN even at relatively high temperatures of up to –2°C (e.g. pseudomonas syringae bacteria). These biological IN could have a strong influence on the formation of clouds and precipitation. We have designed the new BIO IN sensor to analyze the abundance of IN of biological origin. The instrument will be flown on one of the first missions of the new German research aircraft ''HALO'' (High Altitude and LOng Range)

    Pion and Kaon Polarizabilities at CERN COMPASS

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    The electric alpha and magnetic beta pion Compton polarizabilities characterize the pion's deformation in the electromagnetic field of the gamma during gamma-pi Compton scattering. The pion polarizabilities are key observables, and provide stringent tests of our understanding of chiral symmetry, its spontaneous breakdown, the role of explicit symmetry breaking in QCD. The chi_PT effective Lagrangian, using data from radiative pion beta decay, predicts the pion electric and magnetic polarizabilities alpha = -beta = 2.7 +- 0.4, in standard polarizability units. The polarizabilities deduced by Antipov et al. in their low statistics Primakoff experiment (~ 7000 events) were about three times larger than this prediction. For pion polarizability, gamma-pi scattering will be measured in CERN COMPASS via radiative pion Primakoff scattering (pion Bremsstrahlung) in the nuclear Coulomb field: pi + Z --> pi' + gamma + Z; equivalent to gamma + pi --> gamma + pi Compton scattering for laboratory gamma's of order 1 GeV incident on a target pion at rest. The pion polarizabilities are determined by their effect on the shape of the measured gamma-pi Compton scattering angular distribution. One can expect from COMPASS a total measurement uncertainty for alpha of order 0.4 for the pion polarizability. COMPASS can also carry out a first measurement of Kaon ploarizabilities. New high precision pion and Kaon polarizability measurements via radiative pion and Kaon scattering data from COMPASS will provide important new tests of the QCD chiral dynamics polarizability prediction.Comment: Contribution to Advanced Study Institute, "Symmetries and Spin" - Praha-SPIN-2002, Workshop Chairman, M. Finger, http://mfinger.home.cern.ch/mfinger/praha2002/ Prague, Czech Republic, July 2002, 15 pages, 9 figure
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