143 research outputs found

    Production of D∗+(2010)D^{*+}(2010) mesons by high energy neutrinos from the Tevatron

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    Charged vector D∗+(2010)D^{*+}(2010) meson production is studied in a high energy neutrino bubble chamber experiment with mean neutrino energy of 141 GeV. The D∗+D^{*+} are produced in (5.6±1.8)%(5.6 \pm 1.8)\% of the neutrino charged current interactions, indicating a steep increase of cross section with energy. The mean fractional hadronic energy of the D∗+D^{*+} meson is 0.55±0.060.55 \pm 0.06

    A study of the link between cosmic rays and clouds with a cloud chamber at the CERN PS

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    Recent satellite data have revealed a surprising correlation between galactic cosmic ray (GCR) intensity and the fraction of the Earth covered by clouds. If this correlation were to be established by a causal mechanism, it could provide a crucial step in understanding the long-sought mechanism connecting solar and climate variability. The Earth's climate seems to be remarkably sensitive to solar activity, but variations of the Sun's electromagnetic radiation appear to be too small to account for the observed climate variability. However, since the GCR intensity is strongly modulated by the solar wind, a GCR-cloud link may provide a sufficient amplifying mechanism. Moreover if this connection were to be confirmed, it could have profound consequences for our understanding of the solar contributions to the current global warming. The CLOUD (Cosmics Leaving OUtdoor Droplets) project proposes to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical mechanism. CLOUD plans to perform detailed laboratory measurements in a particle beam at CERN, where all the parameters can be precisely controlled and measured. The beam will pass through an expansion cloud chamber and a reactor chamber where the atmosphere is to be duplicated by moist air charged with selected aerosols and trace condensable vapours. An array of external detectors and mass spectrometers is used to analyse the physical and chemical characteristics of the aerosols and trace gases during beam exposure. Where beam effects are found, the experiment will seek to evaluate their significance in the atmosphere by incorporating them into aerosol and cloud models.Recent satellite data have revealed a surprising correlation between galactic cosmic ray (GCR) intensity and the fraction of the Earth covered by clouds. If this correlation were to be established by a causal mechanism, it could provide a crucial step in understanding the long-sought mechanism connecting solar and climate variability. The Earth's climate seems to be remarkably sensitive to solar activity, but variations of the Sun's electromagnetic radiation appear to be too small to account for the observed climate variability. However, since the GCR intensity is strongly modulated by the solar wind, a GCR-cloud link may provide a sufficient amplifying mechanism. Moreover if this connection were to be confirmed, it could have profound consequences for our understanding of the solar contributions to the current global warming. The CLOUD (Cosmics Leaving OUtdoor Droplets) project proposes to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical mechanism. CLOUD plans to perform detailed laboratory measurements in a particle beam at CERN, where all the parameters can be precisely controlled and measured. The beam will pass through an expansion cloud chamber and a reactor chamber where the atmosphere is to be duplicated by moist air charged with selected aerosols and trace condensable vapours. An array of external detectors and mass spectrometers is used to analyse the physical and chemical characteristics of the aerosols and trace gases during beam exposure. Where beam effects are found, the experiment will seek to evaluate their significance in the atmosphere by incorporating them into aerosol and cloud models

    Physics with charm particles produced in neutrino interactions. A historical recollection

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    Results obtained in neutrino unteractions on charm particles are presented

    The optical system for the Big European Bubble Chamber

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    The optical system for the new giant bubble chamber, built for the European Organization for Nuclear Research (CERN), consists of four sets of fisheye windows, each equipped with a wide-angle lens which has an aperture angle of 108 degrees , while the fifth set has a periscope for visual observation of the chamber interior. Each of the fisheye sets is assembled from three hemispherical windows. The largest hemisphere is made from Schott BK7 glass and is exposed to the temperature of liquid hydrogen. The entire optical system has been operated successfully for the past 4 years. (13 refs)

    The bubble chamber and its contribution to particle physics

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    The Big European Bubble Chamber at CERN I

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    A detailed description of the CERN BEBC 35 (22 visible) m/sup 3/ bubble chamber, with a 3.5T (730 MJ) superconducting magnetic field system, is given. (9 refs)

    Nucléation dans les chambres à bulles

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