2,580 research outputs found

    CP-mixing and New Physics in the h→ZZ∗→4ℓ channel in ATLAS

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    The first analysis on the Higgs spin-parity favors the Standard Model hypothesis JP = 0+ against every other hypothesis tested. Hence it is interesting to study carefully the most general decay amplitude of the spin-0 hypothesis, searching for New Physics and CP-mixing effects in the Higgs sector. In this section is presented the ATLAS experiment sensitivity to non-Standard Model contributions in the hZZ vertex estimated for 300 fb−1 and 3000 fb−1 of LHC data at √s = 14TeV and the results rescaled to the statistics collected during the RUN1 at LHC

    A glass spark counter for high rate environments

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    The performance of a glass spark counter prototype, built with glass electrodes of about 1010 Ω cm volume resistivity, is described. The measure

    Genotoxicity testing for radon exposure: Dolichopoda (Orthoptera, Rhaphidophoridae) as potential bio-indicator of confined environments

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    Abstract Radon represents the major source of natural radioactivity in confined environments. Despite the clear evidence of a direct association between residential exposure and human lung cancer provided by case-control studies, results relating indoor exposure and genotoxic/mutagenic effect induction are still contradictory. The present study attempts to estimate the genotoxic effects induced by exposure to radioactive radon in wild cricket populations sampled from caves where varying concentrations of radon are present. Cave crickets are also tested as possible bio-indicator organisms of genotoxic potential of contaminated residential and confined environments. Six caves in Central Italy are considered covering a broad spectrum of radon radioactivity concentration (221–26, 000 Bq/m3). Dolichopoda specimens were sampled from each cave; both haemocytes and brain cells taken from individuals were tested for responsiveness to DNA damage induced by radon through the Comet assay. Specimens from the least radioactive cave, housed in controlled conditions for 60 days before analysis, were used as control group. Statistically significant increase of DNA damage was found in all groups of individuals from each cave, for both cell types. Very low values of all Comet parameters were found in control group individuals, which gave indications of a good responsiveness of the organism to the variable environmental levels of radioactive contamination. Results indicate that cave crickets represent a reliable tool for the detection of genotoxic potential induced by radioactive contamination of confined environments and can be proposed as a possible bio-indicator system for air (-radioactive) pollution related to indoor exposure

    The EEE Project

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    The new experiment ``Extreme Energy Events'' (EEE) to detect extensive air showers through muon detection is starting in Italy. The use of particle detectors based on Multigap Resistive Plate Chambers (MRPC) will allow to determine with a very high accuracy the direction of the axis of cosmic ray showers initiated by primaries of ultra-high energy, together with a high temporal resolution. The installation of many of such 'telescopes' in numerous High Schools scattered all over the Italian territory will also allow to investigate coincidences between multiple primaries producing distant showers. Here we present the experimental apparatus and its tasks.Comment: 4 pages, 29th ICRC 2005, Pune, Indi

    The OPERA magnetic spectrometer

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    The OPERA neutrino oscillation experiment foresees the construction of two magnetized iron spectrometers located after the lead-nuclear emulsion targets. The magnet is made up of two vertical walls of rectangular cross section connected by return yokes. The particle trajectories are measured by high precision drift tubes located before and after the arms of the magnet. Moreover, the magnet steel is instrumented with Resistive Plate Chambers that ease pattern recognition and allow a calorimetric measurement of the hadronic showers. In this paper we review the construction of the spectrometers. In particular, we describe the results obtained from the magnet and RPC prototypes and the installation of the final apparatus at the Gran Sasso laboratories. We discuss the mechanical and magnetic properties of the steel and the techniques employed to calibrate the field in the bulk of the magnet. Moreover, results of the tests and issues concerning the mass production of the Resistive Plate Chambers are reported. Finally, the expected physics performance of the detector is described; estimates rely on numerical simulations and the outcome of the tests described above.Comment: 6 pages, 10 figures, presented at the 2003 IEEE-NSS conference, Portland, OR, USA, October 20-24, 200

    First Measurement of the He3+He3-->He4+2p Cross Section down to the Lower Edge of the Solar Gamow Peak

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    We give the LUNA results on the cross section measurement of a key reaction of the proton-proton chain strongly affecting the calculated neutrino luminosity from the Sun: He3+He3-->He4+2p. Due to the cosmic ray suppression provided by the Gran Sasso underground laboratory it has been possible to measure the cross section down to the lower edge of the solar Gamow peak, i.e. as low as 16.5 keV centre of mass energy. The data clearly show the cross section increase due to the electron screening effect but they do not exhibit any evidence for a narrow resonance suggested to explain the observed solar neutrino flux.Comment: 5 pages, RevTeX, and 2 figures in PostScript Submitted for publicatio

    Impact of a revised 25^{25}Mg(p,Îł\gamma)26^{26}Al reaction rate on the operation of the Mg-Al cycle

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    Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the 25^{25}Mg(p,γ\gamma)26^{26}Al reaction affect the production of radioactive 26^{26}Algs^{gs} as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at LUNA, we provide revised rates of the 25^{25}Mg(p,γ\gamma)26^{26}Algs^{gs} and the 25^{25}Mg(p,γ\gamma)26^{26}Alm^{m} reactions with corresponding uncertainties. In the temperature range 50 to 150 MK, the new recommended rate of the 26^{26}Alm^{m} production is up to 5 times higher than previously assumed. In addition, at T=100=100 MK, the revised total reaction rate is a factor of 2 higher. Note that this is the range of temperature at which the Mg-Al cycle operates in an H-burning zone. The effects of this revision are discussed. Due to the significantly larger 25^{25}Mg(p,γ\gamma)26^{26}Alm^{m} rate, the estimated production of 26^{26}Algs^{gs} in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic 26^{26}Al budget. Similarly, we show that the AGB extra-mixing scenario does not appear able to explain the most extreme values of 26^{26}Al/27^{27}Al, i.e. >10−2>10^{-2}, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of a self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in Globular-Cluster stars

    22Ne and 23Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for 22Ne(p,gamma)23Na

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    We investigate the impact of the new LUNA rate for the nuclear reaction 22^{22}Ne(p,γ)23(p,\gamma)^{23}Na on the chemical ejecta of intermediate-mass stars, with particular focus on the thermally-pulsing asymptotic giant branch (TP-AGB) stars that experience hot-bottom burning. To this aim we use the PARSEC and COLIBRI codes to compute the complete evolution, from the pre-main sequence up to the termination of the TP-AGB phase, of a set of stellar models with initial masses in the range 3.0 M⊙−6.0 M⊙3.0\,M_{\odot} - 6.0\,M_{\odot}, and metallicities Zi=0.0005Z_{\rm i}=0.0005, Zi=0.006Z_{\rm i}=0.006, and Zi=0.014Z_{\rm i} = 0.014. We find that the new LUNA measures have much reduced the nuclear uncertainties of the 22^{22}Ne and 23^{23}Na AGB ejecta, which drop from factors of ≃10\simeq 10 to only a factor of few for the lowest metallicity models. Relying on the most recent estimations for the destruction rate of 23^{23}Na, the uncertainties that still affect the 22^{22}Ne and 23^{23}Na AGB ejecta are mainly dominated by evolutionary aspects (efficiency of mass-loss, third dredge-up, convection). Finally, we discuss how the LUNA results impact on the hypothesis that invokes massive AGB stars as the main agents of the observed O-Na anti-correlation in Galactic globular clusters. We derive quantitative indications on the efficiencies of key physical processes (mass loss, third dredge-up, sodium destruction) in order to simultaneously reproduce both the Na-rich, O-poor extreme of the anti-correlation, and the observational constraints on the CNO abundance. Results for the corresponding chemical ejecta are made publicly available