1,721,006 research outputs found
Photon-axion oscillations and the transparency of the universe
No full textUniverse should be opaque to photons with energy TeV due scattering on the extragalactic background light during their propagation. However, a surprisingly high degree of transparency of the universe has been observed. In order to explain this fact, the conversion between photons and hypothetical axion-like particles in the turbulent extragalactic magnetic field has been invoked. We have derived new equations to calculate the mean survival probability of the photons. We have also found that the photon transfer functions on different lines of sight could have relevant deviations with respect to the mean value, producing both an enhancement or a suppression in the observable photon flux
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Probing supernova shock waves and neutrino flavor transitions in next-generation water-Cherenkov detectors
No full textSeveral current projects aim at building a large water Cherenkov detector, with a fiducial volume about 20 times larger than in the current Super-Kamiokande experiment. These projects include the Underground nucleon decay and Neutrino Observatory (UNO) in the Henderson Mine (Colorado), the Hyper-Kamiokande (HK) detector in the Tochibora Mine (Japan) and the MEgaton class PHYSics (MEMPHYS) detector at the Fréjus site (Europe). We study the physics potential of a reference next-generation detector (0.4 Mton of fiducial mass) in providing information on supernova neutrino flavour transitions with unprecedented statistics. After discussing the ingredients of our calculations, we compute neutrino event rates from inverse beta decay (\bar \nu_{\mathrm {e}} \mathrm {p\to e^+n} ), elastic scattering on electrons and scattering on oxygen, with emphasis on their time spectra, which may encode combined information on neutrino oscillation parameters and on supernova forward (and possibly reverse) shock waves. In particular, we show that an appropriate ratio of low to high energy events can faithfully monitor the time evolution of the neutrino crossing probability along the shock wave profile. We also discuss some background issues related to the detection of supernova relic neutrinos, with and without the addition of gadolinium
Damping of supernova neutrino transitions in stochastic shock-wave density profiles
No full textSupernova neutrino flavour transitions during shock-wave propagation are known to encode relevant information not only about the matter density profile but also about unknown neutrino properties, such as the mass hierarchy (normal or inverted) and the mixing angle θ13. While previous studies have focused on 'deterministic' density profiles, we investigate the effect of possible stochastic matter density fluctuations in the wake of supernova shock-waves. In particular, we study the impact of small-scale fluctuations on the electron (anti)neutrino survival probability, and on the observable spectra of inverse beta-decay events in future water–Cherenkov detectors. We find that such fluctuations, even with relatively small amplitudes, can have significant damping effects on the flavour transition pattern, and can partly erase the shock-wave imprint on the observable time spectra, especially for \sin^2 \theta_{13} \gtrsim {\mathcal O}(10^{-3})
Probing supernova shock waves and matter density fluctuations by neutrino flavor conversions
No full textAnalysis of energy- and time-dependence of supernova shock effects on neutrino crossing probabilities
No full textpreprint hep-ph/030405
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