606 research outputs found

    The Effective Δmee2\Delta m^2_{ee} in Matter

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    In this paper we generalize the concept of an effective Δmee2\Delta m^2_{ee} for νe/νˉe\nu_e/\bar{\nu}_e disappearance experiments, which has been extensively used by the short baseline reactor experiments, to include the effects of propagation through matter for longer baseline νe/νˉe\nu_e/\bar{\nu}_e disappearance experiments. This generalization is a trivial, linear combination of the neutrino mass squared eigenvalues in matter and thus is not a simple extension of the usually vacuum expression, although, as it must, it reduces to the correct expression in the vacuum limit. We also demonstrated that the effective Δmee2\Delta m^2_{ee} in matter is very useful conceptually and numerically for understanding the form of the neutrino mass squared eigenstates in matter and hence for calculating the matter oscillation probabilities. Finally we analytically estimate the precision of this two-flavor approach and numerically verify that it is precise at the sub-percent level.Comment: 9 pages, 6 figures, 1 table, comments welcom

    Sensitivity of full-sky experiments to large scale cosmic ray anisotropies

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    The two main advantages of space-based observation of extreme energy (5×1019\gtrsim5\times10^{19} eV) cosmic rays (EECRs) over ground based observatories are the increased field of view and the full-sky coverage with nearly uniform systematics across the entire sky. The former guarantees increased statistics, whereas the latter enables a clean partitioning of the sky into spherical harmonics. The discovery of anisotropies would help to identify the long sought origin of EECRs. We begin an investigation of the reach of a full-sky space-based experiment such as EUSO to detect anisotropies in the extreme-energy cosmic-ray sky compared to ground based partial-sky experiments such as the Pierre Auger Observatory and Telescope Array. The technique is explained here, and simulations for a Universe with just two nonzero multipoles, monopole plus either dipole or quadrupole, are presented. These simulations quantify the advantages of space-based, all-sky coverage.Comment: 11 pages, 8 figure

    Cosmogenic Neutrinos Through the GRAND Lens Unveil the Nature of Cosmic Accelerators

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    The sources of cosmic rays with energies above 55 EeV are still mysterious. A guaranteed associated flux of ultra high energy neutrinos known as the cosmogenic neutrino flux will be measured by next generation radio facilities, such as the proposed Giant Radio Array for Neutrino Detection (GRAND). By using the orthogonal information provided by the cosmogenic neutrino flux, we here determine the prospects of GRAND to constrain the source redshift evolution and the chemical composition of the cosmic ray sources. If the redshift evolution is known, independently on GRAND's energy resolution, GRAND with 200,000 antennas will constrain the proton/iron fraction to the 510%\sim5-10\% level after one year of data taking; on the other hand, if hints on the average source composition are given, GRAND will measure the redshift evolution of the sources to a 10%\sim 10\% uncertainty. However, the foreseen configuration of GRAND alone will not be able to break the degeneracy between redshift evolution of the sources and their composition. Our findings underline the discriminating potential of next generation radio array detectors and motivate further efforts in this direction.Comment: 18 pages, 6 figures, 1 table, comments welcome; clarifying comments added, matches published versio

    Activating the 4th Neutrino of the 3+1 Scheme

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    Non-Standard Interactions (NSI) of neutrinos with matter has received renewed interest in recent years. In particular, it has been shown that NSI can reconcile the 3+13+1 solution with IceCube atmospheric data with Eν>500E_\nu >500 GeV, provided that the effective coupling of NSI is large, e.g. 6GF\sim 6 G_F. The main goal of the present paper is to show that contrary to intuition, it is possible to build viable models with large NSI by invoking a new U(1)U(1) gauge symmetry with gauge boson of mass 10\sim 10 eV. We refer to these new constructions as 3+1+U(1)3+1+ U(1) models. In the framework of a 3+13+1 solution to LSND and MiniBooNE anomalies, we show that this novel NSI can help to solve the tension with cosmological bounds and constraints from IceCube atmospheric data with Eν>500E_\nu>500 GeV. We then discuss the implications of the MINOS and MINOS+ results for the 3+1+U(1)U(1) scenario.Comment: 24 pages, 5 figure

    The Galactic Contribution to IceCube's Astrophysical Neutrino Flux

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    High energy neutrinos have been detected by IceCube, but their origin remains a mystery. Determining the sources of this flux is a crucial first step towards multi-messenger studies. In this work we systematically compare two classes of sources with the data: Galactic and extragalactic. We assume that the neutrino sources are distributed according to a class of Galactic models. We build a likelihood function on an event by event basis including energy, event topology, absorption, and direction information. We present the probability that each high energy event with deposited energy Edep>60E_{\rm dep}>60 TeV in the HESE sample is Galactic, extragalactic, or background. For Galactic models considered the Galactic fraction of the astrophysical flux has a best fit value of 1.3%1.3\% and is <9.5%<9.5\% at 90\% CL. A zero Galactic flux is allowed at <1σ<1\sigma.Comment: Updated with 6 year HESE data from IceCube, accepted for publication in JCA