1,721,131 research outputs found
How to observe B-8 solar neutrinos in liquid scintillator detectors
No full textWe show that liquid organic scintillator detectors (e.g., KamLAND and Borexino) can measure the B-8 solar neutrino flux by means of the v(e) charged current interaction with the C-13 nuclei naturally contained in the scintillators. The neutrino events can be identified by exploiting the time and space coincidence with the subsequent decay of the produced N-13 nuclei. We perform a detailed analysis of the background in KamLAND, Borexino and in a possible liquid scintillator detector at SNOlab, showing that the B-8 solar neutrino signal can be extracted with a reasonable uncertainty in a few years of data taking. KamLAND should be able to extract about 18 solar neutrino events from the already collected data. Prospects for gigantic scintillator detectors (such as LENA) are also studied. (c) 2005 Elsevier B.V. All rights reserved
Detection of B-8 solar neutrinos in liquid scintillators
No full textWe show that liquid organic scintillator detectors (e. g., KamLAND and Borexino) can measure the B-8 solar neutrino flux by means of the v(e) charged current interaction with the C-13 nuclei naturally contained in the scintillators. The neutrino events can be identified by exploiting the time and space coincidence with the subsequent decay of the produced N-13 nuclei
The galactic diffuse high energy neutrino flux
Full text linkWe calculate the diffuse high energy neutrino flux produced by the interactions of cosmic rays with the gas contained in our Galaxy. In order to quantify the role of uncertainties in the cosmic ray propagation models, we consider three different assumptions for the cosmic ray distribution in the Galaxy. We provide expectations for the spectrum and the angular dependence of the diffuse galactic neutrino flux. We compare our predictions with the isotropic flux required to explain the 54 HESE events observed by IceCube in four years data taking
Turbulent axion-photon conversions in the Milky Way TURBULENT AXION-PHOTON CONVERSIONS in the MILKY ... CARENZA, EVOLI, GIANNOTTI, MIRIZZI, and MONTANINO
Full text linkThe Milky Way magnetic field can trigger conversions between photons and axionlike particles (ALPs), leading to peculiar features on the observable photon spectra. Previous studies considered only the regular component of the magnetic field. However, observations consistently show the existence of an additional turbulent component, with a similar strength and correlated on a scale of a few 10 pc. We investigate the impact of the turbulent magnetic field on the ALP-photon conversions, characterizing the effects numerically and analytically. We show that the turbulent magnetic field can change the conversion probability by up to a factor of two and may lead to observable irregularities in the observable photon spectra from different astrophysical sources
Neutrino masses and mixings: Status of known and unknown 3ν parameters
Full text linkWithin the standard 3ν mass–mixing framework, we present an up-to-date global analysis of neutrino oscillation data (as of January 2016), including the latest available results from experiments with atmospheric neutrinos (Super-Kamiokande and IceCube DeepCore), at accelerators (first T2K ν ̅ and NOνA ν runs in both appearance and disappearance modes), and at short-baseline reactors (Daya Bay and RENO far/near spectral ratios), as well as a reanalysis of older KamLAND data in the light of the “bump” feature recently observed in reactor spectra. We discuss improved constraints on the five known oscillation parameters (δm2, |Δm2|, sin2θ12, sin2θ13, sin2θ23), and the status of the three remaining unknown parameters: the mass hierarchy [sign(±Δm2)], the θ23 octant [sign(sin2θ23−1/2)], and the possible CP-violating phase δ. With respect to previous global fits, we find that the reanalysis of KamLAND data induces a slight decrease of both δm2 and sin2θ12, while the latest accelerator and atmospheric data induce a slight increase of |Δm2|. Concerning the unknown parameters, we confirm the previous intriguing preference for negative values of sinδ (with best-fit values around sinδ≃−0.9), but we find no statistically significant indication about the θ23 octant or the mass hierarchy (normal or inverted). Assuming an alternative (so-called LEM) analysis of NOνA data, some δ ranges can be excluded at >3σ, and the normal mass hierarchy appears to be slightly favored at ∼90% C.L. We also describe in detail the covariances of selected pairs of oscillation parameters. Finally, we briefly discuss the implications of the above results on the three non-oscillation observables sensitive to the (unknown) absolute ν mass scale: the sum of ν masses Σ (in cosmology), the effective νe mass mβ (in beta decay), and the effective Majorana mass mββ (in neutrinoless double beta decay)
Analytical description of quasivacuum oscillations of solar neutrinos
No full textWe propose a simple prescription to calculate the solar neutrino survival probability Pee in the quasivacuum oscillation (QVO) regime. Such a prescription is obtained by matching perturbative and exact analytical results, which effectively take into account the density distribution in the Sun as provided by the standard solar model. The resulting analytical recipe for the calculation of Pee is shown to reach its highest accuracy (|ΔPee|<~2.6×10−2 in the whole QVO range) when the familiar prescription of choosing the solar density scale parameter r0 at the Mikheyev-Smirnov-Wolfenstein (MSW) resonance point is replaced by a new one, namely, when r0 is chosen at the point of “maximal violation of adiabaticity” (MVA) along the neutrino trajectory in the Sun. The MVA prescription admits a smooth transition from the QVO regime to the MSW transition one. We discuss in detail the phase acquired by neutrinos in the Sun, and show that it might be of relevance for the studies of relatively short time scale variations of the fluxes of the solar ν lines in the future real-time solar neutrino experiments. Finally, we elucidate the role of matter effects in the convective zone of the Sun
Status of atmospheric neutrino nu(mu)->nu(tau) oscillations and decoherence after the first K2K spectral data
No full textAxion-like particles from primordial black holes shining through the Universe
No full textWe consider a cosmological scenario in which the very early Universe experienced a transient epoch of matter domination due to the formation of a large population of primordial black holes (PBHs) with masses M ≲ 109 g, that evaporate before Big Bang nucleosynthesis. In this context, Hawking radiation would be a non-thermal mechanism to produce a cosmic background of axion-like particles (ALPs). We assume the minimal scenario in which these ALPs couple only with photons. In the case of ultralight ALPs (m a ≲ 10-9 eV) the cosmic magnetic fields might trigger ALP-photon conversions, while for masses m a ⪆ 10 eV spontaneous ALP decay in photon pairs would be effective. We investigate the impact of these mechanisms on the cosmic X-ray background, on the excess in X-ray luminosity in Galaxy Clusters, and on the process of cosmic reionization
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