The study of the Sun and of the Earth with neutrino probes
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The study of the Sun and of the Earth with neutrino probes Sandra Zavatarelli1
© Springer Nature Switzerland AG 2019
Abstract Astrophysicists have been tracking high-energy particles from space for decades. But neutrinos are different: since they are neutral particles, they travel in a straight line, unaffected by the magnetic fields of space. Neutrinos basically give you a different eye to look at the universe and a unique probe of new physics. The current experimental knowledge on the solar neutrinos and on the terrestrial antineutrinos is here summarised, showing that present and future experiments have the capability to simultaneously look for new physics effects and to probe in detail the interior of the Sun, as well as of the Earth or of distant stars. Keywords Solar neutrinos · Geo-neutrinos
1 Introduction Neutrinos, the most abundant massive particles in the universe, are produced in a multitude of different processes. Medium-low energy neutrinos are essential probes to explore the physics of the stars in more quiet evolutionary stages like the main sequence or to understand the composition of deep Earth. The solar fusion is powered by two series of reactions: the pp-chain, the primary source of solar power and the sub-dominant CNO cycle that fuses heavier elements. The electron neutrinos (νe ) produced in the different reactions can be distinguished on the base of their energy spectra [1] (see Fig. 1-left) . In the sixties the large discrepancy observed between the Standard Solar Model (SSM) predictions and the measured fluxes became famous as the Solar Neutrino Problem (SNP): it was the SNO experiment, in the years 2001 - 2002, to clarify that the reason for the discrepancy is the neutrino flavour conversion [2]. The experimental trick adopted by the SNO collaboration was the choice of an heavy water target, that allows to exploit a neutral current interaction channel, νe + d → p + n + νe . Since the cross section in this case is the
This article is part of the Topical Collection on Proceedings of the 7th Symposium on Symmetries in Subatomic Physics (SSP 2018), Aachen, Germany, 10–15 June 2018 Guest Edited by Hans Str¨oher, J¨org Pretz, Livia Ludhova and Achim Stahl Sandra Zavatarelli
[email protected] 1
INFN and Universit`a degli Studi di Genova, Via Dodecaneso 33, 16146, Genoa, Italy
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Fig. 1 Left - Solar neutrinos energy spectra: the νe survival probability according to the MSW-LMA prediction is shown, in green color for the value of m212 indicated by solar experiments and in blu by the KamLAND reactor antineutrino measure (see text) [3, 4]; Right - The allowed band (RSM spread) for the νe survival probability according to SNO (blue: Bayesan fit, red: maximal likelihood fit) [5]
same for all the neutrino flavours, the total measured neutrino flux came out to be perfectly consistent with solar model predictions. Presently flavour oscillations have been robustly established in terms of the PontecorvoMaki-Nakagawa-Sakata flavor mix
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