XXth International Conference on Neutrino Physics and Astrophysics

Poster Abstract

S.Dev, J.D.Sharma & B.C.Chauhan (Himachal Pradesh University, Shimla, India)

MSW Constraints on the Matter Density Profiles in the Solar Interior

The solar interior is opaque to traditional direct probes like the photons and it has been possible to probe the solar interior only indirectly via Helioseismology. Neutrinos, however, hold the potential of being the real time probes of the stellar interiors as they can travel across the Sun, practically, unperturbed. A neutrino, produced in the solar core via thermonuclear fusion reactions, typically has to collision probability of the order of 10^-6 - 10^-7 while traveling through the Sun so that the energy spectrum of the neutrinos is not altered. It is, now, an undisputed fact that the terrestrial detectors observe far fewer neutrinos as compared to the theoretical expectations [1]. An astrophysical solution of the solar neutrino problem [SNP] has, already, been ruled out. It is, now, widely accepted that the solution of the SNP will require nonstandard neutrino properties such as non-zero mass, a large magnetic moment or flavor changing neutral current interactions. The oscillation solutions of the SNP are the most popular and have been thoroughly investigated with regard to the quality of the data fits and the parameter range predictions. In fact, the earlier Superkamiokande results for atmospheric neutrinos and the most recent results from SNO [2] for solar neutrinos favor the oscillation solutions overwhelmingly. In this work, we have investigated the inverse problem viz. the investigation of the matter density profiles in the solar interior in the light of the solar neutrino observations assuming the MSW effect to be responsible for the solar neutrino deficit. Since the different categories of the solar neutrinos undergo MSW conversion for different densities in different parts of the Sun and most of the MSW conversion occurs in the resonance region, one can use the observed fluxes of the different components of the solar neutrino spectrum for the tomography of the solar matter density in the interior. This is the principle used in the present work. In order to eliminate the effects of possible time variation, we choose the solar neutrino data pertaining to the same period of time from Homestake, Kamiokande (Super K) and the gallium experiments [3] . We restrict ourselves to the currently favored large mixing angle (LMA) solution parameterized by Delta M^2 = 1.8 x 10^-5 eV^2, sin^2(2theta) = 0.76 and calculate |(dNe/dr)/Ne|/F, as a testing factor for the density variations in the Sun [4] and then compare its values with the values obtained for the most commonly used exponential solar matter density profile [5]. Results are similar at the outer part of Sun, however in the inner part of the Sun, the factor differs by the six orders of magnitude.

1. The European Physical Journal 15, 366 (2000).
2. Q.R.Ahmad et al. (SNO collaboration), Phys. Rev. Lett. 87, 071301 (2001).
3. B.C.Chauhan, U.C.Pandey and S.Dev, Phys. Rev. D 59, 083002 (1999). S. Dev and Jyoti Dhar Sharma, Mod. Phys. Lett. A15, 351 (2000), A15, 1445 (2000).
4. T.K.Kuo and J.Pantaleone, Rev. Mod. Phys. 61, 937 (1989).
5. J.N.Bahcall, Neutrino Astrophysics (Cambridge Univ. Press, 1993).

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