XXth International Conference on Neutrino Physics and Astrophysics
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.
REFERENCES
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).