The 51^{51}Cr neutrino source and Borexino: a desirable marriage

Exposure to a $^{51}$Cr neutrino source as that used in Gallex will provide an excellent overall performance test of Borexino, which should collect about 1400 source induced events, with an initial rate of about 35 counts per day. This will be particularly important if MSW-small-angle turns out to be the solution of the solar neutrino problem. In addition, if an independent, accurate calibration is available, one will have an interesting experiment on neutrino properties: as an example, a neutrino magnetic moment of the order $5\cdot10^{-11}\mu_B$could be detected/excluded at the 90\% C.L.Comment: 7 pages, RevTeX, plus 3 postscripts figures, tarred, compresse

Solar opacity, neutrino signals and helioseismology

In connection with the recent suggestion by Tsytovich et al. that opacity in the solar core could be overestimated, we consider the following questions: i) What would a 10\% opacity reduction imply for the solar neutrino puzzle? ii) Is there any hope of solving the solar neutrino puzzle by changing opacity? iii) Is a 10\% opacity reduction testable with helioseismological data?Comment: revtex file of 3 pages + 2 postscipt figures, in a uuencoded compressed tarred file, send any offprint request to [email protected]

Where are the beryllium neutrinos?

We show that present experiments imply that neutrinos are nonstandard at the 87\% C.L., independently of solar or nuclear physics. Moreover, if neutrinos are standard, the $^7$Be flux must be almost zero. Even if we arbitrarily disregard one of the experiments, the neutrino flux must still be less than half of the value predicted by standard solar models.Comment: 8 pages in RevTeX 3.0 plus 2 figures in uuencoded postscript files. Full postscript version available via anonymous ftp from risc0.ca.infn.it:/pub/private/lissia/infnfe-10-94.ps (192.84.132.4) Submitted to Physics Letters

The MSW solution to the solar neutrino problem for non-standard solar models

The difficulties for non-standard solar models (NSSM) in resolving the solar neutrino problem are discussed stressing the incompatibility of the gallium--Kamiokande data, and of the gallium--chlorine data. We conclude that NSSM's cannot explain simultaneously the results of any two of the solar neutrino data (chlorine, Kamiokande and gallium). We address further the question whether the MSW solution exists for NSSM's (e.g. models with $^8$B neutrino flux much lower than the standard one and/or central temperature $T_c$ very different from $T_c^{\text{SSM}}$). We demonstrate that the MSW solution exists and is very stable relative to changes of $S_{17}$ ($S$-factor for $p$ + $^7$Be reaction) and $T_c$. In particular, $\Delta m^2$ is almost constant while $\sin^2 2\theta$ depends on the exact values of $S_{17}$ (or $^8$B-neutrino flux) and $T_c$.Comment: 13 pages in RevTeX 3.0 plus 3 figures in uuencoded postscript files. Full postscript version available via anonymous ftp from risc0.ca.infn.it:/pub/private/lissia/lngs-94-104.ps (192.84.132.4) Submitted to Physics Letters