Can Helium Mixing Explain the Solar Neutrino Shortages?

Has the time come to abandon hope of an astrophysical—as distinguished from particle‐theoretic—solution of the solar neutrino puzzle? Two recent papers espouse different positions on this important issue. In the 18 November Physical Review Letters Wick Haxton (University of Washington) and Andrew Curnrning (a visiting undergraduate from Cambridge University), argued that there might still be an astrophysical explanation for the observed shortfall of ${}^8\mathrm{B}$ decay neutrinos from the Sun and for the even greater shortfall of solar neutrinos from electron capture by ${}^7\mathrm{Be}$: namely the slow mixing of ${}^3\mathrm{He}$ down into the solar core. “This is a very speculative departure from the standard model of how the Sun works,” Haxton told us. “But we’re all willing to carefully examine some rather exotic particlephysics solutions. So it may be equally important to explore unexpected solarphysics solutions.”