The Solar HepHep Process

The $Hep$ process is a weak-interaction reaction, $He3 + p \to He4 + e^+ + \nu_e$, which occurs in the sun. There is renewed interest in $Hep$ owing to current experimental efforts to extract from the observed solar neutrino spectrum information on non-standard physics in the neutrino sector. $Hep$ produces highest-energy solar neutrinos, although their flux is quite modest. This implies that the $Hep$ neutrios can at some level influence the solar neutrino spectrum near its upper end. Therefore, a precise interpretation of the observed solar neutrino spectrum requires an accurate estimate of the $Hep$ rate. This is an interesting but challenging task. We describe the difficulties involved and how the recent theoretical developments in nuclear physics have enabled us to largely overcome these difficulties. A historical survey of $Hep$ calculations is followed by an overview of the latest developments. We compare the results obtained in the conventional nuclear physics approach and those obtained in a newly developed effective field theory approach. We also discuss the current status of the experiments relevant to $Hep$.Comment: Published in Ann. Rev. Nuc. Part. Sci. vol. 54, 19 (2004). AR209 macros are include

Solar neutrinos, SNO and neutrino-deuteron reactions

The standard nuclear physics approach and effective field theory approach for calculations of neutrino–deuteron cross sections for the solar neutrino energies are considered. Their main features, the level of accuracy and problems to be addressed for further developments are discussed

Effective Field Theory For Nuclei: Confronting Fundamental Questions in Astrophysics

Fundamental issues involving nuclei in the celebrated solar neutrino problem are discussed in terms of an effective field theory adapted to nuclear few-body systems, with a focus on the proton fusion process and the hep process. Our strategy in addressing these questions is to combine chiral perturbation theory -- an effective field theory of QCD -- with an accurate nuclear physics approach to arrive at a more effective effective field theory that reveals and exploits a subtle role of the chiral-symmetry scale in short-distance effects encoded in short-range nuclear correlations. Our key argument is drawn from the close analogy of the principal weak matrix element figuring in the hep process to the suppressed matrix elements in the polarized neutron-proton capture at threshold currently being measured in the laboratories.Comment: 11 pages. Invited talk given by MR at the International Conference on Few-Body Problems, Taipei, Taiwan, 6-10 March 200

Nuclear Matrix Elements of Axial-Charge Exchange Currents Derived in Heavy-Fermion Chiral Perturbation Theory

We calculate shell-model matrix elements of the axial-charge exchange current operators that have been obtained up to the next-to-leading order from heavy-fermion chiral perturbation theory. It is found that loop corrections to the soft one-pion-exchange contribution are small (around 10 \%) and have no significant dependence on the nuclear mass number or on the valence-nucleon orbits. These results render further support to the chiral-filtering conjecture.Comment: 19 pages, LaTeX, SNUTP 94-29, USC(NT)-94-

Fixed-Point Analysis of the Low-Energy Constants in the Pion-Nucleon Chiral Lagrangian

In the framework of heavy-baryon chiral perturbation theory, we investigate the fixed point structure of renormalization group equations (RGE) for the ratios of the renormalized low energy constants (LECs) that feature in the pion-nucleon chiral Lagrangian. The ratios of the LECs deduced from our RGE analysis are found to be in semi-quantitative agreement with those obtained from direct fit to the experimental data. The naturalness of this agreement is discussed using a simple dimensional analysis combined with Wilsonian RGEs.Comment: 10 page