The solar Hep process

Key Words solar burning, solar neutrinos, neutrino oscillations, effective field theory PACS Codes 26.65.+t, 25.10.+s, 11.10.−z ■ Abstract The hep process is a weak-interaction reaction, 3He + p → 4He + e+ + νe, 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 nonstandard physics in the neutrino sector. hep produces highest-energy solar neu-trinos, although their flux is quite modest. This implies that the hep neutrinos 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 develope