Low energy electroweak interactions in light nuclear systems (d, 3H, 3He) take
part in many scenarios such as Big Bang nucleosynthesis and evolution of the
Sun.
The energy generated in the Sun comes from an exothermic set of reactions,
called pp chain, in which 4 protons are fused into Helium-4.
The leading reaction in the chain which controls more than 99 % of the
protons is pp fusion. This reaction is a weak reaction and therefore it is the
slowest reaction in the whole chain (approx. billion years) so it determines the
Sun’s lifetime. Due to the slowness of the pp fusion, measurement of its cross
section is impossible, so its rate must be calculated from a fundamental
theory.
For doing so, we apply a method called the pionless effective field theory
(\piFT) which is an appropriate theory for reactions with typical momentum
lower that the pion mass (140 MeV).
For the first time we calculated magnetic momentums of A=3 nuclei using
\piFT, that fit experimental data very well. This calculation has been used to
examine the consistency of \piFT between A=2 and A=3 and to predict the pp
fusion rate which is in good agreement with former estimations.