Speaker
Dr.
Carlo Gustavino
(INFN-Roma)
Description
The LUNA experiment plays an important role in understanding open issue of neutrino physics. As an example, two key reactions of the solar p-p chain $^3He(^3He,2p)^4He$ and $^3He(^4He,\gamma)^7Be$ have been studied at low energy with LUNA, providing an accurate experimental input to the Standard Solar Model and consequently to the study of the neutrino mixing parameters. The LUNA collaboration will study the reaction $^2H(p,\gamma)^3He$ at Big Bang Nucleosynthesis (BBN) energies. This reaction is presently the main source of the $2\%$ uncertainty of the calculated primordial abundance of deuterium in BBN calculations [1]. As it is well known, the abundance of deuterium depends on the number of neutrino families (or any other relativistic species existing in the early Universe, "dark radiation"). Therefore, the comparison of computed and observed deuterium abundances allows to severely constrain the number of neutrino species and/or the lepton degeneracy in the neutrino sector. The paucity of data at BBN energy of the $^2H(p,\gamma)^3He$ reaction is presently the main limitation to exploit the deuterium abundance as a probe of neutrino physics and to improve the BBN estimation of the baryon density. As a matter of fact, the deuterium abundance derived from damped Lyman $\alpha$ (DLA) system observations has presently an error of only $1.5\%$ [1]. The aim of the the new measurement is therefore to substantially improve the $9\%$
error of present $^2H(p,\gamma)^3He$ data at BBN energies [2]. Starting from the present uncertainty of the relevant parameters (i.e. baryon density, observed abundance of deuterium and BBN nuclear cross sections), it will be shown that a renewed study of the $^2H(p,\gamma)^3He$ process is essential to constrain the number of neutrino families and to probe the existence of dark radiation in the early Universe, by using the BBN theory and the cosmic microwave background (CMB) data.
[1] R.J. Cooke and M. Pettini: arXiv:1308.3240v1 [astro-ph.CO] 14 Aug 2013.
[2] L. Ma et al., Phys. Rev. C 55, 588 (1997).
Primary author
Dr.
Carlo Gustavino
(INFN-Roma)
