A New Measurement of the 2H(p,y)3 He Cross Section in the BBN Energy Range at LUNA

Abstract

Fusion reaction cross sections have an influence on the element formation in the earliest stages of the Universe and in all the stellar objects formed later on: a precise knowledge on nuclear physics input is fundamental since the abundances of the primordial elements are sensitive to the physics of the early universe and are therefore a tool to test the cosmological models. Presently the abundance of deuterium deduced from observation of Damped Lyman Alpha (DLA) absorption systems at high redshift is more accurate with respect to the predictions, mainly because the Big Bang Nucleosynthesis (BBN) calculation is affected by the paucity of data for the deuterium burning reaction cross section at the relevant energies. Deep underground in the Gran Sasso Laboratory, Italy, the LUNA collaboration is pursuing a dedicated effort to measure the cross section directly at BBN energies (30–300 keV). The campaign is divided into two phases based on a BGO and a high-purity germanium (HPGe) detector, respectively. The LUNA measurement is here described and the impact on cosmology and particle physics highlighted.