The cosmological 7Li problem from a nuclear physics perspective

• Francesco Lorenzo Villante (L'Aquila University)

Room: Pontecorvo room The primordial abundance of 7Li as predicted by Big Bang Nucleosynthesis (BBN) is about a factor 3 larger than what has been observed in metal-poor halo stars. We analyze the possibility that this discrepancy originates from incorrect assumptions about the nuclear reaction cross sections relevant for BBN.

Measurement of the reactions 17O(a,n)20Ne and 17O(a,g)21Ne and their impact on the s process in massive stars

• Andreas Best (INFN - LNGS)

Room: Pontecorvo room The ratio of the reaction rates of the competing channels 17O(a,g)21Ne and 17O(a ,n)20Ne determines the efficiency of 16O as a neutron poison in the s process in low metallicity rotating stars. It has a large impact on the element production, either producing elements to the mass range of A=90 in case of a significant poisoning effect or extending the mass range up to the region of A=150 if the g channel is of negligible strength. We present results of the first measurement of the reaction 17O(α,g)21Ne and an improved study of the reaction 17O(α,n)20Ne, including an independent measurement of the 17O(α,n1)20Ne channel. A simultaneous R-Matrix fit to both the n0 and the n1 channels has been performed. New reaction rates have been calculated and used as input for stellar network calculations and their impact on the s process in rotating massive stars is discussed.

14N(p,gamma)15O data at high energy

• Louis Wagner (HZDR, TU Dresden)

Room: Pontecorvo room The 14N(p,gamma)15O reaction determines the rate of the CNO cycle because it's the slowest nuclear reaction of the cycle. For a precise cross section extrapolation to low energies one needs accurate knowledge of the excitation function over a wide range of energy. Therefore the non-resonant cross section of 14N(p,gamma)15O was studied at beam energies of 0.5 - 1.5,MeV at the 3,MV Tandetron of Helmholtz-Zentrum Dresden-Rossendorf. The talk presents the preliminary new data for the cross section of 14N(p,gamma)15O. With a R-matrix fit they could contribute to a more accurate extrapolation to the astro-physically relevant cross section at the Gamow-window of the reaction.

Exotic matter in neutron stars

• Giuseppe Pagliara (Ferrara University)

Room: Pontecorvo room I will discuss recent measurements of neutron stars masses and radii and their implications for the equation of state of high density matter. I will focus in particular on the possible appearance of delta resonances, hyperons and strange quark matter and the dynamics of the formation process of such "exotic" degrees of freedom. Finally, I will present neutrino diffusion simulations of the cooling of newly formed strange stars.

"Strange" Neutron Stars

• Hans Josef Schulze (Catania University)

Room: Pontecorvo room The high-density nuclear equation of state within the Brueckner-Hartree-Fock many-body approach is discussed. Particular attention is paid to the effects of nucleonic three-body forces, the presence of hyperons, and the joining with an eventual quark matter phase. The resulting properties of neutron stars, in particular the mass-radius relation, are determined and compared with recent observational data. It turns out that in this approach stars heavier than about 1.4 solar masses contain necessarily quark matter.