P. COLOMBETTI

The 12C/13C ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the 12Cðp; γÞ13N and 13Cðp; γÞ14N reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy down to the lowest energies...

One of the main neutron sources for the astrophysical s process is the reaction 13C(α,n)16O, taking place in thermally pulsing asymptotic giant branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150–230 keV energy window (Gamow peak). At these...

We introduce the LUNA neutron detector array developed for the investigation of the 13C(, )16O reaction towards its astrophysical -process Gamow peak in the low-background environment of the Laboratori Nazionali del Gran Sasso (LNGS). Eighteen 3He counters are arranged in two different configurations (in a vertical and a horizontal orientation)...

Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and...

The 20Ne(p, γ ) 21Na reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below Ec.m. = 352 keV, and of the contribution from the Ec.m. = 368 keV resonance, which dominates...

Background: Among the several inhomogeneities in the composition of globular cluster stars, an overabundance of 23Na is interpreted as the signature of the operation of the neon-sodium (NeNa) cycle. One of the hypothesis to explain the observed O-Na anticorrelation invokes massive asymptotic giant branch stars as the main agents. At...

The CNO cycle is one of the most important nuclear energy sources in stars. At temperatures of hydrostatic H-burning (20 MK < T < 80 MK) the 17O(p; γ)18F reaction rate is dominated by the poorly constrained 64.5 keV resonance. Here, we report on the first direct measurements of its resonance strength and of the direct capture contribution at...

The D(p, γ ) 3He reaction, where 'D' denotes '2H', is of primary importance in cosmology and nuclear physics since it offers a unique opportunity to test predictions based on the description of nuclear interactions. We present a novel approach to extract the angular distribution of the photons emitted by the D(p, γ ) 3 He reaction inferred from...