Abstract
The Coulomb-free
1
S
0
proton-proton (
p
-
p
) scattering length relies heavily on numerous and distinct theoretical techniques to remove the Coulomb contribution. Here, it has been ...determined from the half-off-the-energy-shell
p
-
p
scattering cross section measured at center-of-mass energies below 1 MeV using the quasi-free
p
+
d
→
p
+
p
+
n
reaction. A Bayesian data-fitting approach using the expression of the s-wave nucleon-nucleon scattering cross section returned a
p
-
p
scattering length
$${a}_{pp}=-18.1{7}_{-0.58}^{+0.52}{| }_{stat}\pm 0.0{1}_{syst}$$
a
p
p
=
−
18.1
7
−
0.58
+
0.52
∣
s
t
a
t
±
0.0
1
s
y
s
t
fm and effective range
r
0
= 2.80 ± 0.05
s
t
a
t
± 0.001
s
y
s
t
fm. A model based on universality concepts has been developed to interpret this result. It accounts for the short-range interaction as a whole, nuclear and residual electromagnetic, according to what the s-wave phase-shift
δ
does in the description of low-energy nucleon-nucleon scattering data. We conclude that our parameters are representative of the short-range physics and propose to assess the charge symmetry breaking of the short-range interaction instead of just the nuclear interaction. This is consistent with the current understanding that the charge dependence of nuclear forces is due to different masses of up-down quarks and their electromagnetic interactions. This achievement suggests that these properties have a lesser than expected impact in the context of the charge symmetry breaking.
The Coulomb-free 1S0 proton-proton (p-p) scattering length relies heavily on numerous and distinct theoretical techniques to remove the Coulomb contribution. Here, it has been determined from the ...half-off-the-energy-shell p-p scattering cross section measured at center-of-mass energies below 1 MeV using the quasi-free p + d → p + p + n reaction. A Bayesian data-fitting approach using the expression of the s-wave nucleon-nucleon scattering cross section returned a p-p scattering length app=−18.17−0.58+0.52∣stat±0.01syst fm and effective range r0 = 2.80 ± 0.05stat ± 0.001syst fm. A model based on universality concepts has been developed to interpret this result. It accounts for the short-range interaction as a whole, nuclear and residual electromagnetic, according to what the s-wave phase-shift δ does in the description of low-energy nucleon-nucleon scattering data. We conclude that our parameters are representative of the short-range physics and propose to assess the charge symmetry breaking of the short-range interaction instead of just the nuclear interaction. This is consistent with the current understanding that the charge dependence of nuclear forces is due to different masses of up-down quarks and their electromagnetic interactions. This achievement suggests that these properties have a lesser than expected impact in the context of the charge symmetry breaking.The difference in proton-proton and neutron-neutron scattering lengths contributes to understanding the charges symmetry breaking of nuclear forces, yet, the Coulomb-free proton-proton scattering length (app) cannot be measured directly. The authors apply an innovative technique, the so called Trojan Horse Method, to experimentally determine the Coulomb-free app value and exploit the potentialities of the universal window to assess the short-range physics.
Some observed abundances in globular clusters have suggested the existence of multiple generations of stars within the clusters as the observations require temperature ranges higher than current ...stars. The
30
Si(
p
,γ)
31
P reaction plays a key role in the synthesis of the observed abundances. The study of the
30
Si(
3
He,
d
)
31
P transfer reaction is a tool for constraining the strengths of low-lying resonances, and the proton partial widths are the main ingredients for calculating those strengths. We present the method used for estimating the proton partial widths and their associated uncertainties.
At temperatures (0.5-1.2) X 109 K, the 8Li + 4He -> 11B+n reaction can allow for 12C and heavier element production in the framework of the inhomogeneous big bang nucleosynthesis. At temperatures ...(2.5-5) X 109 K, it can influence the production of seed nuclei, later burnt to heavier elements by means of rapid neutron capture reactions, during Type I delta supernova explosions. Previous determinations of the reaction rate show an untenable disagreement. In this work, a new reaction rate calculation is proposed for the intervals of astrophysical interest. This new recommendation turns out to be up to a factor of five larger than the most recent rate in the literature, thus enforcing the role of 8Li + 4He -> 11B+n as a candidate for key astrophysical reactions. The analytical expression of the recommended reaction rate is given.
The Trojan Horse Method is applied to the investigation of the
18
F(p,
α
)
15
O reaction, by extracting the quasi free contribution to the
2
H(
18
F,
α
15
O)
n
process. For the first time the method ...is applied to a reaction of astrophysical importance involving a radioactive nucleus. After investigating the reaction mechanism populating the a +
15
O + n exit channel, we could extract the
18
F(p,
α
)
15
O cross section and calculate the astrophysical factor over the 0 – 1 MeV energy interval. The possibility of exploring the cross section with no need of extrapolation allowed us to to point out the possible occurrence of a 7/2
+
state at 126 keV, which would strongly influence the trend of the astrophysical factor at the energies of astrophysical interest. However, the low energy resolution prevents us to draw definite conclusions. Possible astrophysical consequences are also discussed, motivating further work on this reaction.
The Trojan Horse Method is an indirect method to measure reaction
cross sections at energies of interest for nuclear astrophysics,
exploiting the nuclei clustering properties. Here it is presented ...with
its general features and detailed for the case of the
^2
2
H(d,p)
^3
3
H
and
^2
2
H(d,n)
^3
3
He
measurements, where interesting results for astrophysics and energy
fusion power plants have been obtained.
In the context of the INFN project PANDORA_Gr3 (Plasma for Astrophysics, Nuclear Decays Observation and Radiation for Archaeometry) and of multi-messenger astronomy, we propose a feasibility study ...for in-laboratory plasma's opacity investigation, in an environment resembling thermodynamic conditions typical of the ejecta of compact binary mergers containing at least a neutron star. We aim to advance knowledge on the physics of kilonovae, the electromagnetic transients following a merger, which are relevant for the study of the origin of heavy nuclei in the Universe produced via r-process nucleosynthesis. In this paper, we present preliminary results of numerical simulations for some physics cases considered in the light of a possible experimental setup for future in-laboratory opacity spectroscopic measurements.
The \(^{13}{\rm C}(\alpha,n)^{16}{\rm O}\) reaction is considered to be the main neutron source responsible for the production of heavy nuclides (from \({\rm Sr}\) to \({\rm Bi}\)) through slow ...\(n\)-capture nucleosynthesis (\(s\)-process) at low temperatures during the asymptotic giant branch (AGB) phase of low mass stars (\(\lesssim 3-4\;{\rm M}_{\odot}\), or LMSs). In recent years, several direct and indirect measurements have been carried out to determine the cross section at the energies of astrophysical interest (around \(190\pm40\;{\rm keV}\)). However, they yield inconsistent results causing a highly uncertain reaction rate and affecting the neutron release in LMSs. In this work we have combined two indirect approaches, the asymptotic normalization coefficient (or ANC) and the Trojan Horse Method (THM), to unambiguously determine the absolute value of the \(^{13}{\rm C}(\alpha,n)^{16}{\rm O}\) astrophysical factor. Therefore, we have determined a very accurate reaction rate to be introduced into astrophysical models of \(s\)-process nucleosynthesis in LMSs. Calculations using such recommended rate have shown limited variations in the production of those neutron-rich nuclei (with \(86\leq A\leq 209\)) receiving contribution only by slow neutron captures.
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