arXiv subjects

Laura Elisa Marcucci

Publications and source records attributed to Laura Elisa Marcucci.

8 recordsLinked to original sources

arXiv2026

A new analysis of the "hep" S-factor and the "hen" cross section

We present a new accurate analysis of the $^3$He$(p,e^+ν_e)$${}^4$He (''hep'') reaction at astrophysical energies. The S-factor is computed using a state-of-the-art method to calculate the four-nucleon scattering and bound-state wave functions (the hyperspherical harmonic expansion), and by using nuclear interactions and accompanying electroweak nuclear currents obtained within the chiral effective field theory framework. Our analysis includes a detailed examination of the theoretical uncertainties coming from two different sources: the truncation of the interaction and current chiral expansions, and the model dependence. Our recommended final theoretical value for the hep S-factor at zero energyis $S(0)=(8.7\pm 0.9)\times 10^{-20}$ keV b. We provide also the energy spectrum of the outgoing hep positrons which may be measured in future experiments. We include also an analysis of the ''sister'' reaction $^3$He$(n,γ)$${}^4$He (''hen'') at low energies, showing that the calculation well reproduce the total cross section from thermal energies to few MeV, validating our results on the hep reaction.

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arXiv2026

Bayesian analysis of proton-proton fusion in chiral effective field theory

The astrophysical $S$-factor for the proton-proton fusion is calculated in the low-energy regime for a variety of nuclear interactions and consistent nuclear currents, derived within chiral effective field theory. We estimate, for the first time, the theoretical uncertainty on the $S$-factor due to the truncation of the chiral expansion of the currents using a Bayesian analysis. In order to reach an accuracy at the percent level in the calculation, the electromagnetic potential includes contributions beyond the leading Coulomb interaction, such as two-photon exchange and vacuum polarization. The initial proton-proton state is expanded in partial waves and only the ${}^1S_0$ contribution is included, as it is known that the other partial-waves effects are negligible. The low-energy constant entering the contact term in the weak axial current operator is calibrated to reproduce the Gamow-Teller matrix element in Tritium $β$-decay. The value $S(0)$ is found to be $S(0)=(4.068 \pm 0.025)\times 10^{-25} \: \text{MeV}\: \text{b}$.

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arXiv2026

ToMCCA-3: A realistic 3-body coalescence model

The formation of light nuclei in high-energy collisions provides valuable insights into the underlying dynamics of the strong interaction and the structure of the particle-emitting source. Understanding this process is crucial not only for nuclear physics but also for astrophysical studies, where the production of rare antinuclei could serve as a probe for new physics. This work presents a three-body coalescence model based on the Wigner function formalism, offering a refined description of light-nucleus production. By incorporating realistic two- and three-body nuclear interaction potentials constrained by modern scattering and femtoscopic correlation data, our approach improves on traditional coalescence models. The framework is validated using event generators applied to proton-proton collisions at $\sqrt{s}=13$ TeV to predict the momentum spectra of light (anti) nuclear nuclei with mass number $A=3$, which are then compared with the experimental data from ALICE. Our results demonstrate the sensitivity of light nucleus yields to the choice of nuclear wave functions, emphasizing the importance of an accurate description of the coalescence process. This model lays the foundation for the extension of coalescence studies of $A=3$ light nuclei to a wider range of collision systems and energies.

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arXiv2025

$A=2,3$ nuclear contact coefficients in the Generalized Contact Formalism

This work focuses on extracting nuclear contact coefficients for $ A = 2 $, $ A = 3 $ and $ A = 4 $ nuclei within the Generalized Contact Formalism framework. We investigate the universality of these coefficients across different nuclear systems and interaction models, using both local (in $ r $-space) and non-local (in $ k $-space) chiral potentials. The Hyperspherical Harmonics method is employed to calculate the nuclear wave functions from which we obtain the two-body momentum distributions and the two-body density functions, which are essential for extracting the contact coefficients. The adopted method is a rigorous ab-initio approach that can be applied to virtually any potential. We present ratios of contact coefficients across various spin and isospin channels, highlighting their independence from the used nuclear potential. This study extends previous work where only local interaction models were employed. Furthermore, we verify whether the contact coefficient ratio between different nuclei remains consistent even when non-local potentials are considered. Future work will extend this analysis to heavier nuclei, such as $ A = 4 $ and $ A = 6 $ nuclei.

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arXiv2024

Bayesian analysis of muon capture on deuteron in chiral effective field theory

We compute the muon capture on deuteron in the doublet hyperfine state for a variety of nuclear interactions and consistent nuclear currents. Our analysis includes a detailed examination of the theoretical uncertainties coming from different sources: the single-nucleon axial form factor, the truncation of the interaction and current chiral expansion, and the model dependence. Moreover, we study the impact of the use of different power counting scheme for the electroweak currents on the truncation error. To estimate the truncation error of the chiral expansion of interactions and currents we use the most modern techniques based on Bayesian analysis. This method enables us to give a clear statistical interpretation of the computed theoretical uncertainties. Finally, we provide the differential capture rate as function of the kinetic energy of the outgoing neutron which may be measured in future experiments. Our recommended theoretical value for the total doublet capture rate is $Γ_{\rm th}=395\pm 10$ s$^{-1}$ ($68\%$ confidence level). We calculated also the capture rate in the quartet hyperfine state, which turns out to be in the range $[13.3-13.8]$ s$^{-1}$ depending on the adopted nuclear interaction.

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arXiv2023

Revisiting proton-proton fusion in chiral effective field theory

We calculate the $S$-factor for proton-proton fusion using chiral effective field theory interactions and currents. By performing order-by-order calculations with a variety of chiral interactions that are regularized and calibrated in different ways, we assess the uncertainty in the $S$-factor from the truncation of the effective field theory expansion and from the sensitivity of the $S$-factor to the short-distance axial current determined from three- and four-nucleon observables. We find that $S(0)=(4.100\pm0.019\mathrm{(syst)}\pm0.013\mathrm{(stat)}\pm0.008(g_A))\times10^{-23}~\mathrm{MeV\,fm}^2\,,$ where the three uncertainties arise, respectively, from the truncation of the effective field theory expansion, use of the two-nucleon axial current fit to few-nucleon observables and variation of the axial coupling constant within the recommended range. The increased value of $S(0)$ compared to previous calculations is mainly driven by an increase in the recommended value for the axial coupling constant and is in agreement with a recent analysis based on pionless effective field theory.

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arXiv2020

Calculation of the ${}^6$Li ground state within the hyperspherical harmonic basis

We have studied the solution of the six-nucleon bound state problem using the hyperspherical harmonic (HH) approach. For this study we have considered only two-body nuclear forces. In particular we have used a chiral nuclear potential evolved with the similarity renormalization group unitary transformation. A restricted basis has been selected by performing a careful analysis of the convergence of different HH classes. Finally, the binding energy and other properties of ${}^6$Li ground state are calculated and compared with the results obtained by other techniques. Then, we present a calculation of matrix elements relevant for direct dark matter search involving ${}^6$Li. The results obtained demonstrate the feasibility of using the HH method to perform calculation beyond $A = 4$.

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arXiv2019

Theoretical calculation of the $p-{}^6{\rm Li}$ radiative capture reaction

We present a new calculation of the ${}^6{\rm Li}(p,γ){}^7{\rm Be}$ radiative capture astrophysical $S$-factor in a cluster model framework. We consider several intercluster potentials, adjusted to reproduce the ${}^7{\rm Be}$ bound state properties and the $p-{}^6{\rm Li}$ elastic scattering phase shifts. Using these potentials, we calculate the astrophysical $S$-factor, obtaining a good agreement with available data, and the photon angular distribution. Finally, we discuss the consequences of a hypothetical resonance-like structure on the $S$-factor.

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