arXiv subjects

C. A. Bertulani

Publications and source records attributed to C. A. Bertulani.

At least 19 recordsLinked to original sources

arXiv2026

A Physics Informed Bayesian Neural Network for the Neutron Star Equation of State

We present a physics-informed Bayesian neural-network framework for inferring neutron-star equations of state from theoretical priors and propagating the resulting uncertainty to stellar observables. Trained on a representative set of hadronic EoSs, the model learns the equation of state through stochastic variational inference by representing the squared speed of sound with a bounded network output and obtaining the pressure by integration, so that causality, thermodynamic stability, and monotonicity are guaranteed by construction, with low-density nuclear and perturbative-QCD normalization anchors. Core EoSs are matched to an SLy4 crust and propagated through a unified Tolman-Oppenheimer-Volkoff-plus-tidal solver to obtain posterior predictions in the mass-radius ($M$-$R$) and mass-tidal-deformability ($M$-$Λ$) planes. The physics-informed prior is then updated with current multi-messenger data: NICER radius measurements, the GW170817 tidal-deformability constraint, and the $2\,M_\odot$ maximum-mass bound; included directly in the variational objective. The observational update moves the canonical radius from $R_{1.4}=13.41\,\mathrm{km}$ in the prior to $R_{1.4}=12.74^{+0.97}_{-0.73}\,\mathrm{km}$ (nominal 90\% variational CI), with $Λ_{1.4}=428^{+249}_{-130}$ and $M_{\mathrm{max}}\gtrsim 2.0\,M_\odot$. This framework provides a non-parametric route from microphysical EoS uncertainty to neutron-star observables.

astro-ph.HE↗

arXiv2026

Nucleon Correlations in Unstable Nuclei via Knockout Reactions

We review the physical ideas and reaction theory underlying one- and two-nucleon removal from fast projectiles, quasi-free proton-induced reactions such as $(p,2p)$ and $(p,pn)$, and the use of exclusive momentum and coincidence observables to diagnose correlations. Particular emphasis is placed on the distinction between independent-particle occupancy, long-range collective and pairing correlations, tensor-driven neutron-proton correlations, and short-range correlations generated by the repulsive core and noncentral components of the nuclear interaction. The discussion develops the overlap-function language, spectroscopic factors, eikonal stripping and diffraction, distorted-wave impulse approximation, factorization and spectral functions, center-of-mass and recoil effects, two-nucleon amplitudes, pair densities, and the relation between measured cross sections and ab initio or shell-model structure. The well-known reduction of experimental single-particle strength relative to simple shell-model expectations, its dependence on separation-energy asymmetry, and the continuing debate over reaction-model systematics are treated in detail.

nucl-th↗

arXiv2026

Interaction Cross Sections as a Structural Probe of the Hypertriton Halo

The hypertriton (${}^{3}_Λ\mathrm H$) is the most weakly bound known hypernucleus and one of the most spatially extended quantum halo systems observed in nature. Despite decades of experimental and theoretical effort, its matter radius and $Λ$ separation energy remain incompletely constrained. We demonstrate theoretically that interaction cross-section measurements provide a direct and highly sensitive probe of both quantities. Realistic three-body hypertriton wavefunctions are combined with a coupled-channel Glauber theory incorporating proton, neutron, and hyperon densities together with $ΛN\leftrightarrowΣN$ channel coupling. The resulting interaction cross section changes by about 400 mb across the currently allowed range of $Λ$ separation energies while retaining theoretical uncertainties below approximately 5\%. A Bayesian inversion demonstrates that future interaction cross-section measurements can determine both the hypertriton matter radius and the $Λ$ separation energy with potentially unprecedented precision. These results establish interaction cross sections as a new structural observable for hypernuclear halo physics.

nucl-th↗

arXiv2026

Neutron Stars and Neutron Skins: Connecting Finite Nuclei to Dense Matter

This is a brief overview of the connection between neutron skin thickness in finite nuclei and the equation of state of neutron-rich matter, with applications to neutron stars. Multiple experimental probes are discussed, including dipole polarizability, parity-violating electron scattering, heavy-ion fragmentation, quasi-free scattering, and ultraperipheral collisions. A consistent picture emerges from Bayesian analyses combining experimental data and energy density functionals, providing constraints on the symmetry energy and its slope.

nucl-th↗

arXiv2026

The dipole strength distribution of $^8$He and decay characteristics

The weak binding and spatially extended neutron densities characteristic of drip-line nuclei give rise to a distinctive low-energy dipole response. The drip-line nucleus $^8$He is the most neutron-rich bound nucleus with a mass-to-charge ratio of $A/Z=4$. We measure the dipole response of $^8$He, including for the first time the four-neutron decay channel. A total dipole strength of $\sum B(E1)(E^*<15$~MeV$)=0.95(16)~e^2$fm$^2$ and a dipole polarizability of $α_D = 0.61(1)$~fm$^3$ are extracted from the differential Coulomb-excitation cross section and compared to state-of-the-art theoretical calculations employing coupled cluster and three-body approaches. We find that the dipole continuum is dominated, even at high excitation energies well above the $4n$ decay threshold, by two-neutron emission, pointing to a $^6$He$+2n$ structure of the excited dipole mode. No indication was found for a $4n$ final-state correlation, while pronounced $nn$ and $^6$He-$n$ final-state correlations are apparent.

nucl-ex↗

arXiv2026

How Threshold Effects in Spectroscopic Factors Influence Heavy-Ion Knockout Reactions

A two-decade-old puzzle in heavy-ion one-nucleon knockout reactions is the strong correlation between the reduction factor $R_s=σ_{\rm exp}/σ_{\rm th}$ and the Fermi surface asymmetry $ΔS$. Theoretical cross sections typically rely on spectroscopic factors (SFs) from shell model (SM) calculations, which neglect continuum coupling effects. Here, we employ the Gamow shell model (GSM), which explicitly incorporates continuum coupling, to compute SFs for $p$-shell nuclei and predict corresponding theoretical cross sections. Systematic calculations demonstrate that using GSM-derived SFs substantially reduces discrepancies between theoretical and experimental results. This improvement is particularly significant for deeply bound nucleon knockout in nuclei near the dripline, where traditional SM-based calculations fall short. As a result, using GSM SFs, the ratio $R_s$ exhibits no pronounced dependence on $ΔS$. Furthermore, both the ratio of GSM SFs to SM SFs and their corresponding reaction cross sections ratios exhibit a strong $ΔS$ dependence. We have also compared GSM SFs and cross sections with those from the no-core shell model calculations, giving a similar pronounced sensitivity to $ΔS$. Detailed analysis attributes these correlations to threshold effects for SFs in weakly bound systems. Overall, incorporating continuum coupling via GSM enhances the reliability of SF predictions for exotic, weakly bound nuclei and provides key insights toward resolving the enduring puzzle in heavy-ion knockout reactions from a nuclear structure perspective.

nucl-th↗

arXiv2025

Solar fusion III: New data and theory for hydrogen-burning stars

In stars that lie on the main sequence in the Hertzsprung-Russel diagram, like our sun, hydrogen is fused to helium in a number of nuclear reaction chains and series, such as the proton-proton chain and the carbon-nitrogen-oxygen cycles. Precisely determined thermonuclear rates of these reactions lie at the foundation of the standard solar model. This review, the third decadal evaluation of the nuclear physics of hydrogen-burning stars, is motivated by the great advances made in recent years by solar neutrino observatories, putting experimental knowledge of the proton-proton chain neutrino fluxes in the few-percent precision range. The basis of the review is a one-week community meeting held in July 2022 in Berkeley, California, and many subsequent digital meetings and exchanges. The relevant reactions of solar and stellar hydrogen burning are reviewed here, from both theoretical and experimental perspectives. Recommendations for the state of the art of the astrophysical S-factor and its uncertainty are formulated for each of them. Several other topics of paramount importance for the solar model are reviewed, as well: recent and future neutrino experiments, electron screening, radiative opacities, and current and upcoming experimental facilities. In addition to reaction-specific recommendations, also general recommendations are formed.

astro-ph.SR↗

arXiv2025

Photonuclear Tomography in Ultraperipheral Heavy-Ion Collisions

We present a theoretical investigation of photonuclear tomography as a novel technique for probing the internal structure of nuclei. In this approach, ultraperipheral heavy-ion collisions (UPCs) serve as a source of intense fluxes of virtual photons, which induce coherent production of vector mesons. By analyzing the probabilities and cross sections of these photon-induced processes, we propose a methodology for reconstructing the spatial distribution of nucleons within the nucleus. Our framework provides a systematic way to access information on the nuclear geometry probed in UPCs, offering new opportunities for studies of nuclear structure using particle production as a probe. Numerical calculations for selected examples illustrate the feasibility and potential of this method.

nucl-th↗

arXiv2025

Nuclear Fragmentation at the Future Electron-Ion Collider

We explore the potential of conducting low-energy nuclear physics studies, including nuclear structure and decay, at the future Electron-Ion Collider (EIC) at Brookhaven. By comparing the standard theory of electron-nucleus scattering with the equivalent photon method applied to Ultraperipheral Collisions (UPC) at the Large Hadron Collider (LHC) at CERN. In the limit of extremely high beam energies and small energy transfers, very transparent equations emerge. We apply these equations to analyze nuclear fragmentation in UPCs at the LHC and $eA$ scattering at the EIC, demonstrating that the EIC could facilitate unique photonuclear physics studies. However, we have also shown that the fragmentation cross-sections at the EIC are about 1,000 times smaller than those at the LHC. At the LHC, the fragmentation of uranium nuclei displays characteristic double-hump mass distributions from fission events, while at the EIC, fragmentation is dominated by neutron emission and fewer few fission products, about 10,000 smaller number of events.

nucl-th↗

arXiv2024

Novel aspects of particle production in ultra-peripheral collisions

One of the hot topics in hadron physics is the study of the new exotic charmonium states and the determination of their internal structure. Another important topic is the search for effects of the magnetic field created in high energy nuclear collisions. In this note we show that we can use ultra-peripheral collisions to address both issues. We compute the cross section for the production of the $D^+ D^-$ molecular bound state in $γ-γ$ collisions. We also show how the magnetic field of the projectile can induce pion production in the target. Both processes have sizeable cross sections and their measurement would be very useful in the study of the topics mentioned above.

hep-ph↗

arXiv2024

Production of meson molecules in ultra-peripheral heavy ion collisons

In this work we present a calculation of exotic charmonium production in ultra-peripheral collisions, in which the exotic state is explicitly treated as a meson molecule. Our formalism is general but we focus on the lightest possible exotic charmonium state: a $D^+ D^-$ molecular bound state. It was proposed some time ago and it has been object of experimental searches. Here we study the production of the open charm pair in the process $γγ\to D^+ D^-$. Then we use a prescription to project the free pair $ |D^+ D^- \rangle$ onto a bound state at the amplitude level and compute the cross section of the process $γγ\to B$ (where $B$ is the bound state). Finally, we convolute this last cross section with the equivalent photon distributions coming from the projectile and target in an ultra-peripheral collision and find the $A A \to A A B$ cross section, which, for $Pb-Pb$ collisions at $\sqrt{s_{NN}} = 5.02$ TeV, is of the order of $3 \, μ\mbox{b}$.

hep-ph↗

arXiv2024

Primordial Nucleosynthesis with Non-Extensive Statistics

The conventional Big Bang model successfully anticipates the initial abundances of 2H(D), 3He, and 4He, aligning remarkably well with observational data. However, a persistent challenge arises in the case of 7Li, where the predicted abundance exceeds observations by a factor of approximately three. Despite numerous efforts employing traditional nuclear physics to address this incongruity over the years, the enigma surrounding the lithium anomaly endures. In this context, we embark on an exploration of Big Bang nucleosynthesis (BBN) of light element abundances with the application of Tsallis non-extensive statistics. A comparison is made between the outcomes obtained by varying the non-extensive parameter q away from its unity value and both observational data and abundance predictions derived from the conventional big bang model. A good agreement is found for the abundances of 4He, 3He and 7Li, implying that the lithium abundance puzzle might be due to a subtle fine-tuning of the physics ingredients used to determine the BBN. However, the deuterium abundance deviates from observations.

nucl-th↗

arXiv2024

Historical introduction to ultra peripheral collisions

This is a brief history of photons, both soft and hard, real and virtual. About 150-100 years ago, Maxwell and Einstein discovered intriguing properties of electromagnetic fields and how to understand them both macroscopically and microscopically. Decades later, physicists developed the theory of renormalized quantum electrodynamics (QED), an incredibly accurate theory describing interactions of photons and other particles. Photons are used everywhere in academia and technological devices, from supermarket lasers and doors to academic studies in atomic, nuclear, and particle physics. In this article, I attempt to convey how the field of relativistic heavy ions rediscovered ultra-peripheral collisions (UPC) as a source of intense, almost real photons, and how it permits the study of a plethora of phenomena in the aforementioned academic fields. These phenomena are not always accessible by other means.

nucl-th↗

arXiv2024

Unveiling the properties of the dimuonium at the energies available at the Large Hadron Collider at CERN

We study the production of the dimuonium (also known as true muonium) in two and three photon fusion processes in nucleus--nucleus collisions at the CERN Large Hadron Collider (LHC) energies. A new formalism is introduced for the production process and valuable new information is extracted which will be helpful in proposals of future experiments. We explore the phase space constraints, the reaction mechanisms, and how the dimounium decay observables might be jeopardized by other physical processes. We show that the energies available at the large hadron collider at CERN might lead to the first identification of the dimounium in a terrestrial laboratory.

hep-ph↗

arXiv2023

How to extract the electromagnetic response of $^6$He in relativistic collisions

I investigate the difficulties in obtaining the electromagnetic response of light, halo-like, nuclei using reactions at radioactive beam facilities. A relativistic coupled-channels theory for the calculation of dissociation cross sections of halo nuclei is compared to first-order perturbation theory. A comparison with semiclassical models frequently used in experimental analysis is also performed. It is shown that the effects of relativity and of the nuclear interaction lead to sizable effects in the extraction of the electromagnetic response of 6He projectiles.

nucl-th↗

arXiv2023

Core destruction in knockout reactions

A model is presented to calculate projectile core destruction in knockout reactions. It incorporates physics arguments similar to the formulation of the state of the art theory to calculate stripping and diffraction dissociation cross sections in heavy ion collisions with bombarding energies around 100 MeV/nucleon and larger. It is shown that secondary collisions between the incoming and struck nucleons and the projectile core decrease the core survival probability by as much as 9.5\%. However, no clear evidence is found for reduction of the cross section with increasing binding energy of the removed nucleon.

nucl-th↗

arXiv2023

Ultra-peripheral nuclear collisions

This article presents a very brief review of the physics of Ultra-Peripheral Collisions (UPC) at the Large Hadron Collider (LHC) and other nuclear facilities. I discuss several processes of interest such as electron-position pair production, the anti-hydrogen atom, giant resonances, exotic meson production and parton distribution functions.

hep-ph↗

arXiv2023

Silicon tracker array for RIB experiments at SAMURAI

This work describes a silicon tracker system developed for experiments with proton-rich radioactive ion beams at the SAMURAI superconducting spectrometer of RIBF at RIKEN. The system is designed for accurate angular reconstruction and atomic number identification of relativistic heavy ions and protons which are simultaneously produced in reactions motivated by studies of proton capture reactions of interest for nuclear astrophysics. The technical characteristics of the tracking array are described in detail as are its performance in two pilot experiments. The physics justification for such a system is also presented.

physics.ins-det↗