Nuclear Theory·nucl-th

Wednesday·July 26, 2023

14 papers—8 primary·6 cross-listed

01
Effective Field Theory for the Bound States and Scattering of a Heavy Charged Particle and a Neutral Atom
Daniel Odell🇺🇸 · Daniel R. Phillips🇺🇸 · Ubirajara van Kolck🇫🇷
We show the system of a heavy charged particle and a neutral atom can be described by a low-energy effective field theory where the attractive $1/ r^{4}$ induced dipole potential determines the long-distance/low-energy wave functions. The $1/ r^{4}$ interaction is renormalized by a contact interaction at leading order. Derivative corrections to that contact interaction give rise to higher-order terms. We show that this ``Induced-dipole EFT'' (ID-EFT) reproduces the $π^{+}$ -hydrogen phase shifts of a more microscopic potential, the Temkin-Lamkin potential, over a wide range of energies. Already at leading order it also describes the highest-lying excited bound states of the pionic-hydrogen ion. Lower-lying bound states receive substantial corrections at next-to-leading order, with the size of the correction proportional to their distance from the scattering threshold. Our next-to-leading order calculation shows that the three highest-lying bound states of the Temkin-Lamkin potential are well-described in ID-EFT.
nucl-thphysics.atom-phPRA(2023)·4 citations
02
Neck Rupture and Scission Neutrons in Nuclear Fission
Ibrahim Abdurrahman · Matthew Kafker · Aurel Bulgac · Ionel Stetcu
Just before a nucleus fissions a neck is formed between the emerging fission fragments. It is widely accepted that this neck undergoes a rather violent rupture, despite no direct experimental evidence, and only a few contentious theoretical treatments of this fission stage were ever performed in the more than eight decades since nuclear fission was experimentally observed by Hahn and Strassmann and described by Meitner and Frisch in 1939. In the same year, Bohr and Wheeler conjectured that the fission of the nuclear liquid drop would likely be accompanied by the rapid formation of tiny droplets, later identified with either scission neutrons or other ternary fission fragments, a process which has not yet been discussed in a fully quantum many-body framework. The main difficulty in addressing both of these stages of nuclear fission is both are highly non-equilibrium processes. Here we will present the first fully microscopic characterization of the scission mechanism, along with the spectrum and the spatial distribution of scission neutrons, and some upper limit estimates for the emission of charged particles.
nucl-thPRL(2024)·26 citations
03
Comparative Study of alpha-alpha interaction potentials constructed using various phenomenological models
Ayushi Awasthi · O. S. K. S. Sastri
In this paper, we have made a comparative study of alpha-alpha scattering using different phenomenological models like Morse, double Gaussian, double Hulthen, Malfliet-Tjon and double exponential for the nuclear interaction and atomic Hulthen as screened coulomb potential. The phase equations for S, D and G channels have been numerically solved using 5th order Runge-Kutta Method to compute scattering phase shifts for elastic scattering region consisting of energies up to 25.5 MeV. The model parameters in each of the chosen potentials were varied in an iterative fashion to minimize the mean absolute percentage error between simulated and expected scattering phase shifts. A comparative analysis revealed that, all the phenomenological models result in exactly similar inverse potentials with closely matching mean absolute percentage error values for S, D and G state. One can conclude that any mathematical function that can capture the basic features of two body interaction would always guide correctly in construction of inverse potentials.
nucl-thTurk.J.Phys.(2024)·9 citations
04
Multi-step particle emission probabilities in superheavy nuclei at moderate excitation energies
A. Rahmatinejad · T. M. Shneidman · G. G. Adamian · N. V. Antonenko · P. Jachimowicz · M. Kowal
The probabilities of $x n$ -, $p x n$ -, and $α x n$ -evaporation channels in excited superheavy nuclei were evaluated using the Monte Carlo method. The calculations utilized microscopically determined nuclear level densities and were compared with results obtained from the phenomenological Jackson formula. Effective temperatures derived from the microscopic approach were incorporated into the Jackson formula for different evaporation channels at low and moderate excitation energies. Additionally, an analytical formula was introduced to estimate the average kinetic energy of emitted particles in multi-step processes.
nucl-thnucl-exPLB(2023)·5 citations
05
Dispersion effects in elastic electron scattering from $^{208}$ Pb
D. H. Jakubassa-Amundsen · X. Roca-Maza
Dispersion corrections to elastic electron scattering from $^{208}$ Pb at energies up to 150 MeV are estimated within the second-order Born approximation. All strong transient nuclear excited states with angular momentum up to $L = 3$ and natural parity are taken into consideration. It is found that at small scattering angles the high-lying $L = 1$ isovector states provide the dominant contribution to the dispersive change of the differential cross section and of the beam-normal spin asymmetry. At the backmost angles these changes are considerably smaller and are basically due to the isoscalar $L = 2$ and, to a lesser extent, $L = 3$ states. In comparison with the findings for $^{12}$ C, the dispersive cross-section modifications for $^{208}$ Pb are significantly larger, while the spin-asymmetry changes are much smaller at all angles. The latter originates from the destructive interference of the multipole contributions in $^{208}$ Pb that switch sign when proceeding from $L$ to $L + 1$ . This mechanism might be the origin of the small beam-normal spin asymmetries recently measured in $^{208}$ Pb at much larger energies.
nucl-thPRC(2023)·6 citations
06
Quantum van der Waals theory meets quarkyonic matter
Roman V. Poberezhnyuk🇺🇦 · Horst Stoecker🇩🇪 · Volodymyr Vovchenko🇩🇪
We incorporate the empirical low-density properties of isospin symmetric nuclear matter into the excluded-volume model for quarkyonic matter by including attractive mean field in the nucleonic sector and considering variations on the nucleon excluded volume mechanism. This corresponds to the quantum van der Waals equation for nucleons, with the interaction parameters fixed to empirical ground state properties of nuclear matter. The resulting equation of state exhibits the nuclear liquid-gas transition at $n_{B} \leq ρ_{0}$ and undergoes a transition to quarkyonic matter at densities $n_{B} \sim 1.5 - 2 ρ_{0}$ that are reachable in intermediate energy heavy-ion collisions. The transition is accompanied by a peak in the sound velocity. The results depend only mildly on the chosen excluded volume mechanism but do require the introduction of an infrared regulator $Λ$ to avoid the acausal sound velocity. We also consider the recently proposed baryquark matter scenario for the realization of the Pauli exclusion principle, which yields a similar equation of state and turns out to be energetically favored in all the considered setups.
nucl-thhep-phPRC(2023)·15 citations
07
Linearly stable and causal relativistic first-order spin hydrodynamics
Nora Weickgenannt🇫🇷
We derive equations of motion for dissipative spin hydrodynamics from kinetic theory up to first order in a gradient expansion. Choosing a specific form of the matching conditions, relating the change in the spin potential to the spin diffusion and spin energy, we then show that the equations of motion, linearized around homogeneous global equilibrium, are causal and stable in any Lorentz frame, if certain sufficient conditions on the transport coefficients are fulfilled.
nucl-thhep-thPRD(2023)·34 citations
08
Optimized nuclear energy density functionals including long-range pion contributions
L. Zurek · S. K. Bogner · R. J. Furnstahl · R. Navarro Pérez · N. Schunck · A. Schwenk
Nuclear energy density functionals successfully reproduce properties of nuclei across almost the entire nuclear chart. However, nearly all available functionals are phenomenological in nature and lack a rigorous connection to systematically improvable nuclear forces. This issue might be solved with an energy density functional obtained from first principles. As an intermediate step towards this goal we construct the GUDE family of functionals that is obtained from a hybrid scheme consisting of long-range pion-exchange contributions derived from chiral effective field theory at the Hartree-Fock level and a phenomenological Skyrme part. When including pion contributions beyond next-to-leading order in the chiral expansion, we find significant improvements over a reference Skyrme functional constructed following the same protocol. We analyze the importance of different pion contributions and identify which terms drive the observed improvements. Since pions are incorporated without adding further optimization parameters to the functionals, the improvements can be attributed to the functional form of these terms. Our work therefore suggests that the considered chiral contributions constitute useful ingredients for true ab initio energy density functionals.
nucl-thnucl-exPRC(2024)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE