Nuclear Theory·nucl-th

Thursday·September 26, 2024

11 papers—6 primary·5 cross-listed

01
Perturbative treatment of nonlocal chiral interactions in auxiliary-field diffusion Monte Carlo calculations
Ryan Curry · Rahul Somasundaram · Stefano Gandolfi · Alexandros Gezerlis · Ingo Tews
Nuclear many-body systems, ranging from nuclei to neutron stars, are some of the most interesting physical phenomena in our universe, and Quantum Monte Carlo (QMC) approaches are among the most accurate many-body methods currently available to study them. In recent decades, interactions derived from chiral effective field theory (EFT) have been widely adopted in the study of nuclear many-body systems. One drawback of the QMC approach is the requirement that the nuclear interactions need to be local, whereas chiral EFT interactions usually contain nonlocalities. In this work, we leverage the capability of computing second-order perturbative corrections to the ground-state energy in order to develop a self-consistent approach to including nonlocal operators in QMC calculations. We investigate both the deuteron and the neutron-matter equation of state in order to show the robustness of our technique, and pave the way for future QMC calculations at higher orders in the EFT, where nonlocal operators cannot be avoided.
nucl-thPRC(2025)·11 citations
02
A novel emulator for fission event generators
Karl Daningburg · A. E. Lovell · R. O'Shaughnessy
A wide variety of emulators have been developed for nuclear physics, particularly for use in quantifying and propagating parametric uncertainties to observables. Most of these methods have been used to emulate structure observables, such as energies, masses, or separation energies, or reaction observables, such as cross sections. Rarely, if ever, have event generators for theory models been emulated. Here, we describe one such novel emulator for the fission fragment decay code, $CGMF$ , which calculates the emission of prompt neutrons and $γ$ rays from fission fragments. The emulator described in this work uses a combination of a noisy emission model and mixture density network to model the neutron and $γ$ -ray multiplicities and energies. In this manuscript, we display the power of this type of emulator for not only modeling average prompt fission observables but also correlations between fission fragment initial conditions and these observables, using both neutron-induced and spontaneous fission reactions.
nucl-thastro-ph.HEphysics.comp-ph1 citation
03
$p Ω$ femtoscopy using baryon-baryon effective potentials
Marc Piquer i Méndez🇪🇸 · Assumpta Parreño🇪🇸 · Juan Torres-Rincon🇪🇸
We have generated an updated version of the $p Ω$ potential for low-energy interactions based on an effective field theory approach at leading order. This potential, together with other potentials based either on different parametrizations or lattice QCD calculations, have been used to solve the Schrödinger equation numerically, obtaining the scattering wave functions for different values of the relative momentum. Using these wave functions, we have computed the $p Ω$ femtoscopic correlation functions, comparing the results with those published by the ALICE collaboration.
nucl-thhep-phPoS(2025)·3 citations
04
Magnetic dipole contribution to the $γ$ -spectrum from $d$ - $t$ collisions
N.K. Timofeyuk
One in about a few hundred thousand sub-Coulomb $d$ - $t$ collisions is accompanied by the emission of a $γ$ -photon. The $γ$ -spectrum from these collisions is dominated by a 16.7 MeV peak, corresponding to the population of the $p$ -wave $3/ 2^{-}$ $α$ - $n$ ground-state resonance in the E1 transition from an intermediate $d$ -wave $α$ - $n$ state, corresponding to the $^{5}$ He excited state around 16.7 MeV. The strength of this spectrum at the large $γ$ -energy endpoint decreases fast both due to kinematic factors and due to centrifugal repulsion between neutron and $α$ -particle at near-zero relative energies. However, no centrifugal repulsion would occur if $s$ -wave $α$ - $n$ states were populated in magnetic dipole transition. Therefore, one can expect that close to the $γ$ -spectrum endpoint around 17.5 MeV the M1 transition could dominate, leading to additional counts in experimental spectra which could be easily misinterpreted as a background. This work presents calculations of the M1 contribution to the $d + t \to α + n + γ$ cross section caused both by convection and magnetization currents. While the first contribution was found to be negligible, the one from magnetization depends strongly on the choice of the model for the $d$ - $t$ channel scattering wave function. Using $d$ - $t$ interaction models from the literature, represented either by a gaussian of by a square well, resulted in unrealistically strong M1 contribution. With constructed in the present work optical folding potential, correctly representing the sizes of deuteron and triton, the M1 contribution near the endpoint is reduced to about 2 $%$ of the 16.7-MeV E1 peak. Arguments in favor of more detailed calculations, that could potentially change this number, are put forward.
nucl-thPRC(2024)·3 citations
05
Constraints on the Equation of State of Nuclear Matter from Systematically Comparing SMASH Calculations to HADES Data
Justin Mohs🇩🇪 · Simon Spies🇩🇪 · Hannah Elfner🇩🇪
We aim to constrain the equation of state of nuclear matter by comparing calculations with the SMASH transport model to directed and elliptic flow measurements for protons and deuterons performed by the HADES collaboration in a systematic way. A momentum-dependent term is included in the potential for which we show that it is needed to describe flow data. We further incorporate a simple symmetry potential in the transport model and present constraints on the stiffness of the equation of state of nuclear matter at saturation density and on the symmetry potential. The constraints are obtained by performing a Bayesian analysis such that we can also provide an uncertainty for the estimated parameters. The posterior distribution is obtained by Markov chain Monte Carlo sampling for which we emulate the transport model with a Gaussian process to lower computational costs. We find that a relatively stiff equation of state is favoured in our analysis with a small uncertainty whereas the constraints obtained for the symmetry potential are rather loose.
nucl-thnucl-exPRC(2025)·17 citations
06
The effect of causality constraints on Bayesian analyses of heavy-ion collisions
Thiago S. Domingues🇧🇷 · Renata Krupczak🇩🇪 · Jorge Noronha🇺🇸 · Tiago Nunes da Silva🇧🇷 · Jean-François Paquet🇺🇸 · Matthew Luzum🇧🇷
There have long been questions about the limits to the validity of relativistic fluid dynamics, and whether it is being used outside its regime of validity in modern simulations of relativistic heavy-ion collisions. An important new tool for answering this question is a causality analysis in the nonlinear regime -- if the solutions of the evolution equations do not respect relativistic causality, they are not a faithful representation of the underlying relativistic theory (in this case, quantum chromodynamics). Using this non-linear criterion, it has recently been shown that hydrodynamics is indeed being used outside its regime of validity in simulations, at least sometimes. Here we explore the phenomenological implications, particularly the quantitative effects of demanding limits on acausality in modern Bayesian parameter estimation. We find that, while typically only a small fraction of the system's energy is initially in an acausal regime, placing strict limits on the allowed energy fraction significantly changes the preferred properties of the initial condition, which in turn alters the extracted medium properties such as bulk viscosity, where large values are no longer favored. These findings highlight the importance of developing better theoretical descriptions of the early-time, out-of-equilibrium dynamics of relativistic heavy-ion collisions.
nucl-thhep-phPRC(2024)·15 citations
07
Chiral effects on radiation and energy loss in quark-gluon plasma
Jeremy Hansen🇺🇸 · Kirill Tuchin🇺🇸
The emergent axion excitations in the quark-gluon plasma are generated by the sphaleron transitions. Their interactions with the photon and gluon fields are governed by the axion electro- and chromodynamics respectively. We discuss the effect of the emergent axion on the photon production and energy loss in the quark-gluon plasma. In particular, we review the Chiral Cherenkov effect, and the impact of the chiral anomaly on bremsstrahlung.
↳ hep-phnucl-thIJMPE(2024)·3 citations
08
Radioactivity of Quark Nuggets
Yang Bai🇺🇸 · Mrunal Korwar🇺🇸
Quark nuggets $_{Z}^{A} Q$ , as Fermionic non-topological solitons, could have their mass per baryon smaller than ordinary nuclei and behave as exotic nuclei with different relations of atomic number and atomic mass number. Using both the degenerate Fermi gas model and the Friedberg-Lee shell model, we calculate the properties of quark nuggets made of up and down quarks. Similar to ordinary nuclei, quark nuggets could exhibit their own radioactivity, including gamma decay, beta decay, and (explosive) spontaneous fission, with the qualitative properties presented here. These quark nugget properties may provide guidance for searching for quark nuggets in situ from binary neutron star mergers.
↳ hep-phastro-ph.HEnucl-thJHEP(2025)·7 citations
09
Disoriented isospin condensates in heavy-ion collisions
Joseph Kapusta🇺🇸 · Scott Pratt🇺🇸 · Mayank Singh🇺🇸
Anomalous neutral to charged kaon correlations measured by the ALICE collaboration have defied usual explanations. We propose that the large fluctuations could arise because of a disoriented isospin condensate where there is an imbalance between up and down condensates at the time kaons hadronize. This could happen in heavy-ion collisions when the quark condensate re-forms as the system cools and the approximate chiral symmetry of QCD is broken. Within the linear sigma model, we show that the energy cost of forming a disoriented isospin condensate is small making it very plausible.
↳ hep-phnucl-thEPJ Web Conf.(2025)·0 citations
10
Spinodal decomposition in Bjorken flow
Joseph Kapusta🇺🇸 · Mayank Singh🇺🇸 · Thomas Welle🇺🇸
The QCD first-order phase transition at large baryon densities is expected to proceed by spinodal decomposition. This spinodal phase is likely to leave its signatures on the experimental observables measured in heavy-ion collision experiments. Identifying these signatures requires phenomenological models integrating surface effects resulting from the phase transition into the hydrodynamical description of the expanding quark gluon plasma. We write the equations of relativistic hydrodynamics with spinodal decomposition and solve it in on a background of Bjorken flow relevant for heavy-ion collisions.
↳ hep-phnucl-thEPJ Web Conf.(2025)·3 citations
11
Finite- and infinite-volume study of $D D π$ scattering
Sebastian M. Dawid🇺🇸 · Fernando Romero-López🇨🇭 · Stephen R. Sharpe🇺🇸
We develop a comprehensive framework for extracting the pole position and properties of the doubly-charmed tetraquark $T_{cc}^{+} (3875)$ from lattice QCD data using the relativistic three-particle formalism. This approach incorporates the effect of the one-pion exchange diagram in $D D π$ and $D D^{*}$ scattering, making it applicable at energies coinciding with the left-hand cut in the partial-wave projected $D D^{*}$ amplitude. We present an example application of this framework to existing lattice QCD data at $m_{π} = 280$ MeV. We solve the integral equations describing the $D D π$ reaction, use LSZ reduction to determine the corresponding $D D^{*}$ amplitude, and find the values of the infinite-volume two- and three-body $K$ matrices that lead to agreement with lattice $D D^{*}$ phase shifts within their uncertainties. Using these $K$ matrices in the three-particle quantization condition, we describe the finite-volume $D D^{*}$ spectrum and find good agreement with the lattice QCD energies. Our results suggest that, at this pion mass, the tetraquark appears as a pair of subthreshold complex poles whose precise location strongly depends on the value of the $D D π$ three-particle $K$ matrix.
↳ hep-lathep-phnucl-thJHEP(2025)·39 citations

Affiliations

first authorsco-authorsvia INSPIRE