Nuclear Theory·nucl-th

Thursday·July 23, 2026

6 papers—4 primary·2 cross-listed

01
PMM-IMSRG emulator for the nuclear equation of state with quantified uncertainties
Patrick Cook🇺🇸 · Kang Yu🇺🇸 · Christian Drischler🇺🇸 · Scott K. Bogner🇺🇸
We introduce a hybrid emulator for in-medium similarity renormalization group (IMSRG) calculations of nuclear matter, based on chiral nucleon-nucleon and three-nucleon interactions and an implicit-reduced-basis method emulator constructed from parametric matrix models (PMMs) which is capable of rigorously estimating its uncertainties via conformal predictions. The resulting PMM-IMSRG emulator enables fast and accurate predictions with trustworthy confidence intervals of the nuclear equation of state (EOS) across a wide range of input parameters, including low-energy couplings, IMSRG flow parameters, densities, and basis sizes. This framework provides the foundation for principled uncertainty quantification of the nuclear EOS and enables computationally demanding applications such as Bayesian parameter estimation using our IMSRG calculations. As a first application, we present results for the coupling constants of the two quark-mass-dependent three-nucleon interactions, recently identified to contribute at next-to-next-to-leading order in the chiral expansion based on a renormalization-group analysis, by fitting them to empirical saturation properties. We then propagate both parametric and emulator uncertainties to the EOS in the limits of pure neutron matter and symmetric nuclear matter.
nucl-th2 citations
02
Charge-Exchange Reactions Accompanied by a Single $π^{+}$ Production in Medium-Energy Heavy-Ion Collisions
Xiao-lei Chen · Jin-yu Yang · Shi-kang Dong · Bao-wei Ding · Bi-tao Hu · Xi-yu Qiu
Heavy-ion charge-exchange (CE) reactions provide a sensitive probe of isospin dynamics in nuclear collisions. We investigate the reaction $^{12} C (^{12} C,^{12} N π^{+})^{12} Be$ at 400--600 A MeV within the ultra-relativistic quantum molecular dynamics model combined with a phase-space coalescence approach. This reaction represents a nontrivial CE channel accompanied by a single $π^{+}$ production in heavy-ion collisions, extending previous studies from lepton-induced to hadronic systems. The $^{12} N$ fragment is formed via nucleon and meson exchange, whereas $π^{+}$ production is primarily governed by $Δ$ resonance excitation and decay, enabling simultaneous investigations of CE processes and $Δ$ -induced pion production within the same reaction system. We calculate the reaction cross section and analyze the four-momentum distributions of $^{12} N$ and $π^{+}$ . Characteristic phase-space features reflect different production mechanisms and provide guidance for future experimental designs. Additionally, this reaction may serve as a potential pathway for rare-isotope production.
nucl-th0 citations
03
Stability of intruder-driven quadrupole and hexadecapole deformation effects in Xenon, Barium, Cerium and Neodymium isotopes
K. Ziyatkhan · R. Rodríguez-Guzmán · L. M. Robledo
Two-dimensional Generator Coordinate Method calculations for the axial quadrupole $β_{2}$ and hexadecapole $β_{4}$ collective deformations are carried out with the Gogny force in a series of Xe, Ba, Ce and Nd isotopes with neutron numbers covering both magic neutron shell closures N=82 and N=126. The underlying mean-field configurations are used to characterize the expected dynamic behavior of the system. Two regions of strong coupling between the quadrupole and hexadecapole degrees of freedom are found and characterized. Quantum fluctuations soften the mean-field ground state values of $β_{2}$ and $β_{4}$ in transitional regions. The ground state correlation energy coming from $β_{4}$ is comparable in size to the one coming from $β_{2}$ , and both together amount to a sizable 1.5 MeV. Shape coexistence in some isotopes and its impact in the excitation energy of the first excited state is analysed. Finally, the role of a second intruder orbital in the explanation of the large deformation parameters of some nuclei in the region is discussed.
nucl-thPRC(2026)·1 citation
04
Diffractive Two-Photon Exchange and Beam Normal-Spin Asymmetries for Elastic Electron Scattering on Nuclei
Volodymyr Tereshchuk🇺🇸 · Andrei Afanasev🇺🇸
We developed a theoretical approach to elastic electron scattering on nuclei that includes a two-photon-exchange mechanism responsible for parity-conserving single-spin beam asymmetries. The two-photon-exchange amplitude at small scattering angles is treated in a diffractive framework similar to that of pion-nucleus elastic scattering applied to the nuclei $_{6}^{12}$ C, $_{20}^{40}$ Ca and $_{82}^{208}$ Pb. The predicted kinematic features of the beam polarization asymmetries for different nuclei may reconcile Jefferson Lab's experimental results at finite scattering angles with a forward limit given by an optical theorem, potentially resolving the so-called ``PREX Puzzle" for $_{82}^{208}$ Pb.
nucl-thhep-ph0 citations
05
Nucleon unpolarized second Mellin moments using lattice QCD ensembles with physical quark masses and in the continuum limit
Constantia Alexandrou (University of Cyprus and The Cyprus Institute)🇨🇾 · Simone Bacchio (The Cyprus Institute)🇨🇾 · Jacob Finkenrath (University of Wuppertal)🇩🇪 · Christos Iona (University of Cyprus and The Cyprus Institute)🇨🇾 · Giannis Koutsou (The Cyprus Institute)🇨🇾 · Christian Kummer (University of Cyprus and Technical University of Berlin)🇨🇾 · Yan Li (The Cyprus Institute)🇨🇾 · Bhavna Prasad (The Cyprus Institute)🇨🇾 · Gregoris Spanoudes (University of Cyprus)🇨🇾
We compute the matrix elements of the energy-momentum tensor of the nucleon using four ensembles of twisted mass clover-improved fermions with the up, down, strange and charm quark masses tuned to approximately their physical values. The four ensembles have similar physical volume and lattice spacings $a = 0.080$ ~fm, $0.068$ ~fm, $0.057$ ~fm, and $0.049$ fm, allowing us to take the continuum limit directly at the physical pion mass point. We compute both connected and disconnected quark contributions as well as gluon contributions. All renormalization functions, including the mixing of the quark singlet with the gluon, are determined non-perturbatively. We extract the gravitational form factors in the continuum limit at $Q^{2} = 0$ and evaluate the contribution of quarks and gluons to the momentum and angular momentum of the proton. Using the values of the intrinsic quark spin computed using the same gauge ensembles we also determine the orbital angular momentum for each quark flavor.
↳ hep-lathep-exhep-phnucl-ex+11 citation
06
Fermionic pairs, from the surface to the bulk
Sandra Brandstetter · Carl Heintze · Fabian Brauneis · Stephanie M. Reimann · Georg Bruun · Maciej Gałka · Selim Jochim
Fermion pairing underlies collective quantum phenomena across widely different forms of matter. In extended systems such as ultracold Fermi gases, pairing is commonly understood through the BCS--BEC crossover, where the pair size evolves from large, overlapping Cooper pairs to tightly bound dimers. In finite systems such as atomic nuclei, superconducting grains and quantum dots, however, the same pairing tendency competes with confinement, shell filling and spatial inhomogeneity, making the microscopic structure of pairs much harder to access. Here, we image pair correlations in a finite, tunable system of few fermionic atoms with single-particle resolution and full counting statistics. We observe that confinement and shell structure re-organize pairing in real space: In the weakly interacting, confinement-dominated regime, closed-shell configurations suppress correlations in the high-density trap center. Pairing is mainly observed toward the low-density surface. Open-shell systems, however, support substantially stronger central pairing. Already for surprisingly small systems, increasing either interaction strength or particle number restores a locally bulk-like Cooper-pair profile in the trap center, whereas the edge retains dimer-like correlations. By resolving where pairs form and how their character changes from localized dimers to overlapping Cooper pairs, our measurements provide a microscopic view of pairing in finite fermionic matter and connect the physics of mesoscopic cold atoms to pairing phenomena in nuclei and superconducting nanostructures.
↳ cond-mat.quant-gasnucl-exnucl-thquant-ph0 citations

Affiliations

first authorsco-authorsvia INSPIRE

PMM-IMSRG emulator for the nuclear equation of state with quantified uncertainties

Charge-Exchange Reactions Accompanied by a Single π+ Production in Medium-Energy Heavy-Ion Collisions

Stability of intruder-driven quadrupole and hexadecapole deformation effects in Xenon, Barium, Cerium and Neodymium isotopes

Diffractive Two-Photon Exchange and Beam Normal-Spin Asymmetries for Elastic Electron Scattering on Nuclei

Nucleon unpolarized second Mellin moments using lattice QCD ensembles with physical quark masses and in the continuum limit

Fermionic pairs, from the surface to the bulk

Affiliations

Charge-Exchange Reactions Accompanied by a Single $π^{+}$ Production in Medium-Energy Heavy-Ion Collisions