Nuclear Theory·nucl-th

Friday·February 20, 2026

8 papers—4 primary·4 cross-listed

01
From $χ$ EFT to Multi-Region Modeling: Neutron star structure with a polytropic extension of $χ$ EFT and MUSES Calculation Engine multi-layer modeling
Federico Nola
Neutron stars provide a unique environment to probe the properties of dense nuclear matter. In this work, we present a comparative study between two approaches to modeling the neutron star structure: a Chiral Effective Field Theory based approach and the MUSES Calculation Engine framework, which uses three different approaches for the three density regions. We analyze the resulting mass-radius relations, discussing the respective advantages and limitations of the two methods.
nucl-thastro-ph.HE0 citations
02
Spectra and elliptic flow of light hadrons in an expanding fire-cylinder model for the RHIC Beam Energy Scan
Anand Rai🇮🇳 · Ashutosh Dwibedi🇮🇳 · Sabyasachi Ghosh🇮🇳
We investigate the transverse momentum spectra ( $p_{T}$ ) and elliptic flow ( $v_{2}$ ) of $π^{\pm}$ , $K^{\pm}$ , $p$ , and $p ˉ$ produced in peripheral Au+Au collisions at $s_{NN} = 7.7$ , 11.5, 19.6, 27, and 39 GeV in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). The analysis is carried out within an expanding elliptic fire-cylinder model that incorporates longitudinal expansion and anisotropic transverse flow. Particle production at kinetic freeze-out is obtained using a local equilibrium distribution function with a blast-wave-like fluid velocity profile derived from the expansion dynamics of the elliptic fire-cylinder. The model parameters governing the collective expansion are first constrained by fitting the midrapidity $p_{T}$ spectra of $π^{\pm}$ and are then applied, without further adjustment, to $K^{\pm}$ , $p$ , and $p ˉ$ . The model provides a consistent description of the $p_{T}$ spectra and reproduces the qualitative behavior of the elliptic flow for all considered particle species.
nucl-thhep-phNPA(2026)·1 citation
03
Model bias and parameter optimisation with the example of INCL/ABLA
Jason Hirtz🇫🇷 · Jean-Christophe David🇫🇷 · Ingo Leya🇨🇭 · José Luís Rodríguez Sánchez🇪🇸 · Georg Schnabel🇦🇹
The accuracy and precision of high-energy spallation models play a crucial role in the design and development of new applications and experiments, as well as in data analysis. We discuss the complementarity between parameter optimisation and model bias estimation approaches within a Bayesian framework. This is illustrated using the IntraNuclear Cascade model of Liège (INCL) together with the Ablation model (ABLA), for which these two approaches for model bias estimation have been applied independently in previous works.
nucl-thEPJA(2026)·0 citations
04
Evidence for Multimodal Superfluidity of Neutrons
Yuan-Zhuo Ma · Georgios Palkanoglou · Joseph Carlson · Stefano Gandolfi · Alexandros Gezerlis · Gabriel Given · Ashe Hicks · Dean Lee · Kevin E. Schmidt · Jiabin Yu
We present theoretical and experimental evidence for a new phase of matter in neutron-rich systems that we call multimodal superfluidity. Using ab initio lattice calculations, we show that the condensate consists of coexisting s-wave pairs, p-wave pairs in entangled double pair combinations, and quartets composed of bound states of two s-wave pairs. We identify multimodal superfluidity as a general feature of single-flavor spin-1/2 fermionic systems with attractive s-wave and p-wave interactions, provided the system is stable against collapse into a dense droplet. Beyond neutrons at sub-saturation densities, we demonstrate that this phase appears in generalized attractive extended Hubbard models in one, two, and three dimensions. We elucidate the mechanism for this coexistence using self-consistent few-body Cooper models and compare with Bardeen-Cooper-Schrieffer theory. We also derive the form of the effective action and show that spin, rotational, and parity symmetries remain unbroken. Finally, we analyze experimental data to show that p-wave pair gaps and quartet gaps are present in atomic nuclei, and we discuss the consequences of this new phase for the structure and dynamics of neutron star crusts.
nucl-thastro-ph.SRcond-mat.supr-connucl-ex+14 citations

Affiliations

first authorsco-authorsvia INSPIRE

From χEFT to Multi-Region Modeling: Neutron star structure with a polytropic extension of χEFT and MUSES Calculation Engine multi-layer modeling

Spectra and elliptic flow of light hadrons in an expanding fire-cylinder model for the RHIC Beam Energy Scan

Model bias and parameter optimisation with the example of INCL/ABLA

Evidence for Multimodal Superfluidity of Neutrons

Affiliations

From $χ$ EFT to Multi-Region Modeling: Neutron star structure with a polytropic extension of $χ$ EFT and MUSES Calculation Engine multi-layer modeling