We present a novel deep generative framework that uses probabilistic diffusion models for ultrafast, event-by-event simulations of heavy-ion collision output. This new framework is trained on ultrarelativistic quantum molecular dynamics (UrQMD) cascade data to generate a full collision event output containing 26 distinct hadron species. The output is represented as a point cloud, where each point is defined by a particle's momentum vector and its corresponding species information. Our architecture integrates a normalizing flow-based condition generator that encodes global event features into a latent vector, and a diffusion model that synthesizes a point cloud of particles based on this condition. A detailed description of the model and an in-depth analysis of its performance is provided. The conditional point-cloud diffusion model learns to generate realistic output particles of collision events which successfully reproduce the UrQMD distributions for multiplicity, momentum, and rapidity of each hadron type. The flexible point-cloud representation of the event output preserves full event-level granularity, enabling direct application to inverse problems and parameter estimation tasks while also making it easily adaptable for accelerating any event-by-event model calculation or detector simulation.

A novel point-cloud diffusion model for relativistic heavy-ion collisions, capable of ultrafast generation of complete, event-by-event collision output, is introduced. When trained on ultrarelativistic quantum molecular dynamics cascade simulations, the model generates realistic collision event output containing 26 distinct hadron species, as a list of particle momentum vectors along with their particle ID. From solving inverse problems to accelerating model calculations or detector simulations, the model can be a promising general-purpose tool for heavy-ion collisions beneficial to both theoretical studies and experimental applications.

We train a generative diffusion model to simulate ultrarelativistic heavy-ion collisions from end to end. The model takes initial entropy density profiles as input and produces two-dimensional final particle spectra, successfully reproducing integrated and differential observables. It also captures higher-order fluctuations and correlations. These findings suggest that the generative model has successfully learned the complex relationship between initial conditions and final particle spectra for various shear viscosities, as well as the fluctuations introduced during initial entropy production and hadronization stages, providing an efficient framework for resource-intensive physical goals.

We construct an equation of state describing cold and dense matter in the core of neutron stars which includes an admixture of fermionic dark matter and incorporates nucleon effective masses derived from the relativistic Brueckner-Hartree-Fock (BHF) many-body approach within a relativistic mean-field model. Such a BHF-informed mixed-model approach increases stellar compactness, with mass-radius configurations that are consistent with smaller, lighter pulsars. The model displays the expected nonmonotonic behavior of sound speed hinted at by neutron-star data and is closer to the conformal bound at maximum mass. We find that the model displays tension with bounds on heavier pulsars, suggesting that the hypothesis of an aggregated dark component in neutron stars needs further critical study.

The self-conjugate nucleus ${}^{164}\mathrm{Pb}$, with equal neutron and proton numbers ($N=Z=82$), lies far beyond the proton dripline and at a traditional magic number. Its possible doubly magic nature is investigated based on the state-of-the-art deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), which incorporates nuclear deformation, pairing correlations, and continuum effects in a fully self-consistent framework. The experimentally known binding energies of neutron-deficient $Z=82$ isotopes and $N=82$ isotones are well reproduced. Pronounced two-neutron and two-proton gaps, together with sizable single-particle shell gaps, support the persistence of the $N=Z=82$ shell closures and point to mutually enhanced magicity in ${}^{164}\mathrm{Pb}$. Potential decay modes, including one-proton, two-proton, and multiproton emissions, are analyzed using the direct decay model with quantified uncertainties, predicting a dominant one-proton emission with a half-life ranging from $22\mathrm{ps}$ to $1.8\mu \mathrm{s}$. These results suggest that ${}^{164}\mathrm{Pb}$ may define the outermost reach of experimentally accessible nuclei beyond the proton dripline, making it a compelling target for future experiments.

A simple algebraic scheme incorporating the prolate-oblate shape phase transition (SPT) is proposed within the framework of the interacting boson model to describe the quadrupole deformation features of Xe isotopes near $A=130$. The analysis demonstrates that novel $\gamma$-soft modes, characterized by the unusual quadrupole moments $Q\left(2_1^{+}\right)<0$ and $0<Q\left(2_2^{+}\right)\ll \left|Q\left(2_1^{+}\right)\right|$, can emerge near the critical point of this SPT. This finding is further applied to interpret the properties of low-lying states in the relevant Xe nuclei, particularly the experimentally observed nearly vanishing spectroscopic quadrupole moment $Q\left(2_2^{+}\right)$, thereby offering new insights into the structure of a $\gamma$-soft deformed nucleus.

Background: The preference for light nuclear systems to coagulate into $\alpha$-particle clusters has been well-studied. The possibility of a linear chain configuration of $\alpha$ particles would allow for a new way to study this phenomenon.

Purpose: A rotational band of states in ${}^{14}\mathrm{C}$ has been claimed showing a ${\pi }^2$ linear chain structure. The mirror system, ${}^{14}\mathrm{O}$, has been studied here to examine how this linear chain structure is affected by replacing the valence neutrons with protons.

Method: A beam of ${}^{10}\mathrm{C}$ was incident into a chamber filled with $\mathrm{He}:{\mathrm{CO}}_2$ gas with the tracks recorded inside the TexAT Time Projection Chamber and the recoil $\alpha$ particles detected by a silicon detector array to measure the ${}^{10}\mathrm{C}(\alpha ,\alpha )$ cross section.

Results: The experimental cross section was compared with previous studies and fit using R-matrix theory with the previously observed ${}^{14}\mathrm{O}$ states being transformed to the ${}^{14}\mathrm{C}$ using mirror symmetry. The measured cross section does not replicate the claimed states, with the predicted cross section exceeding that observed at several energies and angles.

Conclusion: A series of possibilities is highlighted, with the most likely being that the originally seen ${}^{14}\mathrm{C}$ states did not constitute a ${\pi }^2$ rotational band with a potentially incorrect spin assignment due to the limitations of the angular-correlation method with nonzero-spin particles. The work highlights the difficulties in measuring broad resonances corresponding to a linear chain state in a high level density.

To systematically evaluate the synthesis potential of neutron-deficient superheavy nuclei (SHN, $Z$ = 104–113) through cold-fusion reactions, we conducted comprehensive theoretical investigations on 145 projectile-target combinations using the dinuclear system (DNS) model. Our calculations demonstrate that cold-fusion reactions exhibit maximum cross sections predominantly through 1–2 neutron evaporation channels, with optimal beam energies near the Coulomb barrier (excitation energies <30 MeV). Notably, several systems achieve peak cross sections below the Bass barrier, suggesting either limitations in the Bass potential formulation or substantial deformation-induced reductions in effective Coulomb repulsion. Our calculations show excellent agreement with existing experimental data, while revealing a weak positive correlation between neutron richness of projectile isotopes and fusion enhancement. For lead- and bismuth-based cold-fusion reactions, the evaporation residue crosssections (ERCSs) display characteristic linear suppression with increasing proton number of projectile isotopes ($\mathrm{\Delta }Z=9$ corresponds to $\approx {10}^6$ reduction in ERCS). This systematic behavior originates from dual suppression mechanisms: diminishing fusion probabilities and progressively lower fission barriers in heavier SHN products. Quantitative analysis of the contact potential ($V_{\mathrm{in}}$) reveals a linear dependence on the projectile-target proton number product ($Z_{\mathrm{P}}\times Z_{\mathrm{T}}$), with neutron-rich systems exhibiting systematically reduced $V_{\mathrm{in}}$ values. Intriguingly, in configurations where $V_{\mathrm{in}}<V_{\mathrm{S}}$ (saddle point potential), precapture nucleon transfer processes may dominate reaction dynamics. Based on the DNS model, we identify promising projectile-target combinations and energy windows for synthesizing unknown SHN with cross-sections. The comparative analysis identifies cold fusion as the preferred method for synthesizing proton-drip-line nuclei in the $Z$ = 104–113 region due to its clear advantages over alternative approaches. This work provides a quantitative basis for future experiments targeting the neutron-deficient region of SHN synthesis.

We present results for the equation of state of symmetric nuclear matter and pure neutron matter obtained in many-body-perturbation theory (MBPT) up to third order, based on various chiral two- and three-nucleon interactions used in ab initio calculations of nuclei. We extract equation of state properties, such as the incompressibility and the symmetry energy, and discuss estimates of the theoretical uncertainties due to neglected higher-order contributions in the MBPT expansion as well as the chiral effective field theory expansion. In addition, we discuss the Fermi liquid approach to nuclear matter. We calculate all two- and three-nucleon contributions to the quasiparticle interaction up to second order in MBPT and present results for the Landau parameters, effective mass, and speed of sound for pure neutron matter.

The particle rotor model is utilized to systematically investigate the dynamics of nuclear wobbling motion, taking the valence nucleon $h_{11/2}$ combined with a triaxial core as an example. Through comprehensive analysis of wobbling energy, entanglement entropy, and spectroscopic quadrupole moment, the impacts of moments of inertia, axial deformation parameter, triaxial deformation parameter, and Fermi surface on the emergence and characteristics of transverse wobbling, flip mode, and longitudinal wobbling are examined in detail. These investigations reveal intricate correlations between entanglement entropy and nuclear structural properties, providing new insights into the wobbling phenomena.

Dark photons, the hypothetical gauge bosons associated with an additional $U{\left(1\right)}^{\prime }$ symmetry, can couple to standard model particles through a small kinetic mixing parameter $\varepsilon$ with the ordinary photon. This mechanism provides a portal between the dark sector and visible matter. In this study, we present a procedure to derive theoretical upper bounds on the kinetic mixing parameter ${\varepsilon }^2\left(M_U\right)$ by analyzing dilepton spectra from heavy-ion collisions across a broad energy range, from SIS to LHC energies. Our analysis is based on the microscopic parton-hadron-string dynamics (PHSD) transport approach, which successfully reproduces the measured dilepton spectra in $p+p, p+A$, and $A+A$ collisions across the same energy range. Besides the dilepton channels resulting from interactions and decays of standard model particles (such as mesons and baryons), the PHSD has been extended to include the decay of hypothetical dark photons into dileptons, $U\to e^{+}{e}^{-}$. The production of these dark photons occurs via Dalitz decays of ${\pi }^0, \eta , \omega , {\eta }^{\prime }$, and $\mathrm{\Delta }$ resonances; direct decays of $\rho , \omega$, and $\varphi$; the kaon mode $K^{+}\to {\pi }^{+}U$; and thermal $q\overline{q}$ annihilation in the quark-gluon plasma. Our results show that high-precision measurements of dilepton spectra in heavy-ion collisions provide a sensitive and competitive probe of dark photons in the MeV to multi-GeV mass range. Furthermore, we quantify the experimental accuracy required to constrain the remaining viable parameter space of kinetic mixing in dark photon scenarios.

The first measurement of the $e^{+}{e}^{-}$ pair production at midrapidity and low invariant mass in central Pb-Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ at the Large Hadron Collider is presented. The yield of $e^{+}{e}^{-}$ pairs is compared with a cocktail of expected hadronic decay contributions in the invariant mass ($m_{ee}$) and pair transverse momentum ($p_{\mathrm{T},ee}$) ranges $m_{ee}<3.5\mathrm{GeV}/c^2$ and $p_{\mathrm{T},ee}<8\mathrm{GeV}/c$. For $0.18<m_{ee}<0.5\mathrm{GeV}/c^2$ the ratio of data to the cocktail of hadronic contributions amounts to $1.40\pm 0.11\left(\mathrm{stat}.\right)\pm 0.23\left(\mathrm{syst}.\right)\pm 0.16\left(\mathrm{cocktail}\right)$ and $1.42\pm 0.11\left(\mathrm{stat}.\right)\pm 0.23{\left(\mathrm{syst}.\right)}_{-0.29}^{+0.24}\left(\mathrm{cocktail}\right)$, including or not including medium effects in the estimation of the heavy-flavor background, respectively. It is consistent with predictions from two different models for an additional contribution of thermal $e^{+}{e}^{-}$ pairs from the hadronic and partonic phases. In the intermediate-mass range ($1.2<m_{ee}<2.6\mathrm{GeV}/c^2$), the pair transverse impact parameter of the $e^{+}{e}^{-}$ pairs (${\mathrm{DCA}}_{ee}$, where “DCA” denotes “distance of closest approach”) is used for the first time in Pb-Pb collisions to separate displaced dielectrons from heavy-flavor hadron decays from a possible (thermal) contribution produced at the interaction point. The data are consistent with a suppression of $e^{+}{e}^{-}$ pairs from $c\overline{c}$ and an additional prompt component. Finally, the first direct-photon measurement in the 10% most central Pb-Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ is reported via the study of virtual direct photons in the transverse momentum range $1<p_{\mathrm{T}}<5\mathrm{GeV}/c$. A model including prompt photons, as well as photons from the preequilibrium and fluid-dynamic phases, can reproduce the result, while being at the upper edge of the data uncertainties.

We present an updated deep neural network model for inclusive electron–carbon scattering. Using the bootstrap model [B. E. Kowal et al., Phys. Rev. C 110, 025501 (2024)], we incorporate recent experimental data, as well as older measurements in the deep inelastic scattering region, to derive a reoptimized posterior model. We examine the impact of these new inputs on model predictions and associated uncertainties. Finally, we evaluate the resulting cross-section predictions in the kinematic range relevant to the Hyper-Kamiokande and DUNE experiments.

The spectroscopy of ${}^{67}\mathrm{Zn}$ has been investigated via the fusion-evaporation reaction ${}^{64}\mathrm{Ni}({}^{12}\mathrm{C}$, $2\alpha 1n){}^{67}\mathrm{Zn}$. Three collective bands are established. The observation of strong $E1$ transitions and the well-behaved rotational sequence suggest the new negative-parity band built on the $15/2^{-}$ state is an octupole rotational band. The octupole characteristics of ${}^{67}\mathrm{Zn}$ is well described by the newly developed semimicroscopic cluster model. Systematics of the excitation energies of the $3^{-}$ state in even-even Zn isotopes and observation of an octupole rotational band in odd-$A$ ${}^{67}\mathrm{Zn}$ indicate that the strong octupole effects occur around neutron number 38 in Zn isotopes.

We report about a study of the ordinary muon capture in nuclei belonging to the $sd$ shell, an electroweak process that occurs with exchange momenta far larger than ordinary $\beta$ decays $(\approx 100 \mathrm{MeV})$. Such a characteristic places this transition in an energy range that is consistent with the neutrinoless double-$\beta$ decay and represents an interesting test for nuclear models to support their predictions of the nuclear matrix elements for such an unobserved process. For the first time, the calculations are carried out within the realistic shell model, namely employing effective shell-model Hamiltonians and decay operators derived from realistic nuclear forces, without resorting to any empirical adjustment of the coupling constants. This is a chapter of a research program that is aimed to assess the realistic shell model in reproducing the observables related to electroweak processes in nuclei and then to evaluate the reliability of nuclear matrix elements for the neutrinoless double-$\beta$ decay that are calculated within this approach. We calculate the partial capture rates for many nuclear systems in the $sd$-shell region, as well as their spectroscopic properties, and compare the results with the available experimental counterparts. Such a comparison tests the relevance of a microscopic approach to the renormalization of transition operators to reproduce data and provide solid predictions of unknown observables.

The cranked Nilsson-Strutinsky formalism is employed to investigate the band structure of ${}^{115}\mathrm{I}$ from low to high spin. A set of eight rotational bands with well established spins and parities are analyzed. Five bands start at low spin and are assigned to the single-particle proton orbitals $(d_{5/2},$ $g_{7/2}),$ $g_{9/2}, \text{and} h_{11/2}$, which are close to the Z = 53 Fermi surface for a deformation of ${\varepsilon }_2=0.2$. The analysis of the observed level energies relative to a rotating liquid drop and spins versus $\gamma$-ray energies allow one to track the evolution of the configurations with increasing spin. It is of special interest that one band in the valence space is observed to terminate smoothly at $I_{\max }=67/2^{+}$.

In this work, experiments with a beam from the MT-25 microtron at bremsstrahlung end-point energies of 10–23 MeV were carried out using the γ activation method. Theoretical results based on talys-2.0 with standard parameters and a combined model of photonucleon reactions were compared with experimental values of relative yields. Experimental data in the energy range 19–23 MeV can be described with the combined model of photonucleon reactions due to the inclusion of isospin splitting of the giant dipole resonance.

The mean transverse momentum $\langle p_T\rangle$ of hadrons has been observed experimentally and in numerical simulations to have a power-law dependence on the hadronic multiplicity $N$ in ultracentral relativistic heavy-ion collisions: $\langle p_T\rangle \propto N^{b_{\mathrm{UC}}}$. It has been put forward that this exponent $b_{\mathrm{UC}}$ is the speed of sound of quark-gluon plasma measured at a temperature determined from $\langle p_T\rangle$. We study step by step the connection between (i) the energy and entropy of hydrodynamic simulations and (ii) experimentally measurable observables. We show that an argument based on energy and entropy should yield an exponent equal to the pressure over energy density $P/\varepsilon$, rather than the speed of sound $c_s^2$; however, we also observe that $\langle p_T\rangle$ and $N$ are not sufficiently accurate proxies for the energy and entropy to make this possible in practice. From simulations, we find that the exponent $b_{\mathrm{UC}}$ is significantly different whether the “effective volume” is strictly constant or not, a condition that cannot be enforced experimentally. Additional tests using a modified equation of state find that the exponent $b_{\mathrm{UC}}$ exhibits a variable degree of correlations with the speed of sound and with $P/\varepsilon$, but is not an accurate measurement of either quantity in general.

The nucleon exhibits a rich internal structure governed by quantum chromodynamics (QCD), where its electric charge arises from valence quarks, while its spin and mass emerge from complex interactions among valence quarks, sea (anti)quarks, and gluons. At the advent of QCD, an alternative hypothesis emerged suggesting, at high energies, the transport of a nucleon's baryon number could be traced by a nonperturbative configuration of gluon fields connecting its three valence quarks, forming a $Y$-shaped topology known as the gluon junction. Recent measurements by the STAR experiment are compatible with this scenario. In light of these measurements, this study aims to explore the mechanisms of baryon transport in high-energy nuclear collisions using the pythia-8 framework, which incorporates a state-of-the-art hadronization model with advanced color flow (CF) and color reconnection (CR) mechanisms that mimic signatures of a baryon junction. Within this model setup, we investigate (i) the rapidity slope of the net-baryon distributions in photon-included processes $(\gamma +p)$ and (ii) baryon over charge transport in the isobaric $(\mathrm{Ru}+\mathrm{Ru} \text{and} \mathrm{Zr}+\mathrm{Zr})$ collisions. Our study highlights the importance of the CF and CR mechanisms in pythia-8, which play a crucial role in baryon transport. The results show that the CF and CR schemes significantly affect the isobaric baryon-to-charge ratio, leading to different predictions for baryon stopping and underscoring the need to account for CF and CR effects in comparisons with experimental measurements.