The evolution of the “microscopic” Hubble parameter related to the expansion of matter born in heavy-ion collisions was obtained for nucleons and pions. The calculations were carried out within the parton-hadron-string dynamics (PHSD) transport model. $\mathrm{Au}+\mathrm{Au}$ collisions with $\sqrt{s_{NN}}=7.8$ GeV at $b=2.5,5.0,7.5$, and 10.0 fm were considered. A new method for determining the “microscopic” Hubble parameter from simulated data was used. The ballistic motion was obtained for the longitudinal direction after the separation of the nuclei. In earlier times, the evolution of the “microscopic” Hubble parameter in this direction was more complicated. For transverse directions, an exponential low-time asymptotics of the Hubble parameter was observed. The obtained values of the “microscopic” Hubble parameter are about 40 orders of magnitude higher than the cosmological Hubble constant.

This work investigates the influence of parton spin polarization on effective transport and thermodynamic coefficients in noncentral light- and heavy-ion collisions. To model this influence, I consider two sources of spin polarization: thermal vorticity, induced by angular momentum, and thermal shear, arising from local velocity gradients. Using a novel kinetic theory framework, one finds that transport and thermodynamic coefficients—including the speed of sound squared $c_s^2$, specific shear viscosity $\eta /s$, specific bulk viscosity $\zeta /s$, and mean free path $\lambda$—are substantially modified by spin polarization effects. Among the two sources, thermal vorticity-induced spin polarization dominates the modifications to these coefficients. Moreover, both $c_s^2$ and $\zeta /s$ exhibit a nonmonotonic dependence on the collision energy, and the associated scaling behaviors potentially serve as indicators of the critical phenomena of quantum chromodynamics .

New measurements of the β decay of ${}^{64}\mathrm{Ga}$ and ${}^{66}\mathrm{Ga}$ have been carried out using total absorption spectroscopy at CERN-ISOLDE. The purpose of the study was to determine whether systemic effects such as Pandemonium have affected previous measurements and also determine the degree of isospin mixing in these proton-rich nuclei. Our results show that the β strength distribution of ${}^{64}\mathrm{Ga}$ was previously underestimated, while that of ${}^{66}\mathrm{Ga}$ agrees well with previous high-resolution measurements. The results allowed us to determine the amount of isospin mixing in the $0^{+}\to 0^{+}$ transitions to the ground states of the daughter nuclei. From the extracted $logft$ values, we determined the isospin mixing parameter $\alpha$ for the two cases. They were found to be consistent with values for similar transitions in other nuclei. ${}^{64}\mathrm{Ga}$ exhibits the largest amount of isospin mixing in such nuclei. These findings improve our understanding of beta decay and have implications for nuclear structure models and medical applications of ${}^{66}\mathrm{Ga}$ in PET imaging.

Quantifying intermodel uncertainties has gained increasing attention in nuclear theory. In this work, we extend the least-squares covariance analysis method—–commonly used to quantify parameter uncertainties in nuclear energy density functionals (EDFs)—–to address intermodel uncertainty. Two criteria are proposed, motivated by the Laplace approximation to the Bayesian posterior, for frequentist model selection and averaging. As a case study, we compare two liquid-drop models that differ in the form of the symmetry energy term, using both covariance analysis and Bayesian inference. The proposed criteria incorporate parameter uncertainties and correlations, and are shown to serve as efficient surrogates for Bayesian evidence and its variant. Given their computational efficiency, the two criteria are promising tools for addressing model dependence issues in studies based on deterministic theoretical models. In particular, frequentist model comparison based on the two criteria provides a feasible means to quantify intermodel uncertainties among the many widely used nuclear EDFs that have been supplemented with covariance analysis following calibration.

Background: The adiabatic wave approximation (ADWA) is widely applied in systematic studies of ($d,p$) and ($p,d$) single-nucleon transfer reactions. To simplify the calculations, a zero-range approximation (ZRA), usually corrected with a local energy approximation (LEA) to take into account finite-range effects (FREs), is often employed in calculating the $T$ matrix of ($p,d$) and ($d,p$) reactions within the ADWA framework. In addition to the ZRA in the reaction $T$ matrix, a zero-range version of the effective deuteron optical model potential proposed by Johnson and Soper ($U_d^{\text{JS}}$) is also much more widely used in ADWA calculations than its finite-range version proposed by Johnson and Tandy ($U_d^{\text{JT}}$). Therefore, it is necessary to assess the influence of FREs and the effectiveness of finite-range corrections (FRCs) with the LEA in ADWA calculations. Previous systematic studies about this subject were mainly made at relatively low incident energies below about 40 MeV/nucleon and on target nuclei whose mass numbers are mostly larger than 40.

Purpose: To study the FREs in ADWA calculations of the ($p,d$) reactions within a wider energy range on a finer distribution of target masses, so that the systematics of the FREs with respect to the ZRA calculations, and the accuracy of the FRC with the LEA, can be better assessed.

Methods: This study analyzes 48 sets of experimental data of ($p,d$) reactions on 10 targets (${}^{12}\mathrm{C}, {}^{16}\mathrm{O}, {}^{28}\mathrm{Si}, {}^{40}\mathrm{Ca}, {}^{58}\mathrm{Ni}, {}^{90}\mathrm{Zr}, {}^{102}\mathrm{Ru}, {}^{118}\mathrm{Sn}, {}^{142}\mathrm{Nd}$, and ${}^{208}\mathrm{Pb}$) within a wide range of incident energies from 18 to 200 MeV/nucleon. Three types systematic nucleon-nucleus optical model potentials (OMPs), namely, the phenomenological KD02 [A. J. Koning, et al., Nucl. Phys. A 713, 231 (2003)], the semimicroscopic JLMB (Jeukenne-Lejeune-Mahaux-Bruyères) [E. Bauge, et al., Phys. Rev. C 63, 024607 (2001)], and the microscopic CTOM (Optical Model by co-operation between China Nuclear Data Center & Tuebingen University) [R. R. Xu, et al., Phys. Rev. C 94, 034606 (2016)], are used. They allow us to investigate how the FREs depend on the incident energies, on the target masses, and on the choice of systematic OMPs.

Results: Our results demonstrate that (i) the FREs due to $U_d^{\text{JT}}$ do not show clear dependence on incident energies for all three systematic OMPs used; (ii) the FREs in the $T$ matrix depend strongly on the incident energy, rising from around $0\%$ to about $150\%$ within the range of incident energies studied; (iii) the finite-range correction of the $T$ matrix by using the LEA effectively reduced the discrepancy between zero-range and finite-range (FR) calculations, particularly on medium and heavy targets ($A⩾90$); and (iv) on average, the $\mathrm{LEA}+\mathrm{JT}$ calculations overestimate the $\mathrm{FR}+\mathrm{JT}$ calculations by around $7.5\%$ over the whole range of incident energies studied in this work.

Conclusions: These results suggest that although the LEA can greatly improve the zero-range ADWA for ($p,d$) reactions, exact finite-range calculations ($\mathrm{FR}+\mathrm{JT}$) are still recommended in the analysis of ($p,d$) [and ($d,p$)] reactions as much as possible.

Background: Phenomenological relativistic models of strongly interacting systems have proved to be useful for modeling few-nucleon and few-quark systems at the few-GeV scale. They have the advantage that relativistic invariance is exact; however, satisfying cluster properties requires a complicated construction which has never been used in applications. In addition, there is no straightforward connection to local field theories.

Purpose: To explore an alternative approach for constructing relativistic quantum mechanical models that addresses these two deficiencies. This work examines the general structure of the dynamical input to these models.

Method: Relativistic models that address these two deficiencies can be formulated using reflection positive Euclidean kernels. Relaxing the locality requirement of the axioms of Euclidean field theories leads to a weaker form of reflection positivity. Constraints imposed by the spectral condition and cluster properties are used to determine the structure of a class of kernels satisfying this weaker form of reflection positivity.

Results: The resulting kernels lead to a representation of the quantum mechanical Hilbert space in terms of Euclidean variables that has a positive norm, a set of self-adjoint Poincaré generators with a Hamiltonian satisfying cluster properties and a spectral condition. Relativistic dynamical calculations can be performed directly in the Euclidean representation without analytic continuation. Schwinger functions of a local field theory also satisfy the weakened form of reflection positivity, which provides the desired connection with local field theories.

Conclusion: This work provides the structure of a large class of reflection positive kernels that can be used to test this Euclidean formulation of relativistic quantum mechanics. What is still missing is a dynamical principle that generates model kernels with the desired properties.

Predictions of charm-correlation functions and, more specifically, balance functions are presented in proton-proton (pp) collisions at $\sqrt{s_{\text{NN}}}=13\text{TeV}$ based on the Pythia 8.3 event generator. Correlations are computed for identical and cross-species charmed hadrons in both minimum bias and high-$p_{\mathrm{T}}$ biased collisions. We study the strength of correlations as a function of the number of balanced flavors and investigate the impact of variations of Pythia parameters controlling the Lund string fragmentation on the shape and strength of the correlation functions. The feasibility of measurements of the charm-balance function presented is discussed in the context of the future LHC experiments.

The recent mass measurement of ${}^{70}\mathrm{Kr}$ using the $B\rho$-defined isochronous mass spectrometry yields a mass excess of $-41320\left(140\right)$ keV, indicating a 220-keV increase in binding energy compared to the AME2020 prediction. We utilize this experimental mass—the last piece of information needed—to model the potential waiting point ${}^{68}\mathrm{Se}$ in $rp$ process and quantitatively constrain the sequential $p$-capture reaction flow bypassing this waiting point. Our investigation shows that the more tightly bound nature of ${}^{70}\mathrm{Kr}$ enhances this reaction flow up to a factor of four. This enhancement reduces the effective half-life of ${}^{68}\mathrm{Se}$. A one-zone x-ray burst-model calculations reveal that the higher flow of ${}^{70}\mathrm{Kr}$ has distinct effects on the tail structure of light curve and the final SnSbTe abundances in the ashes due to a stronger $rp$-process heating.

A new method for rapidly extracting structural information about two-body clusters from resonance scattering cross sections has been constructed. It assumes that the nonlocal interaction potential between clusters is treated as a small perturbation for the nonantisymmetrized trial wave function, and the wave function derived from the corresponding local potential is employed as the approximate trial wave function within the resonating group method (RGM). The antisymmetrization method of RGM is then applied to compensate for the Pauli blocking absent in the phase function method (PFM). The approach of treating dynamical behavior and antisymmetrization effects separately dates back to 1976. This method significantly reduces the computational effort required to obtain structural information about two-body clusters. In cross-model comparative analyses, this method was used for calculations on ${}^8\mathrm{Be}, {}^{20}\mathrm{Ne}$, and ${}^7\mathrm{Li}$. The resulting phase shifts, cross sections, energy levels, and wave function overlaps demonstrated the effectiveness of the method for two SU(3) scalar clusters.

Oxygen $+$ oxygen ($\mathrm{O}+\mathrm{O}$) collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) offer a unique experimental opportunity to observe the onset of jet quenching in intermediate relativistic collision systems. As with the smaller proton-nucleus or larger nucleus-nucleus systems, measurements of centrality-selected high-$p_{\mathrm{T}}$ processes in $\mathrm{O}+\mathrm{O}$ collisions are expected to be sensitive to selection bias effects, which will be necessary to quantify or mitigate before a definitive conclusion on the presence of jet quenching. Using two Monte Carlo heavy-ion event generators, we provide a survey of centrality bias effects on high-$p_{\mathrm{T}}$ yield and correlation measurements. Some highlights of our findings include that (1) bias factors for the accessible kinematic range at RHIC show a nontrivial $p_{\mathrm{T}}$ dependence, compared to a negligible one at the LHC given the smaller accessible Bjorken-$x$ range, (2) centrality definitions based on multiplicity are less sensitive to bias effects than those based on the transverse energy, (3) the Angantyr generator gives qualitatively similar but larger-magnitude bias factors than Hijing, and (4) correlation measurements have a much smaller sensitivity to bias effects than do yield measurements. The findings here are intended to guide the experimental design and interpretation of $\mathrm{O}+\mathrm{O}$ jet quenching and other hard-process measurements.

We extend previous studies of the deuteron and triton ground-state energies to next-to-next-to-leading order $\left({\mathrm{N}}^2\mathrm{LO}\right)$ in chiral effective field theory, employing a power counting in which subleading interactions are treated perturbatively. Triton calculations are performed using the no-core shell model, and we demonstrate converged perturbative results for regulator cutoffs up to $\mathrm{\Lambda }\approx 1200$ MeV. We analyze exceptional cutoffs in the ${}^3{P}_0$ and ${}^3{S}_1{–}^3{D}_1$ nucleon-nucleon channels and find a resulting cutoff dependence in the triton ground-state energy at ${\mathrm{N}}^2\mathrm{LO}$. The effect associated with the exceptional cutoff in the ${}^3{P}_0$ channel can be mitigated by redefining the leading-order wave function within the freedom allowed by the effective field theory. The same approach applied in the ${}^3{S}_1{–}^3{D}_1$ channel remedies the effect of this exceptional cutoff on the ground state energy of the deuteron, but not for the triton.

We present a comprehensive evaluation of the nuclear structure properties of ${}^{19}\mathrm{Ne}$ using a novel and rigorous Bayesian statistical framework. Precise characterization of ${}^{19}\mathrm{Ne}$ resonance parameters is critical for accurately determining reaction rates of the astrophysically significant ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ and ${}^{18}\mathrm{F}(p,\alpha ){}^{15}\mathrm{O}$ reactions, which govern breakout from the hot CNO cycle in x-ray bursts and influence $\gamma$-ray emission in novae, respectively. By reconstructing likelihood functions from published experimental data—including asymmetric uncertainties and upper or lower limits—we derive posterior distributions for resonance energies, decay widths, and branching ratios. Our Bayesian approach systematically incorporates previously reported discrepancies among measurements, providing a statistically robust and consistent treatment of these uncertainties. The evaluated resonance parameters and associated uncertainties provide crucial input for stellar nucleosynthesis modeling, contributing to a refined understanding of explosive astrophysical phenomena.

We investigate the structures of ${}^{20}\mathrm{Ne}$ in the variation of the multiple bases of the antisymmetrized molecular dynamics (AMD). In this method, the multiple AMD bases are superposed and optimized simultaneously in the total-energy variation. This scheme is beneficial for describing the various configurations in ${}^{20}\mathrm{Ne}$. In the results, we confirm the shell and cluster structures in the $K^{\pi }=0_{1-4}^{+}$ bands, such as the deformed states in the $K^{\pi }=0_{1,4}^{+}$ bands with the $\alpha$ cluster development, and the spherical shell-like states in the $K^{\pi }=0_2^{+}$ band, the latter of which is difficult to describe in the previous AMD calculations imposing the quadrupole deformation. We evaluate the monopole and quadrupole transitions in these states. The negative parity states of ${}^{20}\mathrm{Ne}$ with $K^{\pi }=0^{-}$ and $2^{-}$ are discussed in relation to the shell and cluster structures. As a result, six kinds of the $K^{\pi }$ bands in ${}^{20}\mathrm{Ne}$ are described comprehensively in the microscopic framework of nuclei.

Two-phonon $\gamma$-vibrational states, with energy anharmonicity in the range $2.0\le R_a^{\gamma }$(a = 4, 0) $\le 3.5$, have been investigated in the well-deformed ${}^{164}\mathrm{Dy}$ nucleus using the ${}^{163}\mathrm{Dy}$($n_{\mathrm{th}},\gamma ){}^{164}\mathrm{Dy}$ reaction. The lowest-lying $K^{\pi }$ = $4^{+}$ state at 1978.5 keV ($R_4^{\gamma }$ = 2.60) has been identified. This, together with the one at $E_x$ = 2113.2 keV ($I^{\pi }$ = $5^{+}$), and the two other newly observed levels at 2261.4 ($I^{\pi }$ = $6^{+}$) and 2463.5 ($I^{\pi }$ = $7^{+}$) keVs likely constitute a candidate $K^{\pi }$ = $4^{+}$ two-phonon $\gamma$-vibrational band in this nucleus. Novel calculations in the framework of triaxial projected shell model have been carried out for the two-$\gamma$-phonon bandhead state and the band structure built above it. The results from the calculations have been found to be in fair agreement with the experimental findings.

${}^{140}\mathrm{La}$ is an important isotope in nuclear forensics. It is typically paired with ${}^{140}\mathrm{Ba}$ as a chronometer for dating nuclear events. In this work, we report the results of two measurements performed to fully characterize the decay scheme of ${}^{140}\mathrm{La}$. The experiments were performed using the Gammasphere array at Argonne National Laboratory and the CLARION2 array at Florida State University. Sources of ${}^{140}\mathrm{La}$ were produced through neutron irradiation of natural lanthanum (99.9% ${}^{139}\mathrm{La}$) in the University of Massachusetts Lowell research reactor. We identify a total of 40 transitions, three of which were not previously reported. An angular correlation analysis was conducted confirming current literature $J$ assignments and mixing ratios. By considering all data available in the literature, we provide new recommended values for the intensities of the strongest transitions commonly used in applications.

We investigate the elliptic flow $\left(v_2\right)$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\text{NN}}}=3.0$ and 4.5 GeV using both hadronic and partonic transport models, including JAM, SMASH, AMPT-Hadronic Cascade, and AMPT-String Melting. At 3.0 GeV, the JAM model reproduces the number-of-constituent-quark (NCQ) scaling violation observed by the STAR Collaboration, as well as the particle ordering $(K_S^0>p>{\pi }^{+})$. Model calculations of the centrality dependence indicate that the scaling violation mainly originates from hadronic interactions rather than spectator effects, while the rapidity dependence further constrains the mechanism of the scaling breaking and the underlying longitudinal dynamics. At 4.5 GeV, partonic interactions in the AMPT-String Melting mode significantly enhance NCQ scaling, and turning off final-state hadronic rescattering further clarifies the scaling pattern, highlighting the increasing role of partonic degrees of freedom. The energy dependence of the $p_T$-integrated $v_2$ is also examined within these models.

The fluctuations of elliptic flow $\left(v_2\right)$ in relativistic heavy-ion collisions offer a powerful tool to probe the collective behavior and transport properties of the quark-gluon plasma (QGP). The dependence of these fluctuations on particle species further sheds light on the hadronization mechanism. At CERN Large Hadron Collider energies, the ALICE experiment has measured $v_2$ fluctuations for charged pions, kaons, and (anti)protons via the ratio of $v_2$ measured with respect to the spectator plane $\left(v_2\{{\mathrm{\Psi }}_{\mathrm{SP}}\right\})$ and from the four-particle cumulants $\left(v_2\left\{4\right\}\right)$. However, the observed dependencies on transverse momentum and particle type remain not fully understood. In this study, we perform a phenomenological investigation using a multiphase transport model, which allows us to trace the full evolution of flow fluctuations intertwined with the quark coalescence. The results qualitatively reproduce the ALICE measurements and offer deeper insights into the transport dynamics and hadronization of the QGP.

This study investigates the color-charge dependence of parton energy loss in the quark-gluon plasma (QGP) medium and the associated relative modifications of quark and gluon jet fractions compared to vacuum, using jet axis decorrelation observables. Recent CMS jet axis decorrelation measurements in $\text{PbPb}$ collisions at 5.02 TeV are interpreted using Pythia simulations with varied quark/gluon jet compositions and emulated color-charge dependent energy loss. A template-fit procedure is employed to estimate the limits on gluon jet fractions in the published CMS data and average shift in jet momentum due to quenching for quark- and gluon-initiated jets traversing the QGP. The extracted gluon jet fractions and the estimated quark and gluon energy losses based on this study of jet axis decorrelations are found to be consistent with other model calculations based on inclusive observables. This work illustrates the use of jet substructure measurements for providing constraints on the color-charge dependence of parton energy loss and offers valuable insights for jet quenching models.

Prompt photon measurements in relativistic nuclear collisions serve as an essential comparative basis for heavy-ion studies enabling the separation of medium-induced effects. However, the identification of prompt photons is experimentally challenging due to substantial backgrounds from photons produced in hadron decays and jet fragmentation. Appropriate isolation criteria are applied to suppress these background contributions. We analyze prompt photon spectra using the JETPHOX framework to quantify the relative contributions of fragmentation and direct-production mechanisms to the total photon yield. We perform a systematic study of the impact of isolation criteria on prompt photon production in relativistic nuclear collisions with emphasis on their dependence on beam energy and photon transverse momentum. The fragmentation contribution is found to be substantially large, particularly for $p_T<15$ GeV, and the isolation criterion plays a crucial role in the analysis of prompt photons in that $p_T$ region. A dynamical isolation criterion suppresses the fragmentation component more effectively than a fixed one in this region. Furthermore, the isolation criterion shows a stronger dependence on beam energy and photon $p_T$ than on system size. These observations emphasize the importance of employing carefully selected and consistent isolation criteria when comparing experimental data with theoretical calculations especially for observables sensitive to fragmentation.

Our previous studies revealed evidence of the strange molecular partners of $P_c$ states, $N\left(2080\right)3/2^{-}$ and $N\left(2270\right)3/2^{-}$, in $\gamma p\to K^{*+}{\mathrm{\Sigma }}^0/K^{*0}{\mathrm{\Sigma }}^{+}$ and $\gamma p\to \varphi p$ reactions. Motivated by the differential cross-section data for $\gamma p\to K^{+}{\mathrm{\Sigma }}^0$ from CLAS 2010, which exhibits some bump structures at $W\approx$ 1875, 2080, and 2270 MeV, we extend our previous analysis by investigating the effects of $N\left(1535\right)1/2^{-}$, $N\left(1875\right)3/2^{-}$, $N\left(2080\right)1/2^{-},\text{and}3/2^{-}$ and $N\left(2270\right)1/2^{-},3/2^{-},\text{and}5/2^{-}$ as strange partners of $P_c$ molecular states in the reactions $\gamma p\to K^{+}{\mathrm{\Sigma }}^0$ and $\gamma p\to K^0{\mathrm{\Sigma }}^{+}$. The theoretical model employed in this study utilizes an effective Lagrangian approach in the tree-level Born approximation. It contains contributions from the $s$ channel with exchanges of $N$, $\mathrm{\Delta }$, $N^{*}$ (including the hadronic molecules with hidden strangeness), ${\mathrm{\Delta }}^{*}$; $t$ channel; $u$ channel; and the generalized contact term. The results based on the final fitted parameters are in good agreement with all available experimental data of both cross sections and polarization observables for $\gamma p\to K^{+}{\mathrm{\Sigma }}^0$ and $\gamma p\to K^0{\mathrm{\Sigma }}^{+}$. Notably, the $s$-channel exchanges of molecules significantly contribute to the bump structures in cross sections for $\gamma p\to K\mathrm{\Sigma }$ at $W\approx 1900$, 2080, and 2270 MeV and show considerable coherence with contributions from $s$-channel exchanges of general resonances to construct the overall structures of cross sections. More abundant experiments, particularly for the reaction $\gamma p\to K^0{\mathrm{\Sigma }}^{+}$, are necessary to further strengthen the constraints on the theoretical models.