Nuclear masses are machine-learned as a function of proton and neutron numbers. The neural network with additive Gaussian process regression-optimized activation functions (GPR-NN) method is employed for the first time for this purpose. GPR-NN combines the advantages of both neural networks and Gaussian process regression, in that it possesses the expressive power of a NN, in principle allowing modeling any kind of dependence of nuclear mass on the features, and robustness of a linear regression against overfitting. A study of the GPR-NN approach for interpolation and extrapolation in nuclear mass predictions is presented. It is found that the optimal hyperparameters for the GPR-NN approach in interpolation and extrapolation are different. If an appropriate set of hyperparameters is adopted, the GPR-NN approach can achieve good extrapolation performance for nuclear mass prediction, which could potentially help improve the mass predictions of a large number of currently experimentally unknown nuclei.

The photon strength function (PSF) of nuclear dipole excitation is greatly important to different applications especially including nuclear astrophysics. However, for the $\approx 10000$ nuclei over the whole nuclear chart, the total electric dipole $\left(E1\right)$  and magnetic dipole $\left(M1\right)$ PSF directly derived from large-scale calculation with microscopic theory is not available yet. In this paper, we perform a systematic study on the $M1$ PSF based on the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation (HFB+QRPA) model used in our previous work of the $E1$ PSF. In particular, large-scale calculations of the spin-flip $M1$ strength distributions are performed in the framework of HFB+QRPA under the assumption of spherical symmetry using the BSk27 Skyrme effective interaction. The spin-flip $M1$ PSFs are obtained by folding the QRPA strength distributions with a Lorentz function that describes the damping of nuclear collective motion empirically. The scissors mode and the low-energy upbend contribution to the $M1$ PSFs are both added phenomenologically to the spin-flip component. The resulting BSk27+QRPA $M1$ PSF is shown to be in fairly good agreement with available experimental data. In addition, the comparison between our BSk27+QRPA $M1$ PSF and other theoretical results indicates that the present approach provides an efficient and reliable alternative to describe the $M1$ PSF for a large set of nuclei. When consistently considering both our previous $E1$ and the present $M1$ BSk27+QRPA PSFs, predictions reasonably reproduce multistep $\gamma$-ray cascade spectra, average radiative widths, and Maxwellian-averaged cross sections. A complete set of $E1$ and $M1$ PSFs are determined for $\approx 10000$ nuclei with $8\le Z\le 124$ lying between the proton and the neutron drip lines and used to estimate astrophysical neutron capture rates that are found to be comparable to those obtained with the previous Gogny-$\mathrm{HFB}+\mathrm{QRPA}$ predictions based on the D1M interaction.

We investigate bound states of light ${\mathrm{\Omega }}_{3x}$ clusters $(x=s,c)$, motivated by the ${\mathrm{\Omega }}_{3s}N$ potential recently developed by the HAL QCD collaboration. To regularize this potential, we remove the deeply attractive core at $r<0.4\mathrm{fm}$ and parametrize the long-range component $(r>0.4\mathrm{fm})$ using a two-range Gaussian form. This procedure preserves the relevant two-body bound-state energy while having a negligible effect on the ${\mathrm{\Omega }}_{3s}NN$ and ${\mathrm{\Omega }}_{3s}{\mathrm{\Omega }}_{3s}N$ systems. An effective ${\mathrm{\Omega }}_{3s}\alpha$ potential is then constructed by fitting a two-range Gaussian function to the long-range component of the folding potential, enabling calculations of the bound-state energies of the ${\mathrm{\Omega }}_{3s}\alpha$, ${\mathrm{\Omega }}_{3s}\alpha \alpha$, and ${\mathrm{\Omega }}_{3s}{\mathrm{\Omega }}_{3s}\alpha$ systems. The regularization procedure leads to a substantial reduction in bound-state energies compared to those obtained with the original potential. We further extend the analysis to ${\mathrm{\Omega }}_{3c}$-cluster systems by introducing an ${\mathrm{\Omega }}_{3c}N$ interaction, derived by comparing the existing ${\mathrm{\Omega }}_{3s}{\mathrm{\Omega }}_{3s}$ and ${\mathrm{\Omega }}_{3c}{\mathrm{\Omega }}_{3c}$ potentials. Our results suggest that several parametrizations predict bound states in ${\mathrm{\Omega }}_{3c}$-containing clusters. Finally, the ${\mathrm{\Omega }}_{3s}{\mathrm{\Omega }}_{3s}$ interaction is described using a contactlike potential approach, motivated by the effective field theory.

We study the thermodynamic properties of a noninteracting, relativistic gas of charged scalar bosons in a uniform magnetic field, including both statistical and vacuum contributions at arbitrary field strengths. Focusing on the low-temperature regime and separating the lowest Landau level (LLL) from excited states provides a clearer view of the magnetic field’s impact on thermodynamic quantities. We revisit Bose-Einstein condensation (BEC), specific heat, magnetization, and the equation of state (EoS). A central result is the diffuse character of BEC induced by the magnetic field, reflected in the specific heat, which exhibits two plateaus: the first appears when the system becomes effectively one-dimensional through magnetic confinement, while the second—associated with the true one-particle ground state—is suppressed by the field. Consequently, no critical condensation temperature arises. For magnetization, the LLL contribution shifts from diamagnetic to paramagnetic. As the field strengthens with the inclusion of the excited states, the statistical magnetization remains negative. In contrast, the vacuum contribution dominates at strong fields, driving paramagnetism. We also show that antiparticles increase specific heat, magnetization, and total pressure. These effects are illustrated for a pion gas under neutron star conditions and compared with previous results for a neutral vector boson system.

The excitation scheme of the ${}^{69}\mathrm{Ga}$ ($Z=31,N=38$) nucleus has been studied following its population in the ${}^{59}\mathrm{Co}({}^{13}\mathrm{C},2pn)$ reaction at $E_{\mathrm{lab}}=45,50$ MeV, using an array of Compton suppressed high-purity germanium (HPGe) clover detectors as the detection system. The existing level scheme has been considerably extended with identification of new $\gamma$-ray transitions and their multipolarity assignments. The level energies have been calculated in the framework of the large basis shell model, and their overlap with experimental values is satisfactory, subject to the choice of the interaction. The band structures identified in the nucleus have been characterized with the moment of inertia and aligned angular momentum, and compared to those of similar structures in the neighboring isotopes. The shapes corresponding to these bands have been probed regarding their total Routhian surface (TRS), which exhibited varied deformation characteristics, such as prolate and $\gamma$ softness, associated with the individual sequences. Further, evidence of strong octupole correlation has been identified from an $E$3 transition between bands of opposite parities. The study comprehensively brings forth multiple aspects of single particle and collective characteristics in the level structure of ${}^{69}\mathrm{Ga}$.

The chronology of ${}^3\mathrm{He}$ emission relative to hydrogen isotopes in ${}^{64}\mathrm{Zn}+{}^{197}\mathrm{Au}$ collisions at 35 MeV/u is experimentally investigated using the velocity-gated correlation functions of $p\text{−}d, d\text{−}t, d{\text{−}}^3\mathrm{He}$, and $t{\text{−}}^3\mathrm{He}$ pairs. The velocity-gated correlation functions are constructed with the event classification for semicentral and midperipheral events and the source characterization for intermediate-velocity and projectile-like sources. A model-independent inference of the average emission order of ${}^3\mathrm{He}$ and hydrogen isotopes yields ${\tau }_p>{\tau }_d>{\tau }_{{}^3\mathrm{He}}>{\tau }_t$, where $\tau$ is the average emission time for a given particle, suggesting that on average, ${}^3\mathrm{He}$ is emitted earlier than proton and deuteron, but later than triton. The conclusion is quite general, independent of the impact parameter nor emission source selections. The obtained emission order of hydrogen isotopes are consistent with those inferred in previous works, providing support for our results of ${}^3\mathrm{He}$ emission relative to the hydrogen isotopes.

This study presents a systematic investigation of the transverse-momentum differential radial flow fluctuations observable $v_0\left(p_T\right)$ in relativistic heavy-ion collisions at top Relativistic Heavy Ion Collider ($\sqrt{s_{NN}}=200$ GeV) and Large Hadron Collider ($\sqrt{s_{NN}}=2.76$ and 5.02 TeV) energies. Using a multistage hydrodynamic model, this study assesses the sensitivity of $v_0\left(p_T\right)$ to a wide range of physical effects, including bulk and shear viscosities, off-equilibrium corrections at particlization, the presence of a hadronic afterburner, and the nucleon size in the initial conditions. By employing complementary rescaling strategies, this study demonstrates how different physical effects leave distinct imprints on the shape of $v_0\left(p_T\right)$. A combined double-rescaling of $v_0\left(p_T\right)/v_0$ versus $p_T/\langle p_T\rangle$ reveals a universality across a wide range of energies and model assumptions in the low-$p_T$ regime, a robust signature of collective behavior. This allows us to disentangle the universal dynamics of the bulk medium from model-specific features that emerge at higher $p_T$. These results establish $v_0\left(p_T\right)$ as a powerful and complementary observable for constraining quark-gluon plasma transport properties and initial-state granularity, offering a unique probe of the created QCD medium.

The ${}^{93}\mathrm{Nb}$($t,{}^3\mathrm{He}$) reaction at 115 MeV/nucleon was studied to demonstrate that nuclear level densities and $\gamma$-ray strength functions can be extracted from charge-exchange reactions at intermediate energies using the Oslo technique. The matrix of excitation energy in ${}^{93}\mathrm{Zr}$, reconstructed from the ($t,{}^3\mathrm{He}$) reaction, versus the energy of $\gamma$ rays emitted by the excited ${}^{93}\mathrm{Zr}$ nuclei, was obtained in an experiment with the S800 Spectrograph operated in coincidence with the GRETINA $\gamma$-ray detector. The extracted level density and $\gamma$-ray strength function obtained by applying the Oslo method to this matrix were used to estimate the ${}^{92}\mathrm{Zr}(n,\gamma ){}^{93}\mathrm{Zr}$ cross section by combining the new results with other experimental data and theoretical calculations for $E1$ and $M1$ strength functions at higher energies. Good agreement with direct measurements of the ${}^{92}\mathrm{Zr}(n,\gamma ){}^{93}\mathrm{Zr}$ cross section was found. The contribution from the upbend in the extracted $\gamma$-ray strength function was important to achieve the consistency, as the neutron-capture cross section without this contribution is significantly below the direct measurements otherwise. Since charge-exchange reactions at intermediate energies have long been used for extracting Gamow-Teller strengths, the successful demonstration of the charge-exchange Oslo method enables experiments in which ($n,\gamma$) cross sections and Gamow-Teller strengths can be measured simultaneously, which is of benefit for astrophysical studies.

We investigate the structures of ${}^{10}\mathrm{C}$ focusing on the quadrupole properties in comparison with the mirror nucleus ${}^{10}\mathrm{Be}$. We describe ${}^{10}\mathrm{C}$ and ${}^{10}\mathrm{Be}$ in the variation of the multiple bases of the antisymmetrized molecular dynamics (AMD), in which the multiple AMD bases are optimized simultaneously in the total-energy variation. In the monopole transitions, we confirm the isospin symmetry between ${}^{10}\mathrm{C}$ and ${}^{10}\mathrm{Be}$ by exchanging protons and neutrons. In the quadrupole transitions, most cases show larger values in ${}^{10}\mathrm{C}$ than those of ${}^{10}\mathrm{Be}$, except for the transition of $2_1^{+}\to 0_1^{+}$. The transition of $2_1^{+}\to 0_1^{+}$ shows similar values in the two nuclei in spite of the different proton numbers, which agrees with the experimental situation as an anomaly. This relation comes from the small proton deformation in ${}^{10}\mathrm{C}$ due to its subclosed nature and the large proton deformation in ${}^{10}\mathrm{Be}$ due to two-$\alpha$ clustering. This property can also be seen in the quadrupole moments of the two nuclei. In the neutron deformations of ${}^{10}\mathrm{C}$ and ${}^{10}\mathrm{Be}$, the opposite tendency of protons is confirmed and these results ensure the isospin symmetry between the two nuclei. We also confirm the large quadrupole transitions between the elongated linear-chain states. It would be desirable for future experiments to investigate the present characteristics of the transitions in the two nuclei.

We benchmark two implementations of the in-medium similarity renormalization group (IMSRG) method, IMSRG(2) and IMSRG(2*), for the low-lying states of a pairing-plus-particle-hole model with varying numbers of fermions. In IMSRG(2), all operators are truncated up to the normal-ordered two-body terms, whereas IMSRG(2*) includes an additional term to partially account for higher-body contributions. The results are compared against exact solutions. We find that IMSRG(2*) consistently outperforms IMSRG(2) for both ground and excited states, although achieving convergence for excited states remains more challenging in strongly correlated systems than for the ground state.

The excited states of ${}^{95}\mathrm{Mo}$ have been investigated using the heavy-ion fusion-evaporation reaction ${}^{82}\mathrm{Se}({}^{18}\mathrm{O},5n){}^{95}\mathrm{Mo}$ at the beam energies of 82 and 88 MeV. The level scheme of ${}^{95}\mathrm{Mo}$ was revised and extended up to $E\approx 14\mathrm{MeV}$ and $I^{\pi }=55/2^{(-)}$ with 62 new $\gamma$-ray transitions and 30 new levels. The energy spectrum bears the signature of core breaking viz. presence of high energy $\gamma$ transitions with $E_{\gamma }\simeq 2\text{to}3\mathrm{MeV}$ around the highest observed excitation energy and angular momentum originating due to excitation of nucleons across the $N=50$ core. The proposed level scheme is compared with large basis spherical shell model calculations within a model space including the proton orbitals ($1f_{5/2}, 2p_{3/2}, 2p_{1/2}, 1g_{9/2}$) and neutron orbits ($1g_{9/2}, 1g_{7/2}, 2d_{5/2}, 2d_{3/2}, 3s_{1/2}$). Satisfactory agreement between the experimental observation and shell-model calculations suggests that cross-shell excitations are important up to the maximum spin observed in the current experiment.

The quasielastic scattering (QES) excitation function for the systems ${}^{16}\mathrm{O}+{}^{176}\mathrm{Yb}$ and ${}^{16}\mathrm{O}+{}^{178}\mathrm{Hf}$ are measured by detecting projectile like ions at the back angle using a scattering chamber at Inter-University Accelerator Centre (IUAC), New Delhi. The measurements were performed with energy range from $0.78V_B\text{−}1.10V_B, V_B$ is the Coulomb barrier. The experimental fusion barrier distributions (BD) were derived from the measured data using the point difference formula. The excitation function and the BD are subjected to coupled channel (CC) calculations using a scattering version of the CC code ccfull K. Hagino, et al., Comput. Phys. Commun. 123, 143 (1999), where Woods-Saxon potential parametrization is used. The best fitted optical model parameters are extracted for the real and the imaginary parts. For ${}^{16}\mathrm{O}+{}^{176}\mathrm{Yb}$, considering the coupling of two rotational states $(2^{+},4^{+})$ of the ${}^{176}\mathrm{Yb}$ nucleus along with a pair of neutron transfer $(Q=–0.5\mathrm{MeV})$ both the excitation function and the BD are well reproduced. In case of ${}^{16}\mathrm{O}+{}^{178}\mathrm{Hf}$ too, incorporating the coupling of two rotational states $(2^{+},4^{+})$ of the ${}^{178}\mathrm{Hf}$ nucleus and one pair of neutron transfer $(Q=–1.82\mathrm{MeV})$, both the excitation function and the BD are fairly reproduced. Technique of ${\chi }^2/f$ minimization was used to determine a new set of hexadecapole deformation. The values are found to be ${\beta }_4=-0.019\pm 0.014$ and ${\beta }_4=-0.032\pm 0.017$ for ${}^{176}\mathrm{Yb}$ and ${}^{178}\mathrm{Hf}$ respectively. The excitation functions and the BDs of the two systems are also compared with available experimental data by other groups to better understand the reaction dynamics around the barrier.

The photon strength function (PSF) is important in describing photon emission probabilities; thus, it plays a role in radiative neutron-capture reactions. Experiments have shown an enhancement in the PSF at low energy for some nuclei. This low-energy enhancement (LEE) could have a large effect on $r$-process nucleosynthesis, where many nuclei with unmeasured neutron-capture cross sections are produced in nature. Experiments have shown evidence for an LEE in ${}^{56}\mathrm{Fe}, {}^{57}\mathrm{Fe}$, and ${}^{60}\mathrm{Fe}$ nuclei. Measurement of the PSF of ${}^{58}\mathrm{Fe}$ will help constrain how the LEE evolves across the isotopic chain, offering stronger constraints for predictive Hauser-Feshbach models. The Detector Array for Photons, Protons, and Exotic Residues (DAPPER) was constructed to probe PSFs using $(d,p)$ reactions in inverse kinematics. The inaugural measurement with DAPPER was conducted to measure the PSF and nuclear level density (NLD) of ${}^{58}\mathrm{Fe}$, both of which are important for the modeling of the neutron-capture cross section of ${}^{57}\mathrm{Fe}(n,\gamma )$. For the first time, a forward-type method was used to constrain the NLD and PSF from a $(d,p)$ reaction measurement. Results show behavior consistent with an LEE similar in strength to previous measurements on other iron isotopes, though further efforts on error propagation would be necessary to set hard probability ranges.

By extending our analysis and simulations of our ${}^{37}\mathrm{K}\beta$-decay data set to allow the $\beta$ asymmetry with respect to nuclear spin to vary with $\beta$ energy $E_{\beta }$, we have gained sensitivity to new physics that depends on a helicity factor for the $\beta , m_{\beta }/E_{\beta }$. In particular, we constrain Lorentz scalar and tensor quark-lepton interaction strengths at a sensitivity complementary to the similar Fierz interference term in neutron $\beta$ decay. Our result for that new physics is a Fierz interference term $b=0.033 \pm$ 0.084 (stat) $\pm$ 0.039 (syst), consistent with the standard model electroweak interaction value $b=0$. We consider presently achieved complementarity to $\beta$-decay and particle physics experiments, along with projectable technical improvements to our method.

The Super-Kamiokande detector has measured solar neutrinos for more than 25 years. The sensitivity for solar neutrino measurement is limited by the uncertainties of energy scale and background modeling. Decays of unstable isotopes with relatively long half-lives through nuclear muon capture, such as ${}^{16}\mathrm{N}$, ${}^{15}\mathrm{C}$, ${}^{12}\mathrm{B}$, and ${}^{13}\mathrm{B}$, are detected as background events for solar neutrino observations. In this study, we developed a method to form a pair of stopping muon and decay candidate events and evaluated the production rates of such unstable isotopes. We then measured their branching ratios considering both their production rates and the estimated number of nuclear muon capture processes as $\mathrm{Br}\left({}^{16}\mathrm{N}\right)=(9.0\pm 0.1)\%$, $\mathrm{Br}\left({}^{15}\mathrm{C}\right)=(0.6\pm 0.1)\%$, $\mathrm{Br}\left({}^{12}\mathrm{B}\right)=(0.98\pm 0.18)\%$, $\mathrm{Br}\left({}^{13}\mathrm{B}\right)=(0.14\pm 0.12)\%$, respectively. The result for ${}^{16}\mathrm{N}$ has world-leading precision at present and the results for ${}^{15}\mathrm{C}$, ${}^{12}\mathrm{B}$, and ${}^{13}\mathrm{B}$ are the first branching ratio measurements for those isotopes.

Nuclear effective field theory organizes the calculation of observables as a power series in terms of the ratio of soft and hard momentum scales. The rigorous implementation of this idea requires a mixture of perturbative and nonperturbative methods: On the one hand, nuclei are bound states that require the iteration of part of the nuclear potential, while on the other corrections that are small in the aforementioned power series should be perturbative, in principle. Recently, it has been noted that these corrections are not cutoff independent, as there are a set of exceptional cutoffs for which the couplings cannot be determined, as exemplified with the subleading order ${}^{3}P_0$ phase shifts in two-nucleon scattering. Yet, here it is shown by means of concrete calculations that exceptional cutoffs are a regulator-dependent feature. There exists a well-defined limit when the cutoff is removed, which implies that not every regulator choice (understood not only as the regulator itself, but in tandem with renormalization conditions) is acceptable within the effective field theory framework. The practical implications are minor, though: Except if one is trying to explicitly probe the cutoff independence of the theory, most sensible regulator and cutoff choices are compatible with the renormalized limit within truncation errors.

The tensor force is a well-established, important component of the bare nucleon-nucleon interaction. On the other hand, it is still a matter of debate whether the tensor force is decisively needed or not as a key ingredient of energy density functionals (EDFs) for the description of medium-heavy nuclei. In this paper, the magnetic dipole $\left(M1\right)$ excitations, the charge-exchange Gamow-Teller (GT), and the spin-dipole (SD) excitations, have been employed to constrain the tensor parameters of Skyrme EDFs. The calculations are done using self-consistent Hartree-Fock (HF) $+$ random phase approximation (RPA) or HF-BCS $+$ quasiparticle RPA models. It has been found that the triplet-even parameter $T$ can be well constrained at around 500 MeV ${\mathrm{fm}}^5$ in the case of the $\mathrm{T}ij$ EDFs, where all parameters of the EDFs are fitted on equal footing, and for the SGII as well as SLy5 effective interactions, where tensor terms are added perturbatively on top of the central part. We have also found that the range of the triplet-odd parameter $U$ of the SGII interaction can be narrowed down by the constraint of $M1$ excitation on top of GT and SD excitations, while for the SLy5 interaction the $M1$ excitation does not help much to constrain the $U$ value, as it plays a similar role as the GT excitations.

The quasiparticle finite amplitude method is extended to describe charge-exchange transitions based on the relativistic Hartree-Bogoliubov model, adopting the point-coupling energy density functional DD-PC1 and a finite-range separable pairing force. After validation through comparison with relativistic quasiparticle random-phase approximation results in spherical nuclei, the deformation effects on isobaric analog resonances and Gamow-Teller (GT) transitions in Zn isotopes are investigated. The GT strength exhibits significant fragmentation in deformed nuclei. The analysis of summed strengths and centroid energies in GT resonance region between the $K=0$ and $K=1$ components reveals that prolate configurations exhibit stronger $K=1$ strength and lower $K=1$ centroid energy, while oblate shapes show an opposite behavior, with stronger $K=0$ strength and lower $K=0$ energy. The effects of isoscalar pairing on GT strength distributions for different shape configurations are also examined.

We study the transverse momentum spectra of identified particles in ultrarelativistic collisions of large and small collision systems. In order to isolate information contained in the momentum dependence, we propose to scale the spectra by the total particle number and mean transverse momentum, global quantities which are already well studied. We observe an interesting, nearly universal, centrality-independent shape in the scaled spectra, similar to scalings that have been studied previously. This scaling behavior breaks down at large transverse momentum and for very small systems, such as those produced in $p-p$ collisions. We perform hybrid hydrodynamic simulations and show that, in these simulations, a centrality-independent shape is a consequence of an event-by-event independence. Our results motivate further theoretical and experimental investigations of the regime of validity of this scaling phenomenon and their physical interpretation at different collision energies and systems.

Exclusive photoproduction of $K^{+}\mathrm{\Lambda }$ final states off a proton target has been an important component in the search for missing nucleon resonances and our understanding of the production of final states containing strange quarks. Polarization observables have been instrumental in this effort. The current work is an extension of previously published CLAS results on the beam-recoil transferred polarization observables $C_x$ and $C_z$. We extend the kinematic range up to invariant mass $W=3.33$ GeV from the previous limit of $W=2.5$ GeV with significantly improved statistical precision in the region of overlap. These data will provide for tighter constraints on the reaction models used to unravel the spectrum of nucleon resonances and their properties by not only improving the statistical precision of the data within the resonance region, but also constraining $t$-channel processes that dominate at higher $W$ but extend into the resonance region.