The well-established macroscopic-microscopic (mac-mic) description of nuclear fission enables the prediction of fission-fragment yields for a broad range of fissioning systems. In this work, we present several key enhancements to this approach. We improve upon the microscopic sector of nuclear potential-energy surfaces by magnifying the resolution of the Lipkin-Nogami equations and strengthening the Strutinsky procedure, thus reducing spurious effects from the continuum. We further present a novel deterministic method for calculating fission dynamics under the assumption of strongly damped nucleonic motion. Our technique directly determines the evolution of the scissioned shape distribution according to the number of random-walk steps rather than the statistical accumulation of fission events. We show that our new technique is equivalent to the Metropolis random walk pioneered over the past decade by Randrup and colleagues. It further improves upon it because we remove the need for altering the nuclear landscape via a biased potential. With our final improvement, we calculate fission fragments mass and charge distributions using particle number projection, which affords the simultaneous calculation of both mass- and charge-yield distributions. Fission fragments are thus calculated from the quantum-mechanical $A$-body states of the potential-energy surface rather than from the collective mass asymmetry variable ${\alpha }_{\mathrm{g}}$ of the finite-range liquid-drop model used in past work. We highlight the success of our enhancements by predicting the odd-even staggering and the charge polarization for the neutron-induced fission of ${}^{233}\mathrm{U}$ and ${}^{235}\mathrm{U}$.

The hadronic properties of the $\rho$ meson produced in the inclusive photonuclear reaction have been investigated. The elementary reaction occurring in the nucleus is assumed as $\gamma N\to {\rho }^{0}N$. The $\rho$ meson, while propagating through the nucleus, interacts with the nuclear particles, and therefore the properties of the $\rho$ meson can be modified because of this interaction. Being a short-lived particle, the $\rho$ meson decays to various elementary particles, such as $e^{+}{e}^{-}, {\pi }^{+}{\pi }^{-},\cdots$, etc. The $e^{+}{e}^{-}$ invariant mass, i.e., the $\rho$-meson mass, distribution spectra have been calculated to extract the information about the parameters, viz., mass and width, of the $\rho$ meson in the nucleus. The calculated results have been compared with the data reported from Jefferson Laboratory.

Levels in the ${}^{112}\mathrm{Sn}$ nucleus have been excited by inelastic scattering with ${}^{35}\mathrm{Cl}$ projectile at $E_{\mathrm{lab}}=195\mathrm{MeV}$. The Doppler affected $\gamma$-ray peak arising from the decay of the $2_1^{+}$ level has been analyzed, using updated methodologies, to extract the level lifetime and corresponding electric quadrupole ($E2$) transition probability, $B(E2;0_{\mathrm{g}.\mathrm{s}.}^{+}\to 2_1^{+})$. The present result is discrepant with respect to the results reported from existing lifetime measurements, but in compliance with independent systematic measurements of the low-lying $E2$ transition strengths in the stable even-mass Sn isotopes, by pure Coulomb excitation as well as heavy-ion induced inelastic collisions. The transition probability also confirms an enhancement in collectivity for the $2_1^{+}$ level, and is found to be in good agreement with generalized seniority model (GSM) as well as state-of-the-art Monte Carlo shell model (MCSM) calculations. Within the realm of the MCSM scheme, the enhancement is understood in terms of oblate deformations for both the $0_{\mathrm{g}.\mathrm{s}.}^{+}$ and $2_1^{+}$ states in ${}^{112}\mathrm{Sn}$ arising due to strong proton-core excitations and enhanced proton-neutron interactions. In addition, limits for the lifetime of the $3_1^{-}$ level and the $E1$ transition probability, $B(E1;3_1^{-}\to 2_1^{+})$, have been obtained.

An exact treatment of the operators $Q/e\left(\omega \right)$ and the total momentum is adopted to solve the nuclear matter Bruecker-Bethe-Goldstone equation with two- and three-body forces. The single-particle potential, equation of state, and nucleon effective mass are calculated from the exact $G$ matrix. The results are compared with those obtained under the angle-average approximation and the angle-average approximation with total momentum approximation. It is found that the angle-average procedure, whereas preventing huge calculations of coupled channels, nevertheless provides a fairly accurate approximation. On the contrary, the total momentum approximation turns out to be quite inaccurate compared to its exact counterpart.

We report on spectroscopic information and lifetime measurements of even-even neutron-rich Te isotopes. Excited states were populated in fast-neutron induced fission of ${}^{238}\mathrm{U}$ at the ALTO facility of IJCLab with the LICORNE neutron source and detected using the hybrid $\nu$-ball spectrometer. We provide first results on lifetimes of the $6_1^{+}$ state in ${}^{136}\mathrm{Te}$ and the ($6_1^{+}$), ($4_1^{+}$), and ($2_1^{+}$) states in ${}^{138}\mathrm{Te}$ and discuss the results in the context of large-scale shell-model calculations. The level schemes of ${}^{136}\mathrm{Te}$ and ${}^{138}\mathrm{Te}$ are revised in terms of lifetimes of their $2_1^{+},4_1^{+}$ states and updated information on the $\left(4_2^{+}\right)$ state in ${}^{136}\mathrm{Te}$ is presented. In addition, previously reported data on spectroscopy and lifetimes in ${}^{134}\mathrm{Te}$ are reexamined. This work provides new insights into the evolution of collectivity for Te isotopes with $N=82,84,86$.

The level structure of ${}^{124}\mathrm{I}$ ($Z=53, N=71$) has been studied via the ${}^{122}\mathrm{Sn}({}^7\mathrm{Li},5n){}^{124}\mathrm{I}$ reaction with a beam energy of 54 MeV. Through in-beam and out-of-beam $\gamma$-ray spectroscopy, the sophisticated low-lying levels including isomeric states and numerous collective states have been established for the first time. A positive-parity collective band built on the ${10}^{+}$ state at 1297 keV is interpreted as being associated with the combination of a proton and a neutron in the same intruder $h_{11/2}$ orbital, namely the $\pi h_{11/2}\nu h_{11/2}$ configuration. This band shows a typical quadrupole vibrational character. In contrast, the negative parity bands based on the $\pi g_{7/2}\nu h_{11/2}$ configuration show a soft triaxial rotation. An isomeric $8^{-}$ state at 689 keV with a half-life of 14 ns can be explained as a K isomer due to a proton with an ${\mathrm{\Omega }}_p=9/2$ in the $g_{9/2}$ orbital coupled to a neutron with an ${\mathrm{\Omega }}_n=7/2$ in the $h_{11/2}$ orbital. The excited states based on this $\pi g_{9/2}\nu h_{11/2}$ configuration show a coupled rotational structure. Another coupled rotational band built on the $6^{+}$ state at 714 keV is thought to be based on the $\pi g_{9/2}\nu d_{3/2}$ configuration.

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, in-medium nucleon-nucleon inelastic scattering (which is dominated by pion production at low and intermediate energies) is explored. It is found that the in-medium modification of nucleon-nucleon inelastic scatterings appears to reduce the neutron-to-proton ratio $n/p$ at higher kinetic energies. Although the in-medium modification of nucleon-nucleon inelastic scatterings, as expected, affects the value of ${\pi }^{-}/{\pi }^{+}$ ratio, considering a series of undetermined properties of delta resonance and $\pi$ in medium, the energetic neutron-to-proton ratio $n/p$ is more suitable to be used to probe the in-medium correction of nucleon-nucleon inelastic scatterings.

Background: Reactions involving exotic and stable weakly bound nuclei have been extensively studied in recent years. Although several models have been successfully used to explain particular reaction outcomes, the answers to many questions remain elusive. In previous works, we presented elastic, inelastic, and transfer angular distributions for the ${}^{10}\mathrm{B}+{}^{120}\mathrm{Sn}$ system measured at $E_{\mathrm{Lab}}=31.5$, 33.0, 35.0, and 37.5 MeV. The data set was analyzed through coupled reaction channels calculations in the context of the double-folding São Paulo potential.

Purpose: We investigate nuclear reaction mechanisms for systems involving weakly bound projectiles.

Method: Angular distributions for several nuclear reaction processes were measured for the ${}^{10}\mathrm{B}+{}^{120}\mathrm{Sn}$ system at $E_{\mathrm{Lab}}=39.70$ MeV.

Results: The new data set involves angular distributions for elastic scattering, projectile and target inelastic excitations, one-neutron pickup transfer, one-proton stripping transfer, deuteron pickup transfer, and ${}^{3,4}\mathrm{He}$ stripping transfer. We have also observed ${}^{10}\mathrm{Be}$ nuclei. The effect of the couplings to some nonelastic states on the angular distributions is discussed.

Conclusion: The theoretical calculations within the coupled reaction channels formalism provide an overall good agreement with the corresponding inelastic, one-neutron stripping, one-proton pickup, one-deuteron pickup, and ${}^3\mathrm{He}$ stripping transfer data. However, to improve the description of the elastic scattering angular distribution, the inclusion of additional channels in the coupling scheme might be necessary.

We apply a quark combination model to study yield densities and transverse momentum ($p_T$) spectra of strange (anti)hadrons at midrapidity in central $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=7.7$, 11.5, 19.6, 27, 39, and 200 GeV. We show that the experimental data for $p_T$ spectra of (anti)hadrons in these collisions can be systematically described by the equal velocity combination of constituent quarks and antiquarks at hadronization. We obtain the $p_T$ spectra of quarks and antiquarks at hadronization and study their collision energy dependence. We also reproduce the yield densities of hadrons and antihadrons. In particular, we demonstrate that the yield ratios of antihadrons to hadrons $K^{-}/K^{+}, \overline{p}/p, \overline{\mathrm{\Lambda }}/\mathrm{\Lambda }, {\overline{\mathrm{\Xi }}}^{+}/{\mathrm{\Xi }}^{-}$, and ${\overline{\mathrm{\Omega }}}^{+}/{\mathrm{\Omega }}^{-}$ simply correlate with each other and their experimental data except ${\overline{\mathrm{\Omega }}}^{+}/{\mathrm{\Omega }}^{-}$ at $\sqrt{s_{NN}}=7.7$ GeV are systematically described by the model. These results suggest that the equal velocity combination mechanism for quarks and antiquarks at hadronization plays an important role for the production of these long-lived hadrons in $\mathrm{Au}+\mathrm{Au}$ collisions at low RHIC energies ($\sqrt{s_{NN}}\ge 11.5$ GeV).

Background: A nonperturbative charm production contribution, known as intrinsic charm, has long been speculated but has never been satisfactorily proven. The SeaQuest experiment at the Fermi National Accelerator Laboratory (FNAL) is in an ideal kinematic region to provide evidence of $J/\psi$ production by intrinsic charm.

Purpose: $J/\psi$ production in the SeaQuest kinematics is calculated with a combination of perturbative quantum chromodynamics (QCD) and intrinsic charm to see whether the SeaQuest data can put limits on an intrinsic charm contribution.

Methods: $J/\psi$ production in perturbative QCD is calculated to next-to-leading order in the cross section. Cold nuclear matter effects include nuclear modification of the parton densities, absorption by nucleons, and $p_T$ broadening by multiple scattering. The $J/\psi$ contribution from intrinsic charm is calculated assuming production from a $|uudc\overline{c}\rangle$ Fock state.

Results: The nuclear modification factor $R_{pA}$ is calculated as a function of $x_F$ and $p_T$ for $p+\mathrm{C}, p+\mathrm{Fe}$, and $p+\mathrm{W}$ interactions relative to $p+\mathrm{d}$. Previous data from the E866 experiment at FNAL is also shown and compared with the calculations.

Conclusions: The SeaQuest kinematic acceptance is ideal for testing the limits on intrinsic charm in the proton.

Three models of the nuclear magnetization distribution are applied to predict the hyperfine structure of the hydrogenlike heavy ions and neutral thallium atoms: the uniformly magnetized ball model and single-particle models for the valence nucleon with the uniform distribution and the distribution determined by the Woods-Saxon potential. Results for the hydrogenlike ions are in excellent agreement with previous studies. The application of the Woods-Saxon model is now extended to the neutral systems with the explicit treatment of the electron correlation effects within the relativistic coupled cluster theory using the Dirac-Coulomb Hamiltonian. We estimate the uncertainty for the ratio of magnetic anomalies and numerically confirm its near nuclear-model independence. The ratio is used as a theoretical input to predict the nuclear magnetic moments of short-lived thallium isotopes. We also show that the differential magnetic anomalies are strongly model dependent. The accuracy of the single-particle models significantly surpasses the accuracy of the simplest uniformly magnetized ball model for the prediction of this quantity. Skripnikov [Skripnikov, J. Chem. Phys. 153, 114114 (2020)] has shown that the Bohr-Weisskopf contribution to the magnetic dipole hyperfine structure constant for an atom or a molecule induced by a heavy nucleus can be factorized into the electronic part and the universal nuclear magnetization dependent part. We numerically confirm this factorization for the Woods-Saxon single-particle model with an uncertainty less than 1%.

The fragment emission mechanism in the binary decay of composites formed in the reactions ${}^{20}\mathrm{Ne}+{}^{56}\mathrm{Fe}$ and ${}^{16}\mathrm{O}+{}^{58}\mathrm{Ni}$ has been studied at two different excitation energies. The inclusive energy and angular distributions of the emitted fragments ${}^{6,7}\text{Li}$, ${}^{7,8,9}\text{Be}$, ${}^{10,11}\text{B}$, and ${}^{11,12,13,14}\text{C}$ have been measured in the laboratory angles ranging from ${15}^{\circ }$ to ${35}^{\circ }$ (corresponding angles in center of mass ranging from ${20}^{\circ }$ to ${50}^{\circ }$). The energy distributions of the fragments are found to be Gaussian and peaked at energies higher than those expected from fusion-fission-type reactions. The center-of-mass angular distributions of all the fragments have been found to fall faster than $\approx 1/\sin {\theta }_{\mathrm{c}.\mathrm{m}.}$-like dependence and the average $Q$ values of the fragments are found to decrease with increasing the center-of-mass angle of the emitted fragment for both the systems. The above characteristics of fragments signify that they were emitted from nonequilibrium sources, produced in a highly energy damped deep-inelastic-type reaction. The lifetimes of the dinuclear composites estimated from the angular distributions of these fragments are found to be in the range of $\approx (0.5–2.7)\times {10}^{-22}$ s, which are smaller than the respective compound-nuclear lifetimes $[\approx (1.0–2.0)\times {10}^{-21} \mathrm{s}]$. The angular-momentum dissipations estimated from the average kinetic energies of the fragments are found to be, for lighter fragments in particular, greater than those predicted by the empirical sticking limit.

We have interpreted the recent observation [K. Auranen et al., Phys. Lett. B 792, 187 (2019)] of proton emission from ${}^{108}\mathrm{I}$. We find that $\gamma$ deformation is crucial to reproduce the experimental data, and have identified the decaying state as the $1^{+}$ state. The effect of the residual $np$ interaction is also discussed. With the present calculation, we establish the first microscopic description of a triaxial odd-odd proton emitter.

We discuss an extension of the generator coordinate method (GCM) by taking simultaneously a collective coordinate and its conjugate momentum as generator coordinates. To this end, we follow the idea of the dynamical GCM (DGCM) proposed by Goeke and Reinhard. We first show that the DGCM method can be regarded as an extension of the double projection method for the center of mass motion. As an application of DGCM, we then investigate the particle number projection, for which we not only carry out an integral over the gauge angle as in the usual particle number projection but also take a linear superposition of Barden-Cooper-Schrieffer (BCS) states which have different mean particle numbers. We show that the ground state energy is significantly lowered by such effect, especially for magic nuclei for which the pairing gap is zero in the BCS approximation. This suggests that the present method makes a good alternative to the VAP method, as the method is much simpler than the VAP.

A resonant state at $3.{21}_{-0.04}^{+0.12}\mathrm{MeV}$, located just above the one-neutron separation threshold, was observed for the first time in ${}^{12}\mathrm{Be}$ from the ${}^{11}\mathrm{Be}(d,p){}^{12}\mathrm{Be}$ one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^{-}$ according to the systematics of the level scheme of the $N=8$ isotones and decay-width analysis. Gamow coupled-channel and Gamow shell-model calculations show the importance of the continuum coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in ${}^{12}\mathrm{Be}$ and in its isotonic nucleus ${}^{11}\mathrm{Li}$ are comparably discussed.

Low-energy dipole (LED) excitations in ${}^{18}\mathrm{O}$ were investigated using a combination of the variation after $K$ projection in the framework of antisymmetrized molecular dynamics with $\beta$ constraint with the generator coordinate method. We obtained two LED states, namely, the $1_1^{-}$ state with a dominant shell-model structure and the $1_2^{-}$ state with a large ${}^{14}\mathrm{C}+\alpha$ cluster component. Both these states had significant toroidal dipole (TD) and compressive dipole (CD) strengths, indicating that the TD and CD modes are not separated but mixed in the LED excitations of ${}^{18}\mathrm{O}$. This is unlike the CD and TD modes for well-deformed nuclei such as ${}^{10}\mathrm{Be}$, where the CD and TD modes are generated as $K^{\pi }=0^{-}$ and $K^{\pi }=1^{-}$ excitations, respectively, in a largely deformed state.

We discuss the role of deformation of the target nucleus in the fusion reaction of the ${}^{15}\mathrm{C}+{}^{232}\mathrm{Th}$ system at energies around the Coulomb barrier, in which ${}^{15}\mathrm{C}$ is a well-known one-neutron halo nucleus. To this end, we construct the potential between ${}^{15}\mathrm{C}$ and ${}^{232}\mathrm{Th}$ with the double folding procedure, assuming that the projectile nucleus is composed of the core nucleus, ${}^{14}\mathrm{C}$, and a valence neutron. In addition, we also take into account the coupling to the one-neutron transfer process to the ${}^{14}\mathrm{C}+{}^{233}\mathrm{Th}$ configuration. We show that such calculation simultaneously reproduces the fusion cross sections for the ${}^{14}\mathrm{C}+{}^{232}\mathrm{Th}$ and the ${}^{15}\mathrm{C}+{}^{232}\mathrm{Th}$ systems, implying an important role of the transfer coupling in fusion of neutron-rich nuclei.

Background: An asymmetric fission was reported by Andreyev et al. in β-delayed fission of ${}^{180}\mathrm{Tl}$ [Phys. Rev. Lett. 105, 252502 (2010)]. Subsequent theoretical calculations suggested that the asymmetric nature of the mass distribution is not restricted to the ${}^{180}\mathrm{Hg}$ only but is also expected for many other nuclei in the mass region $A\approx 180$. Thus, it is important to investigate fission fragment mass distribution for different fissioning systems over a wide range of excitation energy in the mass region $A\approx 180$.

Purpose: Present measurements have been carried out to study the nature of the fission fragment mass distribution in the ${}^{32}\mathrm{S}+{}^{144}\mathrm{Sm}\to {}^{176}\mathrm{Pt}$ reaction in the compound nucleus excitation energy range of 38.7–47.5 MeV and investigate the role of multimodal fission.

Method: Mass distributions have been determined from the time of flight (TOF) of the fission fragments, which was measured with respect to the beam pulse. Two multiwire proportional counters were placed at the folding angle to detect the fission fragments. Measured TOF of the fission fragments was used to obtain their velocities, which were further used to obtain the fission fragment mass distribution.

Results: The fission fragment mass distributions at all three beam energies were observed to have flattop natures, which could not be fitted well by a one-Gaussian function. A fit using a two-Gaussian function significantly improved the ${\chi }^2$ values. The ratio of the most probable heavy to light fragment mass ($A_{\mathrm{H}}/A_{\mathrm{L}}$) was observed as $\approx 99.4/76.6$. A systematic study of the centroid values of asymmetric peaks in the mass distribution for different fissioning systems around mass region $A\approx 180$ showed that heavier mass peak is centered around $A_{\mathrm{H}}\approx 100$. Further analysis of $A_{\mathrm{H}}$ and $A_{\mathrm{L}}$ to obtain the corresponding neutron and proton numbers gave heavy fragment neutron number ($N_{\mathrm{H}}$) around $\approx 56$ and light fragment proton number ($Z_{\mathrm{L}}$) in the range of $\approx 34–36$.

Conclusions: Observation of the flattop nature indicated the contributions from multimodal fission having both symmetric and asymmetric fission components, similar to those reported earlier in the mass region $A\approx 180$, although it did not show a clear dip in symmetry as observed in some of the studies. The observed values of the neutron number in the heavy fragment ($N_{\mathrm{H}}$) and proton number in the light fragment ($Z_{\mathrm{L}}$) are consistent with the values recently proposed in Phys. Rev. C 100, 041602(R) (2019) and arXiv:2007.16184] for fissioning systems in the similar mass range. Comparison of the data on the width of the mass distribution from the present paper with those from similar fissioning systems with different $Z_P{Z}_T$ values suggested that the observed width of the mass distribution has a dependence on the neutron-proton configuration along with the entrance channel dynamics.

Light neutron-rich isotopes are populated as products of the multinucleon transfer reaction following the collisions of ${}^{64}\mathrm{Ni}$ beams onto ${}^{130}\mathrm{Te}, {}^{208}\mathrm{Pb}$, and ${}^{238}\mathrm{U}$ targets and ${}^{40}\mathrm{Ar}$ beams onto ${}^{197}\mathrm{Au}, {}^{208}\mathrm{Pb}$, and ${}^{238}\mathrm{U}$ targets at bombarding energies slightly above the Coulomb barrier. Distribution characteristics of projectile-like fragments are studied in the framework of dinuclear system concept where dynamic deformation is taken into account. The odd-even effect in the diffusion process is discussed, and the distribution of final isotopes can be well reproduced by the effective local excitation energies excluding pairing energies. Compared with the experimental data, it is found that the heavier (i.e., larger $N/Z$ ratio) the target is, the more likely it is to produce light neutron-rich isotopes.