The low-lying excited states of ${}^{46}\mathrm{S}$ and ${}^{47}\mathrm{S}$ were investigated using knockout reactions on a liquid hydrogen target combined with $\gamma$-ray spectroscopy. Four new transitions were observed in ${}^{46}\mathrm{S}$, and a single $\gamma$ ray was identified in ${}^{47}\mathrm{S}$. Comparison with shell-model calculations allowed the assignment of the observed transitions to specific theoretical levels. The energies of the $4_1^{+}$ and $2_2^{+}$ states in ${}^{46}\mathrm{S}$ suggest the presence of triaxial deformation.

Background: The synthesis of super heavy elements (SHE) is governed by two major competing processes: quasifission (QF) and fusion-fission (FF). Optimizing SHE production requires an extensive understanding of these processes. The dynamics of QF and FF are being studied experimentally worldwide, with special attention to the quantification of QF. The limited availability of robust theoretical models suggests that achieving higher predictive accuracy necessitates careful benchmarking of the developed models against experimental observations.

Purpose: The present study seeks to identify QF signatures in the fission of ${}^{35}\mathrm{Cl}+{}^{181}\mathrm{Ta}$ at excitation energies around the Coulomb barrier. Furthermore, this study intends to quantify the contribution of QF to total fission events and to compare it with the predictions by the DiNuclear System (DNS) model.

Methods: In the experiment, a pulsed heavy-ion beam around the Coulomb barrier energy was utilized, and the resulting binary fragments were detected using two position-sensitive multiwire proportional counters (MWPCs). By analyzing the time-of-flight (TOF) differences and position information of the binary fragments, mass and total kinetic energy (TKE) distributions were obtained for the reaction ${}^{35}\mathrm{Cl}+{}^{181}\mathrm{Ta}$.

Results: The experimental results showed no significant correlation between fragment mass and angle. The mass-TKE correlation, in contrast, exhibits a deviation from that prediction by the Liquid Drop Model (LDM). The contributions of QF were quantified as 22%, 12%, and 8% at excitation energies of 52.4, 59.1, and 62.4 MeV, respectively, as determined from mass and energy distribution analysis. These findings were found to be consistent with the DNS model's predictions.

Conclusion: Compelling evidence for slow quasifission is observed in the reaction ${}^{35}\mathrm{Cl}+{}^{181}\mathrm{Ta}$. The present analysis indicates that the average TKE and its variance offer the signature of slow quasifission.

Background: Heavy-ion fusion reactions at energies below the Coulomb barrier are strongly influenced by the coupling of different internal degrees of freedom of the interacting nuclei with the relative motion degrees of freedom. These couplings leads to a distribution of fusion barriers which results in significant enhancement in the sub-barrier fusion cross sections.

Purpose: To study the effect of collective excitations and neutron transfer channels in the fusion of ${}^{28}\mathrm{Si}$ with ${}^{142,150}\mathrm{Nd}$ at energies around the Coulomb barrier.

Method: The fusion excitation function for the ${}^{28}\mathrm{Si}+{}^{142,150}\mathrm{Nd}$ reactions were measured at energies $\approx 15\%$ below to $\approx 15\%$ above the Coulomb barrier, using the Heavy Ion Reaction Analyzer. Measured fusion excitation function is analyzed using the coupled-channels formalism. Fusion barrier distributions are extracted from the measured cross sections following the double differential method as well as the Gaussian analytic method.

Results: The vibrational coupling of the target nucleus and rotational coupling of projectile nucleus along with $2n$-transfer channel reasonably reproduced the fusion excitation function for the ${}^{28}\mathrm{Si}+{}^{142}\mathrm{Nd}$ reaction. Transfer coupling strength of 0.23 is used in the calculation. Rotational coupling of ${}^{28}\mathrm{Si}$ and ${}^{150}\mathrm{Nd}$ along with the $2n$-transfer channel could not reproduce the fusion excitation for the ${}^{28}\mathrm{Si}+{}^{150}\mathrm{Nd}$ reaction. The barrier distribution is expressed as a superposition of three Gaussian components for both reactions with minimum ${\chi }^2$ values.

Conclusion: Barrier distribution using Gaussian analytic method is quite useful in understanding the coupling schemes at below barrier energies. The coupling scheme that reproduced the fusion excitation function reasonably could not reproduce the distribution of fusion barrier in case of ${}^{28}\mathrm{Si}+{}^{142}\mathrm{Nd}$ reaction. The rotational excitations of ${}^{28}\mathrm{Si}$ and ${}^{150}\mathrm{Nd}$ along with $2n$-transfer channel also could not reproduce the barrier distribution for the ${}^{28}\mathrm{Si}+{}^{150}\mathrm{Nd}$ reaction, indicating the possible role of other transfer channels.

Reaction dynamics induced by weakly bound nuclei at energies around the Coulomb barrier are now one of the frontier research topics of nuclear physics. In this work, the quasielastic scattering angular distribution of the radioactive nucleus ${}^7\mathrm{Be}$ from a ${}^{120}\mathrm{Sn}$ target was measured by using a silicon detector array with a large solid-angle coverage for the first time at an energy of 48.05 MeV. The data are analyzed using the newly developed continuum-discretized coupled-channels (CDCC) procedure, CDCC-R. The effects of breakup continuum states on the quasielastic scattering are found to be minor by switching on and off the continuum couplings in the CDCC-R calculations. Moreover, the total reaction cross section of ${}^7\mathrm{Be}$ $+$ ${}^{120}\mathrm{Sn}$ is extracted by the combination of the Bayesian method and the optical model. It is in agreement with the systematic trend of the weakly bound nuclei ${}^{6,7,8}\mathrm{Li}$ on the ${}^{120}\mathrm{Sn}$ target, and the influences of different targets are insignificant.

Four-volumes ($V_4=$ spatial-3-volume$\times$lifetime) are calculated within the model of three-fluid dynamics (3FD) and compared with those of the jet AA microscopic transport model (JAM). The calculations are performed for central $\mathrm{Au}+\mathrm{Au}$ collisions at energies of $\sqrt{s_{NN}}=3–19.6\mathrm{GeV}$. These $V_4$'s indicate optimal collision-energy ranges for realizing macroscopic high-baryon-density matter. It is found that the 3FD four-volumes noticeably exceed those in the JAM, which indicates a stronger baryon stopping in the 3FD model as compared to that in the JAM. It is argued that this difference in the baryon stopping correlates with stiffness of the equation of state implemented in these models. Contrary to the JAM, the four-volume, where a baryon density $\left(n_B\right)$ exceeds three times the normal nuclear density $\left(n_0\right)$, does not exhibit a maximum as a function of $\sqrt{s_{NN}}$. It decreases monotonically with increasing $\sqrt{s_{NN}}$, remaining at a fairly macroscopic level (i.e., $V_4\gtrsim 5.5^4{\mathrm{fm}}^4/c$). For higher baryon densities, $V_4$ exhibits maxima in its dependence on $\sqrt{s_{NN}}$. The optimal energy range for densities $n_B/n_0>4$ is located at $\sqrt{s_{NN}}=3.2–8$ GeV. Even for $n_B/n_0>6$, the four-volume remains quite macroscopic ($V_4\gtrsim 4^4{\mathrm{fm}}^4/c$) at $\sqrt{s_{NN}}=4.5–9$ GeV, contrary to the JAM.

In this work, we investigate the interaction between the $\mathrm{\Omega }$ baryon and the $s\overline{s}$ meson within the framework of the quark delocalization color-screening model. The spectra calculations show that no bound state is formed in any of the considered channels, while the scattering indicates that the $\mathrm{\Omega }\varphi$ interaction with $J^P=1/2^{-}$ is weakly attractive. As for the $\mathrm{\Omega }\varphi$ interactions with $J^P=3/2^{-}$ and $5/2^{-}$, as well as the $\mathrm{\Omega }{\eta }^{\prime }$ interaction with $J^P=3/2^{-}$, they are all repulsive. After an investigation on the femtoscopic correlation functions, we find that, due to the spin-averaging effect, the overall $\mathrm{\Omega }\varphi$ correlation function exhibits a weak dependence on the source size, which provides a crucial significance of our model for future experimental examinations in relativistic heavy-ion collisions.

The ${}^{22}\mathrm{Ne}(\alpha ,n){}^{25}\mathrm{Mg}$ reaction acts as an $s$-process neutron source in both the main and weak $s$ processes. By exciting ${}^{22}\mathrm{Ne}$ to highly energetic resonance states above 9.7 MeV, we measured the properties of these difficult-to-access states, which are relevant to the stellar production of this seed isotope through the ${}^{18}\mathrm{O}(\alpha ,\gamma ){}^{22}\mathrm{Ne}$ reaction. At the ISAC II facility of TRIUMF, a 165 MeV beam of ${}^{21}\mathrm{Ne}$ was delivered to a deuterated polyethylene $\left({\mathrm{CD}}_2\right)$ target, resulting in the population of an excited ${}^{22}\mathrm{Ne}$ nucleus and a recoil proton. This reaction mechanism was studied with two surrounding complementary arrays: SHARC, a segmented silicon array for measurement of recoil particles, and TIGRESS, a high-purity, segmented germanium clover array for measurement and correction of Doppler-shifted $\gamma$ rays. Here, we present the first definitive spin-parity assignment and energy constraint of the 217 keV ${}^{18}\mathrm{O}(\alpha ,\gamma ){}^{22}\mathrm{Ne}$ resonance state, as well as the spin confirmation of the 575 keV and 662.1 keV resonances, and discuss the implications of these spin constraints on the production of the ${}^{22}\mathrm{Ne}$ isotope in asymptotic giant branch stars.

The $\gamma$-ray emitting radioisotopes produced during explosive Si-burning in core-collapse supernovae (CCSNe) could serve as a probe to supernovae explosion energetics. Especially important are the three isotopes ${}^{43}\mathrm{K}$, ${}^{47}\mathrm{Sc}$, and ${}^{59}\mathrm{Fe}$ as these are potentially detectable with next generation space-based $\gamma$-ray telescopes. However, current nuclear physics uncertainties hinder model-observation comparisons. The ${}^{28}\mathrm{Al}(p,\alpha ){}^{25}\mathrm{Mg}$ reaction has been shown to be among the most important reactions which impact the production of these three $\gamma$ emitters in CCSNe. We report on the first observation of resonant states in the compound nucleus ${}^{29}\mathrm{Si}$, which were populated via the ${}^{28}\mathrm{Si}(d,p){}^{29}\mathrm{Si}$ reaction. This measurement provides the first experimental determination of the ${}^{28}\mathrm{Al}(p,\alpha ){}^{25}\mathrm{Mg}$ reaction rate. This new measurement, along with associated uncertainty limits, removes one of the most important nuclear physics uncertainties in the production of ${}^{43}\mathrm{K}$, ${}^{47}\mathrm{Sc}$, and ${}^{59}\mathrm{Fe}$ $\gamma$-emitting radioisotopes in CCSNe.

Ordinary muon capture provides a benchmark for the nuclear physics models of neutrinoless 39 double beta decay under comparable momentum transfer conditions. The total capture strength defines the lifetime of the muonic atom. The muon lifetime in ${}^{76}\mathrm{Se}$, the daughter nucleus of ${}^{76}\mathrm{Ge}$, was determined with improved accuracy by the MONUMENT collaboration, using an array of high-purity germanium detectors and a set of scintillator counters at the $\pi \mathrm{E}1$ muon beam line of the Paul Scherrer Institute. The new value of $(135.1\pm 0.5)$ ns agrees with phenomenological calculations based on the quasiparticle random-phase approximation with unquenched axial-vector coupling.

We present a framework for local quantum cooling that can be efficiently applied to large-scale Fermi systems. The method introduces local Hermitian operators as a cooling potential while strictly preserving the unitarity of time evolution. Our formulation scales favorably with system size and can be seamlessly integrated into time-dependent density-functional theory frameworks. We demonstrate that energy cooling arises from the damping of particle currents and pairing-field fluctuations. Furthermore, we develop a variant of the scheme that allows the particle number to vary in time, enabling controlled density scans. The method is generic and versatile, as illustrated by applications to spin-imbalanced unitary Fermi gases and to nuclear matter in the neutron-star crust. The framework can be naturally extended to include stochastic noise, providing a foundation for studying thermalization in strongly interacting Fermi superfluids.

The relativistic plane wave impulse approximation (RPWIA) is benchmarked against the established relativistic distorted wave impulse approximation (RDWIA) for exclusive proton-induced proton knockout reactions ($\vec{p},2\vec{p}$) from the $3{\mathrm{s}}_{1/2}$ state in ${}^{208}\mathrm{Pb}$ at $392\mathrm{MeV}$. While the RDWIA provides a proper description of the reaction, the RPWIA—which neglects nuclear distortion and absorption effects—fails dramatically for absolute cross sections, requiring a scaling factor of $1/26$ to match the data. However, within $\pm 10\mathrm{MeV}$ of the recoilless condition, the RPWIA quantitatively describes the analyzing power ($A_y$) data and yields similar results as the RDWIA predictions for all polarization transfer observables (${\mathrm{D}}_{i^{\prime }j}$). These polarization transfer observables are insensitive to the choice of the Relativistic Mean Field model used. The study establishes clear boundaries for the RPWIA's utility: Computationally simple predictions for polarization observables near zero recoil, but essential reliance on the RDWIA for spectroscopic factor extraction.

The liquid-gas phase transition (LGPT) in heavy-ion collisions is explored using fluctuation observables within the isospin quantum molecular dynamics framework. Scaled variance $\left(\omega \right)$, skewness $\left(S\sigma \right)$, and kurtosis $\left(\kappa {\sigma }^2\right)$ of emitted protons and neutrons are analyzed over a range of beam energies. The analysis reveals a clear minimum in the scaled variance $\omega$ for both neutrons and protons, as well as a separation point between their kurtosis $\kappa {\sigma }^2$ values around 110 MeV/nucleon. Moreover, the skewness $\left(S\sigma \right)$ and kurtosis $\left(\kappa {\sigma }^2\right)$ of intermediate-mass fragments exhibit additional nontrivial fluctuation features in the same energy region. These features correlate with extrema in the energy derivatives of intermediate-mass fragment multiplicity and charge asymmetry between the largest fragment and second largest fragment $\left(a_2\right)$, providing potential indicators of LGPT under finite-size and dynamical conditions. In addition, the impact of sequential decays on the observables was checked using an afterburner sequential decay model $\left(\mathrm{GEMINI++}\right)$, and it was found that the influence on neutron and charge asymmetry $a_2$ is larger.

The model of backward proton production in the exclusive reaction $pd\to ppn$ at proton beam momenta up to several GeV/$c$ is constructed on the basis of Feynman diagrams for one- and two-step amplitudes. The latter include nucleon and $\mathrm{\Delta }\left(1232\right)$ resonance intermediate scattering states with propagators reduced to eikonal form using the generalized eikonal approximation. The model calculations are compared with available experimental data on the energy spectra of protons at backward polar angles in the deuteron rest frame. It is shown that inclusion of two-step amplitudes significantly increases the production of backward protons with energies above $\sim 50$ MeV, thereby significantly improving the agreement with experiment. The remaining theoretical problem related to the description of the off-shell behavior of the elementary amplitudes of the $NN\to NN$ and $NN\leftrightarrow N\mathrm{\Delta }$ transitions is discussed. Partial discrepancies between different sets of experimental data do not allow for conclusion that exotic effects, such as proton interactions with density fluctuations and/or $6q$ clusters in the deuteron, are present.

Background: Alpha decay is a key decay mode for determining the stability and experimental identification of heavy and superheavy nuclei. Within the Wentzel–Kramers–Brillouin tunneling framework $\left(P_{\mathrm{WKB}}\right)$, the half-life depends exponentially on the effective barrier and is therefore highly sensitive to the decay energy $\left(Q_{\alpha }\right)$ and to the $\alpha$-daughter interaction. Although the dominant role of $Q_{\alpha }$ is well established, the relative importance of surface-structure effects—including the neutron-skin change ${\delta }_{n\alpha }$ between parent and daughter nuclei, the isospin asymmetry $\delta$, and the short-range repulsion described by the diffuseness parameter $a_{\mathrm{rep}}$—has not been compared within a common normalized framework. This makes it difficult to rank the mechanisms that control $\alpha$ decay in heavy and superheavy even-even nuclei.

Purpose: We quantify how the decay energy $Q_{\alpha }$ and the neutron-skin change ${\delta }_{n\alpha }$ affect the occurrence of $\alpha$ decay in even-even nuclei with $94\le Z\le 118$. By combining correlation analysis with a normalized sensitivity study of ${log}_{10}{P}_{\mathrm{WKB}}$, we compare the relative effects of $Q_{\alpha }$, ${\delta }_{n\alpha }$, $\delta$, and $a_{\mathrm{rep}}$ on the decay process.

Methods: We systematically survey even-even nuclei in the region $94\le Z\le 118$, where ${\delta }_{n\alpha }$ is computed self-consistently within two independent microscopic frameworks: the Hartree–Fock–Bogoliubov approach in the transformed harmonic-oscillator basis (HFB-THO) and the Hartree–Fock–BCS (HF-BCS) model. To compare the effects of the quantities entering the barrier penetration problem, we introduce a globally normalized linear sensitivity measure for ${log}_{10}{P}_{\mathrm{WKB}}$. For the first time, the short-range repulsive core diffuseness parameter $a_{\mathrm{rep}}$ in the double-folding (DF) potential is analyzed on the same normalized footing as $Q_{\alpha }$, ${\delta }_{n\alpha }$, and the isospin asymmetry.

Results: A systematic analysis in the region $94\le Z\le 118$ shows that the occurrence of $\alpha$ decay is strongly correlated with the behavior of ${\delta }_{n\alpha }$. Nuclei with observed $\alpha$ decay clusters within a narrow interval ${\delta }_{n\alpha }\approx 0.006–0.008\mathrm{fm}$, whereas nondecaying systems often show local deviations from this interval, even when $Q_{\alpha }$ is positive or relatively large. Strong variations of ${\delta }_{n\alpha }$ appear near deformed neutron shells ($N\approx 140\text{to}N\approx 150$) and toward the predicted near-spherical configurations around $N\approx 172$ and $N\approx 184$, where $\alpha$ decay becomes dominant. The normalized sensitivity analysis of ${log}_{10}{P}_{\mathrm{WKB}}$ shows that, beyond the leading role of $Q_{\alpha }$, the quantities $\delta$ and $a_{\mathrm{rep}}$ can make contributions of comparable size in selected nuclear regions. By contrast, local isospin-surface effects mainly provide secondary corrections because ${\delta }_{n\alpha }$ varies only within a limited range among $\alpha$-emitting nuclei. These findings show how decay energy, barrier geometry, and nuclear structure jointly affect the $\alpha$-tunneling probability.

Conclusions: The results show that $\alpha$ decay in heavy and superheavy nuclei is not controlled solely by $Q_{\alpha }$, but is also affected by surface structure and short-range interactions. The quantity ${\delta }_{n\alpha }$ is a sensitive indicator of the structural match between parent and daughter nuclei, and its deviations reflect deeper structural changes such as shell effects or shape transitions rather than acting as a direct control parameter. The relatively high sensitivity of $a_{\mathrm{rep}}$ highlights the role of short-range repulsion and Pauli blocking in shaping the inner part of the Coulomb barrier. This suggests that improved microscopic treatments of the repulsive core may be important for describing $\alpha$ decay in superheavy systems. The present framework provides a quantitative way to assess surface-structure effects across the superheavy region.

Background: Total photoabsorption cross sections are important for an understanding of nuclear structure and for many applications, in particular in astrophysics. The majority of data stems from measurements of neutron emission after photoexcitation, which, in heavy nuclei, represent a good approximation to the total cross sections. However, this does not hold for light nuclei, where charged-particle emission thresholds are typically lower in energy. Accordingly, data in light nuclei are scarce.

Purpose: The present work reports new total photoabsorption cross sections for the $N=Z$ nuclei in the $sd$-shell ${}^{20}\mathrm{Ne}, {}^{24}\mathrm{Mg}, {}^{28}\mathrm{Si}, {}^{32}\mathrm{S}, {}^{36}\mathrm{Ar}$, and for ${}^{26}\mathrm{Mg}$. The results are compared to predictions of a data-driven artificial neural network application and to configuration-interaction shell-model calculations covering the excitation energy region of the isovector giant dipole resonance.

Methods: Double-differential cross sections of the $(p,p^{\prime })$ reaction at an incident proton energy of 295 MeV have been measured between $0^{\circ }$ and ${14}^{\circ }$. The angular distributions of the $E1$ parts due to Coulomb excitation have been extracted with a multipole decomposition analysis for excitation energies 12 to 24 MeV and converted to equivalent photoabsorption cross sections with the virtual photon method.

Results: Reasonable agreement of the photoabsorption cross sections with previous experiments is found for ${}^{24}\mathrm{Mg}$ and ${}^{28}\mathrm{Si}$, while the present results diverge for ${}^{32}\mathrm{S}$. For the first time, data are presented for ${}^{20}\mathrm{Ne}, {}^{26}\mathrm{Mg}$, and ${}^{36}\mathrm{Ar}$. Configuration-interaction shell-model calculations provide an overall satisfactory description of the fragmented $E1$ strength distributions. The same holds for absolute cross sections except for ${}^{26}\mathrm{Mg}$ and ${}^{36}\mathrm{Ar}$, where the experimental results significantly exceed the expected exhaustion of the Thomas-Reiche-Kuhn energy-weighted sum rule.

Conclusions: Despite a reduction of Coulomb relative to nuclear cross sections in light nuclei with respect to previous analyses of the same kind in medium-mass and heavy nuclei, forward-angle proton scattering at energies of several hundred MeV remains a valuable tool to extract the nuclear $E1$ response. However, there is a larger model dependence, in particular for excitation energies above 20 MeV, due to the need to constrain the continuum background with additional assumptions. The overall success of the shell-model approach to describe the features of the experimental photoabsorption cross sections motivates its application in large-scale reaction network calculations aiming at an understanding of the mass composition of ultrahigh-energy cosmic rays.

We present a theoretical framework for calculating the asymptotic properties and decay dynamics of three-body resonances described in a discrete basis. The method involves solving an inhomogeneous Schrödinger equation to determine the non-normalizable resonant state by identifying a normalizable source state, which captures the short-range internal structure. The long-range behavior is then calculated using the free three-body propagator, providing accurate asymptotic coefficients necessary for describing decay correlations. We apply this formalism to the two-neutron decay of the $0^{+}$ ground-state and the $2^{+}$ excited-state resonances of ${}^{16}\mathrm{Be}$ (${}^{14}\mathrm{Be}+n+n$), working within the hyperspherical expansion method with an analytical transformed harmonic oscillator basis. Our results show that the decay is strongly dominated by the lowest hypermomentum components at large separations, reflecting effective three-body barrier penetration dynamics that shape the final state. The calculated relative-energy distributions exhibit clear neutron-neutron correlations for both states, arising from mixing between different asymptotic channels, and are consistent with a direct two-neutron emission mechanism, in agreement with recent experimental observations. This work provides a reliable tool for linking the internal structure of three-body resonances to their decay properties.

We examined the potential impact of decays on the magnitude of fluctuations of net quantum numbers and integrals of balance functions based on a thermal hadron gas model. The calculations are based on a comprehensive list of known hadrons with masses up to $2.5\mathrm{GeV}/c^2$ and include all decays of these hadrons with known branching fractions. The calculations are performed at vanishing baryochemical potential for temperatures between 140 and 200 MeV. We show that the decays feed-down substantially impact the single yield of measurable “stable particles” as well as those of correlated densities of these species. Decays can then potentially have large and nontrivial impacts on measurements of net quantum-number cumulants and balance functions. These observations are particularly important in the context of the search for the QCD critical point at the RHIC Beam Energy Scan as well as efforts to determine chemical susceptibilities near the phase transition at RHIC or LHC energies. Results obtained in this work also shed light on the importance of feed-down in measurements of balance functions in elementary $pp$ and nucleus-nucleus collisions.

To overcome the limitations of existing algorithms for solving self-bound quantum many-body problems—such as those encountered in nuclear and particle physics—that access only a restricted subset of energy levels and provide limited structural information, we introduce and demonstrate a novel quantum-classical approach capable of resolving the complete bound-state spectrum. This method also provides the total angular momentum $J$ associated with each eigenstate. Our approach is based on expressing the Hamiltonian in second-quantized form within a novel input model combined with a scan scheme, enabling broad applicability to configuration-interaction calculations across diverse fields. We apply this hybrid method to compute, for the first time, the bound-state spectrum together with corresponding $J$ values of ${}^{20}\mathrm{O}$ using a realistic strong-interaction Hamiltonian. Our approach applies to hadron spectra and $J$ values solved in the relativistic basis light-front quantization approach.

Short-range correlations (SRCs) provide the link between low- and high-energy nuclear physics and can be quantified by two-nucleon densities. We present calculations of the two-nucleon densities using free-space similarity renormalization group (SRG)-evolved operators and in-medium SRG (IMSRG) ground states with a softened chiral interaction. Our calculations benchmark well against no-core shell model results with unevolved operators and Hamiltonians in ${}^4\mathrm{He}$. We explicitly include the induced three-body (3b) density operators for the first time which, together with the 3b Hamiltonians, provide the full 3b effects. We show pronounced 3b effects in the ${}^{16}\mathrm{O}$ two-nucleon densities. Combined with valence-space IMSRG method, we extend the calculation to the oxygen isotopic chain. This approach enables a consistent ab initio description of low-energy properties and SRCs within one framework and offers predictions for the upcoming SRC measurements in unstable nuclei.

Background: Quasifission is a nonequilibrium phenomenon that strongly suppresses the formation of heavy nuclei in heavy-ion fusion reactions. This process shows a strong entrance channel dependence. Understanding quasifission is crucial for exploring potential avenues to synthesize new superheavy elements and their isotopes.

Purpose: To study the interplay of fusion-fission and quasifission with increasing $Z_p{Z}_t$ for the reactions using ${}^{197}\mathrm{Au}$ as the target. To explore the variation of average sticking time in these reactions with a constant target deformation.

Methods: The mass-angle distributions of fission and fission-like fragments were measured for seven reactions using ${}^{197}\mathrm{Au}$ as the target at energies near the Coulomb barrier. Negligible sequential fission is expected in these reactions; thus, the measured binary products represent the total quasifission yield. Pulsed beams of ${}^{32,36}\mathrm{S}$, ${}^{48}\mathrm{Ca}$, ${}^{50}\mathrm{Ti}$, ${}^{54}\mathrm{Cr}$, ${}^{58}\mathrm{Fe}$, and ${}^{64}\mathrm{Ni}$ were used in the study. A systematic analysis of mass ratio distributions and mass widths has been carried out. The experimental mass-angle distribution is simulated following a phenomenological approach. The average sticking time for the fast quasifission is extracted from the simulations.

Results: Dominant mass-symmetric fission fragments with a slight mass-angle correlation are observed in the most mass-asymmetric (${}^{32,36}\mathrm{S}+{}^{197}\mathrm{Au}$) reactions. In contrast, a $\mathsf{U}$-shaped mass ratio distribution has been observed in the most symmetric (${}^{64}\mathrm{Ni}+{}^{197}\mathrm{Au}$) reaction. A sharp decrease in fusion probability is inferred with increasing $Z_p{Z}_t$. The width of the mass ratio distribution is found to increase exponentially with the increase in mean fissility for a fixed beam energy relative to the barrier. The average sticking time of fast quasifission is found to vary from approximately 14 to 15 zeptoseconds to approximately 4 to 5 zeptoseconds for the systems under study.

Conclusion: The observed transition from a dominant symmetric mass split to an asymmetric mass split with mass-angle correlations indicates the increasing probability of fast quasifission and fusion suppression with increasing $Z_p{Z}_t$. The observation is correlated with the sharp fall in the extracted average sticking time with increasing $Z_p{Z}_t$ from 1264 to 2212.