Bose–Einstein condensation of $\alpha$ clusters in light and medium-heavy nuclei is studied in the frame of the field-theoretical superfluid cluster model. The order parameter of the phase transition from the Wigner phase to the Nambu–Goldstone phase is a superfluid amplitude, square of the moduli of which is the superfluid density distribution. The zero-mode operators due to the spontaneous symmetry breaking of the global phase in the finite number of $\alpha$ clusters are rigorously treated. The theory is systematically applied to $N\alpha$ nuclei from ${}^{12}\mathrm{C}$ to ${}^{52}\mathrm{Fe}$ at various condensation rates. In ${}^{12}\mathrm{C}$ it is found that the energy levels of the gas-like well-developed $\alpha$ cluster states above the Hoyle state are reproduced well in agreement with experiment for realistic condensation rates of $\alpha$ clusters. The electric $E2$ and $E0$ transitions are calculated and found to be sensitive to the condensation rates. The profound raison d'être of the $\alpha$ cluster gas-like states above the Hoyle state, whose structure has been interpreted geometrically in the nuclear models without the order parameter such as the cluster models or ab initio calculations, is revealed. It is found that, in addition to the Bogoliubov–de Gennes vibrational mode states, collective states of the zero-mode operators appear systematically at low excitation energies from the $N\alpha$ threshold energy. These collective states, which are new-type soft modes in nuclei due to the Bose–Einstein condensation of the $\alpha$ clusters, emerge systematically in light– and medium-heavy–mass regions and are also located at high excitation energies from the ground state in contrast to the traditional concept of soft mode in the low-excitation-energy region.

Previous work has quantified the degree of neutron-proton equilibration in heavy-ion nuclear collisions by observing the convergence of isospin observables (such as the isoscaling parameter $\alpha$) to an expected value based on similar symmetric reaction systems. We present a new signature of equilibration: the convergence of the isospin asymmetry (as quantified by three isoscaling metrics) of two mirror asymmetric reaction systems toward each other rather than a predefined point. For the reactions of 35 MeV/$u$ ${}^{64,70}\mathrm{Zn}+{}^{64,70}\mathrm{Zn}$ and ${}^{64}\mathrm{Zn},{}^{64}\mathrm{Ni}+{}^{64}\mathrm{Zn},{}^{64}\mathrm{Ni}$ the neutron-proton equilibration was found to be approximately 80%, and this result is compared directly to previous work.

The possibility of the appearance of $\mathrm{\Delta }$(1232) isobars in neutron star matter and the so-called $\mathrm{\Delta }$ puzzle is investigated in a relativistic quark model where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $\sigma$, $\omega$, and $\rho$ mesons through mean-field approximations. The hyperon couplings are fixed from the hyperon optical potentials at saturation density. Effects of moderate variations in the $\mathrm{\Delta }\text{−}\omega$ and $\mathrm{\Delta }\text{−}\rho$ coupling strengths on the critical density of forming $\mathrm{\Delta }$ resonances and on the mass-radius relation of neutron stars is studied. We have also made an attempt to study the impact of in-medium mass variations of the $\mathrm{\Delta }$ baryon on the structure of neutron stars. It is observed that, within the constraints of the masses of the precisely measured massive pulsars PSR J0348+0432 and PSR $\mathrm{J}1614-2230$, neutron stars with a composition of both $\mathrm{\Delta }$ isobars and hyperons are possible in the present model.

An examination is conducted on a commonly used procedure for extracting (un)polarized $\gamma n\to {\pi }^{-}p$ and $\gamma n\to {\pi }^{0}n$ observables from ${}^2\mathrm{H}(\gamma ,{\pi }^{-})pp$ and ${}^2\mathrm{H}(\gamma ,{\pi }^0)pn$ data, using a model that consists of the impulse term and the final-state interaction (FSI) terms due to nucleon and pion exchange. Recent experimental and theoretical analyses used an extraction method that does not impose a cut on the final $\pi N$ invariant mass $W$. I demonstrate that the use of this method can result in the $\gamma n\to \pi N$ observables that are seriously distorted by the nucleon Fermi motion, and that one can efficiently avoid this problem by imposing a cut on $W$. It is also shown that the use of kinematical cuts of recent experimental analyses can still leave in the selected samples substantial FSI effects that must be corrected in extracting the $\gamma n\to \pi N$ cross sections. In terms of the nucleon- and pion-exchange mechanisms, I give the first qualitative explanation of the FSI corrections, obtained in a recent Mainz Microtron experiment, for extracting $\gamma n\to {\pi }^{0}n$ cross sections.

We construct valence-space Hamiltonians for use in shell-model calculations, where the residual two-body interaction is based on symmetry principles and the low-momentum expansion from chiral effective field theory. In addition to the usual free-space contact interactions, we also include novel center-of-mass–dependent operators that arise due to the Galilean invariance breaking by in-medium effects. We fitted the low-energy constants to 441 ground- and excited-state energies in the $sd$ shell and obtained a root-mean-square derivation of 1.8 MeV at leading order and of 0.5 MeV at next-to-leading order, with natural low-energy constants in all cases. The developed chiral shell-model interactions enable order-by-order uncertainty estimates and show promising predictions for neutron-rich isotopes beyond the fitted data set.

The new isotope ${}^{224}\mathrm{Np}$ was produced in the fusion-evaporation reaction of ${}^{40}\mathrm{Ar}+{}^{187}\mathrm{Re}$ and identified through the evaporation residue (ER)–$\alpha$-decay correlation measurements using the digital pulse processing technique. Two $\alpha$-decay branches with $\alpha$ energies of 9137(20) and 8868(62) keV were assigned to ${}^{224}\mathrm{Np}$, decaying to two excited states in ${}^{220}\mathrm{Pa}$. The half-life of ${}^{224}\mathrm{Np}$ was deduced to be ${38}_{-11}^{+26}\mu \mathrm{s}$.

Identification of α-cluster states analogous to the ${}^{12}\mathrm{C}$ Hoyle state in heavier α-conjugate nuclei can provide tests of the existence of α condensates in nuclei. Such states are predicted for ${}^{16}\mathrm{O}$, ${}^{20}\mathrm{Ne}$, ${}^{24}\mathrm{Mg}$, ${}^{28}\mathrm{Si}$, etc., at excitation energies slightly above the multi- α-particle decay threshold but have not yet been experimentally identified. The thick target inverse kinematics (TTIK) technique can be used to study the breakup of excited self-conjugate nuclei into many α particles. The reaction ${}^{20}\mathrm{Ne}+\alpha$ was studied using a ${}^{20}\mathrm{Ne}$ beam at 12 MeV/nucleon from the K150 cyclotron at Texas A&M University. The TTIK method was used to study both single α-particle emission and multiple α-particle decays. Events with α multiplicity up to four were analyzed. The analysis of the three α-particle emission data allowed the identification of the Hoyle state and other ${}^{12}\mathrm{C}$ excited states decaying into three α particles. The results are shown and compared with other data available in the literature. Although the statistics for events with α-multiplicity four is low, the data show a structure at about 15.2 MeV that could indicate the existence in ${}^{16}\mathrm{O}$ of a state analogous to the ${}^{12}\mathrm{C}$ Hoyle state. Moreover, the reconstructed excitation energy of ${}^{24}\mathrm{Mg}$ for these events peaks at around 34 MeV, very close to the predicted excitation energy for an excited state analogous to the ${}^{12}\mathrm{C}$ Hoyle state in ${}^{24}\mathrm{Mg}$. The structure is further confirmed by the reanalysis of α-multiplicity-four events from a previous experiment performed at 9.7 MeV/nucleon with a similar, but lower granularity, experimental setup.

I have estimated widths for $2n$ decay for all positive-parity states expected in the region of 4.0–5.5 MeV in ${}^{12}\mathrm{Be}$. Results indicate that $2n$ decay could compete with $1n$ decay for one of the states—the fourth $2^{+}$ that is likely to be the state observed in one-proton removal from ${}^{13}\mathrm{B}$.

We study $\beta$ decays within an effective theory that treats nuclei as a spherical collective core with an even number of neutrons and protons that can couple to an additional neutron and/or proton. First, we explore Gamow-Teller $\beta$ decays of parent odd-odd nuclei into low-lying ground, one-photon, and two-phonon states of the daughter even-even system. The low-energy constants of the effective theory are adjusted to data on $\beta$ decays to ground states or Gamow-Teller strengths. The corresponding theoretical uncertainty is estimated based on the power counting of the effective theory. For a variety of medium-mass and heavy isotopes, the theoretical matrix elements are in good agreement with experimental results within the theoretical uncertainties. We then study the two-neutrino double-$\beta$ decay into ground and excited states. The results are remarkably consistent with experiment within theoretical uncertainties, without the necessity to adjust any low-energy constants.

We report here very precise measurements of the spontaneous fission branching ratio for the ${}^{240,242}\mathrm{Pu}$ and ${}^{252}\mathrm{Cf}$ isotopes, performed with a new kind of active scintillating target. It is shown that the method itself leads to unprecedentedly small uncertainties, and that these uncertainties are negligible compared to uncertainties on the isotopic content of the sample. Besides this capability we discuss the possibility to use this kind of detector for the systematic study of charged particle radioactivity, i.e., spontaneous fission, α decay, and heavy-ion radioactivity.

Neutrino-induced reactions on ${}^{16}\mathrm{O}$ are investigated by shell-model calculations with new shell-model Hamiltonians, which can describe well the structure of $p$-shell and $p-sd$-shell nuclei. The distribution of the spin-dipole strengths in ${}^{16}\mathrm{O}$, which give major contributions to the $\nu -{}^{16}\mathrm{O}$ reaction cross sections, is studied with the new Hamiltonians. Muon-capture reaction rates on ${}^{16}\mathrm{O}$ are also studied to discuss the quenching of the axial-vector coupling in the nuclear medium. Charged-current and neutral-current reaction cross sections are evaluated in various particle and $\gamma$ emission channels as well as the total ones at neutrino energies up to $E_{\nu }\approx 100$ MeV. Branching ratios for the various channels are obtained by the Hauser-Feshbach statistical model calculations, and partial cross sections for single- and multiparticle emission channels are evaluated. The cross sections updated are compared with previous continuum random phase approximation calculations. Effects of multiparticle emission channels on nucleosynthesis in core-collapse supernova explosions are investigated. Inclusion of $\alpha p$ emission channels is found to lead to an enhancement of production yields of ${}^{11}\mathrm{B}$ and ${}^{11}\mathrm{C}$ through ${}^{16}\mathrm{O}(\nu ,{\nu }^{\prime }\alpha p){}^{11}\mathrm{B}$ and ${}^{16}\mathrm{O}({\nu }_e,e^{-}\alpha p){}^{11}\mathrm{C}$ reactions, respectively.

Nuclear fission is hindered by dissipation. Using the stochastic Langevin model, we study postsaddle emitted neutrons, protons, and $\alpha$ particles of heavy ${}^{240}\mathrm{Am}$ nuclei as a function of postsaddle dissipation strength $\left(\beta \right)$ at different excitation energies and angular momenta. It is shown that the sensitivity of these particles to $\beta$ is significantly enhanced at a high energy and a large angular momentum. Furthermore, we calculate the evolution of postsaddle particles with $\beta$ under two contrasting initial conditions for the produced heavy nuclei ${}^{240}\mathrm{Am}$: (i) high excitation energy but low angular momentum (available in intermediate-energy heavy-ion collisions) and (ii) low excitation energy but high angular momentum (available via fusion reactions). We find that the former type of conditions not only significantly enhances the influence of dissipation on particle evaporation but also substantially increases the sensitivity of light charged particles to $\beta$. Our findings suggest that on the experimental side, to accurately probe postsaddle dissipation strength by measuring particle emission, in particular light charged particle multiplicity, it is optimal to choose the intermediate-energy heavy-ion collision approach as a way to populate excited heavy nuclear systems.

Angular distributions for the inclusive ${}^4\mathrm{He}$ and ${}^6\mathrm{He}$ production cross sections in the ${}^8\mathrm{He}+{}^{208}\mathrm{Pb}$ system at incident energies of 16 and 22 MeV measured at the SPIRAL facility of the GANIL laboratory are presented. Using a combination of kinematical arguments and distorted wave Born approximation (DWBA) calculations, neutron transfer reactions were inferred to be the dominant contributors to both inclusive cross sections. Model-dependent values for the ratios of two- to one-neutron stripping, ${\sigma }_{2n}/{\sigma }_{1n}$, were derived and compared with previous results for ${}^8\mathrm{He}$ and ${}^6\mathrm{He}$ projectiles incident on other heavy targets. Three- and four-neutron stripping were inferred to be the main processes leading to ${}^4\mathrm{He}$ production, although the exact mechanism remains to be elucidated.

We employ an effective field theory (EFT) that exploits the separation of scales in the $p$-wave halo nucleus ${}^8\mathrm{B}$ to describe the process ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ up to a center-of-mass energy of 500 keV. The key leading-order (LO) and next-to-leading-order (NLO) results appeared in our earlier papers. Here we first present full details of the EFT calculation. We develop the lagrangian and power counting in terms of velocity scaling, thereby making manifest that the Coulomb force between ${}^7\mathrm{Be}$ and proton plays a major role in both scattering and radiative capture at these energies: Coulomb interactions must be included to all orders in ${\alpha }_{\mathrm{em}}$. The EFT calculation of the capture reaction is then carried out using Feynman diagrams computed in time-ordered perturbation theory, so we recover existing quantum-mechanical technology such as the Lippmann-Schwinger equation and the two-potential formalism for the treatment of the Coulomb-nuclear interference. Meanwhile, the strong interactions and the E1 operator are dealt with via EFT expansions in powers of momenta, with a breakdown scale set by the size of the ${}^7\mathrm{Be}$ core, $\mathrm{\Lambda }\approx 70$ MeV/c. This is worked out up to NLO in the EFT expansion; at this order the relevant physics in the different channels that enter the radiative capture reaction is encoded in ten different EFT couplings. The result is a model-independent parametrization for the reaction amplitude in the energy regime of interest. In the second part of the paper we consider other approaches that have been used to describe ${}^7\mathrm{Be}{(p,\gamma )}^8\mathrm{B}$ in this energy range. We discuss the relationship of EFT to each of these approaches in qualitative terms and then make the connection quantitative by determining what the ten NLO EFT coefficients are in five different calculations that we consider representative. The EFT parameters are of natural size in all five cases, which shows that each of these earlier calculations corresponds to a particular point in the EFT parameter space. This understanding of the relationship between EFT and other ways of computing ${}^7\mathrm{Be}{(p,\gamma )}^8\mathrm{B}$ allows us to update earlier results for the dependence of $S\left(0\right)$ on asymptotic normalization coefficients and scattering lengths, since EFT separates dependence on these asymptotic quantities from dependence on shorter-distance contributions to the matrix element. We also summarize the fit to experimental capture data presented in our earlier work and explain why we obtain an extrapolated $S\left(0\right)$ with a markedly smaller error bar than that of the previous standard evaluation. Finally, we demonstrate that the only ${\mathrm{N}}^2\mathrm{LO}$ corrections in ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ come from an inelasticity that is practically of $\mathrm{N}{}^3\mathrm{LO}$ size in the energy range of interest, and so the truncation error in our calculation is effectively $\mathrm{N}{}^3\mathrm{LO}$.

We present measurements of three-particle correlations for various harmonics in Au+Au collisions at energies ranging from $\sqrt{s_{\mathrm{NN}}}=7.7$ to 200 GeV using the STAR detector. The quantity $\langle cos(m{\varphi }_1+n{\varphi }_2-(m+n){\varphi }_3)\rangle$, with $\varphi$ being the azimuthal angles of the particles is evaluated as a function of $\sqrt{s_{\mathrm{NN}}}$, collision centrality, transverse momentum, $p_T$, pseudorapidity difference, $\mathrm{\Delta }\eta$, and harmonics ($m$ and $n$). These data provide detailed information on global event properties such as the three-dimensional structure of the initial overlap region, the expansion dynamics of the matter produced in the collisions, and the transport properties of the medium. A strong dependence on $\mathrm{\Delta }\eta$ is observed for most harmonic combinations, which is consistent with breaking of longitudinal boost invariance. An interesting energy dependence is observed when one of the harmonics $m,n,$ or $m+n$ is equal to two, for which the correlators are dominated by the two-particle correlations relative to the second-harmonic event plane. These measurements can be used to constrain models of heavy-ion collisions over a wide range of temperature and baryon chemical potential.

Constraints set on key parameters of the nuclear matter equation of state (EoS) by the values of the tidal deformability, inferred from GW170817, are examined by using a diverse set of relativistic and nonrelativistic mean-field models. These models are consistent with bulk properties of finite nuclei as well as with the observed lower bound on the maximum mass of neutron star $\approx 2M_{\odot }$. The tidal deformability shows a strong correlation with specific linear combinations of the isoscalar and isovector nuclear matter parameters associated with the EoS. Such correlations suggest that a precise value of the tidal deformability can put tight bounds on several EoS parameters, in particular on the slope of the incompressibility and the curvature of the symmetry energy. The tidal deformability obtained from the GW170817 and its UV, optical and infrared counterpart sets the radius of a canonical $1.4M_{\odot }$ neutron star to be $11.82\le R_{1.4}\le 13.72\mathrm{km}$.

In most simulations of nonrelativistic nuclear systems, the wave functions found solving the many-body Schrödinger equations describe the quantum-mechanical amplitudes of the nucleonic degrees of freedom. In those simulations the pionic contributions are encoded in nuclear potentials and electroweak currents, and they determine the low-momentum behavior. In this work we present an alternative quantum Monte Carlo formalism in which both relativistic pions and nonrelativistic nucleons are explicitly included in the quantum-mechanical states of the system. We report the renormalization of the nucleon mass as a function of the momentum cutoff, a Euclidean time density correlation function that deals with the short-time nucleon diffusion, and the pion cloud density and momentum distributions. In the two-nucleon sector we show that the interaction of two static nucleons at large distances reduces to the one-pion exchange potential, and we fit the low-energy constants of the contact interactions to reproduce the binding energy of the deuteron and two neutrons in finite volumes. We show that the method can be readily applied to light-nuclei.

We calculate the cross section of the electron scattering from a bound nucleon within light-front approximation. The advantage of this approximation is the possibility of systematic account for the off-shell effects, which become essential in high-energy electronuclear processes aimed at probing the nuclear structure at small distances. We derive a new dynamical parameter, which allows us to control the extent of the off-shellness of electron–bound-nucleon electromagnetic current for different regions of momentum transfer and initial light-cone momenta of the bound nucleon. The derived cross section is compared with the results of other approaches in treating the off-shell effects in electron-nucleon scattering.

We calculate two-body $J^{\pi }=0^{+},1^{+}$ and $J^{\pi }=2^{+}$ resonance states of $Y_c$ ($={\mathrm{\Lambda }}_c$, ${\mathrm{\Sigma }}_c$, or ${\mathrm{\Sigma }}_c^{*}$) and $N$ using the complex scaling method. We employ the $Y_{c}N$-CTNN potentials, which were proposed in our previous study, and obtain four resonances near ${\mathrm{\Sigma }}_{c}N$ and ${\mathrm{\Sigma }}_c^{*}N$ thresholds. From the analysis by the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c}N$ resonance states in the heavy-quark limit, where the ${\mathrm{\Sigma }}_{c}N$ and ${\mathrm{\Sigma }}_c^{*}N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets, in agreement with the heavy-quark spin symmetry.