Background: The advent of radioactive ion beams has helped considerably to explore exotic decay modes like proton radioactivity in extremely proton-rich nuclei lying on or beyond the proton drip line. Recently, an experimental study was reported on the structural properties of proton-rich nucleus ${}^{11}\mathrm{O}$. Interestingly, ${}^{11}\mathrm{O}$ is the mirror nucleus of the widely studied $2n$ halo system ${}^{11}\mathrm{Li}$. In addition, ${}^{11}\mathrm{O}$ formed in the experiment was identified through its decay by $2p$ emission. A similar kind of interdependence between neutron halo and its mirror counterpart for $2p$ emission was reported [Charity, Elson, Komarov, Sobotka, Manfredi, and Shane, J. Phys.: Conf. Series 420, 012073 (2013)].

Purpose: To study and analyze whether the mirror nuclei of known $1n$/$2n$ halo systems are $1p$/$2p$ emitters.

Method: The preference for the mirror nuclei of $1n$/$2n$ halo systems for $1p$/$2p$ emission over the other ($2p$/$1p$ emission) is studied by $Q$-value systematics and potential energy minimization using a cluster-core model. The half-lives of the mirror nuclei of neutron halo systems were determined using a recently proposed empirical formula [Sreeja and Balasubramaniam, Eur. Phys. J. A 54, 106 (2018); Sreeja and Balasubramaniam, Eur. Phys. J. A 55, 33 (2019)].

Results: Among the mirror nuclei of $1n$ halo systems, ${}^{11}\mathrm{N}$ (the mirror of ${}^{11}\mathrm{Be}$) and ${}^{15}\mathrm{F}$ (the mirror of ${}^{15}\mathrm{C}$) were found to have a preference for $1p$ emission over $2p$ emission by $Q$-value systematics. The potential energy surface analysis supported the result where both ${}^{11}\mathrm{N}$ and ${}^{15}\mathrm{F}$ were found to be ground-state $1p$ emitters. The trend got changed with an increase in angular momentum where the minimum in potential shifted from $1p$ to $2p$ cluster. Moreover, the half-life calculation matches with the result obtained from $Q$-value systematics.

Conclusion: For the $2n$ halo systems, all the studies made indicate that the respective mirror nuclei have a preference for $2p$ emission. A similar conclusion cannot be drawn for the mirror nuclei of $1n$ halo systems except for ${}^{11}\mathrm{N}$ and ${}^{15}\mathrm{F}$, which were found to be ground-state $1p$ emitters. All the remaining mirror nuclei of $1n$ halo systems prefers $2p$ emission as favorable decay mode than the expected $1p$ emission. The empirical formula can be used as a good tool to evaluate half-life values of proton emitters provided the $Q$ values are known with desirable accuracy.

In ${}^{12}\mathrm{O}$, the $2^{+}$ state whose dominant configuration is ${}^{10}\mathrm{C}\left(2^{+}\right)\times \pi {\left(\mathrm{sd}\right)}_0^2$ should be populated in neutron removal from ${}^{13}\mathrm{O}$, and its primary decay is via $2p$ emission to the $2^{+}$ state of ${}^{10}\mathrm{C}$. My calculations predict that most of the events near $E_{2p}=3.5$ MeV in a recent ${}^{12}\mathrm{O}\to {}^{10}\mathrm{C}+2p$ experiment represent decays to the $2^{+}$ state.

The precise quasielastic excitation function for the ${}^{18}\mathrm{O}+{}^{64}\mathrm{Zn}$ system was measured at energies near and below the Coulomb barrier at ${\theta }_{\mathrm{lab}}={161}^{\circ }$, from which its correlated quasielastic barrier distribution was derived. The excitation functions for the two-neutron, $\alpha$, and tritium transfer reactions have also been measured at the same conditions. These data were well described by the coupled channel and coupled reaction channel calculations. The comparison of the data with theoretical calculations shows the strong influence of three inelastic channels in the coupling process: the quadrupole and octupole vibrational states of ${}^{64}\mathrm{Zn}$, $2_1^{+}$ and $3_1^{-}$, and the quadrupole vibrational state of ${}^{18}\mathrm{O}$, $2_1^{+}$. In addition, theoretical calculations indicate that the two-neutron stripping is mostly due to a one-step process, which has a striking effect on the reaction mechanism of this system.

The very first in-ring reaction experiment at the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), namely proton elastic scattering on stable ${}^{58}\mathrm{Ni}$ nuclei, is presented. The circulating ${}^{58}\mathrm{Ni}^{19+}$ ions with an energy of 95 MeV/u were interacting repeatedly with an internal hydrogen gas target in the experimental storage ring (CSRe). Low-energy proton recoils from the elastic collisions were measured with an ultra-high vacuum compatible silicon-strip detector. Deduced differential cross sections were normalized by measuring $k$-shell x rays from ${}^{58}\mathrm{Ni}^{19+}$ projectiles due to the ${}^{58}\mathrm{Ni}^{19+}\text{−}{\mathrm{H}}_2$ ionization collisions. Compared to the experimental cross sections, a good agreement has been achieved with the theoretical predictions in the measured region, which were obtained by using the global phenomenological optical model potentials. Our results enable new research opportunities for optical model potential studies on exotic nuclides by using the in-ring reaction setup at the HIRFL-CSR facility.

We carry out a principal component analysis of fluctuations in a hydrodynamic simulation of heavy-ion collisions, and compare with experimental data from the CMS Collaboration. The principal components of anisotropic flow reproduce the trends seen in data, but multiplicity fluctuations show a difference in transverse momentum dependence. We construct an analytical toy model and verify that hydrodynamic simulations agree with its predictions. The difference in the momentum trend is likely due to larger fluctuations in transverse momentum of hydrodynamic models than seen experimentally.

We calculate the $\beta$ decay of tritium at next-to-leading order in pionless effective field theory. At this order, a low-energy parameter $l_{1,A}$ enters the calculation that is also relevant for a high-accuracy prediction of the solar proton-proton fusion rate. We use the tritium half-life to determine this parameter and provide uncertainty estimates. We show proper renormalization of our calculation analyzing the residual cutoff dependence of observables. We find that next-to-leading-order corrections contribute about $4\%$ to the triton decay Gamow-Teller strength. We show that these conclusions are insensitive to different arrangements of the effective range expansion.

We study the role of anisotropic escape in generating the elliptic flow of bottomonia produced in ultrarelativistic heavy-ion collisions. We implement temperature-dependent decay widths for the various bottomonium states to calculate their survival probability when traversing through the anisotropic hot medium formed in noncentral collisions. We employ the recently developed $3+1$-dimensional quasiparticle anisotropic hydrodynamic simulation to model the space-time evolution of the quark-gluon plasma. We provide a quantitative prediction for the transverse momentum dependence of bottomonium elliptic flow and the nuclear modification factor for $\mathrm{Pb}+\mathrm{Pb}$ collisions in $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV at the CERN Large Hadron Collider.

In this paper we report two simple relations of masses between corresponding mirror nuclei, the first of which is based on the regularity of empirical neutron-proton interactions, and the second of which is based on the regularity of the one-nucleon separation energy. We demonstrate that, for $N\ge 10$, the empirical neutron-proton interaction of given nucleus with neutron number $N-1$ and proton number $Z$ (we use the convention that $N=Z$ in this paper), or abbreviated by the $(N-1,Z)$ nucleus, equals the neutron-proton interaction of its corresponding mirror nucleus, i.e., the $(N,Z-1)$ nucleus; we also demonstrate that one-proton separation energy $S_p$ and one-neutron separation energy $S_n$ of the $(N-k,Z)$ nucleus ($k=1,2,3,4$) equals one-neutron separation energy $S_n$ and one-proton separation energy $S_p$, respectively, of the $(N,Z-k)$ nucleus, after a simple correction of Coulomb energy and proton-neutron mass difference are considered. Numerical experiments show that these correlations provide us with a remarkably accurate approach to predict masses and separation energies of some proton-rich nuclei with neutron numbers from 10–46. Our predicted masses of proton-rich nuclei are tabulated as a Supplemental Material of this paper.

In the paper, a unique process of the decay of the ${}^{229m}\mathrm{Th}(3/2^{+},8.28\pm 0.17$ eV) low-energy nuclear isomer via the internal conversion (IC) channel on Rydberg states is considered for the first time. The Rydberg atom ${}^{229m}\mathrm{Th}^{+}+e_{Ry}^{-}$ is a unique object where IC is possible exclusively on the Rydberg electron $e_{Ry}^{-}$. It is shown that in the ${}^{229m}\mathrm{Th}^{4+}+e_{Ry}^{-}$ system (a) IC on the electron states with relatively small values of the principal quantum number $n$ and the orbital moment $l$ is practically completely suppressed, (b) IC probability, $W_{IC}$, on the ${\psi }_{n{s}_{1/2}}\left(\mathbf{r}\right)$ states is proportional to $|{\psi }_{n{s}_{1/2}}{\left(0\right)|}^2$ and can be related with the energy of the hyperfine interaction of the Rydberg electron with the nucleus, (c) $W_{IC}$ decreases rapidly with the increase of $n$ in the range from 10 to 50, and in the range $n\gtrsim 150W_{IC}$ changes as $\text{const}/n^3$ typical for hydrogen-like ions, and (d) at $n\approx 10$–30, $W_{IC}$ as a function of $l$ has a characteristic “knee” between $l=3$ and $l=4$, i.e., a decrease of three orders of magnitude in $W_{IC}$ due to the qualitative change in the ratio between the centrifugal and shielding potentials.

Background: Information about the structure of halo nuclei are often inferred from one-neutron knockout reactions. Typically the parallel-momentum distribution of the remaining core is measured after a high-energy collision of the exotic projectile with a light target.

Purpose:We study how the structure of halo nuclei affects knockout observables considering an eikonal model of reaction.

Method: To evaluate the sensitivity of both the diffractive and stripping parallel-momentum distributions to the structure of halo nuclei, we consider several descriptions of the projectile within a halo effective-field theory. We consider the case of ${}^{11}\mathrm{Be}$, the archetypical one-neutron halo nucleus, impinging on ${}^{12}\mathrm{C}$ at 68 MeV/nucleon, which are usual experimental conditions for such measurements. The low-energy constants of the description of ${}^{11}\mathrm{Be}$ are fit to experimental data as well as to predictions of an ab initio nuclear-structure model.

Results: The one-neutron knockout reaction is confirmed to be purely peripheral, the parallel-momentum distribution of the remaining core is sensitive only to the asymptotics of the ground-state wave function and not to its norm. The presence of an excited state in the projectile spectrum reduces the amplitude of the breakup cross section; the corresponding probability flux is transferred to the inelastic-scattering channel. Although the presence of a resonance in the core-neutron continuum significantly affects the energy distribution, it has no impact on the parallel-momentum distribution.

Conclusions: The one-neutron knockout cross section can be used to infer information about the tail of the ground-state wave function, viz. its asymptotic normalization coefficient (ANC). The independence of the parallel-momentum distribution on the continuum description makes the extraction of the ANC from this observable very reliable.

The chemical freeze-out parameters in central nucleus-nucleus collisions are extracted consistently from hadron-yield data within the quantum van der Waals (QvdW) hadron resonance gas model. The beam energy dependencies for skewness and kurtosis of net baryon, net electric, and net strangeness charges are predicted. The QvdW interactions in asymmetric matter, $Q/B\ne 0.5$, between (anti)baryons yield a noncongruent liquid-gas phase transition, together with a nuclear critical point (CP) with critical temperature of $T_c=19.5$ MeV. The nuclear CP shows that the collision energy dependence of the skewness and the kurtosis both deviate significantly from the ideal hadron resonance gas baseline predictions even far away, in the $(T,{\mu }_B)$ plane, from the CP. These predictions can readily be tested by the STAR and NA61/SHINE Collaborations at the RHIC BNL and the SPS CERN, respectively, and by HADES at GSI. The results presented here offer a broad opportunity for the search for signals of phase transition in dense hadronic matter at the future NICA and FAIR high-intensity facilities.

The existence of multineutron systems has always been a debatable question. Indeed, both internucleon correlations and a large continuum coupling occur in these states. We then employ the ab initio no-core Gamow shell model to calculate the resonant energies and widths of the trineutron and tetraneutron systems with realistic interactions. Our results indicate that trineutron and tetraneutron are both unbound and bear broad widths. The calculated energy and width of tetraneutron are also comparable with recent experimental data. Moreover, our calculations suggest that the energy of trineutron is lower than that of tetraneutron, while its resonance width is also narrower. This strongly suggests that trineutron is more likely to be experimentally observed than tetraneutron. We thus suggest experimentalists to search for trineutron at low energy.

The properties of critical parameters and phase diagram structure of liquid-gas phase transition are investigated in thermal symmetric and asymmetric nuclear matter with the covariant density functional (CDF) theory. Although uncertainty remains in predicting the critical parameters such as the critical temperature and pressure from various CDF functionals, several strongly correlated features are proposed among these quantities. These correlations become worse when nuclear matter is more isospin asymmetric, resulting mainly from the effects induced by the symmetry energy. By looking over the isospin dependence of the critical temperature, the role of the symmetry energy in liquid-gas transition properties of asymmetric matter is realized. The change of critical temperature with isospin asymmetry is found to be correlated well with, and as a consequence could be constrained by, the density slope of symmetry energy at saturation density. Then, the structure of phase diagram of thermal nuclear matter is analyzed carefully. It is revealed that the contribution from symmetry energy dominates the size of liquid-gas phase coexistence area. Moreover, the specific pattern of the phase diagram could be determined by the critical temperature at nonzero isospin asymmetry as illustrated from the correlations of the temperature with pressures at several characteristic points, paving the possible way to further explore the structure of liquid-gas phase diagram of thermal nuclear matter.

The forward recoil range distributions and angular distributions of several evaporation residues produced via complete and incomplete fusion (ICF) dynamics in ${}^{16}\mathrm{O}+{}^{148}\mathrm{Nd}$ system at energy $\approx 6$ MeV/nucleon were measured. The measured forward recoil range distributions of various reaction products show the presence of incomplete fusion components apart from complete fusion. Full and partial linear momentum transfer components of reaction products were found in the interaction of ${}^{16}\mathrm{O}$ with ${}^{148}\mathrm{Nd}$. These results were also confirmed by the measurements of angular distributions of evaporation residues. The measured angular distributions of the evaporation residues populated through complete and incomplete fusion channels were found to be distinctly different. The evaporation residues populated via complete fusion channels were trapped in the narrow angular zone as compared to incomplete fusion channels. A systematic study of the dependence of incomplete fusion dynamics on well-known entrance channel parameters shows that the incomplete fusion fraction grows exponentially with mass asymmetry $\left({\mu }_{EC}^{AS}\right)$, Coulomb factor $\left(Z_P{Z}_T\right)$ and $\alpha -Q$ value of the projectile. The present observations suggest an exponential rise of ICF fraction with entrance channel parameters in contrast with the linear pattern reported in some earlier measurements. Further, the correlation of incomplete fusion fraction with the structure of target (T) was investigated employing four different parameters viz. deformation parameter $\left({\beta }_2^T\right)$, interaction radius $\left(R^T\right)$, deformation length $\left({\beta }_2^T{R}^T\right)$ and excess of neutrons ${(N-Z)}^T$ in the target. In the present study, the ICF fraction was found to rise exponentially with these parameters, independently for different projectiles. The three parameters ${\beta }_2^T, {\beta }_2^T{R}^T$, and ${(N-Z)}^T$ were found more sensitive and effective to investigate the entire picture about the influence of projectile and target deformation along with their relative orientations on incomplete fusion dynamics at low projectile energy. Moreover, the interaction radius of target $\left(R^T\right)$ is suitable to explain the characteristics of ICF dynamics in the spherical-spherical collisions. These present results show that incomplete fusion dynamics is strongly affected by the structure of projectile along with the target.

The shape evolutions of the even-even cadmium isotopes ${}^{110–116}\mathrm{Cd}$ are investigated in this work. The giant monopole resonances built on different shape isomeric states are studied using the quasiparticle random phase approximation, which is implemented with a finite amplitude method. We find the local minima corresponding to the prolate, oblate, and triaxial-deformed isomeric states in the even-even cadmium isotopes. Their responses to external monopole perturbations are quite different. Larger deformation tends to make the energy of the giant monopole resonance to shift lower. It is well known that the density functional models have some difficulties in predicting the right positions of the monopole resonances in cadmium isotopes: the centroid energies always seem too large compared to the experimental results. Our calculations show the giant monopole resonances built on the $\gamma$ soft isomeric states in the cadmium isotopes have centroid energies even lower than the experimental measurements. Therefore, if the isomeric branching of these $\gamma$ soft isomeric states turns out to be prominent, isomer mixing may be a good explanation to the longstanding puzzle.

The E12-14-012 experiment performed at Jefferson Lab Hall A has collected inclusive electron-scattering data for different targets at the kinematics corresponding to beam energy 2.222 GeV and scattering angle $15.{54}^{\circ }$. Here we present a comprehensive analysis of the collected data and compare the double-differential cross sections for inclusive scattering of electrons, extracted using solid targets (aluminum, carbon, and titanium) and a closed argon-gas cell. The data extend over broad range of energy transfer, where quasielastic interaction, $\mathrm{\Delta }$-resonance excitation, and inelastic scattering yield contributions to the cross section. The double-differential cross sections are reported with high precision ($\sim 3$%) for all targets over the covered kinematic range.

The neutron star crustal equation of state and transition point properties are computed within a unified metamodeling approach. A Bayesian approach is employed including two types of filters: Bulk nuclear properties are controlled from low-density effective field-theory predictions as well as the present knowledge from nuclear experiments, whereas the surface energy is adjusted on experimental nuclear masses. Considering these constraints, a quantitative prediction of crustal properties can be reached with controlled confidence intervals and increased precision with respect to previous calculations: $\approx 11\%$ dispersion on the crustal width and $\approx 27\%$ dispersion on the fractional moment of inertia. The crust moment of inertia is also evaluated as a function of the neutron star mass, and predictions for mass and radii are given for different pulsars. The origin of Vela pulsar glitches is discussed, and a full crustal origin is excluded if we consider the present largest estimation of crustal entrainment. Further refinement of the present predictions requires a better estimation of the high-order isovector empirical parameters, e.g., $K_{\mathrm{sym}}$ and $Q_{\mathrm{sym}}$, and a better control of the surface properties of extremely neutron rich nuclei.

The radial basis function (RBF) and Bayesian neural network (BNN) approaches have been widely used in nuclear mass predictions. In this work, the predictive powers of RBF and BNN approaches are systematically explored by investigating nuclear masses and single-nucleon separation energies. To improve the description of single-nucleon separation energies, the odd-even effects have to be considered for the RBF approach, named as RBFoe approach. It is found that both RBFoe and BNN approaches significantly improve the description of nuclear masses and single-neutron separation energies in or near the known region, while they show different predictions when extrapolated far away from the known region. Comparing with the BNN approach, the RBFoe approach achieves better interpolation ability, while the extrapolation abilities of RBFoe and BNN approaches depend on the employed nuclear mass models. This indicates we should employ different reconstructed functions of RBF and BNN approaches to achieve better extrapolation ability for different nuclear models. Since the BNN approach is very flexible in designing its input, hidden, and output layers, it is desirable to find the optimal BNN structure to get better extrapolation ability in the future.

A correlation is established between the neutron multiplicity and the neutron number in the fission state of curium and californium isotopes within a microscopic study using relativistic mean field formalism. The study includes the isotopes of Cm and Cf nuclei near the valley of stability, and hence is likely to play an important role in the artificial synthesis of superheavy nuclei. The static fission path, the evolution of the neck, the neutron-proton asymmetry of the neck, and its composition in terms of nucleon numbers are also estimated. We find a maximum ratio for average neutron to proton density, which is about 1.6 in the breakdown of the liquid-drop picture for ${}^{248}\mathrm{Cm}$ and ${}^{252}\mathrm{Cf}$. A strong dependence of the neutron-proton asymmetry on the neutron multiplicity in an isotopic chain is also observed. The present work suggests a breakdown of the liquid-drop picture of the parent nucleus into two heavy fragments along with an $\alpha$ particle at scission point for ${}^{242,244,246,248}\mathrm{Cm}$ and ${}^{248,250,252,254}\mathrm{Cf}$.

Differential cross sections and photon beam asymmetries for the reaction $\gamma p\to {\pi }^{0}p$ have been measured in the photon beam energy range of $1.3–2.4\mathrm{GeV}$ and the ${\pi }^0$ polar angle range of $-1<cos{\theta }_{{\pi }^0}^{\mathrm{c}.\mathrm{m}.}<0.7$. The measurement has been done by using a large acceptance electromagnetic calorimeter in the SPring-8 LEPS2/BGOegg experiment. The results of the photon beam asymmetry in a wide ${\pi }^0$ polar angle range are new for the photon beam energies exceeding $1.9\mathrm{GeV}$. None of the existing partial wave analysis models describe the observed asymmetries in the high energy region. The contribution of multipole amplitudes with an orbital angular momentum of 5 in the $\pi N$ system has been found to be important at these energies.