Background: $\beta$-delayed multiple neutron emission has been observed for some nuclei with $A\le 100$, being the ${}^{100}\mathrm{Rb}$ the heaviest $\beta 2n$ emitter measured to date. So far, only $25P_{2n}$ values have been determined for the $\approx 300$ nuclei that may decay in this way. Accordingly, it is of interest to measure $P_{2n}$ values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with $A>100$ to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition, the decay properties of these nuclei are fundamental for the understanding of astrophysical nucleosynthesis processes, such as the $r$-process, and safety inputs for nuclear reactors.

Purpose: To determine for the first time the two-neutron branching ratio, the $P_{2n}$ value, for ${}^{136}\mathrm{Sb}$ through a direct neutron measurement and to provide precise $P_{1n}$ values for ${}^{136}\mathrm{Sb}$ and ${}^{136}\mathrm{Te}$.

Method: A pure beam of each isotope of interest was provided by the JYFLTRAP Penning trap at the Ion Guide Isotope Separator On-Line (IGISOL) facility of the University of Jyväskylä, Finland. The purified ions were implanted into a moving tape at the end of the beam line. The detection setup consisted of a plastic scintillator placed right behind the implantation point after the tape to register the $\beta$ decays and the BELEN detector, based on neutron counters embedded in a polyethylene matrix. The analysis was based on the study of the $\beta$- and neutron-growth-and-decay curves and the $\beta$-one-neutron and $\beta$-two-neutron time correlations, which allowed us the determination of the neutron-branching ratios.

Results: The $P_{2n}$ value of ${}^{136}\mathrm{Sb}$ was found to be 0.14(3)% and the measured $P_{1n}$ values for ${}^{136}\mathrm{Sb}$ and ${}^{136}\mathrm{Te}$ were found to be 32.2(15)% and 1.47(6)%, respectively.

Conclusions: The measured $P_{2n}$ value is a factor 44 smaller than predicted by the finite-range droplet model plus the quasiparticle random-phase approximation (FRDM+QRPA) model used for $r$-process calculations.

Cross sections of the ${}^{25}\mathrm{Mg}(n,\alpha ){}^{22}\mathrm{Ne}$ and the ${}^{25}\mathrm{Mg}\left(n,{\alpha }_0\right){}^{22}\mathrm{Ne}$ reactions were measured at five neutron energy points in the 4.0–6.0 MeV region. Highly enriched (98.6%) ${}^{25}\mathrm{MgO}$ samples were prepared. A twin-gridded ionization chamber was used as the charged particle detector and the ${}^{238}\mathrm{U}\left(n,f\right)$ reaction was utilized to calibrate the absolute neutron fluence. The present results were compared with those of the existing measurements, evaluations, and calculations.

We examine the leading effects of two-body weak currents from chiral effective field theory on the matrix elements governing neutrinoless double-$\beta$ decay. In the closure approximation these effects are generated by the product of a one-body current with a two-body current, yielding both two- and three-body operators. When the three-body operators are considered without approximation, they quench matrix elements by about 10%, less than suggested by prior work, which neglected portions of the operators. The two-body operators, when treated in the standard way, can produce somewhat larger quenching. In a consistent effective field theory, however, these two-body effects become divergent and must be renormalized by a contact operator, the coefficient of which we cannot determine at present.

The rotational properties of the neutron-rich Nd and Sm isotopes with mass number $A\approx 150$ are systematically investigated by using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. The two-quasiparticle states in even-even Nd and Sm isotopes with excitation energies lower than 2.5 MeV are systematically calculated. The available data can be well reproduced and some possible two- and four-quasiparticle isomers are also suggested for future experiments. The experimentally observed rotational frequency variations of moments of inertia for the even-even and odd-$A$ nuclei are reproduced very well by the calculations. The effects of high-order deformation ${\varepsilon }_6$ on the two-quasiparticle excitation energies and moments of inertia of the ground-state bands in even-even Nd and Sm isotopes are analyzed in detail. By analyzing the occupation probability $n_{\mu }$ of each cranked Nilsson orbitals near the Fermi surface and the contribution of each major shell to the angular-momentum alignments, the alignment mechanism in these nuclei is understood clearly.

The structure of the vibrational-$\gamma$ bands in even ${}^{104-118}\mathrm{Pd}$ isotopes has been investigated in the framework of the IBA-2 model. A detailed comparison of experimental and predicted values of the available spectroscopic data has been performed. The role played by states of mixed symmetry character in the proton and neutron degrees of freedom in reproducing the properties of the vibrational-$\gamma$ bands has been highlighted.

We investigated the Gamow-Teller (GT) transitions from ${}^{22}\mathrm{Ne}$ to ${}^{22}\mathrm{Na}$ by applying the isospin projected antisymmetrized molecular dynamics combined with the generator coordinate method. We found that the GT strength from ${}^{A}Z\left(J^{\pi }T\right)={}^{22}\mathrm{Ne}\left(0_1^{+}1\right)$ is fragmented into two final states ${}^{22}\mathrm{Na}\left(1_{1,2}^{+}0\right)$, which belong to $K=0$ and $K=1$ bands constructed by a prolately deformed ${}^{20}\mathrm{Ne}$ core with an $S=1$ proton-neutron ($pn$) pair. Coupling of the intrinsic spin of the $pn$ pair with the core deformation plays an important role in the GT fragmentation. The symmetry breaking in the intrinsic-spin rotation leads to the $\text{SU}\left(4\right)$ symmetry breaking of the $NN$ pair and causes the GT fragmentation. We compare the features of the GT transitions with those for ${}^{10}\mathrm{Be}\to {}^{10}\mathrm{B}$ and discuss the link between the $\text{SU}\left(4\right)$ symmetry and the GT fragmentation in deformed systems.

The multinucleon exchange mechanism in ${}^{58}\mathrm{Ni}+{}^{60}\mathrm{Ni}$ and ${}^{60}\mathrm{Ni}+{}^{60}\mathrm{Ni}$ collisions is analyzed in the framework of the stochastic mean-field approach. The results of calculations are compared with the time-dependent random-phase approximation (TDRPA) calculations and the recent data of ${}^{58}\mathrm{Ni}+{}^{60}\mathrm{Ni}$. A good description of the data and a relatively good agreement with the TDRPA calculations are found.

The level structure of the $N=82$ nucleus ${}^{136}\mathrm{Xe}$ was studied with the inelastic neutron scattering reaction followed by $\gamma$-ray detection. A number of the spins and parities were reassigned, and many level lifetimes were determined for the first time using the Doppler-shift attenuation method. New shell-model calculations were also performed using both the full $Z=50$–82 model space, and a reduced model space including only the $1d_{5/2}$ and $0g_{7/2}$ orbitals. This new information characterizing ${}^{136}\mathrm{Xe}$ was used to identify the seniority structure of the low-lying levels and to assign ${\left(\pi 0g_{7/2}\right)}_{\upsilon =0}^4$, ${\left(\pi 0g_{7/2}\right)}_{\upsilon =2}^4$, ${\left(\pi 0g_{7/2}\right)}_{\upsilon =4}^4$, $\left(\pi 1d_{5/2}\right){\left(\pi 0g_{7/2}\right)}_{\upsilon =1}^3$, and ${\left(\pi 1d_{5/2}\right)}^2{\left(\pi 0g_{7/2}\right)}_{\upsilon =0}^2$ configurations to describe all observed states below 2.8 MeV.

Background: The nature of low-lying oscillations or excitations around the equilibrium deformed nuclear shape remains an open question in a nuclear structure. The question revolves around the possible degrees of freedom in deformed nuclei. Rotational motion is an expected feature of deformed nuclei; the open challenge is whether the “granularity” of the nuclei allows single or multiple quanta of vibrational oscillations or excitations superimposed on the equilibrium deformed shape of the nucleus. Special emphasis is placed on the $K^{\pi }=0^{+},\beta$ vibration whose existence is open to debate some 40 years after Bohr-Mottelson-Rainwater's Nobel prize for connecting nucleon motion to the emergence of collectivity.

Purpose: The ${}^{156}\mathrm{Gd}$ nucleus is an excellent test case for the search of the predicted oscillations since it has one of the most developed level schemes up to 2.35 MeV and it lies in the well-deformed rare-earth region of the chart of nuclides. This nucleus has previously been studied by $(n,\gamma ),(n,e^{-}),(e,e^{\prime }),(p,p^{\prime }),(d,p)$, and ($d,t$) reactions with six known excited $K^{\pi }=0^{+}$ bands. We measured level lifetimes of ${}^{156}\mathrm{Gd}$ in order to determine the nature of the low-lying excited bands.

Method: The lifetimes of the excited states in the ${}^{156}\mathrm{Gd}$ nucleus were measured following neutron capture using the grid technique at the Institut Laue-Langevin in Grenoble, France.

Results: Twelve level lifetimes were measured from four excitation bands in the ${}^{156}\mathrm{Gd}$ nucleus including the lifetimes of three of the $K^{\pi }=0^{+}$ bands.

Conclusions: There are two $K^{\pi }=0^{+}$ bands in this nucleus connected to the ground-state band. Transitions from the $K^{\pi }=0_2^{+}$ band at 1049.5 keV to the ground-state band are more collective than the ones from the $K^{\pi }=0_3^{+}$ band at 1168.2 keV. The moments of inertia of the various $K^{\pi }=0^{+}$, the $K^{\pi }=2^{+}$, and the $K^{\pi }=4^{+}$ bands show that all the bands except the $K^{\pi }=0_3^{+}$ band at 1168.2 keV have nearly identical moments of inertia with the ground-state band pointing to the fact that all of the bands discussed here with the exception of this indicating $K^{\pi }=0_3^{+}$ band seem to be collective excitations built on the ground state. This result is consistent with various theoretical predictions. $B\left(E2\right)$ calculations for transitions from the $K^{\pi }=2^{+}$ band to the ground-state band supports the assignment of this band as the $\gamma$ band. Also, the $K^{\pi }=0_4^{+}$ and the $K^{\pi }=4_1^{+}$ bands at 1715.2 and 1510.6 keV, respectively, are shown to be strongly connected to the $K^{\pi }=2^{+}\gamma$ band presenting evidence for the observation of a second set of two-phonon $\gamma \gamma$ vibrational excitations albeit with greatly varying degrees of anharmonicity in comparison to the case of ${}^{166}\mathrm{Er}$.

The elliptic and triangular flow coefficients ($v_n,n=2,3$) measured in Pb + Pb ($\sqrt{s_{{}_{\mathrm{NN}}}}=2.76\mathrm{TeV}$) and $p+\mathrm{Pb}(\sqrt{s_{{}_{\mathrm{NN}}}}=5.02\mathrm{TeV}$) collisions are studied as a function of initial-state eccentricity (${\varepsilon }_n$) and dimensionless size characterized by the cube root of the midrapidity charged hadron multiplicity density ${\langle N_{\mathrm{ch}}\rangle }^{1/3}$. The results indicate that the influence of eccentricity ($v_n\propto {\varepsilon }_n$) observed for large $\langle N_{\mathrm{ch}}\rangle$ is superseded by the effects of viscous attenuation for small $\langle N_{\mathrm{ch}}\rangle$, irrespective of the colliding species. Strikingly similar acoustic scaling patterns of exponential viscous modulation with a damping rate proportional to $n^2$ and inversely proportional to the dimensionless size are observed for the eccentricity-scaled coefficients for the two sets of colliding species. The resulting scaling parameters suggest that, contrary to current predilections, the patterns of viscous attenuation as well as the specific shear viscosity $〈\frac{\eta }{s}\left(T\right)〉$ for the matter created in $p+\mathrm{Pb}$ and Pb + Pb collisions are comparable.

The differential cross sections of the ${}^{11}\mathrm{B}(d,p){}^{12}\mathrm{B}$ reaction leading to formation of the $1^{+}$ ground state and the 0.95-MeV $2^{+}$, 1.67-MeV $2^{-}$, 2.62-MeV $1^{-}$, 2.72-MeV $0^{+}$, and 3.39-MeV $3^{-}$ excited states of ${}^{12}\mathrm{B}$ are measured at $E_d$ = 21.5 MeV. The analysis of the data is carried out within the coupled-reaction-channels method for the direct neutron transfer and the Hauser-Feshbach formalism of the statistical compound-nucleus model. The spectroscopic factors, asymptotic normalization coefficients, and rms radii of the last neutron in all states studied are deduced. The existence of the neutron halos in the 1.67-MeV $2^{-}$ and 2.62-MeV $1^{-}$ states is found, consistent with the earlier published data. New information about the enlarged rms radii of the last neutron in the 2.72-MeV $0^{+}$ (5.7 fm) and the unbound 3.389-MeV $3^{-}$ (5.9 fm) states of ${}^{12}\mathrm{B}$ was obtained, resulting in the possible existence of neutron halo-like states in ${}^{12}\mathrm{B}$.

Measurement of forward recoil range distribution (FRRD) of evaporation residues (ERs) populated in the ${}^{16}\mathrm{O}+{}^{89}\mathrm{Y}$ reaction at $E_{\mathrm{lab}}\approx 105$ MeV have been carried out by employing the offline characteristic $\gamma$-ray detection method. The FRRD pattern of ERs populated through $xn$/$pxn$ channels comprises a single peak only whereas ERs populated through $\alpha$ emitting channel have multiple peaks in their FRRD. FRRDs of the observed ERs support the presence of the complete fusion (CF) process in the population of $xn$/$pxn$ channels residues and an admixture of complete and incomplete fusion (ICF) processes in the population of $\alpha$ emitting channel residues. The observed ICF process in the population of $\alpha$ emitting channel residues is explained through the breakup fusion model. The fusion function is derived from the experimental CF cross section data and the extracted fusion function is compared with the universal fusion function to estimate the degree of ICF contribution to the total fusion cross section. An attempt has also been made to explore the dependence of ICF probability on target charge.

Inspired by the recent experimental report by the WASA-at-COSY Collaboration, we investigate the possible existence of the dibaryon candidate $N\mathrm{\Delta }$ with quantum numbers $I{J}^P={21}^{+}\left(D_{21}\right)$. The dynamical calculation shows that we cannot obtain the bound $D_{21}$ state in the models that can obtain the experimental $d^{*}$. The low-energy scattering phase shifts of the $N-\mathrm{\Delta }$ scattering give the same conclusion. Besides, the mass calculation by using the Gursey-Radicati mass formula and the analysis of the matrix elements of the color magnetic interaction show that the mass of $D_{21}$ is larger than that of $D_{12}$ ($N\mathrm{\Delta }$ with $I{J}^P={12}^{+}$), which indicate that it is less possible for the $D_{21}$ than the $D_{12}$ to form bound state.

In this paper we study yrast states of $sd$ bosons under random interactions by revisiting the collective motions and the linear correlations in the Mallmann plot. Both the SU(3) and the conjugate $\overline{\mathrm{SU}\left(3\right)}$ limits are found to play an important role in the rotational motion in the random ensemble. We point out that the seniority-like correlation is represented by the U(5) limit with $s$-boson dominance for yrast low-spin states and $d$-boson condensation for yrast higher-spin states. The so-called $\alpha$ correlation is interpreted in terms of the $s$-boson dominance of the U(5) limit for the vibrational side, the $\mathrm{SU}\left(3\right)/\overline{\mathrm{SU}\left(3\right)}$ limit for the rotational side, and transitions between dynamical symmetry limits for the intermediate region. The $\alpha$ correlation is also reproduced using the consistent-$Q$ Hamiltonian in the Casten's symmetry triangle.

In the present work we have measured pre- and post-scission neutron multiplicities $(M_{\mathrm{pre}}$ and $M_{\mathrm{post}})$ from two compound nuclei, namely ${}^{192,202}\mathrm{Po}$ populated by ${}^{48}\mathrm{Ti}+{}^{144,154}\mathrm{Sm}$ systems at 72 MeV of excitation energy using the National Array of Neutron Detectors (NAND) facility at IUAC, New Delhi. Statistical model analysis has been performed for ${}^{48}\mathrm{Ti}+{}^{144,154}\mathrm{Sm}$ along with already existing data for ${}^{12}\mathrm{C}+{}^{194}\mathrm{Pt}$ and ${}^{18}\mathrm{O}+{}^{192}\mathrm{Os}$ covering compound nuclei of Po $\left({}^{192,202,206,210}\mathrm{Po}\right)$ with neutron number $N_C=108$, 118, 122, and 126 respectively. Variation of experimental $M_{\mathrm{pre}}$ with $N/Z$ of the compound nucleus does not show any special feature at neutron shell closure $\left(N_C=126\right)$ at compound nucleus excitation energy around 72 MeV considered here. In particular, it is found that dissipation alone is unable to reproduce the experimental $M_{\mathrm{pre}}$ for ${}^{192}\mathrm{Po}$, and the role of entrance channel dynamics should be considered in future works.

Recently it has been discovered that the elliptic flow, $v_2$, of composite charged particles emitted at midrapidity in heavy-ion collisions at intermediate energies shows the strongest sensitivity to the nuclear equation of state (EoS), which has been observed up to now within a microscopic model. This dependence on the nuclear EoS is predicted by quantum molecular dynamics (QMD) calculations [A. Le Fèvre et al.. Nucl. Phys. A 945, 112 (2016)], which show as well that the absorption or rescattering of in-plane emitted particles by the spectator matter is not the main reason for the EoS dependence of the elliptic flow at midrapidity but different density gradients (and therefore different forces) in the direction of the impact parameter ($x$ direction) as compared to the direction perpendicular to the reaction plan ($y$ direction), caused by the presence of the spectator matter. The stronger density gradient in the $y$ direction accelerates the particles more and creates therefore a negative $v_2$. When using a soft momentum-dependent EoS, the QMD calculations reproduce the experimental results.

Dissipative processes in relativistic fluids are known to be important in analyses of the hot QCD matter created in high-energy heavy-ion collisions. In this work, I consider dissipative corrections to energy and conserved charge densities, which are conventionally assumed to be vanishing but could be finite. Causal dissipative hydrodynamics is formulated in the presence of these dissipative currents. The relation between hydrodynamic stability and transport coefficients is discussed. I then study their phenomenological consequences on the observables of heavy-ion collisions in numerical simulations. It is shown that particle spectra and elliptic flow can be visibly modified.

A new subevent cumulant method was recently developed, which can significantly reduce the nonflow contributions in long-range correlations for small systems compared to the standard cumulant method. In this work, we study multiparticle cumulants in $p+\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with a multiphase transport model (AMPT), including two- and four-particle cumulants ($c_2\left\{2\right\}$ and $c_2\left\{4\right\}$) and symmetric cumulants [SC(2, 3) and SC(2, 4)]. Our numerical results show that $v_2\left\{2\right\}$ is consistent with the experimental data, while the magnitude of $c_2\left\{4\right\}$ is smaller than the experimental data, which may indicate that either the collectivity is underestimated or some dynamical fluctuations are absent in the AMPT model. For the symmetric cumulants, we find that the results from the standard cumulant method are consistent with the experimental data, but those from the subevent cumulant method show different behaviors. The results indicate that the measurements from the standard cumulant method are contaminated by nonflow effects, especially when the number of produced particles is small. The subevent cumulant method is a better tool to explore the $real$ collectivity in small systems.

A new sine observable, $R_{{\mathrm{\Psi }}_2}\left(\mathrm{\Delta }S\right)$, has been proposed to measure the chiral magnetic effect (CME) in heavy-ion collisions; $\mathrm{\Delta }S=〈sin{\phi }_{+}〉-〈sin{\phi }_{-}〉$, where ${\phi }_{\pm }$ are azimuthal angles of positively and negatively charged particles relative to the reaction plane and averages are event-wise, and $R_{{\mathrm{\Psi }}_2}\left(\mathrm{\Delta }S\right)$ is a normalized event probability distribution. Preliminary STAR data reveal concave $R_{{\mathrm{\Psi }}_2}\left(\mathrm{\Delta }S\right)$ distributions in 200 GeV Au+Au collisions. Studies with a multiphase transport (AMPT) and anomalous-viscous fluid dynamics (AVFD) models show concave $R_{{\mathrm{\Psi }}_2}\left(\mathrm{\Delta }S\right)$ distributions for CME signals and convex ones for typical resonance backgrounds. A recent hydrodynamic study, however, indicates concave shapes for backgrounds as well. To better understand these results, we report a systematic study of the elliptic flow ($v_2$) and transverse momentum ($p_T$) dependences of resonance backgrounds with toy-model simulations and central limit theorem (CLT) calculations. It is found that the concavity or convexity of $R_{{\mathrm{\Psi }}_2}\left(\mathrm{\Delta }S\right)$ depends sensitively on the resonance $v_2$ (which yields different numbers of decay ${\pi }^{+}{\pi }^{-}$ pairs in the in-plane and out-of-plane directions) and $p_T$ (which affects the opening angle of the decay ${\pi }^{+}{\pi }^{-}$ pair). Qualitatively, low $p_T$ resonances decay into large opening-angle pairs and result in more “back-to-back” pairs out of plane, mimicking a CME signal, or a concave $R_{{\mathrm{\Psi }}_2}\left(\mathrm{\Delta }S\right)$. Supplemental studies of $R_{{\mathrm{\Psi }}_3}\left(\mathrm{\Delta }S\right)$ in terms of the triangular flow ($v_3$), where only backgrounds exist but any CME would average to zero, are also presented.