The paradox on the previous interpretation for the nuclear chiral geometry based on the effective angle has been clarified by reexamining the system with the particle-hole configuration $\pi {\left(1h_{11/2}\right)}^1\otimes \nu {\left(1h_{11/2}\right)}^{-1}$ and a rotor with the deformation parameter $\gamma ={30}^{\circ }$. It is found that the paradox is caused by the fact that the angular momentum of the rotor is much smaller than those of the proton and the neutron near the bandhead. Hence, it does not support a chiral rotation interpretation near the bandhead. The nuclear chiral geometry based on the effective angle makes sense only when the angular momentum of the rotor becomes comparable with those of the proton and neutron for a particular range of spin values.

We explore magnetic field effects on the nuclear matter based on the Skyrmion crystal approach for the first time. It is found that the magnetic effect plays the role of a catalyzer for the topology transition in the baryonic matter. Furthermore, we observe that in the presence of the magnetic field, the inhomogeneous chiral condensate persists in both the Skyrmion and the half-Skyrmion phases. Explicitly, as the strength of magnetic field gets larger, the inhomogeneous chiral condensate in the Skyrmion phase tends to be drastically localized, while in the half-Skyrmion phase the inhomogeneity configuration is hardly affected. It also turns out that a large magnetic effect in a low-density region distorts the baryon shape to an elliptic form but the crystal structure is intact. However, in a high-density region, the crystal structure is strongly affected by the strong magnetic field. A possible correlation between the chiral inhomogeneity and the deformation of the Skyrmion configuration is also addressed. The results obtained in this article might be realized in the deep interior of compact stars.

We present a systematic study of the strange particle production at the CERN Large Hadron Collider (LHC) in proton-proton ($pp$) collisions at $\sqrt{s}=7\mathrm{TeV}$ based on paciae simulations. Two different mechanisms accounting for single string structure variations and multiple string interactions are implemented in the simulations. These modifications give rise to increased effective string tension in the Lund fragmentation model and generate more strange particles in the hadronic final state. By comparing the results with a wealth of the LHC data, we find that the inclusion of variable effective string tension yields an improved agreement between theory and experiment, especially for the recently observed multiplicity dependence of strangeness enhancement in $pp$ collisions. This approach provides us a new method to understand the microscopic picture of the novel high multiplicity $pp$ events collected at the LHC in the string fragmentation framework.

The multinucleon transfer reaction or incomplete fusion reaction (ICF) is a powerful tool to study fission of exotic nuclei that cannot be formed by stable heavy-ion fusion reactions. In the present work, mass distributions of fission fragments (FFs) from fissioning nuclei ${}^{241,242,243,244}\mathrm{Pu}$ and ${}^{240,241}\mathrm{Np}$ populated in multinucleon transfer or ICF reactions on ${}^{6,7}\mathrm{Li}+{}^{238}\mathrm{U}$ systems have been studied. Among these, ${}^{244}\mathrm{Pu},{}^{243}\mathrm{Pu}$, and ${}^{241}\mathrm{Np}$ are formed by the capture of unstable nuclei ${}^6\mathrm{He},{}^5\mathrm{He}$, and $t$, respectively, by the target ${}^{238}\mathrm{U}$. Identification of fissioning nuclei and determination of excitation energies have been performed by finding the details of the outgoing projectile-like fragments detected in coincidence with both the fission fragments on an event-by-event basis. The measurements of FF mass distributions and FF folding angle distributions of different ICF channels confirm that these channels are the prime factors for the modifications in the experimental ratio of asymmetric to symmetric fission yields and the width of folding angle distributions for inclusive fission reported earlier on the same reactions. Comparison among the ratio of asymmetric to symmetric fission yields from ${}^{241,242,243,244}\mathrm{Pu}$ and ${}^{240,241}\mathrm{Np}$ nuclei formed in the present reactions, available literature data, and the theoretical calculations using gef code shows that the shell correction for symmetric fission channels plays an important role in describing the experimental mass distribution.

New energy-density functionals (EDFs) inspired by effective-field theories have been recently proposed. The present work focuses on three such functionals, which were developed to produce satisfactory equations of state for nuclear matter. We aim to extend these functionals to treat finite systems including a spin-orbit contribution and pairing correlations. We illustrate here a first step toward this direction, namely a generalization of such functionals tailored to perform applications to neutron gases confined in harmonic traps. Sets of available ab initio results are used as benchmark pseudodata for adjusting the additional parameters (with respect to the nuclear matter case) that have to be introduced for finite-size systems. Several quantities are predicted and compared to ab initio and other EDF results such as total energies, potentials, and density profiles. The associated effective masses are also analyzed. Two of these functionals globally provide predictions that are close to one another as well as to ab initio values when available. It is shown that, in general, this is not the case for several currently used Skyrme functionals. Directions for improving the third functional are discussed.

Excited states of ${}^{87}\mathrm{Zr}$, populated in the reaction ${}^{60}\mathrm{Ni}({}^{31}\mathrm{P}$, $3pn$) at a beam energy of 112.5 MeV, have been studied. Experimental information on two negative-parity bands has been significantly upgraded with the addition of new $\gamma$ rays and levels. Small values of the reduced transition probability $B(E2$) and a general absence of a measurable Doppler shift in the transitions suggest that the states are weakly deformed. Several positive-parity levels have been grouped into two bands based on their observed properties. Spin parities have been proposed for a majority of the states belonging to the different bands. Lifetimes have been measured for the eight states belonging to the two positive-parity bands from Doppler shift attenuation data, including an upper limit for the highest energy state. The behavior of the deduced $B(M1$) and $B(E2$) values as a function of level spin supports the interpretation of one of these bands within the framework of the shears mechanism. A study of these reduced transition probabilities in the light of the semiclassical model of the shears mechanism, proposed by Macchiavelli and co-workers, confirms this interpretation. The effective gyromagnetic ratio and the interaction strength between the two blades of the shears have been estimated from this study.

We present a description of the breakup of halo nuclei in peripheral nuclear reactions by coupling a model of the projectile motivated by halo effective field theory with a fully dynamical treatment of the reaction using the dynamical eikonal approximation. Our description of the halo system reproduces its long-range properties, i.e., binding energy and asymptotic normalization coefficients of bound states and phase shifts of continuum states. As an application we consider the breakup of ${}^{11}\mathrm{Be}$ in collisions on Pb and C targets. Taking the input for our halo-EFT-inspired description of ${}^{11}\mathrm{Be}$ from a recent ab initio calculation of that system yields a good description of the Coulomb-dominated breakup on Pb at energies up to about 2 MeV, with the result essentially independent of the short-distance part of the halo wave function. However, the nuclear dominated breakup on C is more sensitive to short-range physics. The role of spectroscopic factors and possible extensions of our approach to include additional short-range mechanisms are also discussed.

We consider the effect of the chromo-electromagnetic field fluctuations in addition to the collisional as well as the radiative energy losses suffered by heavy quarks while propagating through the hot and dense deconfined medium of quarks and gluons created in relativistic heavy ion collisions. The chromo-electromagnetic field fluctuations play an important role as they lead to an energy gain of heavy quarks of all momenta and are significant at low momentum. We include the effect of these fluctuations, for the first time, while computing the nuclear modification factor ($R_{AA}$) of heavy mesons, viz., $D$ mesons and $B$ mesons, and compare with the experimental measurements in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ and $5.02$ TeV by the CMS and ALICE experiments at the CERN Large Hadron Collider. Our results are found to be in very good agreement with the measurements.

The multinucleon transfer reaction ${}^{160}\mathrm{Gd}$ + ${}^{186}\mathrm{W}$ is investigated within the framework of the dinuclear system (DNS) model combining gemini code. The DNS + gemini model is improved by including deformation degree of freedom. The shell effects on charge equilibration are investigated. Because of shell closure $N=126$, the behavior of inverse charge equilibration is found, which results in remarkable effects on production of exotic nuclei around $N=126$. The incident energy effects on production cross sections are investigated. Interestingly, it is found that the production yields of actinide neutron-rich nuclei strongly depend on the incident energy. However, for producing heavy neutron-rich nuclei around $N=126$ the incident energy effects are weak, in which the slight decrease of yields with increasing incident energy comes from damping of shell effects. Also, the contour map of isotope production cross sections are calculated at different incident energies. We predict that several unknown heavy neutron-rich nuclei around $A=180$ can be produced with cross sections at the order of ${10}^{-6}$ to ${10}^{-4}$ mb.

The nuclear modification factor $R_{AA}$ and the elliptic flow coefficient $v_2$ of charm-strange meson $D_s^{+}$ is systematically studied in Pb-Pb collisions at $\sqrt{s_{\mathit{NN}}}=5.02$ and $2.76\mathrm{TeV}$. During the modeling, the coupling strength between the injected charm quark and the incident medium constituents is extracted from the lattice QCD calculations: $2\pi T{D}_s=\text{const}$ (Model-A) and $2\pi T{D}_s=1.3+{(T/T_c)}^2$ (Model-B). We find that, comparing $R_{AA}\left(D_s^{+}\right)$ with $R_{AA}\left(\text{nonstrange}\right)$, the heavy-light coalescence effect is more pronounced for the former one, resulting in an enhancement behavior in the range $2\lesssim p_T\lesssim 5\mathrm{GeV}$. The predictions for $R_{AA}\left(D_s^{+}\right)$ and $R_{AA}\left(\text{nonstrange}\right)$ favor Model-A to have a better description of the measured $p_T$ dependence at both energies, while the predictions for $v_2$ prefer Model-B at moderate $p_T$ ($2\lesssim p_T\lesssim 4\mathrm{GeV}$). Therefore, it is necessary to consider the temperature and/or momentum dependence of $2\pi T{D}_s$ to describe simultaneously $R_{AA}\left(D_s^{+}\right)$ and $v_2\left(D_s^{+}\right)$ in different centrality classes in Pb-Pb collisions.

If the thermal evolution of the hot young neutron star in the supernova remnant HESS J1731-347 is driven by neutrino emission, it provides a stringent constraint on the coupling of light (mass $\ll 10\mathrm{keV}$) axion-like particles to neutrons. Using Markov-Chain Monte Carlo we find that for the values of axion-neutron coupling $g_{ann}^2>7.7\times {10}^{-20}$ (90% c.l.) the axion cooling from the bremsstrahlung reaction $n+n\to n+n+a$ is too rapid to account for the high observed surface temperature. This implies that the Pecci-Quinn scale or axion decay constant $f_a>6.7\times {10}^7\mathrm{GeV}$ for KSVZ axions and $f_a>1.7\times {10}^9\mathrm{GeV}$ for DFSZ axions. The high temperature of this neutron star also allows us to tighten constraints on the size of the nucleon pairing gaps.

Background: In the $A\approx 50$ mass region $M1$ spin-flip transitions are prominent around 9 MeV. An accumulation of $1^{-}$ states between 5 and 8 MeV generating additional $E1$ strength, also denoted as pygmy dipole resonance, has been established in many nuclei with neutron excess within the last decade.

Purpose: The $\gamma$-decay behavior of $J=1$ states has been investigated in an NRF experiment. $M1$ excitations have been compared to shell model calculations.

Methods: $J=1$ states were excited by quasi-monoenergetic, linearly polarized $\gamma$-ray beams generated by laser-Compton backscattering at the $\mathrm{HI}\gamma \mathrm{S}$ facility, Durham, NC, USA. Depopulating $\gamma$ rays were detected with the multidetector array ${\gamma }^3$.

Results: For eleven beam-energy settings the $\gamma$-decay behavior of dipole states was analyzed by a state-to-state analysis and average $\gamma$-decay branching ratios have been investigated. 34 parity quantum numbers were assigned to $J=1$ states.

Conclusions: Six $1^{-}$ states and two $1^{+}$ states have been investigated in NRF experiments for the first time. The $M1$ strength distribution is in good agreement with shell-model calculations.

Attention is fixed on shells in toroidal nuclei in the intermediate-mass region using a toroidal single-particle potential. We find toroidal shells in the intermediate-mass region with large single-particle energy gaps at various nucleon numbers. These toroidal shells are located at different toroidal deformations characterized by the aspect ratios of the toroidal major radius to the toroidal minor radius, and they provide extra stability at various toroidal deformations. Relative to a toroidal core, the Bohr–Mottelson spin-aligning particle-hole excitations may be constructed to occupy the lowest single-particle Routhian energies to lead to toroidal high-spin isomers with different spins. Furthermore, because a nucleon in a toroidal nucleus possesses a vorticity quantum number, toroidal vortex nuclei may be constructed by making particle-hole excitations in which nucleons of one type of vorticity are promoted to populate unoccupied single-particle orbitals of the opposite vorticity. Methods for producing toroidal high-spin isomers and toroidal vortex nuclei are discussed.

We analyze the electron-energy and angular distribution of neutron ${\beta }^{-}$ decay with a polarized neutron and electron and an unpolarized proton, calculated by Ivanov et al. [Phys. Rev. C 95, 055502 (2017)] within the standard model (SM), by taking into account the contributions of interactions beyond the SM. After the absorption of vector and axial-vector contributions by the axial coupling constant and Cabibbo-Kobayashi-Maskawa (CKM) matrix element [Bhattacharya et al., Phys. Rev. D 85, 054512 (2012) and so on] these are the contributions of scalar and tensor interactions only. The neutron lifetime, correlation coefficients and their averaged values, and asymmetries of neutron ${\beta }^{-}$ decay with a polarized neutron and electron are adapted to the analysis of experimental data in search of contributions of interactions beyond the SM. Using the obtained results we propose some estimates of the values of the scalar and tensor coupling constants of interactions beyond the SM. We use the estimate of the Fierz interference term $b=-0.0028\pm 0.0026$ by Hardy and Towner [Phys. Rev. C 91, 025501 (2015)], the neutron lifetime ${\tau }_n=880.2\left(1.0\right)\mathrm{s}$ [Particle Data Group, Chin. Phys. C 40, 100001 (2016)] and the experimental data $N_{exp}=0.067\pm 0.{011}_{\mathrm{stat}.}\pm 0.{004}_{\mathrm{syst}.}$ for the averaged value of the correlation coefficient of the neutron-electron spin-spin correlations, measured by Kozela et al. [Phys. Rev. C 85, 045501 (2012)]. The contributions of $G$-odd correlations are calculated and found at the level of ${10}^{-5}$ in agreement with the results obtained by Gardner and Plaster [Phys. Rev. C 87, 065504 (2013)].

We apply a multiphase transport (AMPT) model to study two-particle angular correlations in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. In addition to being able to describe the angular correlation functions of meson-meson pairs, a large improvement for the angular correlations of baryon-baryon and antibaryon-antibaryon is achieved. We further find that the AMPT model with new quark coalescence provides an even better description on the anticorrelation feature of baryon-baryon correlations observed in the experiments. We also extend the study to $p$-Pb collisions at $\sqrt{s}=5.02\mathrm{TeV}$ and obtained similar results. These results help us better understand the particle production mechanism in $pp$ and $p$-Pb collisions at Large Hadron Collider energies.