We extend the no-core shell model (NCSM) methodology to incorporate strangeness degrees of freedom and apply it to single-$\mathrm{\Lambda }$ hypernuclei. After discussing the transformation of the hyperon-nucleon ($YN$) interaction into the harmonic-oscillator (HO) basis and the similarity renormalization group transformation applied to it to improve model-space convergence, we present two complementary formulations of the NCSM, one that uses relative Jacobi coordinates and symmetry-adapted basis states to fully exploit the symmetries of the hypernuclear Hamiltonian and one working in a Slater determinant basis of HO states where antisymmetrization and computation of matrix elements is simple and to which an importance-truncation scheme can be applied. For the Jacobi-coordinate formulation, we give an iterative procedure for the construction of the antisymmetric basis for arbitrary particle number and present the formulas used to embed two- and three-baryon interactions into the many-body space. For the Slater-determinant formulation, we discuss the conversion of the $YN$ interaction matrix elements from relative to single-particle coordinates, the importance-truncation scheme that tailors the model space to the description of the low-lying spectrum, and the role of the redundant center-of-mass degrees of freedom. We conclude with a validation of both formulations in the four-body system, giving converged ground-state energies for a chiral Hamiltonian, and present a short survey of the $A\le 7$ hyperhelium isotopes.

Background: Ab initio many-body methods whose numerical cost scales polynomially with the number of particles have been developed over the past fifteen years to tackle closed-shell mid-mass nuclei. Open-shell nuclei have been further addressed by implementing variants based on the concept of spontaneous symmetry breaking (and restoration). These methods typically access ground states properties and some restricted aspects of spectroscopy.

Purpose: In order to access the spectroscopy of open-shell nuclei more systematically while controlling the numerical cost, we design a novel many-body method that combines the merit of breaking and restoring symmetries with those brought about by low-rank individual excitations.

Methods: The recently proposed truncated configuration-interaction method based on optimized symmetry-broken and -restored states is extended to the $\text{SU}\left(2\right)$ group associated with total angular momentum. Dealing more specifically with the Lipkin Hamiltonian, the present study focuses on the breaking and the restoration of the $z$-signature symmetry associated with a discrete subgroup of $\text{SU}\left(2\right)$. The highly-truncated $N$-body Hilbert subspace within which the Hamiltonian is diagonalized is spanned by a $z$-signature broken and restored Slater determinant vacuum and associated low-rank, e.g., one-particle/one-hole and two-particle/two-hole, excitations. Furthermore, the extent by which the symmetry-unrestricted vacuum breaks $z$-signature symmetry is optimized in the presence of projected low-rank particle-hole excitations. The quality of the method is gauged against exact ground- and excited-state eigenenergies for a large range of values of the two-body interaction strength. Furthermore, results are compared to those obtained from the generator coordinate method, the random-phase approximation, and the self-consistent (second) random-phase approximation.

Results: The proposed method provides an excellent reproduction of the ground-state energy and of low-lying excitation energies of various $z$ signatures and total angular momenta across the full range of internucleon coupling defining the Lipkin Hamiltonian and driving the normal-to-deformed quantum phase transition. In doing so, the successive benefits of (i) breaking the symmetry, (ii) restoring the symmetry, (iii) including low-rank particle-hole excitations, and (iv) optimizing the amount by which the underlying vacuum breaks the symmetry are illustrated. While the generator coordinate method, built on the same deformed vacua, provides results of similar quality, this is not the case for the symmetry-restricted random-phase and self-consistent (second) random-phase approximations in the strongly interacting regime.

Conclusions: The numerical cost of the newly designed variational method is polynomial with respect to the system size. It achieves a good accuracy on the ground-state energy and the low-lying spectroscopy for both weakly and strongly interacting systems. The present study confirms the results obtained previously for the attractive pairing Hamiltonian in connection with the breaking and restoration of $\text{U}\left(1\right)$ global gauge symmetry. These two studies constitute a strong motivation to apply this method to realistic nuclear Hamiltonians in view of providing a complementary, accurate and versatile ab initio description of mid-mass open-shell nuclei.

Background: Being able to rigorously quantify the uncertainties in reaction models is crucial to moving this field forward. Even though Bayesian methods are becoming increasingly popular in nuclear theory, they have yet to be implemented and applied in reaction theory problems.

Purpose: The purpose of this work is to investigate, using Bayesian methods, the uncertainties in the optical potentials generated from fits to elastic-scattering data and the subsequent uncertainties in the transfer predictions. We also study the differences in two reaction models where the parameters are constrained in a similar manner, as well as the impact of reducing the experimental error bars on the data used to constrain the parameters.

Method: We use Bayes' theorem combined with a Markov chain Monte Carlo to determine posterior distributions for the parameters of the optical model, constrained by neutron-, proton-, and/or deuteron-target elastic scattering. These potentials are then used to predict transfer cross sections within the adiabatic wave approximation or the distorted-wave Born approximation.

Results: We study a number of reactions involving deuteron projectiles with energies in the range 10–25 MeV/nucleon on targets with mass $A=48$–208. The case of ${}^{48}\mathrm{Ca}(d,p){}^{49}\mathrm{Ca}$ transfer to the ground state is described in detail. A comparative study of the effect of the size of experimental errors is also performed. Five transfer reactions are studied, and their results are compiled in order to systematically identify trends.

Conclusions: Uncertainties in transfer cross sections can vary significantly (25–100 %) depending on the reaction. While these uncertainties are reduced when smaller experimental error bars are used to constrain the potentials, this reduction is not trivially related to the error reduction. We also find smaller uncertainties when using the adiabatic formulation than when using the distorted-wave Born approximation.

We study viscous effects on heavy quark radiative energy loss in a dynamically screened medium with boost-invariant longitudinal expansion. We calculate, to first order in opacity, the energy loss by incorporating viscous corrections in the single-particle phase-space distribution function within relativistic dissipative hydrodynamics. We consider Grad's 14-moment and the Chapman-Enskog-like methods for the nonequilibrium distribution functions. Our numerical results for the charm quark radiative energy loss show that, as compared to an expanding ideal (nonviscous) fluid, viscosity in the evolution leads to somewhat enhanced energy loss which is rather insensitive to the underlying viscous hydrodynamic models used. Further inclusion of a viscous correction induces larger energy loss, and the magnitude and pattern of this enhancement crucially depend on the form of viscous corrections used.

Background: Photoproduction of mesons off quasifree nucleons bound in the deuteron allows us to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets.

Purpose: Study experimentally single ${\pi }^0$ photoproduction off quasifree nucleons from the deuteron. Investigate nuclear effects by a comparison of the results for free protons and quasifree protons. Use the quasifree neutron data (corrected for nuclear effects) to test the predictions of reaction models and partial wave analysis (PWA) for $\gamma n\to n{\pi }^0$ derived from the analysis of the other isospin channels.

Methods: High statistics angular distributions and total cross sections for the photoproduction of ${\pi }^0$ mesons off the deuteron with coincident detection of recoil nucleons have been measured for the first time. The experiment was performed at the tagged photon beam of the Mainz Microtron (MAMI) accelerator for photon energies between 0.45 and 1.4 GeV, using an almost $4\pi$ electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion.

Results: Significant effects from final-state interactions (FSI) were observed for participant protons in comparison to free proton targets (between 30% and almost 40%). The data in coincidence with recoil neutrons were corrected for such effects under the assumption that they are identical for participant protons and neutrons. Reaction model predictions and PWA for $\gamma n\to n{\pi }^0$, based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data.

Conclusions: The results demonstrate clearly the importance of a measurement of the fully neutral final state for the isospin decomposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. The results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood.

The measurements of the $J/\psi \to \gamma p\overline{p}$ decays by the BES Collaboration indicate an enhancement at the $p\overline{p}$ threshold which, however, is not present in the $J/\psi$ decays into $\omega p\overline{p}$ and into $\pi p\overline{p}$. Here, two processes for describing the decays $J/\psi \to \mathcal{B}p\overline{p}$ where $\mathcal{B}=\gamma ,\omega$ are presented in some detail and the cases $\mathcal{B}=\varphi ,\pi$ are briefly touched on. The first one, applied not only to the radiative decay to reproduce the threshold peak but also to the $\omega p\overline{p}$ decay channel to improve the description of the spectrum, postulates a direct emission of the boson before the baryon pair is formed. The second process assumes that the boson $\mathcal{B}$ is emitted from the baryon pair following the $J/\psi$ decay and includes for the decays into $\gamma p\overline{p}$ a final-state nucleon-antinucleon interaction based on the Paris $N\overline{N}$ potential. The reproduction of the $p\overline{p}$ distribution in the $J/\psi \to \omega p\overline{p}$ decays needs a final-state interaction involving a $N\left(2050\right)3/2^{-}$ resonance. The photon- and meson-emission rates are reproduced in a semiquantitative way.

A charge-sensitive in-event correlator is proposed and tested for its efficacy to detect and characterize charge separation associated with the chiral magnetic effect (CME) in heavy ion collisions. Tests, performed with the aid of two reaction models, indicate discernible responses for background- and CME-driven charge separation, relative to the second- (${\mathrm{\Psi }}_2$) and third-order (${\mathrm{\Psi }}_3$) event planes, which could serve to identify the CME. The tests also indicate a degree of sensitivity which would enable robust characterization of the CME via anomalous viscous fluid dynamics (AVFD) model comparisons.

We investigate the prolate-to-oblate shape phase transitions in the neutron-rich Pt, Os, and Ir nuclei in the mass $A\approx 190$ region. The Hamiltonian of the interacting boson-fermion model, used to describe the odd-mass ${}^{185-199}\mathrm{Pt}, {}^{185-193}\mathrm{Os}$, and ${}^{185-195}\mathrm{Ir}$ isotopes, is partially constructed by using as a microscopic input the results of constrained self-consistent mean-field calculations within the Hartree-Fock-Bogoliubov method with the Gogny force. The remaining few parameters are adjusted to experimental data in the odd systems. In this way the calculations reasonably describe the spectroscopic properties of the odd-mass systems considered. Several calculated observables for the odd-mass nuclei, especially the low-energy excitation spectra and the effective deformation parameters, point to a prolate-oblate shape transition as a function of the neutron number for all the isotopic chains considered and similar to the one already observed in the neighboring even-even systems.

In this work we study the simultaneous and sequential two-neutron transfer mechanisms to the ${}^{28}\mathrm{Si}$ nucleus induced by $(t,p)$ and $({}^{18}\mathrm{O},{}^{16}\mathrm{O})$ reactions. New experimental cross sections for the ${}^{28}\mathrm{Si}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{30}\mathrm{Si}$ reaction at 84 MeV are also presented. Direct reaction calculations are carried out within the exact finite range coupled reaction channel, for the simultaneous transfer of the two-neutron cluster, and the second-order distorted wave Born approximation, for the sequential transfer. Two different models are considered to describe the two-neutron cluster. The spectroscopic information was obtained from a shell-model calculation with a psdmod interaction for the target overlaps where the $1p_{3/2}, 1p_{1/2}, 1d_{3/2}, 1d_{5/2}$, and $2s_{1/2}$ orbitals are included as valence subspace. We show that simultaneous and sequential two-neutron transfers are competing mechanisms for the population of the ground state in ${}^{30}\mathrm{Si}$. A systematic analysis of the two-neutron transfer induced by the $({}^{18}\mathrm{O},{}^{16}\mathrm{O})$ reaction indicates that the static deformation of target nuclei impacts the two-neutron transfer mechanism.

If quark-gluon plasma (QGP)–like medium is created in $p$-Pb collisions at extremely high collision energies, charm quarks that move in the medium can hadronize by capturing the comoving light quark(s) or antiquark(s) to form the charm hadrons. Using light quark $p_T$ spectra extracted from the experimental data of light-flavor hadrons and a charm quark $p_T$ spectrum that is consistent with perturbative QCD calculations, the central-rapidity data of $p_T$ spectra and the spectrum ratios for $D$ mesons in the low-$p_T$ range ($p_T\lesssim 7$ GeV/$c$) in minimum-bias $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are well described by the quark combination mechanism in equal-velocity combination approximation. The ${\mathrm{\Lambda }}_c^{+}/D^0$ ratio in quark combination mechanism exhibits the typical increase-peak-decrease behavior as the function of $p_T$, and the shape of the ratio for $p_T\gtrsim 3$ GeV/$c$ is in agreement with the data of the ALICE Collaboration in central rapidity region $-0.96<y<0.04$ and the preliminary data of the LHCb Collaboration in forward rapidity region $1.5<y<4.0$. The global production of single-charm baryons is quantified using the data and the possible enhancement (relative to light flavor baryons) is discussed. The $p_T$ spectra of ${\mathrm{\Xi }}_c^0, {\mathrm{\Omega }}_c^0$ in minimum-bias events and those of single-charm hadrons in high-multiplicity event classes are predicted, which serves as the further test of the possible change of the hadronization characteristic for low-$p_T$ charm quarks in the small system created in $p$-Pb collisions at Large Hadron Collider energies.

Motivated by the existence of candidates for exotic hadrons whose masses are close to both two-body and three-body hadronic thresholds lying close to each other, we study degenerate two-body and three-body coupled-channels systems. We first formulate the scattering problem of non-degenerate two-body and three-body coupled channels as an effective three-body problem, i.e., as effective Alt-Grassberger-Sandhas (AGS) equations. We next investigate the behavior of $S$-matrix poles near the threshold when two-body and three-body thresholds are degenerate. We solve the eigenvalue equations of the kernel of AGS equations instead of AGS equations themselves to obtain the $S$-matrix pole energy. We then face a problem of unphysical singularity: although the physical transition amplitudes have physical singularities only, the kernels of AGS equations have unphysical singularities. We show, however, that these unphysical singularities can be removed by appropriate reorganization of the scattering equations and mass renormalization. The behavior of $S$-matrix poles near the degenerate threshold is found to be universal in the sense that the complex pole energy, $E$, is determined by a real parameter, $c$, as $c+Elog\left(-E\right)=0$, or equivalently, $c+\mathrm{Re}Elog\left(\mathrm{Re}E\right)=0$ and $\mathrm{Im}E=\pi \mathrm{Re}E/log\left(\mathrm{Re}E\right)$. This behavior is different from that of either two-body or three-body systems and is characteristic of the degenerate two-body and three-body coupled-channels system. We expect that this new class of universal behavior might play a key role in understanding exotic hadrons.

The low-lying structure of neutron-rich odd-mass Kr isotopes is studied within the interacting boson-fermion model (IBFM) based on the Gogny-D1M energy density functional. The $(\beta ,\gamma )$-deformation energy surfaces, spherical single-particle energies, and occupation probabilities of the odd-mass systems are obtained using the constrained Hartree-Fock-Bogoliubov approximation. Those quantities are used as a microscopic input to determine most of the parameters of the IBFM Hamiltonian. The remaining parameters are specifically tailored to the experimental spectrum for each of the studied odd-mass nuclei. A gradual structural evolution is predicted for the odd-mass isotopes ${}^{87-95}\mathrm{Kr}$ as a function of the nucleon number, which agrees well with the gradual growth of collectivity observed experimentally in the neighboring even-even isotopes.

We present a detailed analysis of the beam energy dependence of the mechanisms for the generation of directed and elliptic flows in Au + Au collisions focusing on the role of hadronic rescattering and spectator shadowing within a microscopic transport model jam with different equations of state. A systematic study of the beam energy dependence is performed for Au + Au collisions at $\sqrt{s_{\mathit{NN}}}=2.3-62.4$ GeV. The transition of the dynamical origin of the directed flow is observed. We find that the initial Glauber-type nucleon-nucleon collisions generate negative $v_1$ for nucleons at midrapidity due to the presence of spectator matter, and this negative nucleon $v_1$ is turned to be positive by the meson-baryon interactions at the beam energy region of $\sqrt{s_{NN}}<30$ GeV. In contrast, above 30 GeV there is no spectator shadowing at midrapidity, and initial nucleon-nucleon collisions do not generate directed flow, but subsequent rescatterings among produced particles generate negative $v_1$ for nucleons. It is demonstrated that negative pion-directed flows are mostly generated by the interaction with the spectator matter. It is also shown that the squeeze-out effect is largely suppressed in the case of softening, which leads to the enhancement of elliptic flow around $\sqrt{s_{NN}}=5-7$ GeV. The elliptic flow at midrapidity above 10 GeV is not influenced by the squeeze-out due to spectator matter, while its effect is seen at the forward rapidity range of $y/y_{\mathrm{c}.\mathrm{m}.}>0.5$, which decreases as beam energy increases.

The chiral magnetic effect (CME)—the separation of positive and negative electric charges along the direction of the external magnetic field in quark-gluon plasma and other topologically nontrivial media—is a consequence of the coupling of electrodynamics to the topological gluon field fluctuations that form metastable $CP$-odd domains. In phenomenological models it is usually assumed that the domains are uniform and the influence of the domain walls on the electric current flow is not essential. This article challenges the latter assumption. A simple model consisting of a uniform spherical domain in a uniform time-dependent magnetic field is introduced and analytically solved. It is shown that (i) no electric current flows into or out of the domain; (ii) the charge separation current, viz. the total electric current flowing inside the domain in the external field direction, is a dissipative Ohm current; (iii) the CME effect can be produced either by the anomalous current or by the boundary conditions on the domain wall; and (iv) the charge separation current oscillates in plasma long after the external field decays. These properties are qualitatively different from the CME in an infinite medium.

We present new data probing short-range correlations (SRCs) in nuclei through the measurement of electron scattering off high-momentum nucleons in nuclei. The inclusive ${}^4\mathrm{He}/{}^3\mathrm{He}$ cross section ratio is observed to be both $x$ and $Q^2$ independent for $1.5<x<2$, confirming the dominance of two-nucleon short-range correlations. For $x>2$, our data support the hypothesis that a previous claim of three-nucleon correlation dominance was an artifact caused by the limited resolution of the measurement. While 3N-SRCs appear to have an important contribution, our data show that isolating 3N-SRCs is significantly more complicated than for 2N-SRCs.

In this work, we study the $r$-mode instability windows and the gravitational wave signatures of neutron stars in the slow rotation approximation using the equation of state obtained from the density-dependent M3Y effective interaction. We consider the neutron star matter to be $\beta$-equilibrated neutron-proton-electron matter at the core with a rigid crust. The fiducial gravitational and viscous timescales, the critical frequencies, the time evolutions of the frequencies, and the rates of frequency change are calculated for a range of neutron star masses. We show that the young and hot rotating neutron stars lie in the $r$-mode instability region. We also emphasize that if the dominant dissipative mechanism of the $r$ mode is the shear viscosity along the boundary layer of the crust-core interface, then the neutron stars with low $L$ value lie in the $r$-mode instability region and hence emit gravitational radiation.

Magnetic dipole and electric quadrupole moments are calculated for neutron-rich sd-pf cross-shell nuclei. These nuclei include open shell isotopes with the number of protons less than 20 and neutrons greater than 20, for which experimental data are available. Shell model calculations are performed with full $sd$ shell model space for $Z$−8 valence protons and full $pf$ shell model space for $N$−20 valence neutrons, where the remaining 20 neutrons are frozen in $s$, $p$ and $sd$-shells. Also, magnetic and Coulomb electron scattering form factors are calculated for some of these nuclei. Excitation out of major shell space are taken into account through a microscopic theory which allows particle-hole excitation from the core and model space orbits to all higher orbits with $2\hslash \omega$ excitation. Effective charges are obtained for each isotope. Core polarization (CP) is essential for obtaining a reasonable description of the electric quadrupole moments and enhance the Coulomb form factors but has no effect on the dipole magnetic moments but squeezes the magnetic form factors. The magnetic static and dynamic properties can be described by free $g$ factors for the model space nucleons without introducing CP effect, on the contrary to the electric static and dynamic properties, which cannot be described properly by the model space nucleons without taking into account CP effects.

The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double-$\beta$ ($0\nu \beta \beta$) decay in ${}^{136}\mathrm{Xe}$ with a target half-life sensitivity of approximately ${10}^{28}$ yr using $5\times {10}^3$ kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the ${}^{136}\mathrm{Xe}$ mass, the monolithic and homogeneous configuration of the active medium, and the multiparameter measurements of the interactions enabled by the time projection chamber. The detector concept and anticipated performance are presented based upon demonstrated realizable background rates.

The spatial dispersion of the single-nucleon wave functions is analyzed using the self-consistent mean-field framework based on nuclear energy density functionals and with the harmonic-oscillator approximation for the nuclear potential. It is shown that the dispersion depends on the radial quantum number $n$ but displays only a very weak dependence on the orbital angular momentum. An analytic expression is derived for the localization parameter that explicitly takes into account the radial quantum number of occupied single-nucleon states. The conditions for single-nucleon localization and formation of cluster structures are fulfilled in relatively light nuclei with $A\le 30$ and $n=1$ states occupied. Heavier nuclei exhibit the quantum liquid phase of nucleonic matter because occupied levels that originate from $n>1$ spherical states are largely delocalized. Nevertheless, individual $\alpha$-like clusters can be formed from valence nucleons filling single-particle levels originating from $n=1$ spherical mean-field states.