We have studied the solution of the six-nucleon bound state problem using the hyperspherical harmonic (HH) approach. For this study we have considered only two-body nuclear forces. In particular we have used a chiral nuclear potential evolved with the similarity renormalization group unitary transformation. A restricted basis has been selected by performing a careful analysis of the convergence of different HH classes. Finally, the binding energy and other properties of ${}^6\mathrm{Li}$ ground state are calculated and compared with the results obtained by other techniques. Then, we present a calculation of matrix elements relevant for direct dark matter search involving ${}^6\mathrm{Li}$. The results obtained demonstrate the feasibility of using the HH method to perform calculations beyond $A=4$.

We compute nuclear matrix elements of neutrinoless double-$\beta$ decay mediated by light Majorana-neutrino exchange in the $A=6$ system. The goal is to benchmark two many-body approaches, the no-core shell model and the multireference in-medium similarity renormalization group (SRG). We use a SRG-evolved next-to-next-to-next-to-leading chiral order two-body potential for the nuclear interaction, and make the approximation that the isospin is conserved. We compare the results of the two approaches as a function of the cutoff on the many-body basis space. Although differences are seen in the predicted nuclear radii, the ground-state energies and neutrinoless double-$\beta$ decay matrix elements produced by the two approaches show significant agreement. We discuss the implications for calculations in heavier nuclei.

Direct photon produced from first proton-neutron ($p\text{−}n$) collision during the early stage of heavy ion reaction is a sensitive probe to reflect energy and momentum distribution of nucleons. In this work, we embedded the hard photon production channel in an extended quantum molecular dynamics (EQMD) model, and took the direct photon as a possible probe to improve namely the Fermi motion in the EQMD model. A possible scheme is offered to handle the dynamical wave packet width within incoherent bremsstrahlung process. Direct photons calculated by our modified EQMD were compared with data of ${}^{14}\mathrm{N}+{}^{12}\mathrm{C}$ at beam energies $E/A$ = 20, 30, and 40 MeV, and it is found that the yield, inverse slope, and angular distribution of direct photons could be reasonably reproduced. In addition, asymmetric reaction systems of ${}^4\mathrm{He} +$ C and ${}^4\mathrm{He} +$ Zn at $E/A$ = 53 MeV are also simulated in this work. It is found that the symmetric angular distribution in the nucleon-nucleon ($N\text{−}N$) center-of-mass (c.m.) frame and the velocity of the $\gamma$-emission source can be reasonably obtained from our method although there is some quantitative difference.

A completely relativistic quark model in the Bethe-Salpeter framework is employed to calculate the exclusive production ratio of the neutral to charged kaon pair in $e^{+}{e}^{-}$ annihilation continuum region below the $J/\mathrm{\Psi }$ mass. The valence quark charge plays the key role. The cancellation of the diagrams for the same charge case ($K_S+K_L$) and the noncancellation of the diagrams for the different charge case ($K^{-}+K^{+}$) lead to the ratio as ${(m_s-m_d)}^2/M_{kaon}^2\approx 1/10$.

The strength of the $N=28$ magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of ${}^{46\text{–}48}\mathrm{Ar}$, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass values are up to 90 times more precise than previous measurements. While they suggest the persistence of the $N=28$ shell closure for argon, we show that this conclusion has to be nuanced in light of the wealth of spectroscopic data and theoretical investigations performed with the SDPF-U phenomenological shell model interaction. Our results are also compared with ab initio calculations using the valence space in-medium similarity renormalization group and the self-consistent Green's function approaches. Both calculations provide a very good account of mass systematics at and around $Z=18$ and, generally, a consistent description of the physics in this region. This combined analysis indicates that ${}^{46}\mathrm{Ar}$ is the transition between the closed-shell ${}^{48}\mathrm{Ca}$ and collective ${}^{44}\mathrm{S}$.

The unambiguous observation of a chiral magnetic effect (CME)–driven charge separation is the core aim of the isobar program at the Relativistic Heavy Ion Collider (RHIC), consisting of ${}_{40}{}^{96}\mathrm{Zr}+{}_{40}{}^{96}\mathrm{Zr}$ and ${}_{44}{}^{96}\mathrm{Ru}+{}_{44}{}^{96}\mathrm{Ru}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. We quantify the role of the spatial distributions of the nucleons in the isobars on both eccentricity and magnetic field strength within a relativistic hadronic transport approach (simulating many accelerated strongly interacting hadrons, SMASH). In particular, we introduce isospin-dependent nucleon-nucleon spatial correlations in the geometric description of both nuclei, deformation for ${}_{44}{}^{96}\mathrm{Ru}$ and the so-called neutron skin effect for the neutron-rich isobar, i.e., ${}_{40}{}^{96}\mathrm{Zr}$. The main result of this study is a reduction of the magnetic field strength difference between ${}_{44}{}^{96}\mathrm{Ru}+{}_{44}{}^{96}\mathrm{Ru}$ and ${}_{40}{}^{96}\mathrm{Zr}+{}_{40}{}^{96}\mathrm{Zr}$ by a factor of 2, from $10\%$ to $5\%$ in peripheral collisions when the neutron-skin effect is included. Further, we find an increase of the eccentricity ratio between the isobars by up to 10% in ultracentral collisions as due to the deformation of ${}_{44}{}^{96}\mathrm{Ru}$ while neither the neutron skin effect nor the nucleon-nucleon correlations result into a significant modification of this observable with respect to the traditional Woods-Saxon modeling. Our results suggest a significantly smaller CME signal to background ratio for the experimental charge separation measurement in peripheral collisions with the isobar systems than previously expected.

A systematic investigation of the ground state deformation, the physical properties (two-neutron separation energy and neutron, proton, and charge radii), and the possibility of nuclear shape coexistence in Zn, Ge, and Se isotopes was performed using the relativistic Hartree-Bogoliubov formalism using density-dependent zero- and finite-range $NN$ interactions. Shape coexistence does not show up clearly in Zn isotopes. However, it is clear in most of the Ge and Se isotopes; the two coexistence minima are axial and triaxial in the case of Ge, while both are axial in the case of Se. Along all these chains one can see the existence of several transition points, where the ground state shape suddenly changes. This sudden change affects the evolution of the physical properties. The density of states near the Fermi level is a key factor in determining the ground state minima. Both point-coupling and meson-exchange models give similar results with few exceptions. A very good agreement is found with the available experimental data. The SU(3) proxy provides a reasonable prediction of the deformation value in the middle of the isotopic chain.

The asymmetry in the neutrino mean free path for the absorption reaction $\nu +n\to e^{-}+p$ is evaluated within hot neutron matter under a strong magnetic field. We consider densities in the range $0.05\le \rho \le 0.4{\mathrm{fm}}^{-3}$, several temperatures up to 30 MeV, and magnetic field strengths from $B=0$ up to $B={10}^{18}$ G. Polarized neutron matter is described within the nonrelativistic Hartree-Fock model using the LNS Skyrme interaction. The neutrino mean free path has a weak dependence on the temperature and, in the strong magnetic field region, it decreases for growing values of it. This contrasts with the scattering reaction $\nu +n\to {\nu }^{\prime }+n^{\prime }$, where the average mean free path is almost independent of the magnetic field and has a strong dependence on the temperature. We have evaluated the asymmetry from both the absorption and scattering reactions. Our results shows that the total asymmetry depends on the magnetic field intensity, the density, and the temperature. For a density of $0.16{\mathrm{fm}}^{-3}$ and for a magnetic field strength of $B={10}^{17}$ G, the asymmetries in the mean free path are found to be $\approx 9\%$ and $\approx 3.4\%$ for temperatures of $T=15$ and 30 MeV, respectively. The same set of asymmetries for $B={10}^{18}$ G is $\approx 58\%$ and $\approx 48\%$.

Hyperfine-structure parameters and isotope shift of the $9/2^{-}$ isomeric state in ${}^{187}\mathrm{Au}$ relative to ${}^{197}\mathrm{Au}$ for the 267.6-nm atomic transition have been measured for the first time using the in-source resonance-ionization spectroscopy technique. The magnetic dipole moment and change in the mean-square charge radius for this $9/2^{-}$ isomer have been deduced. The observed large isomer shift relative to the $1/2^{+}$ ground state in ${}^{187}\mathrm{Au}$ confirms the occurrence of the shape coexistence in ${}^{187}\mathrm{Au}$ proposed earlier from the analysis of the nuclear spectroscopic data and particle plus triaxial rotor calculations. The analysis of the magnetic moment supports the previously proposed $9/2^{-}$, $1/2^{-}\left[541\right]$ assignment at moderate prolate deformation for ${}^{187}\mathrm{Au}^m$.

The spallation and fragmentation reactions of ${}^{136}\mathrm{Xe}$ induced by proton, deuteron, and carbon targets at 168 MeV/nucleon were studied at RIKEN Radioactive Isotope Beam Factory via the inverse kinematics technique. A wide range of isotopic distributions of the reaction cross sections has been obtained and systematically analyzed by using the Particle and Heavy Ion Transport code System (PHITS) including dynamical and intranuclear cascade processes plus evaporation process, the semi-empirical parametrization for residue cross sections in spallation reactions (SPACS) and empirical parametrization of fragmentation cross sections (EPAX), and the deuteron-induced reaction analysis code system (DEURACS) incorporating the deuteron breakup effect. The carbon target has exhibited strong potential to produce light-mass isotopes far away from the projectile, in comparison to proton and deuteron targets. This may be attributed to the possible higher excitation energies of the prefragment induced by heavier target. It is demonstrated that the deuteron target has advantages to produce isotopic chains very close to the projectile and also the neutron-rich nuclei in other isotopic chains far away from the projectile, due basically to its structure property and the effect of the breakup neutron in the peripheral collision processes. The proton target has the advantage of being able to produce isotopes produced via charge-pickup reactions in comparison to other targets. The prediction powers of various calculation codes are examined with respective to the experimental isotopic distributions. The target and energy dependences of the produced mass distributions are also discussed.

An $sp$-mixing model, which describes a compound nuclear reaction by mixing partial waves, predicts a correlation term in this reaction. A detailed study of the $sp$-mixing model is required to study the feasibility of a new type of time reversal symmetry violation search experiment. The correlation term ${\mathit{\sigma }}_n·\left({\mathit{k}}_n\times {\mathit{k}}_{\gamma }\right)$ in the ${}^{139}\mathrm{La}(\vec{n},\gamma )$ reaction has been studied by measuring $\gamma$-ray and neutron energies utilizing epithermal polarized neutrons and germanium detectors. The transverse asymmetry for single $\gamma$-ray transition was measured to be $0.60\pm 0.19$ in the $p$-wave resonance.

We study the kinematic and thermal vorticities in low-energy heavy-ion collisions by using the ultrarelativistic quantum molecular dynamics model. We explore their time evolution and spatial distribution. We find that the initial vorticities have a nonmonotonic dependence on the collision energy $\sqrt{s_{\mathrm{NN}}}$: as $\sqrt{s_{\mathrm{NN}}}$ grows the vorticities first increase steeply and then decrease with a turning point around $\sqrt{s_{\mathrm{NN}}}\approx 3–5$ GeV depending on the centrality.

Traditionally, the low-$p_{\perp }$ sector is used to infer the features of initial stages before quark-gluon plasma thermalization. On the other hand, a recently acquired wealth of high-$p_{\perp }$ experimental data paves the way to utilize the high-$p_{\perp }$ particles' energy loss in exploring the initial stages. We here study how four different commonly considered initial-stage scenarios—which have the same temperature profile after thermalization, but differ in the “temperature” profile before thermalization—affect predictions of high-$p_{\perp }$ $R_{\mathrm{AA}}$ and $v_2$ observables. Contrary to common expectations, we obtain that high-$p_{\perp }$ $v_2$ is insensitive to the initial stages of medium evolution, being unable to discriminate between different conditions. On the other hand, $R_{\mathrm{AA}}$ is sensitive to these conditions; however, within the current error bars, the sensitivity is not sufficient to distinguish between different initial stages. Moreover, we also reconsider the validity of the widely used procedure of fitting the energy loss parameters, individually for different initial-stage cases, to reproduce the experimentally observed $R_{\mathrm{AA}}$. We here find that previously reported sensitivity of $v_2$ to different initial states is mainly a consequence of the $R_{\mathrm{AA}}$ fitting procedure, which may lead to incorrect conclusions. On the other hand, if a global property, in particular the same average temperature, is imposed to tested temperature profiles, high sensitivity of high-$p_{\perp }$ $v_2$ is again obtained. We show, however, that this sensitivity would be a consequence of differences not in initial stages but rather in final stages. Consequently, the simultaneous study of high-$p_{\perp }$ $R_{\mathrm{AA}}$ and $v_2$, with consistent energy loss parametrization and stringently controlled temperature profiles, is necessary to assess sensitivity of different variables to differences in initial and final stages.

We report measurements of the photon beam asymmetry $\mathrm{\Sigma }$ for the reaction $\vec{\gamma }p\to K^{+}{\mathrm{\Sigma }}^0$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected by using a linearly polarized photon beam in the energy range of 8.2–8.8 GeV incident on a liquid hydrogen target. The beam asymmetry $\mathrm{\Sigma }$ was measured as a function of the Mandelstam variable $t$, and a single value of $\mathrm{\Sigma }$ was extracted for events produced in the $u$ channel. These are the first exclusive measurements of the photon beam asymmetry $\mathrm{\Sigma }$ for the reaction in this energy range. For the $t$ channel, the measured beam asymmetry is close to unity over the $t$ range studied, $-t=(0.1–1.4)$($\mathrm{GeV}/{c)}^2$, with an average value of $\mathrm{\Sigma }=1.00\pm 0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the $K^{*}$(892) Regge trajectory. A value of $\mathrm{\Sigma }=0.41\pm 0.09$ is obtained for the $u$ channel integrated up to $-u=2.0$ ($\mathrm{GeV}/{c)}^2$.

We develop the variational/parquet diagram approach to the structure of nuclear systems with strongly state-dependent interactions. For that purpose, we combine ideas of the general Jastrow-Feenberg variational method and the local parquet-diagram theory for bosons with state-dependent interactions [R. A. Smith and A. D. Jackson, Nucl. Phys. A 476, 448 (1988)]. The most tedious aspect of variational approaches, namely the symmetrization of an operator dependent variational wave function, is thereby avoided. We carry out calculations for neutron matter interacting via the Reid and Argonne $v_6$ models of the nucleon-nucleon interaction. While the equation of state is a rather robust quantity that comes out reasonably well even in very simplistic approaches, we show that effective interactions, which are the essential input for calculating dynamic properties, depend sensitively on the quality of the treatment of the many-body problem.

I study the flavor evolution of a dense neutrino gas by considering vacuum contributions, matter effects, and neutrino self-interactions. Assuming a system of two flavors in a uniform matter background, the time evolution of the many-body system in discretized momentum space is computed. The multiangle neutrino-neutrino interactions are treated exactly and compared to both the single-angle approximation and mean-field calculations. The monoenergetic two-neutrino beam scenario is solved analytically. I proceed to solve flavor oscillations for monoenergetic cubic lattices and quadratic lattices of two energy levels. In addition I study various configurations of 12, 16, and 20 neutrinos. I find that when all neutrinos are initially of the same flavor, all methods agree. When both flavors are present, I find collective oscillations and flavor equilibration develop in the many-body treatment but not in the mean-field method. This difference persists in dense matter with tiny mixing angle and it can be ascribed to non-negligible flavor polarization correlations being present. Entanglement entropy is significant in all such cases. The relevance for supernovae or neutron stars mergers is contingent upon the value of the normalization volume $V$ and the large $N$ dependence of the timescale associated with oscillations. In future work, I intend study this dependence using larger lattices and also include antineutrinos.

We adopt the chiral effective field theory to calculate the ${\mathrm{\Sigma }}_{c}N$ interaction to the next-to-leading order. We consider the contact interactions, one-pion-exchange contributions, two-pion-exchange diagrams, and renormalization effects of the vertices, masses, and wave functions. With the pion-mass-dependent expression, we fit the ${\mathrm{\Sigma }}_{c}N$ interaction from the HAL QCD calculation with $m_{\pi }\approx 410$ MeV and $m_{\pi }\approx 570$ MeV, and then extrapolate it to the physical pion mass. The ${}^{3}S_1(I=1/2){\mathrm{\Sigma }}_{c}N$ interaction is weakly attractive but no bound solution is found. We also propose a quark model to estimate the leading order ${\mathrm{\Sigma }}_{c}N$ contact interaction with the $NN$ interaction as input. This approach combining the quark model and the chiral effective field theory predicts a very attractive interaction in the ${}^{1}S_0(I=3/2){\mathrm{\Sigma }}_{c}N$ channel and a two-body bound state.

Decay of the $49/2^{+}$, $0.51\mu \mathrm{s}$ isomeric state in ${}^{147}\mathrm{Gd}$ was reinvestigated in the $\gamma$-coincidence catcher experiment using the ${}^{76}\mathrm{Ge}({}^{76}\mathrm{Ge},5n$) reaction and the GASP $\gamma$ detector array. A previously suggested extraordinary complexity of the decay was confirmed and established down to intensity level better than ${10}^{-3}$/decay, involving 400 transitions and 89 levels populated between the isomer and the ${}^{147}\mathrm{Gd}$ ground state. The earlier measured electron conversion coefficients (ECC) and $\gamma$ angular distributions, together with the total ECC extracted presently for low-energy transitions from the intensity balance, allowed to assign spin and parity values to all of the observed levels. Discussion of the level structure is restricted to few important cases clarified by the present investigation in the low-energy part of the decay scheme. Those involved the identification of the new $M2$ and $E2$ branches populating two new levels in the decay of the ${27/2}^{-}$ isomer and firm location of positive parity levels arising in the coupling of this isomer with the $3^{-}$ core excitation. In the upper part it was concluded that the observed complexity of the decay is initiated by fast low-energy $M1$ transitions populating a group of similar structure levels located within 7.8–8.0 MeV excitation energy range. Some statistical features of the observed complex isomeric decay are reviewed and discussed.

Energy dissipation and cluster production in central nuclear collisions in the Fermi energy range have been investigated using the large INDRA database. A study of the in-medium nucleon-nucleon cross section, ${\sigma }_{NN}^{*}$, has been performed by comparing the results of a model with the measured isotropy ratio of the kinetic energy distributions of the detected protons. This analysis has been done for a large variety of systems at various incident energies from 20 to 100 MeV/nucleon and confirms nicely previous results with enhanced statistics in a full Monte Carlo treatment. Most importantly, it is found that ${\sigma }_{NN}^{*}$ is drastically reduced as compared to the vacuum values, due partly to Pauli blocking but also to in-medium effects for which mean values and uncertainties are given. Concerning the cluster production, a coalescence model has been developed to study the parallel and perpendicular velocity distributions of the light clusters ($A\le 4$). For $A_C=3$ (${}^3\mathrm{H}, {}^3\mathrm{He}$), it is found that the mean internal kinetic energy of the nucleons in the cluster is reduced as compared to the vacuum value. These two results shows that any comparison between experimental and theoretical predictions in heavy-ions induced reactions around and above the Fermi energy must take into account these in-medium effects.