We calculate the rate of production of hypothetical light vector bosons (LVBs) from nucleon-nucleon bremsstrahlung reactions in hot and dense matter. We use the soft-radiation approximation and express the rates directly in terms of the measured nucleon-nucleon elastic differential cross sections. These results are combined with the observation of neutrinos from supernova SN1987a to deduce constraints on the couplings of vector bosons with masses $\lesssim 200$ MeV to either electric charge (dark photons) or to baryon number. We establish for the first time strong constraints on LVB that couple only to baryon number and revise earlier constraints on the dark photon. For the latter, we find that the excluded region of parameter space is diminished by about a factor of 10.

Particle-$\gamma$ coincidence data have been analyzed to obtain the nuclear level density and the $\gamma$-strength function of ${}^{64}\mathrm{Ni}$ by means of the Oslo method. The level density found in this work is in very good agreement with known energy levels at low excitation energies as well as with data deduced from particle-evaporation measurements at excitation energies above $E_x\approx 5.5$ MeV. The experimental $\gamma$-strength function presents an enhancement at $\gamma$ energies below $E_{\gamma }\approx 3$ MeV and possibly a resonancelike structure centered at $E_{\gamma }\approx 9.2$ MeV. The obtained nuclear level density and $\gamma$-strength function have been used to estimate the $(n,\gamma )$ cross section for the $s$-process branch-point nucleus ${}^{63}\mathrm{Ni}$, of particular interest for astrophysical calculations of elemental abundances.

Recent investigations of heavy-ion reactions at low incident energies have indicated the presence of precompound emission component in considerable strength. In most cases the strength of the precompound component is estimated from the difference in forward-backward distributions of emitted light fast particles and also from the analysis of the measured excitation functions. This paper reports a new method of deciphering the relative contributions of compound and precompound components associated with fusion of ${}^{16}\mathrm{O}$ with ${}^{159}\mathrm{Tb},{}^{169}\mathrm{Tm}$, and ${}^{181}\mathrm{Ta}$ targets by measuring the recoil ranges of heavy residues in an absorbing medium along with the online measurement of the spin distributions in reaction residues produced in the fusion ${}^{16}\mathrm{O}$ beam with ${}^{159}\mathrm{Tb}$ and ${}^{169}\mathrm{Tm}$ targets. Analysis of recoil range and spin distributions of the residues shows two distinct linear momentum-transfer components corresponding to precompound and compound nucleus processes. The input angular momentum associated with precompound products is found to be relatively lower than that associated with compound nucleus process. The precompound components obtained from the present analysis are consistent with those obtained from the analysis of excitation functions.

We estimate the shear and the bulk viscous coefficients for a hot hadronic gas mixture made of pions and nucleons. The viscosities are evaluated in the relativistic kinetic theory approach by solving the transport equation in the relaxation time approximation for binary collisions $(\pi \pi ,\pi N$, and $NN)$. Instead of the vacuum cross sections usually used in the literature we employ in-medium scattering amplitudes in the estimation of the relaxation times. The modified cross sections for $\pi \pi$ and $\pi N$ scattering are obtained using one-loop modified thermal propagators for $\rho ,\sigma$, and $\mathrm{\Delta }$ in the scattering amplitudes which are calculated using effective interactions. The resulting suppression of the cross sections at finite temperature and baryon density is observed to significantly affect the $T$ and ${\mu }_N$ dependence of the viscosities of the system.

A recent paper [A. K. Rhine Kumar and P. Arumugam, Phys. Rev. C 92, 044314 (2015)] presented calculations of the giant dipole resonance width and $\gamma$-ray absorption cross sections for ${}^{152}\mathrm{Gd}$ at various temperatures and angular momenta and compared these with the experimental data. In the comparison of the cross sections, the authors used the linearized representations of the experimental spectra which actually represent the absorption cross sections divided by the $\gamma$-ray energy. In this Comment we make the comparison with the appropriate absorption cross sections derived from the data. The comparison shows a reasonable agreement if the higher value of the dipole-dipole interaction parameter, mentioned in the paper, is used in the calculation.

We reply to the Comment by Chakrabarty and Datar, wherein they have provided a better representation of giant dipole resonance (GDR) cross sections in ${}^{152}\mathrm{Gd}$, along with a revised data analysis. They have demonstrated that the results presented in our original paper calculated with higher dipole-dipole interaction strength ($\eta$) are in better agreement with the data. Consequently, both the cross sections and width could be explained with the same $\eta$, unlike in Sec. III of our original paper. However, the conclusions drawn in our original paper remain intact.

Background: Fragment yields exhibit a strong odd-even staggering (OES). This OES has been experimentally observed in different fragmentation reactions with different projectile-target combinations. However, the experimental data are still scarce for fragments close to drip lines and the origin of this OES is not well understood.

Purpose: More experimental data are needed to explore the origin of this OES in fragment yields and to validate fragmentation reaction models, especially for nuclei close to the drip lines. To study the pronounced OES near the proton drip line, we measured the yields of $T_z=-1$ and $T_z=-3/2$ nuclei over a wide range of mass number.

Methods: The combination of a fragment separator and a storage ring at the Heavy Ion Research Facility in Lanzhou has been used to measure the yields of $T_z=-1$ and $T_z=-3/2$ fragments, produced by ${}^{58}\mathrm{Ni}$ projectiles impinging on a beryllium target at an energy of about 463 MeV/nucleon.

Results: A very strong OES is observed in the measured yields of both $T_z=-1$ and $T_z=-3/2$ fragments. Our experimental data demonstrate that the shell structure has a significant impact on the magnitude of this OES. A comparison of different fragmentation reaction data indicates that this OES is almost independent of the projectile-target combinations and the fragmentation energy between 140 and 650 MeV/nucleon.

Conclusions: Our study reveals that the OES of fragment yields originates mainly from the OES of particle-emission threshold energies, which is very close to the OES of fragment yields when the Coulomb barrier is considered in particle-emission threshold energies.

After the demonstration of the feasibility of hypernuclear spectroscopy with heavy-ion beams, the HypHI Collaboration will next focus on the study of proton- and neutron-rich hypernuclei. The use of a fragment separator for the production and separation of rare-isotope beams is a crucial aspect to producing hypernuclei far from the stability line. Precise spectroscopy of exotic hypernuclei is planned to be carried out at the GSI and later at the FAIR facility with the FRS and Super-FRS fragment separators. A systematic study and an optimization analysis were performed to determine optimal experimental conditions for producing hypernuclei with high isospin. The optimal conditions are obtained based on theoretical models for the heavy-ion induced reaction and hypernuclei production. Experimental efficiencies for the production of exotic secondary beams were also taken into account via Monte Carlo simulations of the fragment separator. The developed methodology is presented to deduce the expected yields of ${}_{\mathrm{\Lambda }}{}^8\mathrm{Be}$ and subsequently other proton-rich and neutron-rich hypernuclei.

In the framework of the quark combination, we derive the yield formulas and study the yield ratios of hidden-charm pentaquark states in ultrarelativistic heavy ion collisions. We propose some interesting yield ratios which clearly exhibit the production relationships between different hidden-charm pentaquark states. We show how to employ a specific quark combination model to evaluate the yields and predict the transverse momentum ($p_T$) spectra of exotic $P_c^{+}\left(4380\right), P_c^{+}\left(4450\right)$, and their partners as pentaquark states on the basis of reproducing the yields and $p_T$ spectra of normal identified hadrons and execute the calculations in central Pb + Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV as an example.

We have calculated microscopically bulk viscosity of hadronic matter, where equilibrium thermodynamics for all hadrons in medium are described by the hadron resonance gas (HRG) model. Considering pions and nucleons as abundant medium constituents, we have calculated their thermal widths, which inversely control the strength of bulk viscosities for respective components and represent their in-medium scattering probabilities with other mesonic and baryonic resonances, present in the medium. Our calculations show that bulk viscosity increases with both temperature and baryon chemical potential, whereas viscosity to entropy density ratio decreases with temperature and with baryon chemical potential, the ratio increases first and then decreases. The decreasing nature of the ratio with temperature has been observed in most of the earlier investigations with few exceptions. We find that the temperature dependence of bulk viscosity crucially depends on the structure of the relaxation time. Along the chemical freeze-out line in nucleus-nucleus collisions with increasing collision energy, bulk viscosity as well as the bulk viscosity to entropy density ratio decreases, which also agrees with earlier references. Our results indicate the picture of a strongly coupled hadronic medium.

Production of a neutrino source through a proton-induced reaction is studied by using the particle transport code geant4. Unstable isotopes such as ${}^{27}\mathrm{Si}$ can be produced when the ${}^{27}\mathrm{Al}$ target is bombarded by 15-MeV energetic proton beams. Through the $\beta$-decay process of the unstable isotope, a new electron-neutrino source in the 0–5.0 MeV energy range is obtained. Proton-induced reactions are simulated with JENDL-4.0 High Energy File (JENDL-4.0/HE). For radioactive decay processes, we use the G4 radioactive decay model based on the Evaluated Nuclear Structure Data File (ENSDF). We suggest detailed target systems required for future solar neutrino experiments, in particular for the vacuum-matter transition region. As for a detection system of the new neutrino source, we evaluate reaction or event rates for available radiochemical detectors and Low Energy Neutrino Astronomy (LENA)–type scintillator detector and discuss effects due to possible sterile neutrinos as an application.

The spin magnetic dipole transitions and the neutron-proton spin-spin correlations in $sd\text{−}\mathrm{shell}$ even-even nuclei with $N=Z$ are investigated using shell-model wave functions. The isoscalar spin-triplet pairing correlation provides a substantial quenching effect on the spin magnetic dipole transitions, especially the isovector (IV) ones. Consequently, an enhanced isoscalar spin-triplet pairing interaction influences the proton-neutron spin-spin correlation deduced from the difference between the isoscalar (IS) and the IV sum rule strengths. The effect of the $\mathrm{\Delta }$ (${\mathrm{\Delta }}_{33}$ resonance)–hole coupling is examined in the IV spin transition and the spin-spin correlations of the ground states.

In Poincaré-covariant continuum treatments of the three valence-quark bound-state problem, the force behind dynamical chiral symmetry breaking also generates nonpointlike interacting diquark correlations in the nucleon and its resonances. We detail the impact of these correlations on the electromagnetically induced nucleon-$\mathrm{\Delta }$ and nucleon-Roper transitions, providing a flavor separation of the latter and associated predictions that can be tested at modern facilities.

Background: Recent work found that core excitations can be important in extracting structure information from $(d,p)$ reactions.

Purpose: Our objective is to systematically explore the role of core excitation in $(d,p)$ reactions and to understand the origin of the dynamical effects.

Method: Based on the particle-rotor model of $n+{}^{10}\mathrm{Be}$, we generate a number of models with a range of separation energies ($S_n=0.1\text{–}5.0$ MeV), while maintaining a significant core excited component. We then apply the latest extension of the momentum-space-based Faddeev method, including dynamical core excitation in the reaction mechanism to all orders, to the ${}^{10}\mathrm{Be}(d,p){}^{11}\mathrm{Be}$-like reactions, and study the excitation effects for beam energies $E_d=15\text{–}90$ MeV.

Results: We study the resulting angular distributions and the differences between the spectroscopic factor that would be extracted from the cross sections, when including dynamical core excitation in the reaction, and that of the original structure model. We also explore how different partial waves affect the final cross section.

Conclusions: Our results show a strong beam-energy dependence of the extracted spectroscopic factors that become smaller for intermediate beam energies. This dependence increases for loosely bound systems.

A detailed study of the charged-current supernova electron neutrino and electron antineutrino scattering off the stable even-mass lead isotopes $A=204$, 206, and 208 is reported in this work. The proton-neutron quasiparticle random-phase approximation (pnQRPA) is adopted to construct the nuclear final and initial states. Three different Skyrme interactions are tested for their isospin and spin-isospin properties and then applied to produce (anti)neutrino-nucleus scattering cross sections for (anti)neutrino energies below 80 MeV. Realistic estimates of the nuclear responses to supernova (anti)neutrinos are computed by folding the computed cross sections with a two-parameter Fermi-Dirac distribution of the electron (anti)neutrino energies. The computed cross sections are compared with earlier calculations and the analyses are extended to take into account the effects coming from the neutrino oscillations.

We study the effect of the chiral symmetry restoration (CSR) on heavy-ion collisions observables in the energy range $\sqrt{s_{NN}}=3$–20 GeV within the parton-hadron-string dynamics (PHSD) transport approach. The PHSD includes the deconfinement phase transition as well as essential aspects of CSR in the dense and hot hadronic medium, which are incorporated in the Schwinger mechanism for the hadronic particle production. We adopt different parametrizations of the nuclear equation of state from the nonlinear $\sigma \text{−}\omega$ model, which enter in the computation of the quark scalar density for the CSR mechanism, in order to estimate the uncertainty in our calculations. For the pion-nucleon $\mathrm{\Sigma }$ term we adopt ${\mathrm{\Sigma }}_{\pi }\approx$ 45 MeV, which corresponds to some world average. Our systematic studies show that chiral symmetry restoration plays a crucial role in the description of heavy-ion collisions at $\sqrt{s_{NN}}=3$–20 GeV, realizing an increase of the hadronic particle production in the strangeness sector with respect to the nonstrange one. We identify particle abundances and rapidity spectra to be suitable probes in order to extract information about CSR, while transverse mass spectra are less sensitive. Our results provide a microscopic explanation for the so-called horn structure in the excitation function of the $K^{+}/{\pi }^{+}$ ratio: The CSR in the hadronic phase produces the steep increase of this particle ratio up to $\sqrt{s_{NN}}\approx 7$ GeV, while the drop at higher energies is associated to the appearance of a deconfined partonic medium. Furthermore, the appearance and disappearance of the horn-structure are investigated as functions of the system size and collision centrality. We close this work by an analysis of strangeness production in the $\left(T,{\mu }_B\right)$ plane (as extracted from the PHSD for central Au+Au collisions) and discuss the possibilities to identify a possible critical point in the phase diagram.

High-spin states in the dipole structure of ${}^{141}\mathrm{Sm}$ have been investigated using the fusion-evaporation reaction ${}^{116}\mathrm{Cd}\left({}^{31}\mathrm{P},p5n\right)$ at beam energy 148 MeV using the Indian National Gamma Array. The spin parity of the observed dipole bands I and II has been established firmly from the spectroscopic measurements. Level lifetimes of several levels in the dipole bands I and II have been measured using the Doppler shift attenuation method. The smooth decrease of the $B\left(M1\right)$ values with spin exhibits a clear signature of the magnetic rotational character of the dipole band I. Comparisons between the experimental characteristics and the semiclassical shears mechanism with the principal axis cranking model calculation show that the dipole band I may be interpreted as a magnetic rotational band.

The existence of the $0_3^{+}$ and $0_4^{+}$ states around 10 MeV excitation energy in ${}^{12}\mathrm{C}$ is confirmed by a fully microscopic $3\alpha$ cluster model. Firstly, a generator coordinate method (GCM) calculation is performed by superposing optimized $2\alpha +\alpha$ Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave functions with the radius-constraint method. The obtained two excited $0^{+}$ states above the Hoyle state are consistent with the recently observed states by experiment. Secondly, a variational calculation using the single $2\alpha +\alpha$ THSR wave function orthogonalized to the ground and Hoyle states is made and it also supports the existence of the $0_3^{+}$ state obtained by the GCM calculation. The analysis of the obtained $0_3^{+}$ state is made by studying its $2\alpha -\alpha$ reduced width amplitude, its $2\alpha$ correlation function, and the large monopole matrix element between this state and the Hoyle state, which shows that this $0_3^{+}$ state is a breathing-like excited state of the Hoyle state. This character of the $0_3^{+}$ state is very different from the $0_4^{+}$ state which seems to have a bent-arm $3\alpha$ structure.

Excited states in the transitional doubly odd ${}^{102}\mathrm{Ag}$ nucleus were populated in the ${}^{75}\mathrm{As}({}^{31}\mathrm{P},p3n)$ fusion-evaporation reaction using the 125 MeV incident ${}^{31}\mathrm{P}$ beam. The subsequent deexcitations were investigated through in-beam $\gamma$-ray spectroscopic techniques using the Indian National Gamma Array spectrometer equipped with 21 clover Ge detectors. The level scheme in ${}^{102}\mathrm{Ag}$ has been established up to excitation energy $\sim 6.5$ MeV and angular momentum $19\hslash$. The earlier reported level scheme is considerably extended and modified to result in a pair of nearly degenerate negative-parity dipole bands. Lifetime measurements for the states of these two dipole bands have been performed by using the Doppler-shift attenuation method. The two nearly degenerate bands exhibit different features with regard to kinetic moment of inertia, and the reduced transition probabilities $\mathrm{B}\left(M1\right)$ and $\mathrm{B}\left(E2\right)$, which do not favor these to be chiral partners. These bands are discussed in the framework of the hybrid version of tilted-axis cranking (tac) model calculations and assigned the $\pi g_{9/2}\otimes \nu h_{11/2}$ and $\pi g_{9/2}\otimes \nu h_{11/2}{(d_{5/2}/g_{7/2})}^2$ configurations. The tac model calculations are extended to the nearly degenerate bands observed in the heavier doubly odd ${}^{104–108}\mathrm{Ag}$ isotopes.

The density-dependent relativistic Hartree-Fock (DDRHF) theory is extended to include $\mathrm{\Delta }$ isobars for the study of dense nuclear matter and neutron stars. To this end, we solve the Rarita-Schwinger equation for spin-3/2 particle. Both the direct and exchange terms of the $\mathrm{\Delta }$ isobars' self-energies are evaluated in detail. In comparison with the relativistic mean field theory (Hartree approximation), a weaker parameter dependence is found for DDRHF. An early appearance of $\mathrm{\Delta }$ isobars is recognized at ${\rho }_B\sim 0.28{\mathrm{fm}}^{-3}$, comparable with that of hyperons. Also, we find that the $\mathrm{\Delta }$ isobars' softening of the equation of state is mainly due to the reduced Fock contributions from the coupling of the isoscalar mesons, while the pion contributions are negligibly small. We finally conclude that with typical parameter sets, neutron stars with $\mathrm{\Delta }$ isobars in their interiors could be as heavy as the two massive pulsars whose masses are precisely measured, with slightly smaller radii than normal neutron stars.