The mass, isotope, and isobar distributions of limiting temperatures for finite nuclei are investigated by using a thermodynamics approach together with the Skyrme energy density functional. The relationship between the width of the isotope (isobar) distribution of limiting temperatures and the stiffness of the density dependence of the symmetry energy clearly is observed. The nuclear symmetry energy with smaller slope parameter $L_{\mathrm{sym}}$ causes a wider isotope (isobar) distribution of limiting temperatures. The widths of the isotope (isobar) distributions of limiting temperatures could be useful observables for exploring the information of the density dependence of the nuclear symmetry energy at finite temperatures.

Background: Fluorine is a key element for nucleosynthetic studies since it is extremely sensitive to the physical conditions within stars. The astrophysical site to produce fluorine is suggested to be asymptotic giant branch stars. In these stars the ${}^{15}\mathrm{N}$($n,\gamma$)${}^{16}\mathrm{N}$ reaction could affect the abundance of fluorine by competing with ${}^{15}\mathrm{N}$($\alpha ,\gamma$)${}^{19}\mathrm{F}$.

Purpose: The ${}^{15}\mathrm{N}$($n,\gamma$)${}^{16}\mathrm{N}$ reaction rate depends directly on the neutron spectroscopic factors of the low-lying states in ${}^{16}\mathrm{N}$. Shell model calculations and two previous measurements of the ($d,p$) reaction yielded the spectroscopic factors with a discrepancy by a factor of $\sim$2. The present work aims to explore these neutron spectroscopic factors through an independent transfer reaction and to determine the stellar rate of the ${}^{15}\mathrm{N}$($n,\gamma$)${}^{16}\mathrm{N}$ reaction.

Methods: The angular distributions of the ${}^{15}\mathrm{N}$(${}^7\mathrm{Li}$,${}^6\mathrm{Li}$)${}^{16}\mathrm{N}$ reaction populating the ground state and the first three excited states in ${}^{16}\mathrm{N}$ are measured using a Q3D magnetic spectrograph and are used to derive the spectroscopic factors of these states based on distorted wave Born approximation analysis.

Results: The spectroscopic factors of these four states are extracted to be 0.96 $\pm$ 0.09, 0.69 $\pm$ 0.09, 0.84 $\pm$ 0.08, and 0.65 $\pm$ 0.08, respectively. Based on the new spectroscopic factors we derive the ${}^{15}\mathrm{N}$($n,\gamma$)${}^{16}\mathrm{N}$ reaction rate.

Conclusions: The accuracy and precision of the spectroscopic factors are enhanced due to the first application of high-precision magnetic spectrograph for resolving the closely spaced ${}^{16}\mathrm{N}$ levels which cannot be achieved in most recent measurements. The present result demonstrates that two levels corresponding to neutron transfers to the 2$s_{1/2}$ orbit in ${}^{16}\mathrm{N}$ are not good single-particle levels although ${}^{15}\mathrm{N}$ is a closed neutron-shell nucleus. This finding is contrary to the shell model expectation. The present work also provides an independent examination to shed some light on the existing discrepancies in the spectroscopic factors and the ${}^{15}\mathrm{N}$($n,\gamma$)${}^{16}\mathrm{N}$ rate.

Background: The equation of state (EoS) of nucleonic matter is central for the understanding of bulk nuclear properties, the physics of neutron star crusts, and the energy release in supernova explosions. Because nuclear matter exhibits a finely tuned saturation point, its EoS also constrains nuclear interactions.

Purpose: This work presents coupled-cluster calculations of infinite nucleonic matter using modern interactions from chiral effective field theory (EFT). It assesses the role of correlations beyond particle-particle and hole-hole ladders, and the role of three-nucleon forces (3NFs) in nuclear matter calculations with chiral interactions.

Methods: This work employs the optimized nucleon-nucleon ($NN$) potential NNLO${}_{\mathrm{opt}}$ at next-to-next-to leading order, and presents coupled-cluster computations of the EoS for symmetric nuclear matter and neutron matter. The coupled-cluster method employs up to selected triples clusters and the single-particle space consists of a momentum-space lattice. We compare our results with benchmark calculations and control finite-size effects and shell oscillations via twist-averaged boundary conditions.

Results: We provide several benchmarks to validate the formalism and show that our results exhibit a good convergence toward the thermodynamic limit. Our calculations agree well with recent coupled-cluster results based on a partial wave expansion and particle-particle and hole-hole ladders. For neutron matter at low densities, and for simple potential models, our calculations agree with results from quantum Monte Carlo computations. While neutron matter with interactions from chiral EFT is perturbative, symmetric nuclear matter requires nonperturbative approaches. Correlations beyond the standard particle-particle ladder approximation yield non-negligible contributions. The saturation point of symmetric nuclear matter is sensitive to the employed 3NFs and the employed regularization scheme. 3NFs with nonlocal cutoffs exhibit a considerably improved convergence than their local cousins. We are unable to find values for the parameters of the short-range part of the local 3NF that simultaneously yield acceptable values for the saturation point in symmetric nuclear matter and the binding energies of light nuclei.

Conclusions: Coupled-cluster calculations with nuclear interactions from chiral EFT yield nonperturbative results for the EoS of nucleonic matter. Finite-size effects and effects of truncations can be controlled. For the optimization of chiral forces, it might be useful to include the saturation point of symmetric nuclear matter.

The magnetic moments of the first excited $2^{+}$ state in even-even nuclei ${}^{102–130}$Sn and the low-lying yrast states in odd-mass nuclei ${}^{101–109,123–131}$Sn are calculated within the framework of the nucleon-pair approximation (NPA) of the shell model, by using the standard multipole-multipole interaction. Our calculations agree reasonably well with available experimental data. The $g\left(2_1^{+}\right)$ values, as well as the contributions from their spin and orbital angular momentum components, are evaluated in terms of the small NPA subspace spanned by $S$ and $D$ nucleon pairs. The magnetic moment is suggested to be a sensitive probe of the nuclear wave function in this region.

Background: Pairing correlations play a critical role in determining numerous properties of open shell nuclei. Traditionally, they are included in a mean field description of atomic nuclei through the approximate Bardeen-Cooper-Schrieffer or Hartree-Fock-Bogoliubov formalism.

Purpose: We propose a new hybrid “relativistic mean field plus pairing” approach in which pairing is treated exactly so the number of particles is conserved. To verify the reliability of the formalism, we apply it to the study of both ground-state properties and isoscalar monopole excitations of the tin isotopes.

Methods: Accurately calibrated relativistic mean field models supplemented by an exact treatment of pairing correlations are used to compute ground-state observables along the isotopic chain in tin. In turn, ground-state densities are used as input to the calculation of giant monopole resonances through a constrained-relativistic approach.

Results: We compute a variety of ground-state observables sensitive to pairing correlations as well as the evolution of giant monopole energies along the isotopic chain in tin. Whereas ground-state properties are consistent with experiment, we find that pairing correlations have a minor effect on the giant monopole energies.

Conclusions: A new mean field plus pairing approach is introduced to compute properties of open shell nuclei. The formalism provides an efficient and powerful alternative to the computation of both ground-state properties and monopole energies of open shell nuclei. We find ground-state properties to be well reproduced in this approach. However, as many have concluded before us, we find that pairing correlations are unlikely to provide an answer to the question, “Why is tin so soft?”

The wobbling motion of a triaxial rotor coupled to a high-$j$ quasiparticle is treated semiclassically. Longitudinal and transverse coupling regimes can be distinguished depending on, respectively, whether the quasiparticle angular momentum is oriented parallel or perpendicular to the rotor axis with the largest moment of inertia. Simple analytical expressions for the wobbling frequency and the electromagnetic $E2$ and $M1$ transition probabilities are derived assuming rigid alignment of the quasiparticle with one of the rotor axes and harmonic oscillations (HFA). Transverse wobbling is characterized by a decrease of the wobbling frequency with increasing angular momentum. Two examples for transverse wobbling, ${}^{163}$Lu and ${}^{135}$Pr, are studied in the framework of the full triaxial particle-rotor model and the HFA. The signature of transverse wobbling, decreasing wobbling frequency, and enhanced $E2$ interband transitions, is found in agreement with experiment.

This work is a study of the influence of shell effects on the formation of binary fragments in damped collision. We have investigated binary reaction channels of the composite system with $Z=108$ produced in the reaction ${}^{88}\mathrm{Sr}$${+}^{176}$Yb at an energy slightly above the Bass barrier ($E_{\text{c.m.}}/E_{\text{Bass}}=1.03$). Reaction products were detected by using the two-arm time-of-flight spectrometer CORSET at the K130 cyclotron of the Department of Physics, University of Jyväskylä. The mass-energy distribution of primary binary fragments has been measured. For targetlike fragments heavier than 190 u, which correspond to a mass transfer as large as twenty nucleons or more, an enhancement of the yields is observed. This striking result can be ascribed to the proton shells at $Z=28$ and 82 and implies the persistence of the shell effects in the formation of reaction fragments even for large mass transfers.

In the light of the very massive neutron stars recently detected and the new possible constraints for the radii of these compact objects, we revisit some equations of state obtained for hadronic and hybrid stars under the influence of strong magnetic fields. We present our results for hadronic matter, taking into account the effects of the inclusion of anomalous magnetic moment. Additionally, the case of hybrid stars under the influence of strong magnetic fields is considered. We study the structure of hybrid stars based on the Maxwell condition (without a mixed phase), where the hadron phase is described by the nonlinear Walecka model (NLW) and the quark phase by the Nambu-Jona-Lasinio model (NJL). The mass-radius relations for all cases are calculated and discussed. We show that both hadronic and hybrid stars can bear very high masses and radii, compatible with the recently observed high-mass neutron stars.

In even-mass Te isotopes with $114\le A\le 122$ the experimentally observed yrast $I^{\pi }={16}^{+}$ states have been interpreted as favored noncollective oblate states based on the fully aligned $\pi {\left[{\left(g_{7/2}\right)}^2\right]}_{6^{+}}\otimes \nu {\left[{\left(h_{11/2}\right)}^2\right]}_{{10}^{+}}$ configuration. For ${}^{124}\mathrm{Te}$ the highest-spin positive-parity state known has $I^{\pi }={10}^{+}$. An extension of the yrast cascade of ${}^{124}\mathrm{Te}$ is needed to spin at least 16${}^{+}$ in order to answer the question of whether this noncollective oblate state lies along the yrast line in this isotope. The level structure of ${}^{124}\mathrm{Te}$ has been studied via prompt $\gamma$-ray spectroscopy. ${}^{124}\mathrm{Te}$ was produced in the fission of the compound systems formed in two heavy-ion-induced reactions, ${}^{24}\mathrm{Mg}$ (134.5 MeV) + ${}^{173}\mathrm{Yb}$ and ${}^{23}\mathrm{Na}$ (129 MeV) + ${}^{176}\mathrm{Yb}$. $\gamma$-ray spectroscopy was accomplished with the Gammasphere array. The yrast cascade of ${}^{124}\mathrm{Te}$ was extended up to 5481-keV excitation energy with a tentative 16${}^{+}$ assignment for the highest observed state. This state does not exhibit the characteristics of the favored noncollective oblate states with $I^{\pi }={16}^{+}$ observed in the lighter doubly even Te isotopes, indicating that such a state is probably no longer yrast in ${}^{124}\mathrm{Te}$.

A very simple model is applied to the first four negative-parity states of ${}^{12}\mathrm{Be}$. Energies of the corresponding four states in ${}^{14}\mathrm{C}$ are used to validate the model and to determine the doublet splitting parameters. Predictions for ${}^{12}\mathrm{Be}$ are in remarkable agreement with excitation energies of the known 1${}^{-}$ at 2.70 MeV and the suspected (3${}^{-}$) at 4.56 MeV. Predicted excitation energies of 0${}^{-}$ and 2${}^{-}$ are 3.59 and 5.12 MeV, respectively.

Rotational bands of the deformed proton emitter ${}^{141}$Ho are studied by using the projected shell model. The known experimental states are well reproduced. Strongly suppressed $\gamma$ transition from the low-lying $I^{\pi }=3/2^{+}$ state makes this state isomeric, in favor of the suggestion that a proton emission could become the favorite decay mode for this state. Variations in the dynamical moment of inertia are found due to band crossings and a detailed structure in the crossing region is suggested. The role of hexadecapole deformation for this nucleus is emphasized.

The ${}_{\Lambda \Lambda }^4$H bound state and the $S$-wave hypertriton(${}_{\Lambda }^3$H)-$\Lambda$ scattering in spin singlet and triplet channels below the hypertriton breakup momentum scale are studied in halo/cluster effective field theory at leading order by treating the ${}_{\Lambda \Lambda }^4$H system as a three-cluster ($\Lambda$-$\Lambda$-deuteron) system. In the spin singlet channel, the amplitude is insensitive to the cutoff parameter ${\Lambda }_c$ introduced in the integral equation, and we find that there is no bound state. In this case, the scattering length of the hypertriton-$\Lambda$ scattering is found to be $a_0^{}=16.0\pm 3.0$ fm. In the spin triplet channel, however, the amplitude obtained by the coupled integral equations is sensitive to ${\Lambda }_c$, and we introduce the three-body contact interaction $g_1^{}\left({\Lambda }_c\right)$. After phenomenologically fixing $g_1^{}\left({\Lambda }_c\right)$, we find that the correlation between the two-$\Lambda$ separation energy $B_{\Lambda \Lambda }$ from the ${}_{\Lambda \Lambda }^4$H bound state and the scattering length $a_{\Lambda \Lambda }^{}$ of the $S$-wave $\Lambda$-$\Lambda$ scattering is significantly sensitive to the value of ${\Lambda }_c$.

Heavy ion cross sections totaling several hundred barns have been calculated previously for the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). These total cross sections are more than an order of magnitude larger than the geometric ion-ion cross sections primarily due to bound-free pair production (BFPP) and electromagnetic dissociation (EMD). Apart from a general interest in verifying the calculations experimentally, an accurate prediction of the losses created in the heavy ion collisions is of practical interest for the LHC, where some collision products are lost in cryogenically cooled magnets and have the potential to quench these magnets. In the 2012 RHIC run uranium ions collided with each other at $\sqrt{s_{NN}}=192.8$ GeV with nearly all beam losses due to collisions. This allows for the measurement of the total cross section, which agrees with the calculated cross section within the experimental error.

The ${}^{18}$Ne($\alpha$,$p$)${}^{21}$Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the $rp$ process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus ${}^{22}$Mg have been investigated by measuring the resonant elastic scattering of ${}^{21}$Na + $p$. An 89-MeV ${}^{21}$Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm${}^2$ thick polyethylene (CH${}_2$)${}_n$ target. The ${}^{21}$Na beam intensity was about $2\times 10$${}^5$ pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of ${\theta }_{\mathrm{c}.\mathrm{m}.}\approx 175.2$${}^{\circ }$, 152.2${}^{\circ }$, and 150.5${}^{\circ }$ by three sets of $\Delta E$-$E$ telescopes, respectively. The excitation function was obtained with the thick-target method over energies $E_x{(}^{22}\text{Mg})=5.5$–9.2 MeV. In total, 23 states above the proton-threshold in ${}^{22}$Mg were observed, and their resonant parameters were determined via an $R$-matrix analysis of the excitation functions. We have made several new $J^{\pi }$ assignments and confirmed some tentative assignments made in previous work. The thermonuclear ${}^{18}$Ne($\alpha$,$p$)${}^{21}$Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the ${}^{18}$Ne($\alpha$,$p$)${}^{21}$Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, and onset temperature of this breakout reaction in these astrophysical phenomena.

We analyze total reaction cross sections, ${\sigma }_R$, to explore their sensitivity to the neutron-skin thickness of nuclei. We cover 91 nuclei of O, Ne, Mg, Si, S, Ca, and Ni isotopes. The cross sections are calculated in the Glauber theory using the density distributions obtained with the Skyrme-Hartree-Fock method in three-dimensional coordinate space. Defining a reaction radius, $a_R=\sqrt{{\sigma }_R/\pi }$, to characterize the nuclear size and target (proton or ${}^{12}$C) dependence, we find an empirical formula for expressing $a_R$ with the point matter radius and the skin thickness, and assess two practical ways of determining the skin thickness from proton-nucleus ${\sigma }_R$ values measured at different energies or from ${\sigma }_R$ values measured for different targets.

We examine how the universality of two-nucleon interactions evolved using similarity renormalization group (SRG) transformations correlates with $T$-matrix equivalence, with the ultimate goal of gaining insight into universality for three-nucleon forces. With sufficient running of the SRG flow equations, the low-energy matrix elements of different realistic potentials evolve to a universal form. Because these potentials are fit to low-energy data, they are (approximately) phase equivalent only up to a certain energy, and we find universality in evolved potentials up to the corresponding momentum. More generally we find universality in local energy regions, reflecting a local decoupling by the SRG. The further requirements for universality in evolved potential matrix elements are explored using two simple alternative potentials. We see evidence that in addition to predicting the same observables, common long-range potentials (i.e., explicit pion physics) is required for universality in the potential matrix elements after SRG flow. In agreement with observations made previously for $V_{\mathrm{low}k}$ evolution, regions of universal potential matrix elements are restricted to where half-on-shell $T$-matrix equivalence holds.

We investigate how the possible existence of hadronic bound states above the deconfinement transition temperature $T_c$ affects heavy-quark observables, such as the nuclear modification factor, the elliptic flow, and azimuthal correlations. Lattice QCD calculations suggest that above $T_c$ the effective degrees of freedom might not be exclusively partonic but that a certain fraction of hadronic degrees of freedom might already form at higher temperatures. This is an interesting question by itself but also has a strong influence on other probes of the strongly interacting matter produced in ultrarelativistic heavy-ion collisions. A substantial fraction of hadronic bound states above $T_c$ reduces on average the interaction of the heavy quarks with colored constituents of the medium. We find that all studied observables are highly sensitive to the active degrees of freedom in the quark-gluon plasma.

The isotopes ${}^{122,124,126}\mathrm{Cd}$ were studied in a “safe” Coulomb-excitation experiment at the radioactive ion-beam facility REX-ISOLDE at CERN. The reduced transition probabilities $B(E2;0_{\mathrm{g}.\mathrm{s}.}^{+}\to 2_1^{+}$) and limits for the quadrupole moments of the first 2${}^{+}$ excited states in the three isotopes were determined. The onset of collectivity in the vicinity of the $Z=50$ and $N=82$ shell closures is discussed by comparison with shell model and beyond mean-field calculations.

Background: An accurate assessment of the hyperon-nucleon interaction is of great interest in view of recent observations of very massive neutron stars. The challenge is to build a realistic interaction that can be used over a wide range of masses and in infinite matter starting from the available experimental data on the binding energy of light hypernuclei. To this end, accurate calculations of the hyperon binding energy in a hypernucleus are necessary.

Purpose: We present a quantum Monte Carlo study of $\Lambda$ and $\Lambda \Lambda$ hypernuclei up to $A=91$. We investigate the contribution of two- and three-body $\Lambda$-nucleon forces to the $\Lambda$ binding energy.

Method: Ground state energies are computed solving the Schrödinger equation for nonrelativistic baryons by means of the auxiliary field diffusion Monte Carlo algorithm extended to the hypernuclear sector.

Results: We show that a simple adjustment of the parameters of the $\Lambda NN$ three-body force yields a very good agreement with available experimental data over a wide range of hypernuclear masses. In some cases no experiments have been performed yet, and we give new predictions.

Conclusions: The newly fitted $\Lambda NN$ force properly describes the physics of medium-heavy $\Lambda$ hypernuclei, correctly reproducing the saturation property of the hyperon separation energy.

High spin states of ${}^{142}$Sm have been investigated using the fusion-evaporation reaction ${}^{116}$Cd (${}^{31}$P, $p4n$) at beam energy 148 MeV using the Indian National Gamma Array (INGA). Approximately sixty new gamma transitions have been placed in the proposed level scheme, which has been extended up to $\approx 12.5$ MeV. Several band-like structures including one dipole band and three quadrupole bands have been observed in the proposed level scheme. Lifetimes of several levels in the dipole band and quadrupole bands have been measured using doppler shift attenuation method (DSAM). The deduced $B\left(M1\right)$ values for the dipole band have been compared with the semiclassical shears mechanism with the principle axis cranking (SPAC) model, and the dipole band has been interpreted as a magnetic rotational band. Comparisons between the experimental characteristics and cranked Nilsson-Strutinsky (CNS) calculations for the observed quadrupole bands indicate that these bands have been formed on the triaxial deformed shape of ${}^{142}$Sm.