We study clustering of baryons at the freeze-out point of relativistic heavy-ion collisions. Using a Walecka-Serot model for the nucleon-nucleon ($NN$) interaction we analyze how the modified critical $\sigma$ mode—responsible for the $NN$ attraction—allows for clustering of nucleons when the system is close to a possible critical point of QCD. We investigate clusters of few nucleons, and also the internal cluster configuration when the system is long lived. For realistic heavy-ion collisions we study to what extent light clusters, such as ${}^4\mathrm{He}$, can be formed in several $\mathrm{fm}/c$, and perform the statistical analysis of proton cumulants and higher-order moments (skewness and kurtosis) for collisions at the beam energy scan of the Relativistic Heavy-Ion Collider.

We calculate the scattering $T$-matrix of $I=0$ $\overline{K}N\text{−}\pi \mathrm{\Sigma }$ coupled channels taking a ladder sum of the Weinberg-Tomozawa interaction without on-shell factorization, regularizing three types of divergent meson-baryon loop functions by dimensional regularization and renormalizing them by introducing counter terms. We show that not only infinite but also finite renormalization is important for the renormalized physical scattering $T$-matrix to have the form of the Weinberg-Tomozawa interaction. The results with and without on-shell factorization are compared. The difference of the scattering $T$-matrix is small near the renormalization point, close to the observed $\mathrm{\Lambda }$(1405). The difference, however, increases with the distance from the renormalization point. The scattering $T$-matrix without on-shell factorization has two poles in the complex center-of-mass energy plane as with on-shell factorization, the real part of which is close to the observed $\mathrm{\Lambda }$(1405). While the difference is small with and without on-shell factorization in the position of the first pole, closer to the observed $\mathrm{\Lambda }$(1405), the difference is considerably large in the position of the second pole: the imaginary part of the center-of-mass energy of the second pole without on-shell factorization is as large as or even larger than twice that with on-shell factorization. Also, we discuss the origin of the contradiction about the second pole between two approaches, the chiral unitary approach with on-shell factorization and the phenomenological approach without on-shell factorization.

General expressions for the unpolarized differential cross section and for various polarization observables in coherent pseudoscalar meson photo- and electroproduction on a deuteron target have been obtained in the one-photon-exchange approximation. The spin structure of the matrix element is explicitly derived in terms of structure functions. The correspondence with the helicity amplitudes is given. The polarization effects have been investigated for the case of a longitudinally polarized electron beam and a vector or tensor polarized deuteron target. The polarization (vector or tensor) of the scattered deuteron for the case of an unpolarized or a longitudinally polarized electron beam is also considered. In the case of the photoproduction reaction, we consider a linearly, circularly, or elliptically polarized photon beam. Numerical estimations have been done for the unpolarized differential cross section and for some polarization observables.

High-spin states of ${}^{113}\mathrm{In}$ have been populated using the ${}^{110}\mathrm{Pd}({}^7\mathrm{Li},4n){}^{113}\mathrm{In}$ reaction at beam energies of 38 and 50 MeV. More than 50 new $\gamma$ transitions are observed in ${}^{113}\mathrm{In}$. Three previously observed magnetic dipole bands are extended to higher spin states, and several new $E2$ crossover transitions within the bands are observed in two of the dipole bands. A new positive-parity $▵I=2$ band built on the $\pi d_{5/2}$ configuration is established. The known $▵I=2$ band is extended to $51/2^{+}$ state, and a gentle up-bend associated to the alignment of neutrons in the normal-parity $\nu g_{7/2}/d_{5/2}$ orbitals is found. The properties of this band are discussed based on the self-consistent tilted axis cranking relativistic mean-field model calculations. The predicted $B\left(E2\right)$, deformation parameters ${\beta }_2$ and $\gamma$, and $J^{\left(2\right)}/B\left(E2\right)$ ratios indicate that the $▵I=2$ band based on the $\pi g_{9/2}^{-2}{g}_{7/2}\otimes \nu {\left(h_{11/2}\right)}^2$ and $\pi g_{9/2}^{-2}{g}_{7/2}\otimes \nu {\left(h_{11/2}\right)}^2{(g_{7/2}/d_{5/2})}^2$ configurations, has the characteristics of antimagnetic rotation. Furthermore, the two-shears-like mechanism for the possible antimagnetic rotational bands is examined by investigating the orientation of the angular momenta.

Excited states in the ${}^{158}\mathrm{Eu}$ nucleus have been determined with the ${}^{160}\mathrm{Gd}(d,\alpha ){}^{158}\mathrm{Eu}$ reaction, studied at an incident energy of 18.0 MeV with the Munich tandem and Q3D spectrograph. More than 50 excited states have been determined up to 1.6 MeV excitation, some of them corresponding to states previously observed in the ${\beta }^{-}$ decay of ${}^{158}\mathrm{Sm}$. The number of levels found in this nucleus at low excitation energies follows the systematic trend of the level densities in the other isotopes with mass 152–156.

The structure of the odd-$A$ isotopes ${}^{193,195,197}\mathrm{Pt}$, which lie along the line of stability, has been studied up to high spin through multinucleon transfer reactions. Positive- and negative-parity sequences in ${}^{193,195}\mathrm{Pt}$ have been considerably extended and multiple band crossings established. An isomer with $T_{1/2}=5.0\left(5\right)$ ns and $I^{\pi }=25/2^{-}$ is present in ${}^{195}\mathrm{Pt}$. The isotopes ${}^{193,195}\mathrm{Pt}$ are characterized by moderate oblate deformation, and angular momentum generation at high spin in the yrast, positive-parity sequences is attributed to the rotation alignment of $i_{13/2}$ neutrons and $h_{11/2}$ protons. A detailed understanding of the observed features is presented using calculations based on tilted axis cranking covariant density functional theory as well as others with the ultimate cranker code.

The structure of decoupled positive-parity and semidecoupled negative-parity bands up to high spin in ${}^{197,199}\mathrm{Hg}$ has been studied using multinucleon transfer reactions with the Gammasphere array. A positive-parity band in ${}^{199}\mathrm{Hg}$ with the ${\left(\nu i_{13/2}\right)}^3$ decoupled configuration that deexcites to levels in the negative-parity sequences is newly established. The semidecoupled sequences in both isotopes are extended to higher spin. Rotation-aligned angular momenta and crossing frequencies determined from experiment are in fair agreement with those from cranking calculations. A transition from oblate collective rotation at low spin to triaxial noncollective shapes at high spin is indicated.

Background: The $\gamma$ softness of ${}^{136}\mathrm{Nd}$ makes it possible to study the shape changes induced by two-proton or two-neutron excitation.

Purpose: We measure the lifetimes of two-quasiparticle states of the bands based on the ${10}^{+}$ states at 3296 and 3279 keV to investigate the shape change induced by the alignment of two protons or two neutrons in the $h_{11/2}$ orbital.

Methods: The recoil-distance Doppler shift method was used for the study of ${}^{136}\mathrm{Nd}$ studies, which was formed by the fusion reaction ${}^{120}\mathrm{Sn}({}^{20}\mathrm{Ne},4n){}^{136}\mathrm{Nd}$, at $E_{beam}=85$ MeV. Calculations were performed within the microscopic-macroscopic approach, based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy.

Results: The lifetime of the ${10}^{+}$ state at 3279 keV of ${}^{136}\mathrm{Nd}$ was measured to be $T_{1/2}^{{10}^{+}}=1.63\left(9\right)$ ns. The lifetimes of the $2^{+}$ state at 374 keV and of the ${12}^{+}$ state at 3686 keV of the ground band were also measured to be $T_{1/2}^{2^{+}}=26.5\left(14\right)$ ps and $T_{1/2}^{{12}^{+}}=22.5\left(14\right)$ ps.

Conclusions: The measured lifetime of ${10}^{+}$ the state at 3279 keV together with other observables confirm the structure change in ${}^{136}\mathrm{Nd}$. A rather small reduced hindrance of the electromagnetic decay of the ${10}^{+}$ state at 3279 keV would be consistent with its $K$-mixed character.

Capture rates of ordinary muon capture (OMC) to the intermediate nuclei of neutrinoless double beta ($0\nu \beta \beta$) decays of current experimental interest are computed. The corresponding OMC (capture-rate) strength functions have been analyzed in terms of multipole decompositions. The computed low-energy OMC-rate distribution to ${}^{76}\mathrm{As}$ is compared with the available data of Zinatulina et al. [Phys. Rev. C 99, 024327 (2019)]. The present OMC computations are performed using the Morita-Fujii formalism by extending the original formalism beyond the leading order. The participant nuclear wave functions are obtained in extended no-core single-particle model spaces using the spherical version of proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-exchange $G$ matrix. The Hamiltonian parameters are taken from our earlier work [Jokiniemi et al., Phys. Rev. C 98, 024608 (2018)], except for $A=82$ nuclei for which the parameters were determined in this work. Both the OMC and $0\nu \beta \beta$ decays involve momentum exchanges of the order of 100 MeV and thus future measurements of the OMC strength functions for $0\nu \beta \beta$ daughter nuclei help trace the in-medium renormalization of the weak axial couplings with the aim to improve the accuracy of the $0\nu \beta \beta$-decay nuclear matrix elements.

The multiplicities of $\alpha$ particles and neutrons have been measured simultaneously for the reaction ${}^{16}\mathrm{O}+{}^{196}\mathrm{Pt}$ forming ${}^{212}\mathrm{Rn}$ compound nucleus at excitation energies of 56 MeV, 61 MeV, and 68 MeV. Neutrons and $\alpha$ particles were detected at various angles in coincidence with the fission fragments. To extract the contribution of pre- and postmultiplicities using the total $\alpha$-particle and neutron spectra, moving source formalism was implemented. In the case of $\alpha$ particle, near scission contribution has also been extracted. Study of the fission mechanism using light particle emissions are helpful in understanding the detailed fusion-fission reaction dynamics. The statistical model code joanne2, which includes deformation-dependent particle transmission coefficients, binding energies and level densities, has been used to reproduce the measured multiplicities of neutrons and $\alpha$ particles by varying the transient (${\tau }_{tr}$) and saddle to scission (${\tau }_{ssc}$) times. It is found that the fission time scales of the order of $50–70\times {10}^{-21}$ sec are required to reproduce the neutron and $\alpha$-particles multiplicities simultaneously. The fission time scales are the measure of the nuclear viscosity, which is responsible for the dynamic hindrance of the fission process.

Starting from a color glass condensate (CGC) framework, based on a running-coupling improved $k_T$-factorized formula, we calculate bulk observables in several heavy-ion collision systems. This is done in two ways: first we calculate the particle distribution directly implied from the CGC model, and we compare this to the case where it is instead used as the initial condition for a hybrid hydrodynamic simulation. In this way, we can assess the effects of hydrodynamic and hadronic evolution by quantifying how much they change the results from a pure initial state approach and, therefore, to what extent initial condition models can be directly compared to experimental data. We find that entropy production in subsequent hydrodynamic evolution can increase multiplicity by as much as 50%. However, disregarding a single overall normalization factor, the centrality, energy, and system size dependencies of charged hadron multiplicity are only affected at the $\sim 5$% level. Because of this, the parameter-free prediction for these dependencies gives reasonable agreement with experimental data whether or not hydrodynamic evolution is included. On the other hand, our model results are not compatible with the hypothesis that hydrodynamic evolution is present in large systems, but not in small systems like $p$-Pb, in which case the dependence of multiplicity on system size would be stronger than seen experimentally. Moreover, we find that hydrodynamic evolution significantly changes the distribution of momentum, so that observables such as the mean transverse momentum are very different from the initial particle production and much closer to measured data. Finally, we find that a good agreement to anisotropic flow data cannot be achieved due to the large eccentricity generated by this model.

The impact of beyond-mean-field predictions of stellar weak interaction rates of ${}^{68}\mathrm{Se}$ and ${}^{72}\mathrm{Kr}$ waiting point nuclei on the $rp$-process in type-I x-ray bursts is investigated including the contribution of thermally populated low-lying states for both ${\beta }^{+}$ decay and continuum electron capture. The realistic description of the effects of shape coexistence and mixing in the structure of parent and daughter nuclei on the stellar weak rates is obtained within the complex excited Vampir model. We performed a series of post-processing calculations revealing significant effects on the energy generation, reaction flow, and final composition of the burst ashes.

In this work, we have studied the isothermal compressibility (${\kappa }_T$) as a function of temperature, baryon chemical potential, and center-of-mass energy ($\sqrt{s_{NN}}$) using hadron resonance gas (HRG) and excluded-volume hadron resonance gas (EV-HRG) models. A mass cut-off dependence of isothermal compressibility has been studied for a physical resonance gas. Further, we study the effect of heavier resonances ($>2\mathrm{GeV}$) on the isothermal compressibility by considering the Hagedorn mass spectrum, $\rho \left(m\right)\sim exp\left(bm\right)/{(m^2+m_0^2)}^{5/4}$. Here the parameters $b$ and $m_0$ are extracted after comparing the results of recent lattice QCD simulations at finite baryonic chemical potential. We find a significant difference between the results obtained in EV-HRG and HRG models at higher temperatures. The inclusion of the Hagedorn mass spectrum in the partition function for hadron gas has a large effect at a higher temperature. A higher mass cut-off in the Hagedorn mass spectrum takes the isothermal compressibility to a minimum value, which occurs near the Hagedorn temperature ($T_H$). We show explicitly that at the future low-energy accelerator facilities like FAIR (CBM), Darmstadt, and NICA, Dubna, the created matter would have higher compressibility compared to the high-energy facilities like the Relativistic Heavy Ion Collider and Large Hadron Collider.

We extend the parton-hadron string dynamics (PHSD) transport approach in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections as a function of temperature $T$ and baryon chemical potential ${\mu }_B$ on the basis of the effective propagators and couplings from the dynamical quasiparticle model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature $T_c$ from lattice QCD. We calculate the collisional widths for the partonic degrees of freedom at finite $T$ and ${\mu }_B$ in the timelike sector and conclude that the quasiparticle limit holds sufficiently well. Furthermore, the ratio of shear viscosity $\eta$ over entropy density $s$, i.e., $\eta /s$, is evaluated using the collisional widths and compared to lattice QCD calculations for ${\mu }_B=0$ as well. We find that the novel ratio $\eta /s$ does not differ very much from that calculated within the original DQPM on the basis of the Kubo formalism. Furthermore, there is only a very modest change of $\eta /s$ with the baryon chemical ${\mu }_B$ as a function of the scaled temperature $T/T_c\left({\mu }_B\right)$. This also holds for a variety of hadronic observables from central $A+A$ collisions in the energy range 5 GeV $\le \sqrt{s_{NN}}\le 200$ GeV when implementing the differential cross sections into the PHSD approach. We only observe small differences in the antibaryon sector $\left(\overline{p},\overline{\mathrm{\Lambda }}+{\overline{\mathrm{\Sigma }}}^0\right)$ at $\sqrt{s_{NN}}=17.3\mathrm{GeV}$ and 200 GeV with practically no sensitivity of rapidity and $p_T$ distributions to the ${\mu }_B$ dependence of the partonic cross sections. Small variations in the strangeness sector are obtained in all collisional systems studied $(A+A$ and C $+$ Au); however, it will be very hard to extract a robust signal experimentally. Since we find only small traces of a ${\mu }_B$ dependence in heavy-ion observables—although the effective partonic masses and widths as well as their partonic cross sections clearly depend on ${\mu }_B$—this implies that one needs a sizable partonic density and large space-time QGP volume to explore the dynamics in the partonic phase. These conditions are only fulfilled at high bombarding energies where ${\mu }_B$ is, however, rather low. On the other hand, when decreasing the bombarding energy and thus increasing ${\mu }_B$, the hadronic phase becomes dominant and accordingly it will be difficult to extract signals from the partonic dynamics based on “bulk” observables.

A set of hadronic equations of state (EoSs) derived from relativistic density-functional theory and constrained by terrestrial experiments, astrophysical observations, in particular by the GW170817 event, and chiral effective field theory $\left(\chi \mathrm{EFT}\right)$ of neutron matter is used to explore the sensitivity of the EoS parameterization on the few nuclear-matter characteristics defined at the saturation density. We find that the gross properties of compact stars are most sensitive to the isoscalar skewness coefficient $Q_{\text{sat}}$ and the isovector slope coefficient $L_{\text{sym}}$ around saturation density, since the higher-order coefficients, such as $K_{\text{sym}}$, are fixed by our model. More specifically, (i) among these $Q_{\text{sat}}$ is the dominant parameter controlling both the maximum mass and the radii of compact stars while $L_{\mathrm{sym}}$ is constrained somewhat by $\chi \mathrm{EFT}$ of neutron matter, (ii) massive-enough $(M\sim 2.0M_{\odot })$ compact stars featuring both hyperons and $\mathrm{\Delta }$ resonances can be obtained if the value of $Q_{\text{sat}}$ is large enough, and (iii) the emergence of $\mathrm{\Delta }$'s reduces the radius of a canonical mass $(M\sim 1.4M_{\odot })$ compact star thus easing the tension between the predictions of the relativistic density functionals and the inferences from the x-ray observation of nearby isolated neutron stars.

We report on the observation of a microsecond isomeric state in the single-proton-hole, three-neutron-particle nucleus ${}^{134}\mathrm{In}$. The nuclei of interest were produced by in-flight fission of a ${}^{238}\mathrm{U}$ beam at the Radioactive Isotope Beam Factory at RIKEN. The isomer depopulates through a $\gamma$ ray of energy 56.7(1) keV and with a half-life of $T_{1/2}=3.5\left(4\right)\mu \mathrm{s}$. Based on the comparison with shell-model calculations, we interpret the isomer as the $I^{\pi }=5^{-}$ member of the $\pi 0g_{9/2}^{-1}\otimes \nu 1f_{7/2}^3$ multiplet, decaying to the $I^{\pi }=7^{-}$ ground state with a reduced-transition probability of $B(E2;5^{-}\to 7^{-})=0.53\left(6\right)\mathrm{W}.\mathrm{u}.$ Observation of this isomer, and lack of evidence in the current work for a $I^{\pi }=5^{-}$ isomer decay in ${}^{132}\mathrm{In}$, provides a benchmark of the proton-neutron interaction in the region of the nuclear chart “southeast” of ${}^{132}\mathrm{Sn}$, where experimental information on excited states is sparse.

Gamma-ray spectroscopy and lifetime measurements using the Doppler shift attenuation method (DSAM) were performed on the nucleus ${}^{28}\mathrm{Mg}$ near the $N=20$ “island of inversion,” which was populated using a ${}^{12}\mathrm{C}({}^{18}\mathrm{O},2\mathrm{p}){}^{28}\mathrm{Mg}$ fusion-evaporation reaction to investigate the impact of shell evolution on its high-lying structure. Three new levels were identified at 7203(3), 7747(2), and 7929.3(12) keV along with several new gamma rays. A newly extracted $B(E2;4_1^{+}\to 2_1^{+})$ of 42(7) $e^2{\mathrm{fm}}^4$ indicates reduced collectivity in the yrast band at high spin, consistent with ab initio symmetry adapted no-core shell model (SA-NCSM) calculations. At high excitation energy, evidence for the population of intruder orbitals was obtained through identification of negative parity levels $[I^{\pi }={(0,4)}^{-}$, ${(4,5)}^{-}]$. Calculations using the SDPF-MU interaction indicate that these levels arise from single neutron excitation to the $pf$ shell and provides evidence for the lowering of these intruder orbitals approaching the island of inversion.