Relativistic $p+A$ collisions may produce droplets of quark-gluon plasma (QGP) that quickly develop a toroidal vortex structure similar to that of an expanding smoke ring. We present viscous relativistic hydrodynamic calculations of ultracentral $p+A$ collisions and develop an experimental observable to probe the structure, correlating the polarization and momentum of hyperons emitted from the collision. This effect is robust against changes in the definition of vorticity used to calculate the polarization. Experiments at the Brookhaven National Laboratory Relativistic Heavy Ion Collider and the CERN Large Hadron Collider may test the existence and strength of the vortex toroids, bringing new evidence to bear on the question of collectivity in the smallest QGP droplets.

The question of whether quark matter exists in neutron stars is a long standing one. Generally one finds that a first order phase transition from baryons to quarks softens the equation of state so much that the star would collapse into a black hole. We consider a crossover equation of state, similar to the crossover that is found in lattice QCD studies at finite temperature and zero or small baryon chemical potentials. We find that with reasonable parameters it may be possible to support neutron stars up to about 2.2 solar masses. In that case 1% to 10% of the pressure would be contributed by quark matter in the central core of the highest mass stars.

Magnetic and quadrupole moments of the $7/2^{+}$ ground state in ${}^{133}\mathrm{Sb}$ and the $\left(7^{-}\right)$ isomer in ${}^{134}\mathrm{Sb}$ have been measured by collinear laser spectroscopy to investigate the single-particle behavior above the doubly magic nucleus ${}^{132}\mathrm{Sn}$. The comparison of experimental data of the $7/2^{+}$ states in ${}^{133}\mathrm{Sb}$ and neighboring $N=82$ isotones to shell-model calculations reveals the sensitivity of magnetic moments to the splitting of the spin-orbit partners $\pi 0g_{9/2}$ and $\pi 0g_{7/2}$ across the proton shell closure at $Z=50$. In contrast, quadrupole moments of the $N=82$ isotones are insensitive to cross-shell excitations, but require the full proton model space from $Z=50\text{to}82$ for their accurate description. In fact, the linear trend of the quadrupole moment follows approximately the expectation of the seniority scheme when filling the $\pi 0g_{7/2}$ orbital. As far as the isomer in ${}^{134}\mathrm{Sb}$ is concerned, its electromagnetic moments can be perfectly described by the additivity rule employing the moments of ${}^{133}\mathrm{Sb}$ and ${}^{133}\mathrm{Sn}$, respectively. These findings agree with shell-model calculations and thus confirm the weak coupling between the valence proton and neutron in ${}^{134}\mathrm{Sb}$.

Precise characterization of detector time resolution is of crucial importance for next-generation cryogenic-bolometer experiments searching for neutrinoless double-beta decay, such as CUPID, in order to reject background due to pileup of two-neutrino double-beta decay events. In this paper, we describe a technique developed to study the pileup rejection capability of cryogenic bolometers. Our approach, which consists of producing controlled pileup events with a programmable wave-form generator, has the benefit that we can reliably and reproducibly control the time separation and relative energy of the individual components of the generated pileup events. The resulting data allow us to optimize and benchmark analysis strategies to discriminate between individual and pileup pulses. We describe a test of this technique performed with a small array of detectors at the Laboratori Nazionali del Gran Sasso, in Italy; we obtain a $90\%$ rejection efficiency against pulser-generated pileup events with rise time of $\sim 15\mathrm{ms}$ down to time separation between the individual events of about $2\mathrm{ms}$.

We present a new algebraic method for solving the inverse problem of quantum scattering theory based on the Marchenko theory (fixed-$l$ inversion). We applied a triangular wave set for the Marchenko equation kernel expansion in a separable form. The separable form allows a reduction of the Marchenko equation to a system of linear equations. For the zero orbital angular momentum $l$, a linear expression of the kernel expansion coefficients is obtained in terms of the Fourier series coefficients of $q(1-S(q\left)\right)$ function [$S\left(q\right)$ is the scattering matrix] depending on the momentum $q$ and determined by the scattering data in the finite range $0\le q\le \pi /h$. It is shown that this Fourier series defines the potential function of the corresponding radial Schrödinger equation with $h$-step accuracy. Based on the developed method, a numerical algorithm is obtained for reconstructing complex partial potentials from scattering data on a finite range of $q$. The reconstructed potentials describe with a required accuracy a partial $S$ matrix that is unitary below the threshold of inelasticity and nonunitary (absorptive) above the threshold. The developed procedure is applied to analyze the ${}^{1}S_{0}NN$ data up to 3 GeV. We show that these data are described by energy-independent complex partial potential.

The neutron-rich nuclei to the southwest of ${}^{132}\mathrm{Sn}$ are studied comprehensively by large-scale, shell-model calculations with the extended pairing plus multipole-multipole force (EPQQM) model. A regular correlation driven by the monopole interaction between the neutron orbits $h_{11/2}$ and $d_{3/2}$ is found in this nuclear region for different isotonic chains with $N=79,80,81$. The ground-state inversions from ${}^{130}\mathrm{In}$ $\left({}^{129}\mathrm{Cd}\right)$ to ${}^{128}\mathrm{In}$ $\left({}^{127}\mathrm{Cd}\right)$ seen experimentally are well described for the first time by this regular correlation. The regular correlation in different isotonic chains is also supported by a systematic comparison between the observed spectra of ${}^{126}\mathrm{Ag}$ and ${}^{128}\mathrm{In}$, and further confirmed by the investigation of isomeric states of ${}^{126}\mathrm{Pd}$, ${}^{128}\mathrm{Cd}$, and ${}^{129}\mathrm{In}$ the in $N=80$ isotonic chain. This regular correlation in different isotonic chains should provide useful guidance for further experiments in this region of nuclei.

Neutron energy-dependent angular distributions were observed for individual $\gamma$ rays from the 0.74 eV $p$-wave resonance of ${}^{139}\mathrm{La}+n$ to several lower excited states of ${}^{140}\mathrm{La}$. The $\gamma$-ray signals were analyzed in a two-dimensional histogram of the $\gamma$-ray energy, measured with distributed germanium detectors, and neutron energy, determined with the time-of-flight of pulsed neutrons, to identify the neutron energy dependence of the angular distribution for each individual $\gamma$ rays. The angular distribution was also found for a photopeak accompanied with a faint $p$-wave resonance component. Our results can be interpreted as interference between $s$- and $p$-wave amplitudes, which may be used to study discrete symmetries of fundamental interactions.

Background: The experimental knowledge of nuclear reaction data and decay properties plays a vital role in searching for novel and exotic radioisotopes, prompting us to widen the experimental study of heavy-ion induced reactions.

Purpose: The aim is to study the production of mass separated (i.e., separation of different masses of residues, where each mass group consists of isobaric nuclei) evaporation residues (ERs) populated in ${}^{32}\mathrm{S}+{}^{70}\mathrm{Zn}$ and ${}^{32}\mathrm{S}+{}^{68}\mathrm{Zn}$ reactions within 115–135 and 130–150 MeV incident energy ranges, respectively, and optimization of masses 97 and 95 u that consist of ${}^{97}\mathrm{Pd}$, ${}^{97}\mathrm{Rh}$, ${}^{97}\mathrm{Ru}$, and ${}^{95}\mathrm{Pd}$, ${}^{95}\mathrm{Rh}$, ${}^{95}\mathrm{Ru}$, ${}^{95}\mathrm{Tc}$ isobaric residues, respectively.

Method: Mass separation of ERs has been achieved at the focal plane of the Heavy Ion Reaction Analyser (HIRA) at the 15 UD Pelletron facility, IUAC, India. The residues were detected at the focal plane of HIRA using a multiwire proportional counter (MWPC).

Results: Competing production of masses 97 and 95 u through the fusion of ${}^{32}\mathrm{S}$ ions with ${}^{70}\mathrm{Zn}$ and ${}^{68}\mathrm{Zn}$, respectively, have been observed in comparison to their neighboring masses within the measured energy range. The maximum cumulative production of ${}^{97}\mathrm{Ru}$ has been found to be $\approx 99\pm 9.9$ $\mathrm{Bq}/\mathrm{h}\mathrm{pnA}(\mathrm{mg}/{\mathrm{cm}}^2$) at 125 MeV, while for ${}^{95}\mathrm{Ru}$ it is $\approx 69\pm 6.9$ $\mathrm{Bq}/\mathrm{h}\mathrm{pnA}(\mathrm{mg}/{\mathrm{cm}}^2$) at 135 MeV. Comparisons of experimental results with the theoretical calculations indicate that the residues are mainly populated through the compound reaction mechanism.

Conclusions: As anticipated from theory, significant yields of ${}^{97}\mathrm{Ru}$ and ${}^{95}\mathrm{Ru}$ in reactions ${}^{32}\mathrm{S}+{}^{70}\mathrm{Zn}$ and ${}^{32}\mathrm{S}+{}^{68}\mathrm{Zn}$ have been achieved via cumulative production of different isobars of mass 97 and 95 u, respectively. Cumulative yield of ${}^{97}\mathrm{Ru}$ has been found to be equivalent, i.e., the same order of magnitude [viz., $\approx {10}^7$ nuclei/h pnA(mg/${\mathrm{cm}}^2$)], compared to its independent production through ${}^{11}\mathrm{B}$ and ${}^7\mathrm{Li}$ projectile induced reactions.

Production cross sections for the ${}^{93}\mathrm{Nb}(p,x){}^{90}\mathrm{Mo},{}^{92m,90,89m}\mathrm{Nb},{}^{89,88,86}\mathrm{Zr}$, and ${}^{88,87m,87g}\mathrm{Y}$ reactions were measured using a stacked-foil technique in the proton energy range of 58–100 MeV. The target was arranged in the stack including Nb, Al, Au foils, and Pb plates and was irradiated with 100-MeV protons. After the irradiation, the production yields of the interested radionuclei were measured by a $\gamma$-ray spectroscopy system using HPGe detectors. Proton beam intensities were measured using the ${}^{27}\mathrm{Al}(p,3pn){}^{24}\mathrm{Na},{}^{197}\mathrm{Au}(p,p3n){}^{194}\mathrm{Au}$, and ${}^{197}\mathrm{Au}(p,pn){}^{196}\mathrm{Au}$ monitor reactions. Some 54 cross section data points were measured, including independent and cumulative cross sections and were compared with other experimental data. The excitation functions of the reactions were also calculated by nuclear models using the talys code with a default mode as well as different nuclear level-density models. The calculated cross sections were compared to the measured data and to the tendl library. It was figured out that the theoretical calculations could reproduce the shape of the measured cross sections well, whereas the magnitude of the cross sections was not reproduced. It was also shown that the preequilibrium mechanism played an important role in the cross section calculations in this paper.

We parametrize the transverse momentum distribution of outgoing hadrons in ultrarelativistic nucleus-nucleus collisions as a superposition of boosted thermal distributions. In this approach, which generalizes the conventional blast wave, the momentum distribution is determined by the distribution of the fluid velocity. We analyze the difference between this generalized blast-wave parametrization and a full hydrodynamic calculation. We then apply the generalized blast-wave fit to experimental data on $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=2.76$ TeV. The fit is reasonable up to $p_t\sim 6$ GeV, much beyond the range where hydrodynamics is usually applied but not perfect. Based on the differences between the fit and the data, we argue that an ideal hydrodynamic calculation cannot fit simultaneously all identified particle spectra, irrespective of the specific implementation. In particular, data display a significant excess of pions at low $p_t$, whose physical interpretation is discussed. Data also show that the distribution of the fluid velocity becomes broader as the collision becomes less central. This broadening is explained by event-by-event hydrodynamic calculations, where it results from the centrality dependence of initial-state fluctuations.

Background: The evolution of shell structure around doubly magic exotic nuclei is of great interest in nuclear physics and astrophysics. In the ‘southwest’ region of ${}^{78}\mathrm{Ni}$, the development of deformation might trigger a major shift in our understanding of explosive nucleosynthesis. To this end, new spectroscopic information on key close-lying nuclei is very valuable.

Purpose: We intend to measure the isomeric and $\beta$ decay of ${}^{75}\mathrm{Co}$, with one-proton and two-neutron holes relative to ${}^{78}\mathrm{Ni}$, to access new nuclear structure information in ${}^{75}\mathrm{Co}$ and its $\beta$-decay daughters ${}^{75}\mathrm{Ni}$ and ${}^{74}\mathrm{Ni}$.

Methods: The nucleus ${}^{75}\mathrm{Co}$ is produced in relativistic in-flight fission reactions of ${}^{238}\mathrm{U}$ at the Radioactive Ion Beam Factory in the RIKEN Nishina Center. Its isomeric and $\beta$ decay are studied exploiting the BigRIPS and EURICA setups.

Results: We obtain partial $\beta$-decay spectra for ${}^{75}\mathrm{Ni}$ and ${}^{74}\mathrm{Ni}$, and report a new isomeric transition in ${}^{75}\mathrm{Co}$. The energy $[E_{\gamma }=1914\left(2\right)\mathrm{keV}]$ and half-life $[t_{1/2}=13\left(6\right)\mu \mathrm{s}]$ of the delayed $\gamma$ ray lend support for the existence of a $J^{\pi }=(1/2^{-})$ isomeric state at 1914(2) keV. A comparison with PFSDG-U shell-model calculations provides a good account for the observed states in ${}^{75}\mathrm{Ni}$, but the first calculated $1/2^{-}$ level in ${}^{75}\mathrm{Co}$, a prolate $K=1/2$ state, is predicted about 1 MeV below the observed $(1/2^{-})$ level.

Conclusions: The spherical-like structure of the lowest-lying excited states in ${}^{75}\mathrm{Ni}$ is proved. In the case of ${}^{75}\mathrm{Co}$, the results suggest that the dominance of the spherical configurations over the deformed ones might be stronger than expected below ${}^{78}\mathrm{Ni}$. Further experimental efforts to discern the nature of the $J^{\pi }=(1/2^{-})$ isomer are necessary.

Based on the empirical coupled-channel model for calculating capture cross section and the statistical model for calculating survival probability, we propose an analytical formula for describing the fusion probability. The cold-fusion and hot-fusion reactions leading to superheavy nuclei have been systematically investigated. For both the cold-fusion and hot-fusion reactions, the measured evaporation-residual (ER) cross sections can be reproduced acceptably well by using the formula with the same parameter set. Simultaneously, the ER cross sections for some reactions producing elements $Z=119$ and 120 are studied. It is found that the projectile-target combinations ${}^{50}\mathrm{Ti}$ $+$ ${}^{249}\mathrm{Bk}$ and ${}^{50}\mathrm{Ti}$ $+$ ${}^{249,251}\mathrm{Cf}$ are considered as the most promising reactions for the syntheses of the next two superheavy elements beyond Og. The maximal ER cross section for ${}^{50}\mathrm{Ti}$ $+$ ${}^{249}\mathrm{Bk}$ is 48.2 fb at the incident energy $E_{\mathrm{c}.\mathrm{m}.}$ = 226 MeV. For ${}^{50}\mathrm{Ti}$ $+$ ${}^{249,251}\mathrm{Cf}$, the maximal ER cross section is about 10 fb at the incident energies around $E_{\mathrm{c}.\mathrm{m}.}=232$ MeV.

Background: The hadron-deuteron correlation function has attracted much interest as a potential method to access three-hadron interactions. However, the weakly bound nature of deuterons has not been considered in the preceding studies.

Purpose: The breakup effect of deuterons in the deuteron-${\mathrm{\Xi }}^{-}$ $(d-{\mathrm{\Xi }}^{-})$ correlation function $C_{d{\mathrm{\Xi }}^{-}}$ is investigated.

Methods: The $d-{\mathrm{\Xi }}^{-}$ scattering is described by a nucleon-nucleon-$\mathrm{\Xi }$ three-body reaction model. The continuum-discretized coupled-channels method, which is a fully quantum-mechanical and nonperturbative reaction model, is adopted.

Results: $C_{d{\mathrm{\Xi }}^{-}}$ turns out to be sensitive to the strong interaction and enhanced by the deuteron breakup effect by 6%–8% for a $d\text{−}{\mathrm{\Xi }}^{-}$ relative momentum below about 70 MeV/$c$. Low-lying neutron-neutron continuum states are responsible for this enhancement.

Conclusions: Within the adopted model, the deuteron breakup effect on $C_{d{\mathrm{\Xi }}^{-}}$ is found to be appreciable but not very significant. Except for the enhancement by several percent, studies on $C_{d{\mathrm{\Xi }}^{-}}$ without the deuteron breakup effect can be justified.

In a recent paper [Phys. Rev. C 101, 041302(R) (2020)] Demol et al. published an interesting method to improve results from finite-order perturbation theory. Their applications on nuclear many-body problems show that the numerical results are very accurate, capable of converting divergent series to fast-converging sequences. We argue that one reason for this impressive accuracy is connected to those of related methods which proved to be useful in many-electron theory.

Two resonant states above the ${}^6\mathrm{He}+t$ threshold in ${}^9\mathrm{Li}$ have been observed using a ${}^9\mathrm{Li}$ beam bombarding a ${}^{208}\mathrm{Pb}$ target at the incident energy of 32.7 MeV/nucleon. An angular correlation analysis and the continuum discretized coupled channels (CDCC) method have been applied to identify the spin-parities of observed resonant states. The obtained results from the present methods of calculations indicate the first resonant state at 9.8 MeV with a spin-parity of $3/2^{-}$. The second resonant state at 12.8 MeV with limited statistics might suggest the spin-parity of $7/2^{-}$, which needs to be further investigated. The monopole matrix element of the $3/2^{-}$ state is extracted as 8.1(8) ${\mathrm{fm}}^2$ with a multipole decomposition analysis based on a distorted wave Born approximation (DWBA) calculation. These results give the first experimental evidence supporting the theoretical prediction of the generator coordinate method (GCM) and disclose the feature of clustering structure involving two neutron-rich clusters in the neutron-rich nucleus ${}^9\mathrm{Li}$.

In Phys. Rev. C 98, 041603 (2018) it was demonstrated that the noncoplanar degrees of freedom (or azimuthal angle ${\mathrm{\Phi }}_c\ne 0^0$), including higher-multipole deformations ${\beta }_{\lambda i}$ ($\lambda =2,3,4;i=1,2$), and the compact orientations ${\theta }_{ci}$ are the most essential set of parameters in the dynamical cluster-decay model (DCM), in order to study heavy-ion reactions. In this work, we study the comparison between the coplanar ($\mathrm{\Phi }=0^{\circ }$) and noncoplanar (${\mathrm{\Phi }}_c\ne 0^{\circ }$) configurations, including higher multipole deformations, for ${}^{196}\mathrm{Pt}^{*}$ formed via the ${}^{132}\mathrm{Sn}+{}^{64}\mathrm{Ni}$ reaction. This reaction was earlier studied [M. K. Sharma et al., J. Phys. G: Nucl. Part. Phys. 38, 055104 (2011)] by one of our collaborators but only with $\mathrm{\Phi }=0^{\circ }$, including quadrupole deformations, ${\beta }_{2i}$ alone having “optimum” orientations (${\theta }_{\mathrm{opt}.}$), with the result of noncompound nucleus [nCN, equivalently quasi-fission (qf)] contribution at higher energies. The only parameter of the DCM is the neck length $\mathrm{\Delta }R$, whose value for the nuclear proximity potential used here remains within its range of validity ($\approx 2$ fm). The evaporation residues (ERs) and fission cross section (${\sigma }_{ff}$) are calculated in reference to available experimental data at near- and sub-barrier energies for ${}^{196}\mathrm{Pt}^{*}$. As a result of inclusion of ${\mathrm{\Phi }}_c\ne 0^{\circ }$, the nCN contribution approaches zero at higher energies and corresponds to $P_{\mathrm{CN}}=1$, which is rather significant for the $\mathrm{\Phi }=0^{\circ }$ configuration. Secondly, in this attempt we have tried to explore the evolution of the neck-length parameter ($\mathrm{\Delta }R$), which will help us to estimate the cross sections of unobserved decay channels.

Pion electroproduction off the proton is analyzed in a new framework based on a general parametrization of transition amplitudes, including constraints from gauge invariance and threshold behavior. Data with energies $1.13\mathrm{GeV}<W<1.6$ GeV and $Q^2$ below $6{\mathrm{GeV}}^2$ are included. The model is an extension of the latest Jülich-Bonn solution incorporating constraints from pion-induced and photoproduction data. Performing large-scale fits ($\approx {10}^5$ data) we find a set of solutions with ${\chi }_{\mathrm{dof}}^2=1.69–1.81$ which allows us to assess the systematic uncertainty of the approach.

The evolutions of the energy difference between the neutron states $1i_{13/2}$ and $1h_{9/2}$ in the $N=82$ isotones and that between the proton states $1h_{11/2}$ and $1g_{7/2}$ in the $Z=50$ isotopes are investigated within the framework of the relativistic Hartree-Fock theory, using the density-dependent effective interactions PKA1, $\mathrm{P}\mathrm{K}\mathrm{O}i$ ($i=1$, 2, 3), and a new interaction developed in this study. By identifying the contributions of the tensor force, which is naturally induced via the Fock terms, we find that the tensor force plays crucial roles in the evolution of the shell structure. The strength of the tensor force is also explored. It is found that moderately increasing the coupling strength of pion-nucleon coupling, i.e., $f_{\pi }$, will significantly improve the description of the shell-structure evolution. In particular, reducing the density dependence of $f_{\pi }$ is shown to be preferable, in comparison to enlarging $f_{\pi }$ with a factor. This is consistent with the idea of “tensor renormalization persistency” and provides valuable guidance for the development of the nuclear energy density functional in the relativistic framework.

Background: The half-life of the famous ${}^{14}\mathrm{C}\beta$ decay is anomalously long, with different mechanisms: the tensor force, cross-shell mixing, and three-body forces, proposed to explain the cancellations that lead to a small transition matrix element.

Purpose: We revisit and analyze the role of the tensor force for the $\beta$ decay of ${}^{14}\mathrm{C}$ as well as of neighboring isotopes.

Methods: We add a tensor force to the Gogny interaction, and derive an effective Hamiltonian for shell-model calculations. The calculations were carried out in a $p\text{−}sd$ model space to investigate cross-shell effects. Furthermore, we decompose the wave functions according to the total orbital angular momentum $L$ in order to analyze the effects of the tensor force and cross-shell mixing.

Results: The inclusion of the tensor force significantly improves the shell-model calculations of the $\beta$-decay properties of carbon isotopes. In particular, the anomalously slow $\beta$ decay of ${}^{14}\mathrm{C}$ can be explained by the isospin $T=0$ part of the tensor force, which changes the components of ${}^{14}\mathrm{N}$ with the orbital angular momentum $L=0,1$, and results in a dramatic suppression of the Gamow-Teller transition strength. At the same time, the description of other nearby $\beta$ decays are improved.

Conclusions: Decomposition of wave function into $L$ components illuminates how the tensor force modifies nuclear wave functions, in particular suppression of $\beta$-decay matrix elements. Cross-shell mixing also has a visible impact on the $\beta$-decay strength. Inclusion of the tensor force does not seem to significantly change, however, binding energies of the nuclei within the phenomenological interaction.

Transport and Langevin equations are employed to study hadronic medium effects on charmonium elliptic flows in heavy-ion collisions. In Pb-Pb collisions, the anisotropic energy density of the quark-gluon plasma (QGP) in the transverse plane is transformed into hadron momentum anisotropy after the phase transition. Charmonia with high transverse momentum $p_T$ are produced via the primordial hard process and undergo different degrees of dissociation along different paths in the QGP. They then scatter with light hadrons in the hadron phase. Both contributions to the charmonium elliptic flows are studied at moderate and high transverse momenta. The elliptic flows of the prompt $J/\psi$ are found to be considerably enhanced at high transverse momentum when the charmonium diffusion coefficients in the hadronic medium are parametrized through the geometry scale approximation. This hadronic medium effect is negligible for quarkonia with larger mass such as bottomonia.