A new series of neutron-rich indium mass measurements is reported from the TITAN multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). These mass measurements cover ${}^{125-134}\mathrm{In}$ ($N=76–85$) and include ground states as well as isomeric states. The masses of nuclei in this region are known to be of great importance for accurately modeling $r$-process nucleosynthesis, and the significance of the reported neutron-rich indium masses is discussed in this context. Results are compared with earlier experimental data where available as well as theoretical mass models. The measurements reported here include the first mass measurements of ${}^{133,134}\mathrm{In}$, as well as the first direct mass measurement of ${}^{132}\mathrm{In}$. The masses of ${}^{125-131}\mathrm{In}$ ground states and several isomers were previously measured to higher precision by Penning trap mass spectrometry, which also resolved some low-lying isomers that could not be resolved in this work. The earlier Penning trap measurements serve as excellent cross-checks for the MR-TOF-MS measurements, and in some cases the MR-TOF-MS measurements improve the literature uncertainties of higher-lying isomer masses and excitation energies. A new isomeric state for ${}^{128}\mathrm{In}$, recently reported for the first time by the JYFLTRAP group, is also confirmed by the TITAN MR-TOF-MS, with a measured excitation energy of 1813(17) keV.

Background: The $B(E2:2_1^{+}\to 0_1^{+})$ of the Sn isotopes for $N\le 64$ exhibit enhancements hitherto unexplained. The same is true for all the Cd isotopes.

Purpose: To describe the electromagnetic properties of the Sn and Cd isotopes.

Method: Shell-model calculations are performed with a minimally renormalized realistic interaction, supplemented by quasi- and pseudo-SU3 symmetries and Nilsson-SU3 self-consistent calculations. Special care is devoted to the monopole part of the Hamiltonian.

Results: (1) Shell-model calculations with the neutron effective charge as single free parameter describe well the $B(E2:2_1^{+}\to 0_1^{+})$ and $B(E2:4_1^{+}\to 2_1^{+})$ rates for $N\le 64$ in the Cd and Sn isotopes. The former exhibit weak permanent deformation corroborating the prediction of a pseudo-SU3 symmetry, which remains of heuristic value in the latter, where the pairing force erodes the quadrupole dominance. Calculations in ${10}^7$- and ${10}^{10}$-dimensional spaces exhibit almost identical $B\left(E2\right)$ behavior: A vindication of the shell model. (2) Nilsson-SU3 calculations describe $B(E2:2_1^{+}\to 0_1^{+})$ patterns in ${}^{112–120}\mathrm{Cd}$ and ${}^{116–118}\mathrm{Sn}$ isotopes having sizable quadrupole moment of non-rotational origin denoted as $q$ vibrations.

Conclusion: A radical reexamination of traditional interpretations in the region has been shown to be necessary, in which approximate symmetries involving the quadrupole force and a high quality monopole Hamiltonian play a major role. What emerges is a bumpy but coherent view.

The ground-state properties of neutron-rich ${}^{106}\mathrm{Nb}$ and its $\beta$ decay into ${}^{106}\mathrm{Mo}$ have been studied using the CARIBU radioactive-ion-beam facility at Argonne National Laboratory. Niobium-106 ions were extracted from a ${}^{252}\mathrm{Cf}$ fission source and mass separated before being delivered as low-energy beams to the Canadian Penning Trap, as well as the X-Array and SATURN $\beta$-decay-spectroscopy station. The measured ${}^{106}\mathrm{Nb}$ ground-state mass excess of $-66202.0\left(13\right)$ keV is consistent with a recent measurement but has three times better precision; this work also rules out the existence of a second long-lived, $\beta$-decaying state in ${}^{106}\mathrm{Nb}$ above 5 keV in excitation energy. The decay half-life of ${}^{106}\mathrm{Nb}$ was measured to be 1.097(21) s, which is $8\%$ longer than the adopted value. The level scheme of the decay progeny, ${}^{106}\mathrm{Mo}$, has been expanded up to $\approx 4\mathrm{MeV}$. The distribution of decay strength and considerable population of excited states in ${}^{106}\mathrm{Mo}$ of $J\ge 3$ emphasizes the need to revise the adopted $J^{\pi }=1_{}^{-}$ ground-state spin-parity assignment of ${}^{106}\mathrm{Nb}$; it is more likely to be $J\ge 3$.

Background: Generalized polarizabilities (GPs) are important observables to describe the nucleon structure, and measurements of these observables are still scarce.

Purpose: This paper presents details of a virtual Compton scattering (VCS) experiment, performed at the A1 setup at the Mainz Microtron by studying the $ep\to ep\gamma$ reaction. The article focuses on selected aspects of the analysis.

Method: The experiment extracted the $P_{\mathrm{LL}}-P_{\mathrm{TT}}/\epsilon$ and $P_{LT}$ structure functions, as well as the electric and magnetic GPs of the proton, at three new values of the four-momentum transfer squared $Q^2$: 0.10, 0.20, and $0.45{\mathrm{GeV}}^2$.

Results: We emphasize the importance of the calibration of experimental parameters. The behavior of the measured $ep\to ep\gamma$ cross section is presented and compared to the theory. A detailed investigation of the polarizability fits reveals part of their complexity, in connection with the higher-order terms of the low-energy expansion.

Conclusions: The presented aspects are elements which contribute to minimize the systematic uncertainties and improve the precision of the physics results.

The reaction $\gamma p\to K^{+}\mathrm{\Lambda }\left(1520\right)$ using photoproduction data from the CLAS $g12$ experiment at Jefferson Lab is studied. The decay of $\mathrm{\Lambda }\left(1520\right)$ into two exclusive channels, ${\mathrm{\Sigma }}^{+}{\pi }^{-}$ and ${\mathrm{\Sigma }}^{-}{\pi }^{+}$, is studied from the detected $K^{+}$, ${\pi }^{+}$, and ${\pi }^{-}$ particles. A good agreement is established for the $\mathrm{\Lambda }\left(1520\right)$ differential cross sections with the previous CLAS measurements. The differential cross sections as a function of center-of-mass angle are extended to higher photon energies. Newly added are the differential cross sections as a function of invariant four-momentum transfer $t$, which is the natural variable to use for a theoretical model based on a Regge-exchange reaction mechanism. No new $N^{*}$ resonances decaying into the $K^{+}\mathrm{\Lambda }\left(1520\right)$ final state are found.

We explore the possibility of a structured hadron-quark mixed phase forming in the interior of neutron stars. The quark-meson coupling (QMC) model, which explicitly incorporates the internal quark structure of the nucleon, is employed to describe the hadronic phase, while the quark phase is described by the same bag model as the one used in the QMC framework, so as to keep consistency between the two coexisting phases. We analyze the effect of the appearance of hadron-quark pasta phases on the neutron-star properties. We also discuss the influence of nuclear symmetry energy and the bag constant $B$ in quark matter on the deconfinement phase transition. For the treatment of the hadron-quark mixed phase, we use the energy minimization method and compare it with the Gibbs construction. The finite-size effects like surface and Coulomb energies are taken into account in the energy minimization method; they play crucial roles in determining the pasta configuration during the hadron-quark phase transition. It is found that the finite-size effects can significantly reduce the region of the mixed phase relative to that of the Gibbs construction. Using a consistent value of $B$ in the QMC model and quark matter, we find that hadron-quark pasta phases are formed in the interior of massive stars, but no pure quark matter can exist.

Nucleon-transfer sum rules have been assessed via a consistent reanalysis of cross-section data from neutron-adding ($d,p$) and -removing ($d,t$) reactions on well-deformed isotopes of Gd, Dy, Er, Yb, and W, with $92\le N\le 108$, studied at the Niels Bohr Institute in the 1960s and 1970s. These are complemented by new measurements of cross sections using the ($d,p$), ($d,t$), and ($p,d$) reactions on a subset of these nuclei. The sum rules, defined in a Nilsson-model framework, are remarkably consistent. A single overall normalization is used in the analysis, which appears to be sensitive to assumptions about the reaction mechanism, and in the case of sums using the ($d,t$) reaction, differs from values determined from reactions on spherical systems.

Analytic average mean-field potentials of the Fermi-function (Woods-Saxon) type for the whole nuclear chart with space-dependent effective mass are deduced from the D1S Gogny force. Those ready-for-use potentials are advertised as an alternative to other existing phenomenological mean-field potentials.

In the previous paper [Bhagwat, Centelles, Viñas, and Schuck, Phys. Rev. C 103, 024320 (2021)] we have shown that self-consistent extended Thomas-Fermi (ETF) potentials and densities associated with a given finite-range interaction can be parametrized by generalized Fermi distributions. As a next step, a comprehensive calculation of ground-state properties of a large number of spherical and deformed even-even nuclei is carried out in the present paper using the Gogny D1S force within the ETF scheme. The parametrized ETF potentials and densities of the previous paper are used to calculate the smooth part of the energy and the shell corrections within the Wigner-Kirkwood semiclassical averaging scheme. It is shown that the shell corrections thus obtained, along with a simple liquid drop prescription, yield a good description of ground-state masses and potential-energy surfaces for nuclei spanning the entire periodic table.

The effective interactions between two nuclear clusters, $d+d, t+t$, and $\alpha +\alpha$, are investigated within a cluster model using local nucleon-nucleon ($NN$) forces. It is shown that the interaction in the spin-aligned $d+d$ system is repulsive for all intercluster distances, whereas the $\alpha +\alpha$ and spin-aligned $t+t$ systems are attractive at intermediate distances. The Pauli blocking between identical-nucleon pairs is responsible for the cluster-cluster repulsion and becomes dominant in the shallow binding limit. We demonstrate that two $d$ clusters could be bound if the $NN$ force has nonzero range and is strong enough to form a deeply bound $d$ cluster, or if the $NN$ force has both even-parity and odd-parity attraction. Effective dimer-dimer interactions for general quantum systems of two-component fermions are also discussed in heavy-light mass limit, where one component is much heavier than the other, and their relation to intercluster interactions in nuclear systems are discussed. Our findings provide a conceptual foundation for conclusions obtained numerically in the literature, that increasing the range or strength of the local part of the attractive nucleon-nucleon interaction results in a more attractive cluster-cluster interaction.

Nuclear fission is hindered by dissipation. Using the stochastic Langevin model, we calculate the drop of fission cross sections caused by friction with respect to its standard statistical-model values, ${\sigma }_f^{\mathrm{drop}}$, as a function of the presadde dissipation strength $\left(\beta \right)$ for ${}^{226}\mathrm{U}$, ${}^{234}\mathrm{U}$, and ${}^{242}\mathrm{U}$. It is shown that the sensitivity of ${\sigma }_f^{\mathrm{drop}}$ to $\beta$ is substantially enhanced with increasing the isospin of the U fissioning system. Furthermore, we find that under typical conditions of excitation energy and angular momentum populating ${}^{240}\mathrm{U}$ (via radioactive beams) and ${}^{200}\mathrm{Tl}$ (via stable beams), the fission cross section of the high-isospin heavy ${}^{240}\mathrm{U}$ demonstrates a greater sensitivity to friction than that of the light ${}^{200}\mathrm{Tl}$. Our findings suggest that on the experimental side, to accurately probe presaddle dissipation with fission cross sections of heavy nuclei, it is useful to choose radioactive nuclear beams induced reactions as a way to populate excited heavy fissioning systems with high isospin.

Semi-inclusive transverse momentum spectra observed in proton-proton and proton-lead nuclear collisions at LHC energies obey a geometric scaling with a scaling variable using multiplicity-dependent saturation momentum. The saturation momentum extracted from the experimental data is proportional to the 1/6 power of the hadron multiplicity in the final state. However, the system's transverse size is proportional to the 1/3 power of the multiplicity, and the saturation momentum and the transverse size of the system are strongly correlated with the hadron multiplicity in the final state. Since the saturation momentum is proportional to the average transverse momentum of hadrons, one predicts average transverse momentum is also proportional to the 1/6 power of the multiplicity, which is consistent with experimental results at the LHC energy. It is also found that a nuclear modification factor $R_{\mathrm{pPb}}$ calculated by the multiplicity-dependent saturation momentum decreases in $p_{\mathrm{T}}\lesssim$ 1 $\mathrm{GeV}/c$ and that the $R_{\mathrm{pPb}}$'s behavior thought to be caused by nuclear shadowing can partially explained. However, Cronin enhancement experimentally observed at $2\lesssim p_{\mathrm{T}}\lesssim$ 6 $\mathrm{GeV}/c$ is not reproduced. However, the experimental result, including the Cronin effect, can be reproduced well by introducing $p_{\mathrm{T}}$ dependence as at most 4–5% correction to the multiplicity-dependent saturation momentum. The relationship between the geometric scaling in the semi-inclusive distributions and the string percolation model is also discussed.

The nature of the $\mathrm{\Lambda }nn$ and ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}^{*}(J^{\pi }=3/2^{+},I=0)$ states is investigated within a pionless effective field theory at leading order, constrained by the low-energy $\mathrm{\Lambda }N$ scattering data and hypernuclear three- and four-body data. Bound-state solutions are obtained using the stochastic variational method, and the continuum region is studied by employing two independent methods: the inverse analytic continuation in the coupling constant method and the complex scaling method. Our calculations yield both the $\mathrm{\Lambda }nn$ and ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}^{*}$ states unbound. We conclude that the excited state ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}^{*}$ is a virtual state and the $\mathrm{\Lambda }nn$ pole located close to the three-body threshold in a complex energy plane could convert to a true resonance with $\mathrm{Re}\left(E\right)>0$ for some considered $\mathrm{\Lambda }N$ interactions. Finally, the stability of resonance solutions is discussed and limits of the accuracy of performed calculations are assessed.

We study the ${}^{1}S_0$ proton pairing gap in $\beta$-equilibrated neutron star matter within the framework of chiral effective field theory. We focus on the role of three-body forces, which strongly modify the effective proton-proton spin-singlet interaction in dense matter. We find that three-body forces generically reduce both the size of the pairing gap and the maximum density at which proton pairing may occur. The pairing gap is computed within Bardeen-Cooper-Schrieffer theory using a single-particle dispersion relation calculated up to second order in perturbation theory. Model uncertainties are estimated by varying the nuclear potential (its order in the chiral expansion and high-momentum cutoff) and the choice of single-particle spectrum in the gap equation. We find that a second-order perturbative treatment of the single-particle spectrum suppresses the proton ${}^{1}S_0$ pairing gap relative to the use of a free spectrum. We estimate the critical temperature for the onset of proton superconductivity to be $T_c=\left(3.2\text{–}5.1\right)\times {10}^9$ K, which is consistent with previous theoretical results in the literature and marginally within the range deduced from a recent Bayesian analysis of neutron star cooling observations.

In the context of the massive secondary object recently observed in the compact-star merger GW190814, we investigate the possibility of producing massive neutron stars from a few different equation of state models that contain exotic degrees of freedom, such as hyperons and quarks. Our work shows that state-of-the-art relativistic mean-field models can generate massive stars reaching $\gtrsim 2.05{\mathrm{M}}_{\mathrm{Sun}}$, while being in good agreement with gravitational-wave events and x-ray pulsar observations, when quark vector interactions and nonstandard self-vector interactions are introduced. In particular, we present a new version of the Chiral Mean Field (CMF) model in which a different quark-deconfinement potential allows for stable stars with a pure quark core. When rapid rotation is considered, our models generate stellar masses that approach, and in some cases surpass $2.5{\mathrm{M}}_{\mathrm{Sun}}$. We find that in such cases fast rotation does not necessarily suppress exotic degrees of freedom due to changes in stellar central density, but require a larger amount of baryons than what is allowed in the nonrotating stars. This is not the case for pure quark stars, which can easily reach $2.5{\mathrm{M}}_{\mathrm{Sun}}$ and still possess approximately the same amount of baryons as stable nonrotating stars. We also briefly discuss possible origins for fast rotating stars with a large amount of baryons and their stability, showing how the event GW190814 can be associated with a star containing quarks as one of its progenitors.

We report a measurement of the ${\pi }^{-}$ photoproduction beam asymmetry for the reaction $\vec{\gamma }p\to {\pi }^{-}{\mathrm{\Delta }}^{++}$ using data from the GlueX experiment in the photon beam energy range 8.2–8.8 GeV. The asymmetry $\mathrm{\Sigma }$ is measured as a function of four-momentum transfer $t$ to the ${\mathrm{\Delta }}^{++}$ and compared to phenomenological models. We find that $\mathrm{\Sigma }$ varies as a function of $t$: negative at smaller values and positive at higher values of $\left|t\right|$. The reaction can be described theoretically by $t$-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. This is the first measurement of the process at this energy.

Geiger-Nuttall law is the simplest relation in radioactive decay relating the half-life and the decay energy. Initially restricted to $\alpha$ decay of individual isotopes, generalizations unifying different isotopes and decay modes under a single set of constant coefficients were subsequently achieved. This motivates investigating to what extent such generalizations are possible. We also examine whether there exists a universal Geiger-Nuttall law that can simultaneously describe all decay modes and nuclei including heavy clusters. We show that the validity of Geiger-Nuttall law and its generalizations hinges on the assumption that half-life can be approximated linearly as a function of the square root of the ratio of the decay energy to the Coulomb barrier height. Systematic calculation of the ratio across the nuclear chart for 12 decay modes reveals that it varies over its whole range between 0 and 1. Consequently, no linear approximation can unify all the nuclei and decay modes under a single set of coefficients, and thus no universal Geiger-Nuttall law is possible in contrast to previous claims. In cluster decay, the ratio varies within 0.6–1 where nonlinearity becomes significant such that no generalized Geiger-Nuttall description of heavy clusters is possible. In the ongoing attempts of unification, it might be necessary to go beyond the Geiger-Nuttall law and incorporate additional terms proportional to the decay energy and/or its square root.