We have performed high-precision mass measurements of neutron-rich rare-earth Tb, Dy, and Ho isotopes using the phase-imaging ion-cyclotron-resonance technique at the JYFLTRAP double Penning trap. We report on the first experimentally determined mass values for ${}^{169}\mathrm{Tb}$, ${}^{170}\mathrm{Dy}$, and ${}^{171}\mathrm{Dy}$, as well as the first high-precision mass measurements of ${}^{169}\mathrm{Dy}$ and ${}^{169–171}\mathrm{Ho}$. For ${}^{170}\mathrm{Ho}$, the two long-lived ground and isomeric states were resolved and their mass measured, yielding an isomer excitation energy of $E_{\text{exc}}=150.8\left(54\right)$ keV. In addition, we have performed independent crosschecks of previous Penning-trap values obtained for ${}^{167\text{,}168}\mathrm{Tb}$ and ${}^{167\text{,}168}\mathrm{Dy}$. We have extended the systematics of two-neutron separation energies to the neutron midshell at $N=104$ in all of the studied isotopic chains. Our updated and new mass measurements provide better mass-related constraints for the neutron-capture reaction rates relevant to the astrophysical rapid neutron capture $\left(r\right)$ process. The $r$-process abundances calculated with the new mass values seem to produce a steeper minimum at $A=170$ and differ by around 15–30% from the abundances computed with the Atomic Mass Evaluation 2020 values.

We study the leading radiative correction to proton-proton fusion using the pionless effective field theory framework at leading order. We derive the relevant matrix elements and evaluate them using the method of regions. We benchmark the accuracy of our approximations by carrying out numerical computations of the full expressions. We show that the first order radiative corrections due to the exchange of a Coulomb photon between positron and proton-proton systems map onto the Sirlin function and the $\mathcal{O}\left(\alpha \right)$ contribution from the Fermi function. We furthermore find that the nuclear structure dependent radiative correction omitted in the previous analysis by Kurylov et al. [Phys. Rev. C 67, 035502 (2003)] gives an up to $0.2\%$ correction to the $pp$ fusion $S$ factor with its size ultimately depending on a two-nucleon counterterm $L_{1A}$ that renormalizes the axial two-body current.

The neutron structure function, $F_{2n}$, has historically been extracted from measurements of the deuteron structure function, which is limited by our understanding of the nuclear effects on the bound proton and neutron. The MARATHON Collaboration recently extracted $F_{2n}$ from the comparison of ${}^3\mathrm{H}$ and ${}^3\mathrm{He}$ targets, where the nuclear effects are larger but nearly identical, yielding a precise extraction of $F_{2n}/F_{2p}$. To ensure that this comparison is not biased by the specific model of nuclear effects used by MARATHON, we examine a range of models of the nuclear effects to obtain a more conservative, but more model-independent, extraction of $F_{2n}/F_{2p}$ for comparison with deuteron extractions. Even with this approach, the results are precise enough to compare to deuteron extractions, providing new constraints on the nuclear effects in the deuteron and indicating the need for larger nuclear corrections than those included in most models.

Faddeev calculations of low-energy $\mathrm{\Lambda }$-deuteron elastic scattering are performed up to $E_{cm}=20$ MeV crossing the deuteron threshold. The phase shifts of the $s$ wave with $J=1/2$ and $J=3/2$ are calculated using strangeness $S=-1$ hyperon-nucleon interactions in chiral effective field theory NLO13 and NLO19 parametrized by the Jülich-Bonn group. The effective range parameters, specifically the scattering length and effective range, are ascertained through the calculated phase shifts. The present study evaluates the momentum correlation functions of the $\mathrm{\Lambda }$-deuteron system using the $\mathrm{\Lambda }$-deuteron relative wave function, constructed from half-off-shell $t$ matrices. The results are then compared with those obtained using an approximate formula.

Evaporation residue (ER) cross sections and ER-gated $\gamma$-ray fold distributions are measured for the ${}^{32}\mathrm{S}+{}^{154}\mathrm{Sm}$ nuclear reaction above the Coulomb barrier at six different beam energies from 148 to 191 MeV. $\gamma$-ray multiplicities and spin distributions are extracted from the ER-gated fold distributions. The ER cross sections measured in the present work are found to be much higher than what was reported in a previous work using a very different target-projectile $({}^{48}\mathrm{Ti}+{}^{138}\mathrm{Ba})$ combination, leading to the same compound nucleus ${}^{186}\mathrm{Pt}$, with much less mass asymmetry in the entrance channel than the present reaction. This clearly demonstrates the effect of the entrance channel on ER production cross section. The ER cross sections measured in the present work are compared with the results of both the statistical model calculations and the dynamical model calculations. Statistical model calculations have been performed to generate a range of parameter space for both the barrier height and Kramers's viscosity parameter over which the ER cross-section data can be reproduced. The calculations performed using the dinuclear system (DNS) model reproduce the data considering both complete and incomplete fusion processes. DNS calculations indicate the need for the inclusion of an incomplete fusion channel at higher energies to reproduce the ER cross sections.

Data for the angular distribution of the inclusive ${}^7\mathrm{Be}$ production cross section in the ${}^8\mathrm{B}+{}^{208}\mathrm{Pb}$ system at an incident energy of 50 MeV, equivalent to the nominal Coulomb barrier height, were measured at the CRIB facility. A coupled discretized continuum channel calculation was able to describe the data well, with no evidence for a significant contribution from nonelastic breakup. The energy dependence of the breakup cross section was investigated with the aid of previous measurements of the inclusive ${}^7\mathrm{Be}$ production cross section for the same system at a deep sub-barrier energy and at approximately four times the Coulomb barrier. We infer an increasing importance of nonelastic breakup as the incident energy is increased above the barrier, ruling out proton-stripping as a possible mechanism for this process due to the increasingly badly $Q$-matched character of this transfer reaction as the incident energy increases.

The phase space density, ${\rho }^Q$, of quarks in nuclei is studied using realistic models of unintegrated quark distributions, known as transverse momentum densities (TMDs). If this density exceeds unity for matter at normal nuclear densities, the effects of the quark Pauli principle must play a role in nuclei, and models in which the nucleon density at low momentum is small (quarkyonic matter) may become a starting point for an entirely new description of nuclei. We denote the nuclear density for which ${\rho }^Q=1$ to be a transmutation density, $n_T$, because quark degrees of freedom must be relevant at that density. Including the TMDs of [G. F. de Teramond et al., Phys. Rev. Lett. 120, 182001 (2018)] for the valence quarks and phenomenological TMDs for the sea quarks, we find that $n_T=0.17\pm 0.04{\mathrm{fm}}^{-3}$, a density range that includes current determinations of the density of normal nuclear matter, $0.16\pm 0.01{\mathrm{fm}}^{-3}$. Some of the implications of this finding are discussed.

The ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ is an important destructive reaction for the ${}^{10}\mathrm{B}$ abundance in different astrophysical scenarios. Meanwhile, it may have a unignorable impact on models of new reactors for clean energy generation, and could provide an independent test for temperature analysis in the new generation of laser-driven facilities. $S$ factors were determined for the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ reaction at $E_p=120\text{–}274\mathrm{keV}$ through an activation method. The 478 keV $\gamma$ rays arising from the decay of ${}^7\mathrm{Be}$ were detected by a low-background $\gamma$-ray spectrometer. The present data show a significant inconsistency with respect to previous results using the activation technique, but agree well with the data of direct $\alpha$ detection. A global $R$-matrix analysis has been implemented based on the present and previous data. Further, a revised reaction rate was extracted relying on the fitting parameters.

The $\sigma$-cut scheme was recently proposed as a method of stiffening the neutron-star equation of state (EoS) at high densities without altering its behavior around the nuclear saturation density. We use the $\sigma$-cut scheme to describe the dense matter containing hyperons and kaons, enabling us to obtain high-mass neutron stars without having to modify the relativistic mean field (RMF) model parameters. Using three different parametrizations of the RMF model, we investigate the effects of the $\sigma$-cut scheme on particle populations, tidal deformability, nonradial oscillations, and thermal evolution of neutron stars. Our investigations yielded promising results, supporting the use of the $\sigma$-cut scheme as a viable method for incorporating additional exotic degrees of freedom in neutron-star matter. This is particularly evident in the thermal evolution calculations, where it significantly enhances the alignment between the theoretical predictions and the observed temperatures of neutron stars.

Using the fourth-order extended Thomas-Fermi method with Strutinsky-integral shell and pairing corrections, we calculate the inner crust of neutron stars with the BSk31 functional, whose pairing has two terms: (i) a term that is fitted to the results of microscopic calculations on homogeneous nuclear matter (accounting for both medium polarization and self-energy effects) that are more realistic than those of our earlier functionals; (ii) an empirical term that is dependent on the density gradient, which permits an excellent fit to nuclear masses. Both proton and neutron pairing are taken into account, the former in the BCS theory and the latter in the local density approximation. We found that the equilibrium value of the proton number $Z$ remains 40 over the entire density range considered, whether or not neutron pairing is included. The new equation of state and the composition are very similar to those of our previously preferred functional, BSk24. However, the predicted neutron pairing fields are quite different. In particular, clusters are found to be impermeable to the neutron superfluid. The implications for the neutron superfluid dynamics are briefly discussed. Since the new pairing is more realistic, the functional BSk31 is better suited for investigating neutron superfluidity in neutron-star crusts.

We test the BUQEYE model of correlated effective field theory (EFT) truncation errors on Reinert, Krebs, and Epelbaum's semilocal momentum-space implementation of the chiral EFT ($\chi \mathrm{EFT}$) expansion of the nucleon-nucleon (NN) potential. This Bayesian model hypothesizes that dimensionless coefficient functions extracted from the order-by-order corrections to NN observables can be treated as draws from a Gaussian process (GP). We combine a variety of graphical and statistical diagnostics to assess when predicted observables have a $\chi \mathrm{EFT}$ convergence pattern consistent with the hypothesized GP statistical model. Our conclusions are that, first, the BUQEYE model is generally applicable to the potential investigated here, which enables statistically principled estimates of the impact of higher EFT orders on observables. Second, parameters defining the extracted coefficients such as the expansion parameter $Q$ must be well chosen for the coefficients to exhibit a regular convergence pattern—a property we exploit to obtain posterior distributions for such quantities. Third, the assumption of GP stationarity across lab energy and scattering angle is not generally met; this necessitates adjustments in future work. We provide a workflow and interpretive guide for our analysis framework, and show what can be inferred about probability distributions for $Q$, the EFT breakdown scale ${\mathrm{\Lambda }}_b$, the scale associated with soft physics in the $\chi \mathrm{EFT}$ potential $m_{\mathrm{eff}}$, and the GP hyperparameters. All our results can be reproduced using a publicly available Jupyter notebook, which can be straightforwardly modified to analyze other $\chi \mathrm{EFT}$ NN potentials.

Low-energy nuclear interactions have been extensively studied in the framework of chiral effective field theory. The corresponding potentials have been worked out using dimensional regularization to evaluate ultraviolet divergent loop integrals. An additional cutoff is then introduced in the nuclear Schrödinger equation to calculate observables. Recently, we showed that such a mixture of two regularization schemes violates chiral symmetry when applied beyond the two-nucleon system and/or to processes involving external probes. To solve this issue, three- and four-nucleon forces as well as exchange current operators need to be rederived using symmetry-preserving cutoff regularization. While it is possible to introduce a symmetry-preserving cutoff already in the effective chiral Lagrangian, the appearance of high-order time derivatives of the pion field, caused by the regulator, makes the standard Hamiltonian-based methods not well suited for the calculation of nuclear potentials. Here, we propose a new approach to derive nuclear interactions using the path integral method with no reliance on the canonical quantization. To this aim, the interaction part of the action is brought to an instantaneous form via suitably chosen nonlocal field redefinitions. Loop contributions to the nuclear potentials are then generated through functional determinants, induced by the field redefinitions. We discuss in detail the application of these ideas to the case of a regularized Yukawa-type model of pion-nucleon interactions. Our new method allows one to perform a systematic quantum mechanical reduction within the quantum field theory framework and opens the way for deriving consistently regularized nuclear forces and current operators from the effective chiral Lagrangian.

Low-energy nuclear structure and reactions can be described in a systematically improvable way using the framework of chiral effective field theory. This requires solving the quantum mechanical many-body problem with regularized nuclear forces and current operators, derived from the most general effective chiral Lagrangian. To maintain the chiral and gauge symmetries, a symmetry preserving cutoff regularization has to be employed when deriving nuclear potentials. Here, we discuss various regularization techniques and show how this task can be accomplished by regularizing the pion field in the effective chiral Lagrangian using the gradient flow method. The actual derivation of the nuclear forces and currents from the regularized effective Lagrangian can be carried out utilizing the novel path-integral approach introduced in our earlier paper.

We explore the impact of retaining three-body operators within the in-medium similarity renormalization group (IMSRG), as well as various approximations schemes. After studying two toy problems, identical fermions with a contact interaction and the Lipkin-Meshkov-Glick model, we employ the valence-space formulation of the IMSRG to investigate the even-$A$ carbon isotopes with a chiral two-body potential. We find that retaining only those commutators expressions that scale as $N^7$ provides an excellent approximation of the full three-body treatment.

We describe an approximation to the in-medium similarity renormalization group (IMSRG) method in which we include the effects of intermediate three-body operators arising within nested commutators. As an initial step, we present the relevant equations for two nested commutators, all of which can be factorized so that the method scales like the standard IMSRG(2) approximation, enabling large-scale calculations. We test the accuracy of this approximation scheme, and apply it to the isotopic chains of carbon, sulfur and nickel isotopic chains. We obtain an improved description of spectroscopy and a reduced dependence on the choice of the valence space. In addition, we provide an explanation of the relative importance of the diagram topologies included, with an eye toward assessing the impact of remaining omitted terms.

Background: In recent years, the implementation of nuclear physics models in quantum computers has emerged as a promising and novel area of research. Simultaneously, the study of quantum shape phase transitions in nuclear models has gained significant attention. Specifically, the phase diagram of the interacting boson approximation (IBA) has been extensively explored, particularly in connection with large-particle-number-limit considerations. Interestingly, the extended Lipkin model (ELM) serves as a valuable alternative for mimicking the IBA phase diagram and holds the advantage of being more straightforward to implement within a quantum computing platform.

Purpose: We explore the ELM and provide: (i) calculations of the ground-state energy using a variational quantum eigensolver; (ii) a comprehensive formulation for implementing the dynamics of the ELM within a quantum computing platform, enabling the experimental exploration of the IBA phase diagram for systems with a small number of particles; and (iii) a determination of the phase diagram of the model using different machine learning (ML) methods. We note that in the ELM, unlike the usual Lipkin model, both first- and second-order quantum shape phase transitions take place depending on the model parameters.

Methods: Initially, we employ the adaptive derivative-assembled pseudo-Trotter ansatz variational quantum eigensolver (ADAPT-VQE) to calculate the ground-state energy of the ELM. Next, we introduce the essential formulation and procedures required to implement this model effectively in a quantum computing environment. Finally, we use ML techniques to identify the different phases and critical points of the ELM.

Results: We successfully reproduce the ground-state energy of the ELM across the complete phase space of the model using the ADAPT-VQE algorithm. We provide the necessary framework for implementing the ELM in a quantum computing platform, ensuring that the model can be executed with controlled errors. Finally, we obtain meaningful ML predictions that allow us to determine the phase diagram of the model.

Conclusions: Our findings offer compelling evidence that the implementation of a nuclear model like the ELM in a quantum computing environment is not only feasible but can also be achieved with manageable error rates. This realization opens the door to detailed experimental investigations of the phase diagram of the ELM (and indirectly of the IBA) in a quantum computer, further advancing our understanding of quantum shape phase transitions and nuclear structure.

We perform a systematic study of inelastic nuclear rainbow scattering for the ${}^{16}\mathrm{O}$ +${}^{12}\mathrm{C}$ system to the $2^{+}$ (4.44 MeV) state of ${}^{12}\mathrm{C}$ at incident energies of 100–608 MeV with the coupled-channels method. The recently generalized nearside-farside decomposition for inelastic scattering was applied in combination with the multichannel deflection function analysis to elucidate the origin of the nuclear rainbow phenomenon and the suppression of the primary and supernumerary Airy minima in the inelastic-scattering cross section. The systematic evolution of the Airy minima for the excited $2^{+}$ (4.44 MeV) state of ${}^{12}\mathrm{C}$ was unambiguously determined. Our work suggests that there is no clear shift in the positions of the first Airy minima and a small shift at low energies for the second and third Airy minima between the inelastic- and elastic-scattering cross sections. Using the $K$-subamplitudes splitting technique combined with the generalized nearside-farside decomposition and deflection function, the distinct refractive pattern commonly suppressed in the inelastic heavy-ion scattering can be interpreted and provides new insights into the relationship between elastic and inelastic nuclear rainbow scattering.

Cross-section data for Th nuclei produced in the ${}^{48}\mathrm{Ca}+{}^{170}\mathrm{Yb}$ and ${}^{54}\mathrm{Cr}+{}^{164}\mathrm{Dy}$ fusion-evaporation reactions leading to the same ${}^{218}\mathrm{Th}^{*}$ compound nucleus (CN) were obtained with the Dubna Gas-Filled Recoil Separator (DGFRS-2) at energies around the fusion barriers. These data, corresponding to the neutron evaporation channels in both reactions, are considered from the point of view of the CN formation probability in going from the ${}^{48}\mathrm{Ca}$- to ${}^{54}\mathrm{Cr}$-induced reactions. Such interest stems from searching for ways to synthesize superheavy nuclei (SHN) in reactions with projectiles heavier than ${}^{48}\mathrm{Ca}$, bearing in mind that numerous calculations show a significant drop in the SHN production cross section when going from ${}^{48}\mathrm{Ca}$ to heavier projectiles. The mutual comparison of Th production cross sections for ${}^{48}\mathrm{Ca}+{}^{170}\mathrm{Yb}$ and ${}^{54}\mathrm{Cr}+{}^{164}\mathrm{Dy}$ reactions allowed us to obtain the CN formation probability imposed by the quasifission effect, which is more inherent in the ${}^{54}\mathrm{Cr}+{}^{164}\mathrm{Dy}$ reaction as compared to ${}^{48}\mathrm{Ca}+{}^{170}\mathrm{Yb}$.

We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the jetscape framework. The details of the multistage model and the various parameter choices are described in [Phys. Rev. C 107, 034911 (2023)]. A novel feature of this model is the presence of two stages of jet modification: a high-virtuality phase [modeled using the modular all twist transverse-scattering elastic-drag and radiation model (matter)], where modified coherence effects diminish medium-induced radiation, and a lower virtuality phase [modeled using the linear Boltzmann transport model (lbt)], where parton splits are fully resolved by the medium as they endure multiple scattering induced energy loss. Energy-loss calculations are carried out on event-by-event viscous fluid dynamic backgrounds constrained by experimental data. The uniform and consistent descriptions of multiple experimental observables demonstrate the essential role of modified coherence effects and the multistage modeling of jet evolution. Using the best choice of parameters from [Phys. Rev. C 107, 034911] (2023)], and with no further tuning, we present calculations for the medium modified jet fragmentation function, the groomed jet momentum fraction $z_g$ and angular separation $r_g$ distributions, as well as the nuclear modification factor of groomed jets. These calculations provide accurate descriptions of published data from experiments at the Large Hadron Collider. Furthermore, we provide predictions from the multistage model for future measurements at the BNL Relativistic Heavy Ion Collider.

With the STAR experiment at the BNL Relativistic Heavy Ion Collider, we characterize $\sqrt{s_{NN}}=200\mathrm{GeV}$ $p+\text{Au}$ collisions by event activity (EA) measured within the pseudorapidity range $\eta \in [-5,-3.4]$ in the Au-going direction and report correlations between this EA and hard- and soft-scale particle production at midrapidity $(\eta \in [-1,1\left]\right)$. At the soft scale, charged particle production in low-EA $p+\text{Au}$ collisions is comparable to that in $p+p$ collisions and increases monotonically with increasing EA. At the hard scale, we report measurements of high transverse momentum $\left(p_{\mathrm{T}}\right)$ jets in events of different EAs. In contrast with the soft particle production, high-$p_{\mathrm{T}}$ particle production and EA are found to be inversely related. To investigate whether this is a signal of jet quenching in high-EA events, we also report ratios of $p_{\mathrm{T}}$ imbalance and azimuthal separation of dijets in high- and low-EA events. Within our measurement precision, no significant differences are observed, disfavoring the presence of jet quenching in the highest 30% EA $p+\text{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$.