We present an ab initio study of the charge and matter radii of oxygen isotopes from ${}^{16}\mathrm{O}$ to ${}^{20}\mathrm{O}$ using nuclear lattice effective field theory (NLEFT) with high-fidelity ${\mathrm{N}}^3\mathrm{LO}$ chiral interactions. To efficiently address the Monte Carlo sign problem encountered in nuclear radius calculations, we introduce the partial pinhole algorithm, significantly reducing statistical uncertainties and extending the reach to more neutron-rich and proton-rich isotopes. Our computed charge radii for ${}^{16}\mathrm{O}$, ${}^{17}\mathrm{O}$, and ${}^{18}\mathrm{O}$ closely match experimental data, and we predict a charge radius of 2.810(32) fm for ${}^{20}\mathrm{O}$. The calculated matter radii show excellent agreement with values extracted from low-energy proton and electron elastic scattering data, but are inconsistent with those derived from interaction cross sections and charge-changing cross section measurements. These discrepancies highlight model-dependent ambiguities in the experimental extraction methods of matter radii and underscore the value of precise theoretical benchmarks from NLEFT calculations.

The rapid proton-capture process is one of the primary, explosive thermonuclear burning processes that drive type I x-ray bursts. A possible termination of the rapid proton-capture process at around ${}^{84}\mathrm{Mo}$ was previously suggested by the formation of a ZrNb cycle. We report here precision mass measurements at around ${}^{84}\mathrm{Mo}$ that conclude the issue regarding the possibility of the cycle. The experiment was conducted using the multireflection time-of-flight spectrograph at RIKEN Radioactive Isotope Beam Factory, and the masses of ${}^{79}\mathrm{Y}$, ${}^{83}\mathrm{Nb}$, ${}^{84}\mathrm{Mo}$, ${}^{88}\mathrm{Ru}$, and an isomer in ${}^{78}\mathrm{Y}$ were measured. For ${}^{84}\mathrm{Mo}$, ${}^{88}\mathrm{Ru}$, and the isomeric state of ${}^{78}\mathrm{Y}$, their masses were experimentally determined for the first time with uncertainties of $\delta m\approx 20\mathrm{keV}/{\mathrm{c}}^2$. The mass precisions of ${}^{79}\mathrm{Y}$ and ${}^{83}\mathrm{Nb}$ were improved to 13 and $9.6\mathrm{keV}/{\mathrm{c}}^2$, respectively. The new $\alpha$-separation energy of ${}^{84}\mathrm{Mo}$, 1.434(83) MeV, unambiguously rules out the possibility of forming the ZrNb cycle. The x-ray burst simulation with the new masses shows that our measurements effectively remove the large final abundance uncertainties in the $A=80–90$ mass region. The new mass values improve the prediction power for the composition of the nuclear ashes in x-ray bursts.

In confined hadronic matter, the spontaneous breaking and restoration of chiral symmetry can be described by considering nucleons, $N_{+}(939)$, and excited states of opposite parity, $N_{-}(1535)$. In a cold, dense hadronic phase where chiral symmetry remains spontaneously broken, direct Urca decay processes involving the $N_{-}$ are possible, e.g., $N_{-}\to N_{+}+e^{-}+{\overline{\nu }}_e$. We show that at low temperature and moderate densities, because the $N_{-}$ are much heavier than the $N_{+}$, such cooling dominates over standard $N_{+}$ direct Urca processes. This provides a strong astrophysical signature of the pattern of chiral symmetry restoration in neutron stars.

Understanding the equation of state (EOS) of pure neutron matter is necessary for interpreting multimessenger observations of neutron stars. Reliable data analyses of these observations require well-quantified uncertainties for the EOS input, ideally propagating uncertainties from nuclear interactions directly to the EOS. This, however, requires calculations of the EOS for a prohibitively larger number of nuclear Hamiltonians, solving the nuclear many-body problem for each one. Quantum Monte Carlo methods, such as auxiliary-field diffusion Monte Carlo (AFDMC), provide precise and accurate results for the neutron matter EOS, but they are very computationally expensive, making them unsuitable for the fast evaluations necessary for uncertainty propagation. Here, we employ parametric matrix models to develop fast emulators for AFDMC calculations of neutron matter and use them to directly propagate uncertainties of coupling constants in the Hamiltonian to the EOS. As these uncertainties include estimates of the effective field theory truncation uncertainty, this approach provides robust uncertainty estimates for use in astrophysical data analyses. This Letter will enable novel applications such as using astrophysical observations to put constraints on coupling constants for nuclear interactions.

The shapes of the beta spectra of ${}^{92}\mathrm{Rb}$ and ${}^{142}\mathrm{Cs}$, two of the beta decays most relevant for the prediction of the antineutrino spectrum in reactors, have been measured. A new setup composed of two $\mathrm{\Delta }E\text{−}E$ telescopes has been used. High-purity radioactive beams of the isotopes of interest were provided by the IGISOL facility using the JYFLTRAP double Penning trap. The resulting beta spectra have been compared with model predictions using beta decay feedings from total absorption gamma spectroscopy measurements and shape corrections employed in the calculation of the antineutrino spectrum, corroborating both further. The procedure can be extended to other relevant nuclei in the future, providing solid ground for the prediction of the antineutrino spectrum in reactors.

The properties of bound states are fundamental to hadronic spectroscopy and play a central role in the transition from hadronic matter to a quark-gluon plasma (QGP). In a strongly coupled QGP (sQGP), the interplay of temperature, binding energy, and large collisional widths of the partons poses formidable challenges in evaluating the in-medium properties of hadronic states and their eventual melting. In particular, the existence of heavy quarkonia in the QGP is a long-standing problem that is hard to solve by considering their spectral properties on the real-energy axis. We address this problem by analyzing in-medium thermodynamic quarkonium $T$ matrices in the complex energy plane. We first validate this method in vacuum, where the $T$-matrix poles of observed states are readily identified. When deploying this approach to recent self-consistently calculated $T$ matrices in the QGP, we find that poles in the complex energy plane can persist to surprisingly large temperatures, depending on the strength of the in-medium interactions. While the masses and widths of the pole positions are precisely defined, the notion of a binding energy is not due to the absence of thresholds caused by the (large) widths of the underlying quark or anti-quark spectral functions. Our method thus provides a new and definitive quantum-mechanical criterion to determine the melting temperature of hadronic states in the sQGP while increasing the accuracy in the theoretical determination of transport parameters.

The polarization of the $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ hyperons along the beam direction has been measured in proton-lead ($p\text{-Pb}$) collisions at a center-of-mass energy per nucleon pair of 8.16 TeV. The data were obtained with the CMS detector at the LHC and correspond to an integrated luminosity of $186.0\pm 6.5{\mathrm{nb}}^{-1}$. A significant azimuthal dependence of the hyperon polarization, characterized by the second-order Fourier sine coefficient $P_{z,\mathrm{s}2}$, is observed. The $P_{z,\mathrm{s}2}$ values decrease as a function of charged particle multiplicity, but increase with transverse momentum. A hydrodynamic model that describes the observed $P_{z,\mathrm{s}2}$ values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the $p\text{-Pb}$ results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies.

The question of whether there are enough superfluid neutrons in the inner crust of neutron stars to explain pulsar glitches remains a topic of debate. Previous band structure calculations suggest that the entrainment effect significantly reduces the superfluid density. In this Letter, a new derivation of the BCS expression for the superfluid density is given. We compute it in the superfluid band theory framework through linear response theory, for a small relative velocity between superfluid and normal components, under the assumption that the pairing gap in the rest frame of the superfluid is constant and not affected by the perturbation. Our result suggests that a formula extensively used in neutron star physics is incomplete. Numerical evaluations for two realistic configurations reveal that the previously neglected contribution drastically alters the picture of the superfluid reservoir in the inner crust of neutron stars, suggesting that about 90% of the neutrons are effectively superfluid.

Analysis of neutron-capture cross sections in the resolved resonance range reveals that a large fraction of them (13 of 21, or 62%) exhibit highly significant ($>99.9\%$ confidence level) oscillations about their average value. Oscillations exceed a significance level of $5\sigma$ in nine cases (43%). Oscillations comprise $10.86\pm 0.64\%$ of the average cross section with periods ranging from 68.2 to 2380 eV. This contradicts random matrix theory (RMT), which predicts that fluctuations about the average cross section should be entirely random and demonstrates that deviations from RMT are common and widespread in neutron-capture data. These facts suggest there is a widespread physical mechanism that is missing from current nuclear physics models describing neutron-capture cross sections.

We investigate the residual energy distribution in the electron capture (EC) process of ${}^{159}\mathrm{Dy}$, emphasizing the role of subthreshold atomic states, which have typically been omitted in conventional spectral analyses. By incorporating these energetically forbidden hole states into the spectral function $P(E)$, we demonstrate a significant enhancement—over an order of magnitude—in the EC rate near the zero-momentum neutrino emission region. This enhancement increases further with larger $Q$ values, contrary to standard expectations. Our analysis shows that $P(E)$ can be experimentally determined, resolving ambiguities near the end point and enabling new approaches to “ultralow $Q$ value” EC reactions for neutrino mass studies.

We compute medium corrections to the energy-energy correlator (EEC) for jets in electron-nucleus collisions at leading order in the QCD coupling and the interaction of the jet with the medium. We derive an analytical expression for the modification of the EEC as a function of the opening angle and show that the modification is strongest at large angles within the jet cone. We obtain explicit results for the dependence of the modification on the jet energy, the scattering power of cold nuclear matter, and the path length within the medium. We extend our calculations to gluon jets in proton-nucleus collisions and compare our results with recent preliminary data for proton-lead collisions at the LHC. We also discuss the role of comovers on the EEC in $\mathrm{p}+\mathrm{Pb}$ collisions.

Bound states of charm and anticharm quarks, known as charmonia, have a rich spectroscopic structure that can be used to probe the dynamics of hadron production in high-energy hadron collisions. Here, the cross section ratio of excited $(\psi (2S))$ and ground state $(J/\psi )$ vector mesons is measured as a function of the charged-particle multiplicity in proton-lead ($p\mathrm{Pb}$) collisions at a center-of-mass (CM) energy per nucleon pair of 8.16 TeV. The data corresponding to an integrated luminosity of $175{\mathrm{nb}}^{-1}$ were collected using the CMS detector. The ratio is measured separately for prompt and nonprompt charmonia in the transverse momentum range $6.5<p_{\mathrm{T}}<30\mathrm{GeV}$ and in four rapidity ranges spanning $-2.865<y_{\mathrm{CM}}<1.935$. For the first time, a statistically significant multiplicity dependence of the prompt cross section ratio is observed in proton-nucleus collisions. There is no clear rapidity dependence in the ratio. The prompt measurements are compared with a theoretical model which includes interactions with nearby particles during the evolution of the system. These results provide additional constraints on hadronization models of heavy quarks in nuclear collisions.

We present a new measurement of the $2\nu \beta \beta$ half-life of ${}^{130}\mathrm{Te}$ ($T_{1/2}^{2\nu }$) using the first complete model of the CUORE data, based on 1038 kg yr of collected exposure. Thanks to optimized data selection, we achieve a factor of two improvement in precision, obtaining $T_{1/2}^{2\nu }=(9.32{}_{-0.04}^{+0.05}\mathrm{stat}{}_{-0.07}^{+0.07}\mathrm{syst})\times {10}^{20}\mathrm{yr}$. The signal-to-background ratio is increased by 70% compared to our previous results, enabling the first application of the improved $2\nu \beta \beta$ formalism to ${}^{130}\mathrm{Te}$. Within this framework, we determine a credibility interval for the effective axial coupling in the nuclear medium as a function of nuclear matrix elements. We also extract values for the higher-order nuclear matrix element ratios: second-to-first and third-to-first. The second-to-first ratio agrees with nuclear model predictions, while the third-to-first ratio deviates from theoretical expectations. These findings provide essential tests of nuclear models and key inputs for future $0\nu \beta \beta$ searches.

The 247-keV state in ${}^{54}\mathrm{Sc}$, populated in the $\beta$ decay of ${}^{54}\mathrm{Ca}$, is reported here as a nanosecond isomer with a half-life of 26.0(22) ns. The state is interpreted as the $1^{+}$ member of the $\pi f_{7/2}\otimes \nu f_{5/2}$ spin-coupled multiplet, which decays to the $3^{+},\pi f_{7/2}\otimes \nu p_{1/2}$ ground state. The new half-life corresponds to a pure $E2$ transition with a strength of 1.93(16) W.u., providing the most precise, unambiguous $B(E2)$ value in the neutron-rich $fp$ region to date for a nucleus with valence protons above $Z=20$. Notably, it is roughly 4 times larger than the $B(E2;1/2^{-}\to 5/2^{-})$ value in ${}^{55}\mathrm{Ca}$. The results, as compared to semiempirical and ab initio shell-model calculations, indicate (1) a weak $N=34$ subshell gap relative to $N=32$, (2) a large $E2$ enhancement in Sc as compared to Ca due to $1p-1h$ proton excitations across $Z=28$, and (3) empirical effective proton and neutron charges $e_{\pi }=1.30(8)e$ and $e_{\nu }=0.452(7)e$, respectively, that are in contrast to reports of $e_{\pi }\approx 1.1–1.15e$ and $e_{\nu }\approx 0.6–0.8e$ for $fp$-shell nuclei near $N=Z$. We demonstrate that these reports are erroneous and that, in fact, a universal set of effective charges can be used across the $sd$ and $fp$ shells.

Diffusion wake accompanying a Mach cone is a unique feature of the medium response to projectiles traveling at a speed faster than the velocity of sound. This is also the case for jet-medium interaction inside the quark-gluon plasma in high-energy heavy-ion collisions. It leads to a depletion of soft hadrons in the opposite direction of the propagating jet and, recently, has been observed in $Z$-jet events of $\mathrm{Pb}+\mathrm{Pb}$ collisions at LHC. In dijet events, however, the diffusion wake of one jet usually overlaps with the medium-induced hadron enhancement of the other jet without a clear signal except a reduction of the hadron enhancement, unless there is a large rapidity gap between the two jets. We propose to use the rapidity asymmetry of jet-hadron correlations in dijets with a finite rapidity gap relative to that without, as a robust and background-free signal of the diffusion wake. The asymmetry emerges because the diffusion wake of one jet is shifted to a finite rapidity relative to the other jet. Consequently, a depletion of soft hadrons appears in the shifted rapidity region of the diffusion wake and an enhancement in the rapidity region of the other jet whose soft hadron enhancement is no longer or less reduced by the diffusion wake as in dijets without a rapidity gap. We predict the rapidity asymmetry using both theoretical and mixed-event background subtraction for different values of the rapidity gap within the CoLBT-hydro model. Future measurements of this rapidity asymmetry with high statistics data on dijets should provide more precise insights into the jet-induced diffusion wake and properties of the quark-gluon plasma.

Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow $v_2$ in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of $v_2$ of ${\pi }^{\pm }$, $K^{\pm }$, $K_S^0$, $p$, and $\mathrm{\Lambda }$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=3.2$, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of $v_2$ for all hadrons studied provides evidence for the onset of dominant partonic interactions by $\sqrt{s_{\mathrm{NN}}}=4.5\mathrm{GeV}$.

In nuclei with an odd nucleon number the nonvanishing spin number density is the source of a pseudomagnetic field, which favors the splitting of the nucleon Cooper pairs. Such a pseudomagnetic field is generated always in the dynamics of any nucleus, but its effects on Cooper pairs are significantly enhanced in the dynamic evolution of nuclei with an odd number of nucleons. We present for the first time a microscopic study of the induced fission of the odd neutron compound nuclei ${}^{239}\mathrm{U}$, ${}^{241,243}\mathrm{Pu}$, and the odd proton, odd neutron compound nucleus ${}^{238}\mathrm{Np}$, performed within the time-dependent density functional theory extended to superfluid fermion systems, without any simplifying assumptions, with controlled numerical approximations, and for a very large number of initial conditions. Because of the presence of the unpaired odd nucleon(s), the time-reversal symmetry of the fission compound nucleus is spontaneously broken, an aspect routinely neglected in the most advanced microscopic approaches of the past. The emerging fission fragment properties are quite similar to the properties of fission fragments of neighboring even-even nuclei. The time from saddle-to-scission is often significantly longer in odd-odd or odd-mass nuclei than for even-even nuclei, since systems with unpaired nucleons are easier to excite and the potential energy surfaces of these nuclei have more structure, often resembling a very complicated obstacle course, rather than a more direct evolution of the nuclear shape from the top of the outer fission barrier to the scission configuration. The Pauli blocking approximation, often invoked in the literature, expected to inhibit the fission of nuclei with unpaired nucleons, is surprisingly strongly violated during the fission dynamics.