We place unprecedented constraints on recoil corrections in the $\beta$ decay of ${}^8\mathrm{Li}$, by identifying a strong correlation between them and the ${}^8\mathrm{Li}$ ground state quadrupole moment in large-scale ab initio calculations. The results are essential for improving the sensitivity of high-precision experiments that probe the weak interaction theory and test physics beyond the standard model. In addition, our calculations predict a $2^{+}$ state of the $\alpha +\alpha$ system that is energetically accessible to $\beta$ decay but has not been observed in the experimental ${}^8\mathrm{Be}$ energy spectrum, and has an important effect on the recoil corrections and $\beta$ decay for the $A=8$ systems. This state and an associated $0^{+}$ state are notoriously difficult to model due to their cluster structure and collective correlations, but become feasible for calculations in the ab initio symmetry-adapted no-core shell-model framework.

We demonstrate in a general and analytic way how high-density information about the equation of state (EOS) of strongly interacting matter obtained using perturbative quantum chromodynamics constrains the same EOS at densities reachable in physical neutron stars. Our approach is based on utilizing the full information of the thermodynamic potentials at the high-density limit together with thermodynamic stability and causality. This requires considering the pressure as a function of chemical potential $p(\mu )$ instead of the commonly used pressure as a function of energy density $p(\epsilon )$. The results can be used to propagate the perturbative quantum chromodynamics calculations reliable around $40n_s$ to lower densities in the most conservative way possible. We constrain the EOS starting from only a few times the nuclear saturation density $n\gtrsim 2.2n_s$, and at $n=5n_s$ we exclude at least 65% of otherwise allowed area in the $\epsilon \text{−}p$ plane. This provides information complementary to astrophysical observations that should be taken into account in any complete statistical inference study of the EOS. These purely theoretical results are independent of astrophysical neutron-star input, and hence, they can also be used to test theories of modified gravity and beyond the standard model physics in neutron stars.

We report precision measurements of hypernuclei ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ lifetimes obtained from $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=3.0\mathrm{GeV}$ and 7.2 GeV collected by the STAR experiment at the Relativistic Heavy Ion Collider, and the first measurement of ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ midrapidity yields in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=3.0\mathrm{GeV}$. ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$, being the two simplest bound states composed of hyperons and nucleons, are cornerstones in the field of hypernuclear physics. Their lifetimes are measured to be $221\pm 15(\mathrm{stat})\pm 19(\mathrm{syst})\mathrm{ps}$ for ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and $218\pm 6(\mathrm{stat})\pm 13(\mathrm{syst})\mathrm{ps}$ for ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$. The $p_T$-integrated yields of ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ is different for 0%–10% and 10%–50% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ yield well, while underestimating the ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ yield. Transport models, combining baryonic mean-field and coalescence (jam) or utilizing dynamical cluster formation via baryonic interactions (phqmd) for light nuclei and hypernuclei production, approximately describe the measured ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ yields. Our measurements provide means to precisely assess our understanding of the fundamental baryonic interactions with strange quarks, which can impact our understanding of more complicated systems involving hyperons, such as the interior of neutron stars or exotic hypernuclei.

We present the first systematic feasibility study of accessing generalized parton distributions of the pion at an electron-ion collider through deeply virtual Compton scattering. Relying on state-of-the-art models for pion GPDs, we show that quarks and gluons interfere destructively, modulating the expected event rate and maximizing it when parton content is generated via radiation from valence dressed quarks. Moreover, gluons are found to induce a sign inversion for the beam-spin asymmetry in every model studied, being a clear signal for pinning down the regime of gluon superiority.

The ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ reaction plays an important role in understanding the nucleosynthesis of $A\ge 30$ nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure ${}^{31}\mathrm{Cl}$ $\beta$-delayed proton decay through the key $J^{\pi }=3/2^{+}$, 260-keV resonance. The intensity $I_{\beta p}^{260}=8.3_{-0.9}^{+1.2}\times {10}^{-6}$ represents the weakest $\beta$-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of ${\mathrm{\Gamma }}_p/\mathrm{\Gamma }=2.5_{-0.3}^{+0.4}\times {10}^{-4}$. By combining this measurement with shell-model calculations for ${\mathrm{\Gamma }}_{\gamma }$ and past work on other resonances, the total ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of ${}^{30}\mathrm{Si}$:${}^{28}\mathrm{Si}$ excesses in presolar nova grains and the calibration of nuclear thermometers.

In the exothermic process of fission decay, an atomic nucleus splits into two or more independent fragments. Several aspects of nuclear fission are not properly understood, in particular the formation of the neck between the nascent fragments, and the subsequent mechanism of scission into two or more independent fragments. Using an implementation of time-dependent density functional theory, based on a relativistic energy density functional and including pairing correlations, we analyze the final phase of the process of induced fission of ${}^{240}\mathrm{Pu}$, and show that the timescale of neck formation coincides with the assembly of two $\alpha$-like clusters. Because of its much larger binding energy, the dynamical synthesis of ${}^4\mathrm{He}$ in the neck predominates over other light clusters, e.g., ${}^3\mathrm{H}$ and ${}^6\mathrm{He}$. At the instant of scission the neck ruptures exactly between the two $\alpha$-like clusters, which separate because of the Coulomb repulsion and are eventually absorbed by the two emerging fragments. The mechanism of light charged clusters formation at scission could also be linked to ternary fission.

The production of $J/\psi$ mesons in heavy-ion collisions at the Large Hadron Collider is believed to be dominated by the recombination of charm and anticharm quarks in a hot QCD medium. However, measurements of the elliptic flow ($v_2$) of $J/\psi$ mesons in these reactions are not well described by existing calculations of $J/\psi$ recombination for transverse momenta $p_T\gtrsim 4\mathrm{GeV}$. We revisit these calculations in two main aspects. Employing the resonance recombination model, we implement distribution functions of charm quarks transported through the quark-gluon plasma using state-of-the-art Langevin simulations and account for the space-momentum correlations of the diffusing charm and anticharm quarks in a hydrodynamically expanding fireball. This extends the relevance of the recombination processes to substantially larger momenta than before. We also revisit the suppression of primordially produced $J/\psi$’s by propagating them through the same hydrodynamic medium, leading to a marked increase of their $v_2$ over previous estimates. Combining these developments into a calculation of the $p_T$-dependent nuclear modification factor and $v_2$ of inclusive $J/\psi$ production in semicentral Pb-Pb collisions at the LHC, we find a good description of the experimental results by the ALICE Collaboration. Our results thus resolve the abovementioned $v_2$ puzzle and imply the relevance of recombination processes for $p_T$’s of up to $\sim 8\mathrm{GeV}$.

Some nuclear isomers are known to store a large amount of energy over long periods of time, with a very high energy-to-mass ratio. Here, we describe a protocol to achieve the external control of the isomeric nuclear decay by using electron vortex beams whose wave function has been especially designed and reshaped on demand. Recombination of these electrons into the isomer’s atomic shell can lead to the controlled release of the stored nuclear energy. On the example of ${}^{93m}\mathrm{Mo}$, we show theoretically that the use of tailored electron vortex beams increases the depletion by 4 orders of magnitude compared to the spontaneous nuclear decay of the isomer. Furthermore, specific orbitals can sustain an enhancement of the recombination cross section for vortex electron beams by as much as 6 orders of magnitude, providing a handle for manipulating the capture mechanism. These findings open new prospects for controlling the interplay between atomic and nuclear degrees of freedom, with potential energy-related and high-energy radiation source applications.

The ${}^{18}\mathrm{O}(\alpha ,\gamma ){}^{22}\mathrm{Ne}$ reaction is an essential part of a reaction chain that produces the ${}^{22}\mathrm{Ne}(\alpha ,n){}^{25}\mathrm{Mg}$ neutron source for both the weak and main components of the slow neutron-capture process. At temperatures of stellar helium burning, the astrophysically relevant resonances in the ${}^{18}\mathrm{O}(\alpha ,\gamma ){}^{22}\mathrm{Ne}$ reaction that dominate the reaction rate occur at $\alpha$ particle energies $E_{\mathrm{lab}}$ of 472 and 569 keV. However, previous experiments have shown the strengths of these two resonances to be very weak, and only upper limits or partial resonance strengths could be obtained. This Letter reports the first direct measurement of the total resonance strength for the 472- and 569-keV resonances, $0.26\pm 0.05$ and $0.63\pm 0.30\mu \mathrm{eV}$, respectively. New resonance strengths for the resonances at $\alpha$ particle energies of 662.1, 749.9, and 767.6 keV are also provided. These results were achieved in an experiment optimized for background suppression and detection efficiency. The experiment was performed at the Sanford Underground Research Facility, in the 4850-foot underground cavity dedicated to the Compact Accelerator System for Performing Astrophysical Research. The experimental end station used the $\gamma$-summing High EffiCiency TOtal absorption spectrometeR. Compared to previous works, the results decrease the stellar reaction rate by as much as $\approx 46_{-11}^{+6}\%$ in the relevant temperature range of stellar helium burning.

The Rare-RI Ring (R3) is a recently commissioned cyclotronlike storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory (RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF—${}^{127}\mathrm{Sn}$, ${}^{126}\mathrm{In}$, ${}^{125}\mathrm{Cd}$, ${}^{124}\mathrm{Ag}$, ${}^{123}\mathrm{Pd}$—were injected in R3. Masses of ${}^{126}\mathrm{In}$, ${}^{125}\mathrm{Cd}$, and ${}^{123}\mathrm{Pd}$ were measured whereby the mass uncertainty of ${}^{123}\mathrm{Pd}$ was improved. This is the first reported measurement with a new storage ring mass spectrometry technique realized at a heavy-ion cyclotron and employing individual injection of the preidentified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new ${}^{123}\mathrm{Pd}$ result on the solar $r$-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction $Y_e$. It is found that the neutron capture cross section on ${}^{123}\mathrm{Pd}$ increases by a factor of 2.2 and $\beta$-delayed neutron emission probability, $P_{1\mathrm{n}}$, of ${}^{123}\mathrm{Rh}$ increases by 14%. The neutron capture cross section on ${}^{122}\mathrm{Pd}$ decreases by a factor of 2.6 leading to pileup of material at $A=122$, thus reproducing the trend of the solar $r$-process abundances. The trend of the two-neutron separation energies (${\mathrm{S}}_{2n}$) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the ${\mathrm{S}}_{2n}$ value at $N=77$. Such large increase of the ${\mathrm{S}}_{2n}$ values before $N=82$ was proposed as an alternative to the quenching of the $N=82$ shell gap to reproduce $r$-process abundances in the mass region of $A=112–124$.

The impact of nuclear deformation can been seen in the systematics of nuclear charge radii, with radii generally expanding with increasing deformation. In this Letter, we present a detailed analysis of the precise relationship between nuclear quadrupole deformation and the nuclear size. Our approach combines the first measurements of the changes in the mean-square charge radii of well-deformed palladium isotopes between $A=98$ and $A=118$ with nuclear density functional calculations using Fayans functionals, specifically Fy(std) and $\mathrm{Fy}(\mathrm{\Delta }r,\mathrm{HFB})$, and the UNEDF2 functional. The changes in mean-square charge radii are extracted from collinear laser spectroscopy measurements on the $4d^{9}5s{{}^{3}D}_3\to 4d^{9}5p{}^3{P}_2$ atomic transition. The analysis of the Fayans functional calculations reveals a clear link between a good reproduction of the charge radii for the neutron-rich Pd isotopes and the overestimated odd-even staggering: Both aspects can be attributed to the strength of the pairing correlations in the particular functional which we employ.

We report the first measurement of the parity-violating elastic electron scattering asymmetry on ${}^{27}\mathrm{Al}$. The ${}^{27}\mathrm{Al}$ elastic asymmetry is $A_{\mathrm{PV}}=2.16\pm 0.11(\mathrm{stat})\pm 0.16(\text{syst})\mathrm{ppm}$, and was measured at $⟨Q^2⟩=0.02357\pm 0.00010{\mathrm{GeV}}^2$, $⟨{\theta }_{\mathrm{lab}}⟩=7.61°\pm 0.02°$, and $⟨E_{\mathrm{lab}}⟩=1.157\mathrm{GeV}$ with the ${\mathrm{Q}}_{\mathrm{weak}}$ apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the ${}^{27}\mathrm{Al}$ neutron radius $R_n=2.89\pm 0.12\mathrm{fm}$ was determined using a many-models correlation technique. The corresponding neutron skin thickness $R_n-R_p=-0.04\pm 0.12\mathrm{fm}$ is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the ${}^{27}\mathrm{Al}$ weak radius $R_w=3.00\pm 0.15\mathrm{fm}$, and the weak skin thickness $R_{\mathrm{wk}}-R_{\mathrm{ch}}=-0.04\pm 0.15\mathrm{fm}$. The weak form factor at this $Q^2$ is $F_{\mathrm{wk}}=0.39\pm 0.04$.

Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives ${\alpha }_{E1}^p=13.8\pm 1.2_{\mathrm{stat}}\pm 0.1_{\mathrm{BSR}}\pm 0.3_{\mathrm{theo}},{\beta }_{M1}^p=0.2\mp 1.2_{\mathrm{stat}}\pm 0.1_{\mathrm{BSR}}\mp 0.3_{\mathrm{theo}}$ in units of ${10}^{-4}{\mathrm{fm}}^3$.

A precise measurement of the differential cross sections $d\sigma /d\mathrm{\Omega }$ and the linearly polarized photon beam asymmetry ${\mathrm{\Sigma }}_3$ for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-$t$ dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: ${\alpha }_{E1}=10.99\pm 0.16\pm 0.47\pm 0.17\pm 0.34$, ${\beta }_{M1}=3.14\pm 0.21\pm 0.24\pm 0.20\pm 0.35$; in units of ${10}^{-4}{\mathrm{fm}}^3$ where the errors are statistical, systematic, spin polarizability dependent, and model dependent.

The gradient expansion is the fundamental organizing principle underlying relativistic hydrodynamics, yet understanding its convergence properties for general nonlinear flows has posed a major challenge. We introduce a simple method to address this question in a class of fluids modeled by Israel-Stewart–type relaxation equations. We apply it to ($1+1$)-dimensional flows and provide numerical evidence for factorially divergent gradient expansions. This generalizes results previously only obtained for ($0+1$)-dimensional comoving flows, notably Bjorken flow. We also demonstrate that the only known nontrivial case of a convergent hydrodynamic gradient expansion at the nonlinear level relies on Bjorken flow symmetries and becomes factorially divergent as soon as these are relaxed. Finally, we show that factorial divergence can be removed using a momentum space cutoff, which generalizes a result obtained earlier in the context of linear response.

Understanding gluon density distributions and how they are modified in nuclei are among the most important goals in nuclear physics. In recent years, diffractive vector meson production measured in ultraperipheral collisions (UPCs) at heavy-ion colliders has provided a new tool for probing the gluon density. In this Letter, we report the first measurement of $J/\psi$ photoproduction off the deuteron in UPCs at the center-of-mass energy $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ in $\mathit{d}+\mathrm{Au}$ collisions. The differential cross section as a function of momentum transfer $-t$ is measured. In addition, data with a neutron tagged in the deuteron-going zero-degree calorimeter is investigated for the first time, which is found to be consistent with the expectation of incoherent diffractive scattering at low momentum transfer. Theoretical predictions based on the color glass condensate saturation model and the leading twist approximation nuclear shadowing model are compared with the data quantitatively. A better agreement with the saturation model has been observed. With the current measurement, the results are found to be directly sensitive to the gluon density distribution of the deuteron and the deuteron breakup process, which provides insights into the nuclear gluonic structure.

The spectra measurements of charged hadrons produced in the shower of a parton originating in the same hard scattering with a leptonically decaying $Z$ boson are reported in lead-lead nuclei (Pb-Pb) and proton-proton ($pp$) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Both Pb-Pb and $pp$ data sets are recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of $1.7{\mathrm{nb}}^{-1}$ and $320{\mathrm{pb}}^{-1}$, respectively. Hadronic collision data with one reconstructed $Z$ boson candidate with the transverse momentum $p_T>30\mathrm{GeV}/\mathrm{c}$ are analyzed. The $Z$ boson constrains the initial energy and direction of the associated parton. In heavy ion events, azimuthal angular distributions of charged hadrons with respect to the direction of a $Z$ boson are sensitive to modifications of the in-medium parton shower and medium response. compared to reference data from $pp$ interactions, the results for central Pb-Pb collisions indicate a modification of the angular correlations. The measurements of the fragmentation functions and $p_T$ spectra of charged particles in $Z$ boson events, which are sensitive to medium modifications of the parton shower longitudinal structure, are also reported. Significant modifications in central Pb-Pb events compared to the $pp$ reference data are also found for these observables.

We have measured the $3d\to 2p$ transition x rays of kaonic ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We determined the energies to be $6224.5\pm 0.4(\mathrm{stat})\pm 0.2(\mathrm{syst})\mathrm{eV}$ and $6463.7\pm 0.3(\mathrm{stat})\pm 0.1(\mathrm{syst})\mathrm{eV}$, and widths to be $2.5\pm 1.0(\mathrm{stat})\pm 0.4(\mathrm{syst})\mathrm{eV}$ and $1.0\pm 0.6(\mathrm{stat})\pm 0.3(\mathrm{stat})\mathrm{eV}$, for kaonic ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations based on optical-potential models.