The production of the $\psi (2S)$ charmonium state was measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity ($2.5<y<4$). The measurement of the ratio of the inclusive production cross sections of the $\psi (2S)$ and $\mathrm{J}/\psi$ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region $p_T<12\mathrm{GeV}/c$. The results are compared with the corresponding measurements in $pp$ collisions, by forming the double ratio $[{\sigma }^{\psi (2S)}/{\sigma }^{J/\psi }{]}_{\mathrm{Pb}\text{−}\mathrm{Pb}}/[{\sigma }^{\psi (2S)}/{\sigma }^{J/\psi }{]}_{pp}$. It is found that in Pb-Pb collisions the $\psi (2S)$ is suppressed by a factor of $\sim 2$ with respect to the $J/\psi$. The $\psi (2S)$ nuclear modification factor $R_{\mathrm{AA}}$ was also obtained as a function of both centrality and $p_T$. The results show that the $\psi (2S)$ resonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up to $\sim 3$ with respect to $pp$. Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and of $R_{\mathrm{AA}}$ with higher-$p_T$ results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC.

Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent $J/\psi$ photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon ($W_{\gamma \mathrm{N}}^{\mathrm{Pb}}$) over a wide range of $40<W_{\gamma \mathrm{N}}^{\mathrm{Pb}}<400\mathrm{GeV}$. Results are obtained using data at the nucleon-nucleon center-of-mass energy of 5.02 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of $1.52{\mathrm{nb}}^{-1}$. The cross section is observed to rise rapidly at low $W_{\gamma \mathrm{N}}^{\mathrm{Pb}}$, and plateau above $W_{\gamma \mathrm{N}}^{\mathrm{Pb}}\approx 40\mathrm{GeV}$, up to $400\mathrm{GeV}$, entering a new regime of small Bjorken-$x$ ($\approx 6\times {10}^{-5}$) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models.

The excited states of unstable ${}^{20}\mathrm{O}$ were investigated via $\gamma$-ray spectroscopy following the ${}^{19}\mathrm{O}(d,p){}^{20}\mathrm{O}$ reaction at $8A\mathrm{MeV}$. By exploiting the Doppler shift attenuation method, the lifetimes of the $2_2^{+}$ and $3_1^{+}$ states were firmly established. From the $\gamma$-ray branching and $E2/M1$ mixing ratios for transitions deexciting the $2_2^{+}$ and $3_1^{+}$ states, the $B(E2)$ and $B(M1)$ were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of $\gamma$-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.

Nuclear isomer effects are pivotal in understanding nuclear astrophysics, particularly in the rapid neutron-capture process where the population of metastable isomers can alter the radioactive decay paths of nuclei produced during astrophysical events. The $\beta$-decaying isomer ${}^{128\mathrm{m}}\mathrm{Sb}$ was identified as potentially impactful since the $\beta$-decay pathway along the $A=128$ isobar funnels into this state bypassing the ground state. We report the first direct mass measurements of the ${}^{128}\mathrm{Sb}$ isomer and ground state using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. We find mass excesses of $-84564.8(25)\mathrm{keV}$ and $-84608.8(21)\mathrm{keV}$, respectively, resulting in an excitation energy for the isomer of 43.9(33) keV. These results provide the first key nuclear data input for understanding the role of ${}^{128\mathrm{m}}\mathrm{Sb}$ in nucleosynthesis, and we show that it will influence the flow of the rapid neutron-capture process.

Quantum Monte Carlo simulations are powerful and versatile tools for the quantum many-body problem. In addition to the usual calculations of energies and eigenstate observables, quantum Monte Carlo simulations can in principle be used to build fast and accurate many-body emulators using eigenvector continuation or design time-dependent Hamiltonians for adiabatic quantum computing. These new applications require something that is missing from the published literature, an efficient quantum Monte Carlo scheme for computing the inner product of ground state eigenvectors corresponding to different Hamiltonians. In this work, we introduce an algorithm called the floating block method, which solves the problem by performing Euclidean time evolution with two different Hamiltonians and interleaving the corresponding time blocks. We use the floating block method and nuclear lattice simulations to build eigenvector continuation emulators for energies of ${}^4\mathrm{He}$, ${}^8\mathrm{Be}$, ${}^{12}\mathrm{C}$, and ${}^{16}\mathrm{O}$ nuclei over a range of local and nonlocal interaction couplings. From the emulator data, we identify the quantum phase transition line from a Bose gas of alpha particles to a nuclear liquid.

Isomers close to doubly magic ${}_{28}{}^{78}{\mathrm{Ni}}_{50}$ provide essential information on the shell evolution and shape coexistence near the $Z=28$ and $N=50$ double shell closure. We report the excitation energy measurement of the $1/2^{+}$ isomer in ${}_{30}{}^{79}{\mathrm{Zn}}_{49}$ through independent high-precision mass measurements with the JYFLTRAP double Penning trap and with the ISOLTRAP multi-reflection time-of-flight mass spectrometer. We unambiguously place the $1/2^{+}$ isomer at 942(10) keV, slightly below the $5/2^{+}$ state at 983(3) keV. With the use of state-of-the-art shell-model diagonalizations, complemented with discrete nonorthogonal shell-model calculations which are used here for the first time to interpret shape coexistence, we find low-lying deformed intruder states, similar to other $N=49$ isotones. The $1/2^{+}$ isomer is interpreted as the bandhead of a low-lying deformed structure akin to a predicted low-lying deformed band in ${}^{80}\mathrm{Zn}$, and points to shape coexistence in ${}^{79,80}\mathrm{Zn}$ similar to the one observed in ${}^{78}\mathrm{Ni}$. The results make a strong case for confirming the claim of shape coexistence in this key region of the nuclear chart.

We report on the results obtained with the global CUPID-0 background model, which combines the data collected in the two measurement campaigns for a total exposure of $8.82\mathrm{kg}\times \mathrm{yr}$ of ${}^{82}\mathrm{Se}$. We identify with improved precision the background sources within the 3 MeV energy region, where neutrinoless double $\beta$ decay of ${}^{82}\mathrm{Se}$ and ${}^{100}\mathrm{Mo}$ is expected, making more solid the foundations for the background budget of the next-generation CUPID experiment. Relying on the excellent data reconstruction, we measure the two-neutrino double $\beta$-decay half-life of ${}^{82}\mathrm{Se}$ with unprecedented accuracy: $T_{1/2}^{2\nu }=[8.69\pm 0.05(\mathrm{stat}){}_{-0.06}{}^{+0.09}(\mathrm{syst})]\times {10}^{19}\mathrm{yr}$.

The evolution of single-particle strengths as the neutron-to-proton asymmetry changes informs us of the importance of short- and long-range correlations in nuclei and has therefore been extensively studied for the last two decades. Surprisingly, the strong asymmetry dependence of these strengths and their extreme values for highly asymmetric nuclei inferred from knockout reaction measurements on a target nucleus are not consistent with what is extracted from electron-induced, transfer, and quasi-free reaction data, constituting a two-decade old puzzle. This work presents the first consistent analysis of one-nucleon transfer and one-nucleon knockout data, in which theoretical uncertainties associated with the nucleon-nucleus effective interactions considered in the reaction models are quantified using a Bayesian analysis. Our results demonstrate that, taking into account these uncertainties, the spectroscopic strengths of loosely bound nucleons extracted from both probes agree with each other and, although there are still discrepancies for deeply bound nucleons, the slope of the asymmetry dependence of the single-particle strengths inferred from transfer and knockout reactions are consistent within $1\sigma$. Both probes are consistent with a small asymmetry dependence of these strengths. The uncertainties obtained in this work represent a lower bound and are already significantly larger than the original estimates.

We consider the binding energy of a two-body system with a repulsive Coulomb interaction in a finite periodic volume. We define the finite-volume Coulomb potential as the usual Coulomb potential, except that the distance is defined as the shortest separation between the two bodies in the periodic volume. We investigate this problem in one and three-dimensional periodic boxes and derive the asymptotic behavior of the volume dependence for bound states with zero angular momentum in terms of Whittaker functions. We benchmark our results against numerical calculations and show how the method can be used to extract asymptotic normalization coefficients for charged-particle bound states. The results we derive here have immediate applications for calculations of atomic nuclei in finite periodic volumes for the case where the leading finite-volume correction is associated with two charged clusters.

Emergent bulk properties of matter governed by the strong nuclear force give rise to physical phenomena across vastly different scales, ranging from the shape of atomic nuclei to the masses and radii of neutron stars. They can be accessed on Earth by measuring the spatial extent of the outer skin made of neutrons that characterizes the surface of heavy nuclei. The isotope ${}^{208}\mathrm{Pb}$, owing to its simple structure and neutron excess, has been in this context the target of many dedicated efforts. Here, we determine the neutron skin from measurements of particle distributions and their collective flow in ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ collisions at ultrarelativistic energy performed at the Large Hadron Collider, which are mediated by interactions of gluons and thus sensitive to the overall size of the colliding ${}^{208}\mathrm{Pb}$ ions. By means of state-of-the-art global analysis tools within the hydrodynamic model of heavy-ion collisions, we infer a neutron skin $\mathrm{\Delta }{r}_{np}=0.217\pm 0.058\mathrm{fm}$, consistent with nuclear theory predictions, and competitive in accuracy with a recent determination from parity-violating asymmetries in polarized electron scattering. We establish thus a new experimental method to systematically measure neutron distributions in the ground state of atomic nuclei.

The polarization of $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar $\mathrm{Ru}+\mathrm{Ru}$ and $\mathrm{Zr}+\mathrm{Zr}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild $p_T$ dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagrees with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and $p_T$ dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.

Traditional photonuclear reactions primarily excite giant dipole resonances, making the measurement of isovector giant resonances with higher multipolarities a great challenge. In this Letter, the manipulation of collective excitations of different multipole transitions in even-even nuclei via vortex $\gamma$ photons is investigated. We develop the calculation method for photonuclear cross sections induced by the vortex $\gamma$ photon beam using the fully self-consistent random-phase approximation plus particle-vibration coupling ($\mathrm{RPA}+\mathrm{PVC}$) model based on Skyrme density functional. We find that the electromagnetic transitions with multipolarity $J<|m_{\gamma }|$ are forbidden for vortex $\gamma$ photons due to the angular momentum conservation, with $m_{\gamma }$ being the projection of total angular momentum of $\gamma$ photon on its propagation direction. For instance, this allows for probing the isovector giant quadrupole resonance without interference from dipole transitions using vortex $\gamma$ photons with $m_{\gamma }=2$. Furthermore, the electromagnetic transition with $J=|m_{\gamma }|+1$ vanishes at a specific polar angle. Therefore, the giant resonances with specific multipolarity can be extracted via vortex $\gamma$ photons. Moreover, the vortex properties of $\gamma$ photons can be meticulously diagnosed by measuring the nuclear photon-absorption cross section. Our method opens new avenues for photonuclear excitations, generation of coherent $\gamma$ photon laser and precise detection of vortex particles, and consequently, has significant impact on nuclear physics, nuclear astrophysics and strong laser physics.

Understanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed ${\mathit{D}}^0$ meson. The measurement is made in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$, in the low jet transverse-momentum interval of $15\le p_T^{\text{jet ch}}<30\mathrm{GeV}/c$ where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.