A central question in strong-interaction physics, governed by quantum chromodynamics (QCD), is whether femtoscale droplets of quark-gluon plasma form in small collision systems involving projectiles significantly smaller than heavy ions. Collisions of light ions such as ${}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}$ offer a unique opportunity to probe the emergence of collective behavior in QCD matter. This Letter presents the first measurements of the elliptic ($v_2$) and triangular ($v_3$) flow of charged particles in ${}^{16}\mathrm{O}–{}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}–{}^{20}\mathrm{Ne}$ collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.36\mathrm{TeV}$ with the ALICE detector. The hydrodynamic model predictions, explicitly incorporating the nuclear structures of ${}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}$, exhibit a good agreement with the flow measurements presented. The observed increase of $v_2$ in central Ne–Ne collisions relative to OO collisions, driven by the nuclear geometries, highlights the importance of utilizing light nuclei with well-defined geometric shapes to constrain the initial conditions. These findings support the presence of nuclear geometry-driven hydrodynamic flow in light-ion collisions at the LHC.

The long-range collective flow of particles produced in oxygen-oxygen ($\mathrm{O}+\mathrm{O}$) and neon-neon ($\mathrm{Ne}+\mathrm{Ne}$) collisions is measured with the CMS detector at the CERN LHC. The data samples were collected at a center-of-mass energy per nucleon pair of 5.36 TeV, with integrated luminosities of $7{\mathrm{nb}}^{-1}$ and $0.8{\mathrm{nb}}^{-1}$ for $\mathrm{O}+\mathrm{O}$ and $\mathrm{Ne}+\mathrm{Ne}$ collisions, respectively. Two- and four-particle azimuthal correlations are measured over nearly five units of pseudorapidity. Significant elliptic ($v_2$) and triangular ($v_3$) flow harmonics are observed in both systems. The ratios of $v_n$ coefficients between $\mathrm{Ne}+\mathrm{Ne}$ and $\mathrm{O}+\mathrm{O}$ collisions suggest sensitivity to the intrinsic nuclear structure of the respective Ne and O ions. Hydrodynamic models with ab initio nuclear structure inputs qualitatively reproduce the collision-overlap dependence of both the $v_n$ values and the $\mathrm{Ne}+\mathrm{Ne}$ to $\mathrm{O}+\mathrm{O}$ ratios. These measurements provide new constraints when modeling the interplay of nuclear structure and collective dynamics in collisions of ${}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}$ ions, respectively.

The ground-state rotational band of ${}^{252}\mathrm{Fm}$ ($Z=100$, $N=152$) was investigated using two different experimental setups at the JAEA Tandem Accelerator Laboratory. The $2^{+}\to 0^{+}$ and $4^{+}\to 2^{+}$ transitions were observed in the $\alpha$ decay of ${}^{256}\mathrm{No}$ via $\alpha \text{−}\gamma$ coincidence spectroscopy. The energies of the $(6^{+})\to (4^{+})$, $(8^{+})\to (6^{+})$, and $(10^{+})\to (8^{+})$ transitions were identified in the prompt $\gamma$-ray spectrum of ${}^{252}\mathrm{Fm}$ produced in the ${}^{18}\mathrm{O}+{}^{249}\mathrm{Cf}$ multinucleon transfer reaction. The new data reveal that, compared with neighboring fermium isotopes and $N=152$ isotones in the region, ${}^{252}\mathrm{Fm}$ has the lowest first excited $2^{+}$-state energy, 41.88(16) keV, and the largest kinematic moment of inertia. These properties constitute new evidence for the deformed shell gaps at $Z=100$ and $N=152$, supporting the understanding of ${}^{252}\mathrm{Fm}$ as a deformed doubly magic nucleus.

We present the first direct measurement of the $Z=6$ shell gap in the neutron-rich ${}^{20}\mathrm{O}$ nucleus. The one-proton removal transfer reaction ${}^2\mathrm{H}({}^{20}\mathrm{O},{}^3\mathrm{He}){}^{19}\mathrm{N}$ has been studied using the ACTAR TPC setup at GANIL. The use of ACTAR TPC enabled the measurement of low-cross section proton-removal reactions while preserving resolution. Eight $p$-hole states with $\ell =1$ were identified in ${}^{19}\mathrm{N}$ accounting for total strengths of 86% and 72% of the $0p_{3/2}$ and $0p_{1/2}$ single-particle orbitals, respectively. The energies and spectroscopic factors of the measured states allowed to determine the proton spin-orbit splitting $\pi 0p_{3/2}-\pi 0p_{1/2}$ in ${}^{20}\mathrm{O}$. The $Z=6$ shell gap has been established to be 5.30(14) MeV. These findings indicate a reduction of the $Z=6$ shell gap while adding neutrons to the $sd$-valence orbitals, consistent with the effects of the tensor force predicted by state-of-the-art shell model interaction SFO-tls while at variance with the emergence of a large $Z=6$ gap observed in other studies.

The solar system currently traverses the Local Interstellar Cloud (LIC), one of several warm cloudlets of the Complex of Local Interstellar Clouds (CLIC) in the solar neighborhood. The origin of these cloudlets is unknown and could be related to supernova shock wave dynamics. If supernovae are the source of these cloudlets or influence their properties, the CLIC may act as a cosmic archive for the supernova-produced radionuclide ${}^{60}\mathrm{Fe}$. We detected minuscule traces of interstellar ${}^{60}\mathrm{Fe}$ in 295 kg of the European Project for Ice Coring in Antarctica Dronning Maud Land ice core, covering the time period 40–81 kyr ago. We find an ${}^{60}\mathrm{Fe}/{}^{53}\mathrm{Mn}$ ratio of $(8\pm 5)\times {10}^{-4}$, slightly above the expected cosmogenic production, corresponding to an interstellar deposition rate of (${0.22}_{-0.12}^{+0.14}$) ${}^{60}\mathrm{Fe}$ $\mathrm{at}/{\mathrm{cm}}^2/\mathrm{yr}$. This influx is significantly lower than that observed in recent Antarctic snow and marine sediment records during the last 40 kyr. These results suggest that the LIC is a cosmic archive for supernova-produced ${}^{60}\mathrm{Fe}$. The imprinted ${}^{60}\mathrm{Fe}$ time profile is evidence for a changing local interstellar environment over the last 80 kyr.

A hot and dense state of nuclear matter, known as the quark-gluon plasma, is created in collisions of ultrarelativistic heavy nuclei. Highly energetic quarks and gluons, collectively referred to as partons, lose energy as they travel through this matter, leading to suppressed production of particles with large transverse momenta ($p_{\mathrm{T}}$). Conversely, high-$p_{\mathrm{T}}$ particle suppression has not been seen in proton-lead collisions, raising questions regarding the minimum system size required to observe parton energy loss. Oxygen-oxygen (OO) collisions examine a region of effective system size that lies between these two extreme cases. The CMS detector at the CERN LHC has been used to quantify charged-particle production in inclusive OO collisions for the first time via measurements of the nuclear modification factor ($R_{\mathrm{AA}}$). The $R_{\mathrm{AA}}$ is derived by comparing particle production to expectations based on proton-proton ($pp$) data and has a value of unity in the absence of nuclear effects. The data for OO and $pp$ collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_{\mathrm{NN}}}=5.36\mathrm{TeV}$ correspond to integrated luminosities of $6.1{\mathrm{nb}}^{-1}$ and $1.02{\mathrm{pb}}^{-1}$, respectively. The $R_{\mathrm{AA}}$ is below unity with a minimum of $0.69\pm 0.04$ around $p_{\mathrm{T}}=6\mathrm{GeV}$. The data exhibit better agreement with theoretical models incorporating parton energy loss as compared to baseline models without energy loss.

The missing mass of the ${}^{12}\mathrm{C}(p,d)$ reaction has been measured near the ${\eta }^{\prime }$-meson emission threshold in coincidence with a high-momentum proton to selectively collect ${\eta }^{\prime }\text{−}{}^{11}\mathrm{C}$ mesic nucleus formation events at GSI, Germany. A 2.5 GeV proton excites a carbon nucleus in order to form an ${\eta }^{\prime }$-mesic nucleus emitting a deuteron forward with an energy of $\sim 1.5\mathrm{GeV}$. The deuteron is momentum analyzed by the fragment separator used as a high-resolution spectrometer to deduce the excitation energy of the residual system. The large-acceptance detector WASA surrounding the target identifies high-momentum protons emitted in the decay of the ${\eta }^{\prime }$-mesic nucleus. The measured semiexclusive spectrum exhibits structures below the threshold though the statistical significance is limited. The spectrum is fitted by theoretically calculated spectra varying optical-potential parameters of the ${\eta }^{\prime }$-nucleus interaction. The analysis results indicate possible formation of ${\eta }^{\prime }$-mesic nuclei for the real potential depth of $\sim -61\mathrm{MeV}$ with a local statistical significance of $3.5\sigma$ and, taking into account the look-elsewhere effect, a global significance of $2.1\sigma$.

Isomer depletion serves as a prerequisite for a variety of important applications. Several mechanisms are proposed to trigger the isomer depletion. In the previous work [Chiara et al., Nature (London) 554, 216 (2018).], isomer depletion with an exceptionally high probability in ${}^{93m}\mathrm{Mo}$ was reported and attributed to nuclear excitation by electron capture (NEEC). However, contradictory probability values were subsequently reported from both experimental and theoretical aspects. This Letter reports a new and more precise measurement of the isomer depletion of high-energy ${}^{93m}\mathrm{Mo}$ ions during the slowing-down processes in lead and carbon foils via a low-background beam-based experimental approach. By employing a purified isomer beam, the depletion probabilities are determined to be $2.0(2)\times {10}^{-5}$ in lead and $4.7(13)\times {10}^{-6}$ in carbon, agreeing well with the inelastic nuclear scattering calculations. We conclude that the observed isomer depletion in ${}^{93m}\mathrm{Mo}$ arises from inelastic nuclear scattering rather than the previously proposed NEEC mechanism.

Magic numbers lie at the heart of nuclear structure, reflecting enhanced stability in nuclei with closed shells. While the emergence of magic numbers beyond 20 is commonly attributed to strong spin-orbit coupling, the microscopic origin of the spin-orbit potential remains elusive, owing to its dependence on the resolution scale and renormalization scheme of nuclear forces. Here, we investigate the evolution of nuclear shell structure with varying momentum resolution in nuclear interactions derived from chiral effective field theory, using the similarity renormalization group to link different scales. We uncover a novel transition from spin symmetry to pseudospin symmetry as the resolution scale decreases, during which magic numbers emerge naturally. A similar pattern is found in calculations using relativistic one-boson-exchange potentials, underscoring the robustness of the phenomenon. This establishes a direct connection between realistic nuclear forces with a high resolution scale and effective nuclear forces at coarse-grained scales, offering a first-principles explanation for the origin of magic numbers and pseudospin symmetry in nuclear shell structure and new insights into the structure of exotic nuclei far from stability.

Anisotropic flow and radial flow are two key probes of the expansion dynamics and properties of the quark-gluon plasma (QGP). While anisotropic flow has been extensively studied, radial flow, which governs the system’s radial expansion, has received less attention. Notably, direct experimental evidence for the global and collective nature of radial flow fluctuations has been lacking. This Letter presents the first measurement of transverse momentum ($p_{\mathrm{T}}$) dependence of radial flow fluctuations ($v_0(p_{\mathrm{T}})$) over $0.5<p_{\mathrm{T}}<10\mathrm{GeV}$ and demonstrates its collective nature using a two-particle correlation method in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The data reveal three key features supporting the collective nature of radial flow: long-range correlation in pseudorapidity, factorization in $p_{\mathrm{T}}$, and centrality-independent shape in $p_{\mathrm{T}}$. The comparison with a hydrodynamic model demonstrates the sensitivity of $v_0(p_{\mathrm{T}})$ to bulk viscosity, a crucial transport property of the QGP. These findings establish a new, powerful tool for probing collective dynamics and properties of the QGP.

This Letter presents measurements of long-range transverse-momentum correlations using a new observable, $v_0(p_{\mathrm{T}})$, serving as a probe of event-by-event radial-flow fluctuations, the underlying radial expansion, and the medium’s properties in heavy-ion collisions. Results are reported for inclusive charged particles, pions, kaons, and protons across various centrality intervals in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, recorded by the ALICE detector. A pseudorapidity-gap technique, similar to that used in anisotropic-flow studies, is employed to suppress short-range correlations. At low $p_{\mathrm{T}}$, a characteristic mass ordering consistent with hydrodynamic collective flow is observed. At higher $p_{\mathrm{T}}$ ($>3\mathrm{GeV}/c$), protons exhibit larger $v_0(p_{\mathrm{T}})$ than pions and kaons, in agreement with expectations from quark-recombination models. Comparisons to viscous hydrodynamic calculations with varying bulk viscosity and equation of state demonstrate the sensitivity of the $v_0(p_{\mathrm{T}})$ observable to these key medium properties. The findings establish $v_0(p_{\mathrm{T}})$ as a valuable addition to the set of observables used in Bayesian analyses for extracting the transport properties and constraining the equation of state of strongly interacting matter, while also helping to systematically explore its sensitivity and impact within such global studies.

Quantum Monte Carlo (QMC) methods offer exact solutions for quantum many-body systems but face severe limitations in fermionic systems like atomic nuclei due to the sign problem. While sign-problem-free QMC algorithms exist and provide valuable insights across disciplines, they have been restricted to simple models with limited quantitative predictive power. Here we overcome this barrier by developing a novel lattice nuclear force that is rigorously sign-problem-free for even-even nuclei. This interaction achieves a standard deviation of $\sigma =2.932\mathrm{MeV}$ from experimental binding energies for 76 even-even nuclei ($N,Z\le 28$), matching state-of-the-art phenomenological mean-field models. Key innovations include the first sign-problem-free implementation of spin-orbit coupling for shell evolutions and an efficient QMC-optimized framework for global parameter fitting. Using this approach, we compute binding energies from ${}^4\mathrm{He}$ to ${}^{132}\mathrm{Sn}$ with unprecedented one-thousandth level numerical precision, reproduce symmetric nuclear matter saturation, and reveal novel spin-orbit-driven clustering in light nuclei. This Letter transforms sign-problem-free QMC simulation into a scalable and predictive nuclear structure tool, while establishing a high-fidelity, nonperturbative foundation for ab initio calculations of heavy nuclei.

The GW170817 neutron star merger event and the PREX-2 experiment probing neutron skin thickness provide crucial clues for understanding the nuclear equation of state (EoS). However, an apparent inconsistency exists between the tidal polarizability ${\mathrm{\Lambda }}^{1.4}$ inferred from GW170817 and the neutron skin thickness $R_{\mathrm{np}}^{208}$ of ${}^{208}\mathrm{Pb}$ measured by PREX-2, based on relativistic energy density functionals (EDFs). This Letter employs both relativistic and nonrelativistic EDFs to identify a multipole correlation involving ${\mathrm{\Lambda }}^{1.4}$, $R_{\mathrm{np}}^{208}$, and the symmetry energy curvature $K_{\mathrm{sym}}$ at saturation density. We demonstrate the essential role of $K_{\mathrm{sym}}$ in reconciling the conflicting ${\mathrm{\Lambda }}^{1.4}\text{−}{R}_{\mathrm{np}}^{208}$ correlations derived from nonrelativistic versus relativistic EDFs and in resolving the discrepancy between the GW170817 and PREX-2 data constraints. Furthermore, we obtain a joint constraint on $K_{\mathrm{sym}}$ from these datasets, providing a vital constraint on the symmetry energy of the nuclear EoS.

We report precision measurements on cumulants ($C_n$) and factorial cumulants (${\kappa }_n$) of (net) proton number distributions up to fourth order in $\mathrm{Au}+\mathrm{Au}$ collisions over center-of-mass energies $\sqrt{s_{NN}}=7.7–27\mathrm{GeV}$ from phase II of the Beam Energy Scan program at RHIC. (Anti)protons are selected at midrapidity ($|y|<0.5$) within a transverse momentum range of $0.4<p_T<2.0\mathrm{GeV}/c$. Relative to various noncritical-point model calculations and peripheral collision 70%–80% data, the net proton $C_4/C_2$ measurement in 0%–5% collisions shows a minimum around 19.6 GeV for significance of deviation at $\sim 2–5\sigma$. A minimum in $C_4/C_2$ with respect to a noncritical baseline is expected to be a characteristic feature of the signature associated with a critical point in the QCD phase diagram. In addition, deviations from noncritical baselines around the same collision energy region are also seen in proton factorial cumulant ratios, especially in ${\kappa }_2/{\kappa }_1$ and ${\kappa }_3/{\kappa }_1$. Dynamical model calculations including a critical point are called for in order to understand these precision measurements.

Incoherent $J/\psi$ photoproduction in heavy ion ultraperipheral collisions (UPCs) provides a sensitive probe of localized, fluctuating gluonic structures within heavy nuclei. This Letter reports the first measurement of the photon-nucleon center-of-mass energy ($W_{\gamma \mathrm{N}}$) dependence of this process in PbPb UPCs at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using $1.52{\mathrm{nb}}^{-1}$ of data recorded by the CMS experiment. The measurement covers a wide $W_{\gamma \mathrm{N}}$ range of $\approx 40–400\mathrm{GeV}$, probing gluons carrying a fraction $x$ of nucleon momentum down to an unexplored regime of $6.5\times {10}^{-5}$. Compared to baseline predictions neglecting nuclear effects, the measured cross sections exhibit significantly greater suppression at lower $x$. Additionally, the ratio of incoherent to coherent photoproduction is found to be constant across the probed $W_{\gamma \mathrm{N}}$ and $x$ range, disfavoring the establishment of the black disk limit. This Letter provides critical insights into the $x$-dependent evolution of fluctuating gluonic structures within nuclei and calls for further advancements in theoretical models incorporating nuclear shadowing and gluon saturation.

Measurements of the EMC effect in the tritium and helium-3 mirror nuclei are reported. The data were obtained by the MARATHON Jefferson Lab experiment, which performed deep inelastic electron scattering from deuterium and the three-body nuclei, using a cryogenic gas target system and the high resolution spectrometers of the Hall A Facility of the Lab. The data cover the Bjorken $x$ range from 0.20 to 0.83, corresponding to a squared four-momentum transfer $Q^2$ range from 2.7 to $11.9(\mathrm{GeV}/c{)}^2$, and to an invariant mass $W$ of the final hadronic state greater than $1.84\mathrm{GeV}/c^2$. The tritium EMC effect measurement is the first of its kind. The MARATHON experimental results are compared to results from previous measurements by DESY-HERMES and JLab–Hall C experiments, as well as with few-body theoretical predictions.

Decay properties of the neutron-deficient Sg isotopes were studied at the gas-filled recoil separator TASCA at GSI, Darmstadt by using the ${}^{52}\mathrm{Cr}+{}^{206,208}\mathrm{Pb}$ reactions. We report on the discovery of the new isotope ${}^{257}\mathrm{Sg}$. Its ground state, tentatively assigned to have $9/2^{-}$[734] configuration, was observed to decay by both spontaneous fission and $\alpha$-particle emission with a half-life of ${12.6}_{-2.3}^{+3.7}\mathrm{ms}$. The alpha decay from this high-spin state was followed by fission of ${}^{253}\mathrm{Rf}$ after $11\mathrm{\mu }\mathrm{s}$. In ${}^{259}\mathrm{Sg}$, we observed strong evidence for the occurrence of a $K$-isomeric state for the first time in superheavy nuclei with 106 protons. The current experimental findings, discussed within the experimental systematics and theory, indicate that hitherto unseen features of the shell effect on the fission process may be found in the neutron-deficient superheavy nuclei.

We propose a method to numerically determine the location of a critical point in general systems using the finite-size scaling of Lee-Yang zeros. This method makes use of the fact that the ratios of Lee-Yang zeros on various spatial volumes intersect at the critical point. While the method is similar to the Binder-cumulant analysis, it is advantageous in suppressing the finite-volume effects arising from the mixing of variables in general systems. We show that the method works successfully for numerically locating the critical point in the three-dimensional three-state Potts model with a nonzero external field.

In this Letter, the first evidence of the ${}_{\overline{\mathrm{\Lambda }}}{}^4\overline{\mathrm{He}}$ antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number $A=4$, specifically $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$. In addition, the antiparticle-to-particle ratios for both hypernuclei (${}_{\overline{\mathrm{\Lambda }}}{}^4\overline{\mathrm{H}}/{}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and ${}_{\overline{\mathrm{\Lambda }}}{}^4\overline{\mathrm{He}}/{}_{\mathrm{\Lambda }}{}^4\mathrm{He}$) are shown, which are sensitive to the baryochemical potential of the strongly interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb-Pb collisions, collected during the 2018 LHC data taking at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The yields measured for the average of the charge-conjugated states are found to be $[0.78\pm 0.19(\mathrm{stat})\pm 0.17(\mathrm{syst})]\times {10}^{-6}$ for the $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $[1.08\pm 0.34(\mathrm{stat})\pm 0.20(\mathrm{syst})]\times {10}^{-6}$ for the $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$, and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$ excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of $3.3\sigma$ from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within $0.6\sigma$ with the present measurements. Additionally, the measured $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$ masses are compatible with the world-average values within the uncertainties.

Top-quark pair production is observed in lead–lead ($\mathrm{Pb}+\mathrm{Pb}$) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ at the Large Hadron Collider with the ATLAS detector. The data sample was recorded in 2015 and 2018, amounting to an integrated luminosity of $1.9{\mathrm{nb}}^{-1}$. Events with exactly one electron and one muon and at least two jets are selected. Top-quark pair production is measured with an observed (expected) significance of 5.0 (4.1) standard deviations. The measured top-quark pair production cross section is ${\sigma }_{t\overline{t}}=3.6{}_{-0.9}^{+1.0}(\mathrm{stat}){}_{-0.5}^{+0.8}(\mathrm{syst})\mathrm{\mu }\mathrm{b}$, with a total relative uncertainty of 31%, and is consistent with theoretical predictions using a range of different nuclear parton distribution functions. The observation of this process consolidates the evidence of the existence of all quark flavors in the preequilibrium stage of the quark-gluon plasma at very high energy densities, similar to the conditions present in the early Universe.