Neutrinoless double beta decay ($0\nu \beta \beta$) processes sample a wide range of intermediate forbidden nuclear transitions, which may be impacted by quenching of the axial vector coupling constant ($g_A/g_V$), the uncertainty of which plays a pivotal role in determining the sensitivity reach of $0\nu \beta \beta$ experiments. In this Letter, we present measurements performed on a high-resolution ${\mathrm{LiInSe}}_2$ bolometer in a “$\text{source}=\text{detector}$” configuration to measure the spectral shape of the fourfold forbidden $\beta$ decay of ${}^{115}\mathrm{In}$. The value of $g_A/g_V$ is determined by comparing the spectral shape of theoretical predictions to the experimental $\beta$ spectrum taking into account various simulated background components as well as a variety of detector effects. We find evidence of quenching of $g_A/g_V$ at $>5\sigma$ with a model-dependent quenching factor of $0.655\pm 0.002$ as compared to the free-nucleon value for the interacting shell model. We also measured the ${}^{115}\mathrm{In}$ half-life to be $[5.18\pm 0.06(\mathrm{stat}{)}_{-0.015}^{+0.005}(\mathrm{sys})]\times {10}^{14}\mathrm{yr}$ within the interacting shell model framework. This Letter demonstrates the power of the bolometeric technique to perform precision nuclear physics single-$\beta$ decay measurements, which along with improved nuclear modeling can help reduce the uncertainties in the calculation of several decay nuclear matrix elements including those used in $0\nu \beta \beta$ sensitivity calculations.

Even though the total hadronic nucleus-nucleus cross section is among the most fundamental observables, it has only recently been measured precisely for lead-lead collisions at the LHC. This measurement implies the nucleon width should be below 0.7 fm, which is in contradiction with all known state-of-the-art Bayesian estimates. We study the implications of the smaller nucleon width on quark-gluon plasma properties such as the bulk viscosity. The smaller nucleon width dramatically improves the description of several triple-differential observables.

The Cryogenic Underground Observatory for Rare Events (CUORE) at Laboratori Nazionali del Gran Sasso of INFN in Italy is an experiment searching for neutrinoless double beta ($0\nu \beta \beta$) decay. Its main goal is to investigate this decay in ${}^{130}\mathrm{Te}$, but its ton-scale mass and low background make CUORE sensitive to other rare processes as well. In this Letter, we present our first results on the search for $0\nu \beta \beta$ decay of ${}^{128}\mathrm{Te}$, the Te isotope with the second highest natural isotopic abundance. We find no evidence for this decay, and using a Bayesian analysis we set a lower limit on the ${}^{128}\mathrm{Te}$ $0\nu \beta \beta$ decay half-life of $T_{1/2}>3.6\times {10}^{24}\mathrm{yr}$ (90% CI). This represents the most stringent limit on the half-life of this isotope, improving by over a factor of 30 the previous direct search results, and exceeding those from geochemical experiments for the first time.

Starting from the kinetic theory description of massive spin-$\frac{1}{2}$ particles in the presence of a magnetic field, equations for relativistic dissipative nonresistive magnetohydrodynamics are obtained in the small polarization limit. We use a relaxation-time approximation for the collision kernel in the relativistic Boltzmann equation and calculate nonequilibrium corrections to the phase-space distribution function of spin-polarizable particles. We demonstrate that our framework naturally leads to emergence of the well-known Einstein–de Haas and Barnett effects. We obtain multiple transport coefficients and show, for the first time, that the coupling between spin and magnetic field appear at gradient order in the hydrodynamic equation.

We report the first precise measurement of a $\beta$-recoil correlation from a radioactive noble gas (${}^6\mathrm{He}$) confined via a magneto-optical trap. The measurement is motivated by the search for exotic tensor-type contributions to the charged weak current. Interpreted as tensor currents with right-handed neutrinos, the measurements yield $|C_T/C_A{|}^2\le 0.022$ (90% confidence limit, C.L.). On the other hand, for left-handed neutrinos the limits are $0.007<C_T/C_A<0.111$ (90% C.L.). The sensitivity of the present measurement is mainly limited by experimental uncertainties in determining the time response properties and the distance between the atom cloud and the microchannel plate used for recoil ion detection.

We present the first measurement of dihadron angular correlations in electron-nucleus scattering. The data were taken with the CLAS detector and a 5.0 GeV electron beam incident on deuterium, carbon, iron, and lead targets. Relative to deuterium, the nuclear yields of charged-pion pairs show a strong suppression for azimuthally opposite pairs, no suppression for azimuthally nearby pairs, and an enhancement of pairs with large invariant mass. These effects grow with increased nuclear size. The data are qualitatively described by the gibuu model, which suggests that hadrons form near the nuclear surface and undergo multiple scattering in nuclei.These results show that angular correlation studies can open a new way to elucidate how hadrons form and interact inside nuclei.

The $\beta$-delayed one- and two-neutron emission probabilities ($P_{1n}$ and $P_{2n}$) of 20 neutron-rich nuclei with $N\ge 82$ have been measured at the RIBF facility of the RIKEN Nishina Center. $P_{1n}$ of ${}^{130,131}\mathrm{Ag}$, ${}^{133,134}\mathrm{Cd}$, ${}^{135,136}\mathrm{In}$, and ${}^{138,139}\mathrm{Sn}$ were determined for the first time, and stringent upper limits were placed on $P_{2n}$ for nearly all cases. $\beta$-delayed two-neutron emission ($\beta 2n$) was unambiguously identified in ${}^{133}\mathrm{Cd}$ and ${}^{135,136}\mathrm{In}$, and their $P_{2n}$ were measured. Weak $\beta 2n$ was also detected from ${}^{137,138}\mathrm{Sn}$. Our results highlight the effect of the $N=82$ and $Z=50$ shell closures on $\beta$-delayed neutron emission probability and provide stringent benchmarks for newly developed macroscopic-microscopic and self-consistent global models with the inclusion of a statistical treatment of neutron and $\gamma$ emission. The impact of our measurements on $r$-process nucleosynthesis was studied in a neutron star merger scenario. Our $P_{1n}$ and $P_{2n}$ have a direct impact on the odd-even staggering of the final abundance, improving the agreement between calculated and observed Solar System abundances. The odd isotope fraction of Ba in $r$-process-enhanced ($r\text{−}\mathrm{II}$) stars is also better reproduced using our new data.

We have performed the first direct measurement of two resonances of the ${}^7\mathrm{Be}(\alpha ,\gamma ){}^{11}\mathrm{C}$ reaction with unknown strengths using an intense radioactive ${}^7\mathrm{Be}$ beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of $1.73\pm 0.25(\mathrm{stat})\pm 0.40(\mathrm{syst})\mathrm{eV}$ and ${125}_{-25}^{+27}(\mathrm{stat})\pm 15(\mathrm{syst})\mathrm{meV}$, respectively. The present results have reduced the uncertainty in the ${}^7\mathrm{Be}(\alpha ,\gamma ){}^{11}\mathrm{C}$ reaction rate to $\sim 9.4\%–10.7\%$ over $T=1.5–3\mathrm{GK}$, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae ($\nu p$ process). We find no effect of the new, constrained reaction rate on $\nu p$-process nucleosynthesis.

Absolute cross sections for the addition of $s$- and $d$-wave neutrons to ${}^{14}\mathrm{C}$ and ${}^{14}\mathrm{N}$ have been determined simultaneously via the $(d,p)$ reaction at $10\mathrm{MeV}/\mathrm{u}$. The difference between the neutron and proton separation energies, $\mathrm{\Delta }S$, is around $-20\mathrm{MeV}$ for the ${}^{14}\mathrm{C}+n$ system and $+8\mathrm{MeV}$ for ${}^{14}\mathrm{N}+n$. The population of the $1s_{1/2}$ and $0d_{5/2}$ orbitals for both systems is reduced by a factor of approximately 0.5 compared with the independent single-particle model, or about 0.6 when compared with the shell model. This finding strongly contrasts with results deduced from intermediate-energy knockout reactions between similar nuclei on targets of ${}^9\mathrm{Be}$ and ${}^{12}\mathrm{C}$. The simultaneous technique used removes many systematic uncertainties.

The root mean square radii of the proton density distribution in ${}^{16–24}\mathrm{O}$ derived from measurements of charge changing cross sections with a carbon target at $\sim 900A\mathrm{MeV}$ together with the matter radii portray thick neutron skin for ${}^{22–24}\mathrm{O}$ despite ${}^{22,24}\mathrm{O}$ being doubly magic. Imprints of the shell closures at $N=14$ and 16 are reflected in local minima of their proton radii that provide evidence for the tensor interaction causing them. The radii agree with ab initio calculations employing the chiral ${\mathrm{NNLO}}_{\mathrm{sat}}$ interaction, though skin thickness predictions are challenged. Shell model predictions agree well with the data.

Efficient excitation of nuclei via exchange of a real or virtual photon has a fundamental importance for nuclear science and technology development. Here, we present a mechanism of nuclear excitation based on the capture of a free muon into the atomic orbits ($\mathrm{NE}\mu \mathrm{C}$). The cross section of such a proposed process is evaluated using the Feshbach projection operator formalism and compared to other known excitation phenomena, i.e., photoexcitation and nuclear excitation by electron capture (NEEC), showing up to 10 orders of magnitude increase in cross section. $\mathrm{NE}\mu \mathrm{C}$ is particularly interesting for MeV excitations that become accessible thanks to the stronger binding of muons to the nucleus. The binding energies of muonic atoms have been calculated introducing a state of the art modification to the Flexible Atomic Code. An analysis of experimental scenarios in the context of modern muon production facilities shows that the effect can be detectable for selected isotopes. The total probability of $\mathrm{NE}\mu \mathrm{C}$ is predicted to be $P\approx 1\times {10}^{-6}$ per incident muon in a beam-based scenario. Given the high transition energy provided by muons, $\mathrm{NE}\mu \mathrm{C}$ can have important consequences for isomer feeding and particle-induced fission.

Nuclear charge radii of ${}^{55,56}\mathrm{Ni}$ were measured by collinear laser spectroscopy. The obtained information completes the behavior of the charge radii at the shell closure of the doubly magic nucleus ${}^{56}\mathrm{Ni}$. The trend of charge radii across the shell closures in calcium and nickel is surprisingly similar despite the fact that the ${}^{56}\mathrm{Ni}$ core is supposed to be much softer than the ${}^{48}\mathrm{Ca}$ core. The very low magnetic moment $\mu ({}^{55}\mathrm{Ni})=-1.108(20){\mu }_N$ indicates the impact of $M1$ excitations between spin-orbit partners across the $N,Z=28$ shell gaps. Our charge-radii results are compared to ab initio and nuclear density functional theory calculations, showing good agreement within theoretical uncertainties.

The ${}^{13}\mathrm{C}(\alpha ,n){}^{16}\mathrm{O}$ reaction is the main neutron source for the slow-neutron-capture process in asymptotic giant branch stars and for the intermediate process. Direct measurements at astrophysical energies in above-ground laboratories are hindered by the extremely small cross sections and vast cosmic-ray-induced background. We performed the first consistent direct measurement in the range of $E_{\mathrm{c}.\mathrm{m}.}=0.24$ to 1.9 MeV using the accelerators at the China Jinping Underground Laboratory and Sichuan University. Our measurement covers almost the entire intermediate process Gamow window in which the large uncertainty of the previous experiments has been reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing datasets, and provides a more reliable reaction rate for the studies of the slow-neutron-capture and intermediate processes along with the first direct determination of the alpha strength for the near-threshold state.

Detailed spectroscopy of the neutron-deficient nucleus ${}^{36}\mathrm{Ca}$ was obtained up to 9 MeV using the ${}^{37}\mathrm{Ca}(p,d){}^{36}\mathrm{Ca}$ and the ${}^{38}\mathrm{Ca}(p,t){}^{36}\mathrm{Ca}$ transfer reactions. The radioactive nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce light ejectiles (the deuteron $d$ or triton $t$) that were detected in the MUST2 detector array, in coincidence with the heavy residues identified by a zero-degree detection system. Our main findings are (i) a similar shift in energy for the $1_1^{+}$ and $2_1^{+}$ states by about $-250\mathrm{keV}$, as compared with the mirror nucleus ${}^{36}\mathrm{S}$; (ii) the discovery of an intruder $0_2^{+}$ state at 2.83(13) MeV, which appears below the first $2^{+}$ state, in contradiction with the situation in ${}^{36}\mathrm{S}$; and (iii) a tentative $0_3^{+}$ state at 4.83(17) MeV, proposed to exhibit a bubble structure with two neutron vacancies in the $2s_{1/2}$ orbit. The inversion between the $0_2^{+}$ and $2_1^{+}$ states is due to the large mirror energy difference (MED) of $-516(130)\mathrm{keV}$ for the former. This feature is reproduced by shell model calculations, using the $sd\text{−}pf$ valence space, predicting an almost pure intruder nature for the $0_2^{+}$ state, with two protons (neutrons) being excited across the $Z=20$ magic closure in ${}^{36}\mathrm{Ca}$ (${}^{36}\mathrm{S}$). This mirror system has the largest MEDs ever observed, if one excludes the few cases induced by the effect of the continuum.

The reduced transition probabilities for the $4_1^{+}\to 2_1^{+}$ and $2_1^{+}\to 0_1^{+}$ transitions in ${}^{92}\mathrm{Mo}$ and ${}^{94}\mathrm{Ru}$ and for the $4_1^{+}\to 2_1^{+}$ and $6_1^{+}\to 4_1^{+}$ transitions in ${}^{90}\mathrm{Zr}$ have been determined in this experiment making use of a multinucleon transfer reaction. These results have been interpreted on the basis of realistic shell-model calculations in the $f_{5/2}$, $p_{3/2}$, $p_{1/2}$, and $g_{9/2}$ proton valence space. Only the combination of extensive lifetime information and large scale shell-model calculations allowed the extent of the seniority conservation in the $N=50$ $g_{9/2}$ orbital to be understood. The conclusion is that seniority is largely conserved in the first $\pi g_{9/2}$ orbital.

Carbon burning is a key step in the evolution of massive stars, Type 1a supernovae and superbursts in x-ray binary systems. Determining the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion cross section at relevant energies by extrapolation of direct measurements is challenging due to resonances at and below the Coulomb barrier. A study of the ${}^{24}\mathrm{Mg}(\alpha ,{\alpha }^{\prime }){}^{24}\mathrm{Mg}$ reaction has identified several $0^{+}$ states in ${}^{24}\mathrm{Mg}$, close to the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ threshold, which predominantly decay to ${}^{20}\mathrm{Ne}(\text{ground state})+\alpha$. These states were not observed in ${}^{20}\mathrm{Ne}(\alpha ,{\alpha }_0){}^{20}\mathrm{Ne}$ resonance scattering suggesting that they may have a dominant ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ cluster structure. Given the very low angular momentum associated with sub-barrier fusion, these states may play a decisive role in ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion in analogy to the Hoyle state in helium burning. We present estimates of updated ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction rates.

We performed the first simultaneous extraction of the six leading-order proton polarizabilities. We reached this milestone thanks to both new high-quality experimental data and an innovative bootstrap-based fitting method. These new results provide a self-consistent and fundamental benchmark for all future theoretical and experimental polarizability estimates.

The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-${\pi }^0$s produced at forward pseudorapidities ($2.6<\eta <4.0$) in $p+p$, $p+\mathrm{Al}$, and $p+\mathrm{Au}$ collisions at a center-of-mass energy of 200 GeV. We observe a clear suppression of the correlated yields of back-to-back ${\pi }^0$ pairs in $p+\mathrm{Al}$ and $p+\mathrm{Au}$ collisions compared to the $p+p$ data. The observed suppression of back-to-back pairs as a function of transverse momentum suggests nonlinear gluon dynamics arising at high parton densities. The larger suppression found in $p+\mathrm{Au}$ relative to $p+\mathrm{Al}$ collisions exhibits a dependence of the saturation scale $Q_s^2$ on the mass number $A$. A linear scaling of the suppression with $A^{1/3}$ is observed with a slope of $-0.09\pm 0.01$.