At high baryon chemical potential ${\mu }_B$, the equation of state of QCD allows a weak-coupling expansion in the QCD coupling ${\alpha }_s$. The result is currently known up to and including the full next-to-next-to-leading order ${\alpha }_s^2$. Starting at this order, the computations are complicated by the modification of particle propagation in a dense medium, which necessitates nonperturbative treatment of the scale ${\alpha }_s^{1/2}{\mu }_B$. We apply a hard-thermal-loop scheme for capturing the contributions of this scale to the weak-coupling expansion, and we use it to determine the leading-logarithm contribution to next-to-next-to-next-to-leading order: ${\alpha }_s^3{\ln }^2{\alpha }_s$. This result is the first improvement to the equation of state of massless cold quark matter in 40 years. The new term is negligibly small and thus significantly increases our confidence in the applicability of the weak-coupling expansion.

The lifetimes of the first excited $2^{+}$, $4^{+}$, and $6^{+}$ states in ${}^{98}\mathrm{Zr}$ were measured with the recoil-distance Doppler shift method in an experiment performed at GANIL. Excited states in ${}^{98}\mathrm{Zr}$ were populated using the fission reaction between a $6.2\mathrm{MeV}/\mathrm{u}$ ${}^{238}\mathrm{U}$ beam and a ${}^9\mathrm{Be}$ target. The $\gamma$ rays were detected with the EXOGAM array in correlation with the fission fragments identified by mass and atomic number in the VAMOS++ spectrometer. Our result shows a very small $B(E2;2_1^{+}\to 0_1^{+})$ value in ${}^{98}\mathrm{Zr}$, thereby confirming the very sudden onset of collectivity at $N=60$. The experimental results are compared to large-scale Monte Carlo shell model and beyond-mean-field calculations. The present results indicate the coexistence of two additional deformed shapes in this nucleus along with the spherical ground state.

Lifetime measurements of excited states of the light $N=52$ isotones ${}^{88}\mathrm{Kr}$, ${}^{86}\mathrm{Se}$, and ${}^{84}\mathrm{Ge}$ have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities $B(E2;2^{+}\to 0^{+})$ and $B(E2;4^{+}\to 2^{+})$ were obtained for the first time for the hard-to-reach ${}^{84}\mathrm{Ge}$. While the $B(E2;2^{+}\to 0^{+})$ values of ${}^{88}\mathrm{Kr}$, ${}^{86}\mathrm{Se}$ saturate the maximum quadrupole collectivity offered by the natural valence ($3s$, $2d$, $1g_{7/2}$, $1h_{11/2}$) space of an inert ${}^{78}\mathrm{Ni}$ core, the value obtained for ${}^{84}\mathrm{Ge}$ largely exceeds it, suggesting that shape coexistence phenomena, previously reported at $N\lesssim 49$, extend beyond $N=50$. The onset of collectivity at $Z=32$ is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector $\rho$ field in shell-structure evolution.

A fast charged particle crossing the boundary between chiral matter and vacuum radiates transition radiation. Its most remarkable features—the resonant behavior at a certain emission angle and the circular polarization of the spectrum—depend on the parameters of the chiral anomaly in a particular material or matter. Chiral transition radiation can be used to investigate the chiral anomaly in such diverse media as the quark-gluon plasma, Weyl semimetals, and axionic dark matter.

Observation of neutrinoless double beta decay, a lepton number violating process that has been proposed to clarify the nature of neutrino masses, has spawned an enormous world-wide experimental effort. Relating nuclear decay rates to high-energy, beyond the standard model (BSM) physics requires detailed knowledge of nonperturbative QCD effects. Using lattice QCD, we compute the necessary matrix elements of short-range operators, which arise due to heavy BSM mediators, that contribute to this decay via the leading order ${\pi }^{-}\to {\pi }^{+}$ exchange diagrams. Utilizing our result and taking advantage of effective field theory methods will allow for model-independent calculations of the relevant two-nucleon decay, which may then be used as input for nuclear many-body calculations of the relevant experimental decays. Contributions from short-range operators may prove to be equally important to, or even more important than, those from long-range Majorana neutrino exchange.

The ${}^{22}\mathrm{Ne}(p,\gamma ){}^{23}\mathrm{Na}$ reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at $E_p=156.2$, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at $E_p=71$ and 105 keV. Here, new ${}^{22}\mathrm{Ne}(p,\gamma ){}^{23}\mathrm{Na}$ data with high statistics and low background are reported. Stringent upper limits of $6\times {10}^{-11}$ and $7\times {10}^{-11}\mathrm{eV}$ (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant $S$ factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the ${}^{22}\mathrm{Ne}(p,\gamma ){}^{23}\mathrm{Na}$ rate is now reduced by 3 orders of magnitude.

The ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced $\alpha$ width, ${\gamma }_{11}$, of the bound $1^{-}$ level in ${}^{16}\mathrm{O}$ is particularly important to determine the cross section. The magnitude of ${\gamma }_{11}$ is determined via sub-Coulomb $\alpha$-transfer reactions or the $\beta$-delayed $\alpha$ decay of ${}^{16}\mathrm{N}$, but the latter approach is presently hampered by the lack of sufficiently precise data on the $\beta$-decay branching ratios. Here we report improved branching ratios for the bound $1^{-}$ level [$b_{\beta ,11}=(5.02\pm 0.10)\times {10}^{-2}$] and for $\beta$-delayed $\alpha$ emission [$b_{\beta \alpha }=(1.59\pm 0.06)\times {10}^{-5}$]. Our value for $b_{\beta \alpha }$ is 33% larger than previously held, leading to a substantial increase in ${\gamma }_{11}$. Our revised value for ${\gamma }_{11}$ is in good agreement with the value obtained in $\alpha$-transfer studies and the weighted average of the two gives a robust and precise determination of ${\gamma }_{11}$, which provides significantly improved constraints on the ${}^{12}\mathrm{C}(\alpha ,\gamma )$ cross section in the energy range relevant to hydrostatic He burning.

We study the motion of vortex filaments in chiral media and find a semiclassical analog of the anomaly-induced chiral magnetic effect. The helical solitonic excitations on vortices in a parity-breaking medium are found to carry additional energy flow along the vortex in the direction dictated by the sign of chirality imbalance; we call this new transport phenomenon the chiral propulsion effect. The dynamics of vortex filaments in the parity-breaking background is described by a modified version of the localized induction equation. We analyze the linear stability of simple vortex solutions and study the effects of chiral media on the excitation spectrum and the growth rate of the unstable modes. We also show that, if the equation of motion of the filament is symmetric under the simultaneous reversal of parity and time, planar-shape solutions cannot transport energy.

The key parameter to discuss the possibility of the pion condensation in nuclear matter, i.e., the so-called Landau-Migdal parameter $g^{\prime }$, was extracted by measuring the double-differential cross sections for the $(p,n)$ reaction at $216\mathrm{MeV}/\mathrm{u}$ on a neutron-rich doubly magic unstable nucleus, ${}^{132}\mathrm{Sn}$ with the quality comparable to data taken with stable nuclei. The extracted strengths for Gamow-Teller (GT) transitions from ${}^{132}\mathrm{Sn}$ leading to ${}^{132}\mathrm{Sb}$ exhibit the GT giant resonance (GTR) at the excitation energy of $16.3\pm 0.4(\mathrm{stat})\pm 0.4(\mathrm{syst})\mathrm{MeV}$ with the width of $\mathrm{\Gamma }=4.7\pm 0.8\mathrm{MeV}$. The integrated GT strength up to $E_x=25\mathrm{MeV}$ is $S_{\mathrm{GT}}^{-}=53\pm {5(\mathrm{stat})}_{-10}^{+11}(\mathrm{syst})$, corresponding to 56% of Ikeda’s sum rule of $3(N-Z)=96$. The present result accurately constrains the Landau-Migdal parameter as $g^{\prime }=0.68\pm 0.07$, thanks to the high sensitivity of the GTR energy to $g^{\prime }$. In combination with previous studies on the GTR for ${}^{90}\mathrm{Zr}$ and ${}^{208}\mathrm{Pb}$, the result of this work shows the constancy of this parameter in the nuclear chart region with $(N-Z)/A=0.11$ to 0.24 and $A=90$ to 208.

We report first measurements of $e^{+}{e}^{-}$ pair production in the mass region $0.4<M_{ee}<2.6\mathrm{GeV}/c^2$ at low transverse momentum ($p_T<0.15\mathrm{GeV}/c$) in noncentral $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ and $\mathrm{U}+\mathrm{U}$ collisions at $\sqrt{s_{NN}}=193\mathrm{GeV}$. Significant enhancement factors, expressed as ratios of data over known hadronic contributions, are observed in the 40%–80% centrality of these collisions. The excess yields peak distinctly at low $p_T$ with a width ($\sqrt{⟨p_T^2⟩}$) between 40 and $60\mathrm{MeV}/c$. The absolute cross section of the excess depends weakly on centrality, while those from a theoretical model calculation incorporating an in-medium broadened $\rho$ spectral function and radiation from a quark gluon plasma or hadronic cocktail contributions increase dramatically with an increasing number of participant nucleons. Model calculations of photon-photon interactions generated by the initial projectile and target nuclei describe the observed excess yields but fail to reproduce the $p_T^2$ distributions.

The elastic properties of neutron star crusts are relevant for a variety of currently observable or near-future electromagnetic and gravitational wave phenomena. These phenomena may depend on the elastic properties of nuclear pasta found in the inner crust. We present large-scale classical molecular dynamics simulations where we deform nuclear pasta. We simulate idealized samples of nuclear pasta and describe their breaking mechanism. We also deform nuclear pasta that is arranged into many domains, similar to what is known for the ions in neutron star crusts. Our results show that nuclear pasta may be the strongest known material, perhaps with a shear modulus of $10^{30}{\mathrm{ergs}/\mathrm{cm}}^3$ and a breaking strain greater than 0.1.

The ${}^{36}\mathrm{Ar}(n,\gamma ){}^{37}\mathrm{Ar}$ ($t_{1/2}=35\mathrm{d}$) and ${}^{38}\mathrm{Ar}(n,\gamma ){}^{39}\mathrm{Ar}$ (269 yr) reactions were studied for the first time with a quasi-Maxwellian ($kT\sim 47\mathrm{keV}$) neutron flux for Maxwellian average cross section (MACS) measurements at stellar energies. Gas samples were irradiated at the high-intensity Soreq applied research accelerator facility-liquid-lithium target neutron source and the ${}^{37}\mathrm{Ar}/{}^{36}\mathrm{Ar}$ and ${}^{39}\mathrm{Ar}/{}^{38}\mathrm{Ar}$ ratios in the activated samples were determined by accelerator mass spectrometry at the ATLAS facility (Argonne National Laboratory). The ${}^{37}\mathrm{Ar}$ activity was also measured by low-level counting at the University of Bern. Experimental MACS of ${}^{36}\mathrm{Ar}$ and ${}^{38}\mathrm{Ar}$, corrected to the standard 30 keV thermal energy, are 1.9(3) and 1.3(2) mb, respectively, differing from the theoretical and evaluated values published to date by up to an order of magnitude. The neutron-capture cross sections of ${}^{36,38}\mathrm{Ar}$ are relevant to the stellar nucleosynthesis of light neutron-rich nuclides; the two experimental values are shown to affect the calculated mass fraction of nuclides in the region $A=36–48$ during the weak $s$ process. The new production cross sections have implications also for the use of ${}^{37}\mathrm{Ar}$ and ${}^{39}\mathrm{Ar}$ as environmental tracers in the atmosphere and hydrosphere.

We address the $\mathrm{\Lambda }$ hypernuclear “overbinding problem” in light hypernuclei which stands for a 1–3 MeV excessive $\mathrm{\Lambda }$ separation energy calculated in ${}_{\mathrm{\Lambda }}{}^5\mathrm{He}$. This problem arises in most few-body calculations that reproduce ground-state $\mathrm{\Lambda }$ separation energies in the lighter $\mathrm{\Lambda }$ hypernuclei within various hyperon-nucleon interaction models. Recent pionless effective field theory ($\cancel{\pi }\mathrm{EFT}$) nuclear few-body calculations are extended in this work to $\mathrm{\Lambda }$ hypernuclei. At leading order, the $\mathrm{\Lambda }N$ low-energy constants are associated with $\mathrm{\Lambda }N$ scattering lengths, and the $\mathrm{\Lambda }NN$ low-energy constants are fitted to $\mathrm{\Lambda }$ separation energies ($B_{\mathrm{\Lambda }}^{\exp }$) for $A\le 4$. The resulting $\cancel{\pi }\mathrm{EFT}$ interaction reproduces in few-body stochastic variational method calculations the reported value $B_{\mathrm{\Lambda }}^{\exp }({}_{\mathrm{\Lambda }}{}^5\mathrm{He})=3.12\pm 0.02\mathrm{MeV}$ within a fraction of MeV over a broad range of $\cancel{\pi }\mathrm{EFT}$ cutoff parameters. Possible consequences and extensions to heavier hypernuclei and to neutron-star matter are discussed.

Differences in mean-square nuclear charge radii of ${}^{100–130}\mathrm{Cd}$ are extracted from high-resolution collinear laser spectroscopy of the $5s{{}^{2}S}_{1/2}\to 5p{{}^{2}P}_{3/2}$ transition of the ion and from the $5s5p{{}^{3}P}_2\to 5s6s{{}^{3}S}_1$ transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete $sdgh$ shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius.

The isotope ${}^{98}\mathrm{Tc}$ decays to ${}^{98}\mathrm{Ru}$ with a half-life of $4.2\times {10}^6\mathrm{yr}$ and could have been present in the early Solar System. In this Letter, we report on the first calculations of the production of ${}^{98}\mathrm{Tc}$ by neutrino-induced reactions in core-collapse supernovae (the $\nu$ process). Our predicted ${}^{98}\mathrm{Tc}$ abundance at the time of solar system formation is not much lower than the current measured upper limit raising the possibility for its detection in the not too distant future. We show that, if the initial abundance were to be precisely measured, the ${}^{98}\mathrm{Tc}$ nuclear cosmochronometer could be used to evaluate a much more precise value of the duration time from the last core-collapse supernova to the formation of the solar system. Moreover, a unique and novel feature of the ${}^{98}\mathrm{Tc}$ $\nu$-process nucleosynthesis is the large contribution ($\sim 20\%$) from charged current reactions with electron antineutrinos. This means that ${}^{98}\mathrm{Tc}$ becomes a unique new $\nu$-process probe of the temperature of the electron antineutrinos.

Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum ($k_F$). A fundamental characteristic of SRC pairs is having large relative momenta as compared to $k_F$, and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton ($pp$) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the $A(e,e^{\prime }pp)$ reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to $170\mathrm{MeV}/c$, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.

Nuclear response theory beyond the one-loop approximation is formulated for the case of finite temperature. For this purpose, the time blocking approximation to the time-dependent part of the in-medium nucleon-nucleon interaction amplitude is adopted for the thermal (imaginary-time) Green’s function formalism. We found that introducing a soft blocking, instead of a sharp blocking at zero temperature, brings the Bethe-Salpeter equation to a single-frequency variable equation also at finite temperatures. The method is implemented self-consistently in the framework of quantum hadrodynamics and designed to connect the high-energy scale of heavy mesons and the low-energy domain of nuclear medium polarization effects in a parameter-free way. In this framework, we investigate the temperature dependence of dipole spectra in the even-even nuclei ${}^{48}\mathrm{Ca}$ and ${}^{100,120,132}\mathrm{Sn}$ with a special focus on the giant dipole resonance’s width problem and on the low-energy dipole strength distribution.

Neutron-deficient selenium isotopes are thought to undergo a rapid shape change from a prolate deformation near the line of beta stability towards oblate deformation around the line of $N=Z$. The point at which this shape change occurs is unknown, with inconsistent predictions from available theoretical models. A common feature in the models is the delicate nature of the point of transition, with the introduction of even a modest spin to the system sufficient to change the ordering of the prolate and oblate configurations. We present a measurement of the quadrupole moment of the first-excited state in radioactive ${}^{72}\mathrm{Se}$—a potential point of transition—by safe Coulomb excitation. This is the first low-energy Coulomb excitation to be performed with a rare-isotope beam at the reaccelerated beam facility at the National Superconducting Cyclotron Laboratory. By demonstrating a negative spectroscopic quadrupole moment for the first-excited $2^{+}$ state, it is found that any low-spin shape change in neutron-deficient selenium does not occur until ${}^{70}\mathrm{Se}$.

The elliptic azimuthal anisotropy coefficient ($v_2$) is measured for charm ($D^0$) and strange ($K_S^0$, $\mathrm{\Lambda }$, ${\mathrm{\Xi }}^{-}$, and ${\mathrm{\Omega }}^{-}$) hadrons, using a data sample of $p+\mathrm{Pb}$ collisions collected by the CMS experiment, at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=8.16\mathrm{TeV}$. A significant positive $v_2$ signal from long-range azimuthal correlations is observed for all particle species in high-multiplicity $p+\mathrm{Pb}$ collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller $v_2$ than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, also presented.