The measurement of $J/\psi$ azimuthal anisotropy is presented as a function of transverse momentum for different centralities in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The measured $J/\psi$ elliptic flow is consistent with zero within errors for transverse momentum between 2 and $10\mathrm{GeV}/c$. Our measurement suggests that $J/\psi$ particles with relatively large transverse momenta are not dominantly produced by coalescence from thermalized charm quarks, when comparing to model calculations.

Neutron time-of-flight spectra from inertial confinement fusion experiments with tritium-filled targets have been measured at the National Ignition Facility. These spectra represent a significant improvement in energy resolution and statistics over previous measurements, and afford the first definitive observation of a peak resulting from sequential decay through the ground state of ${}^5\mathrm{He}$ at low reaction energies $E_{\mathrm{c}.\mathrm{m}.}\lesssim 100\mathrm{keV}$. To describe the spectrum, we have developed an $R$-matrix model that accounts for interferences from fermion symmetry and intermediate states, and show these effects to be non-negligible. We also find the spectrum can be described by sequential decay through $\ell =1$ states in ${}^5\mathrm{He}$, which differs from previous interpretations.

Cross sections for proton knockout observed in ($e$,$e^{\prime }p$) reactions are apparently quenched by a factor of $\sim 0.5$, an effect attributed to short-range correlations between nucleons. Here we demonstrate that such quenching is not restricted to proton knockout, but a more general phenomenon associated with any nucleon transfer. Measurements of absolute cross sections on a number of targets between ${}^{16}\mathrm{O}$ and ${}^{208}\mathrm{Pb}$ were analyzed in a consistent way, with the cross sections reduced to spectroscopic factors through the distorted-wave Born approximation with global optical potentials. Across the 124 cases analyzed here, induced by various proton- and neutron-transfer reactions and with angular momentum transfer $\ell =0–7$, the results are consistent with a quenching factor of 0.55. This is an apparently uniform quenching of single-particle motion in the nuclear medium. The effect is seen not only in ($d$,$p$) reactions but also in reactions with $A=3$ and 4 projectiles, when realistic wave functions are used for the projectiles.

The structure and decay of ${}^{26}\mathrm{O}$ are investigated in a three-body ${}^{24}\mathrm{O}+n+n$ model suitable for studies of the long-lived (including radioactivity time scale) states. We have found extremely strong effects of the subbarrier configuration mixing on the decay width of true $2n$ emitters due to core recoil and neutron-neutron final state interaction. This effect far exceeds the analogous effect in the true $2p$ emitters. Our calculations provide reasonably narrow boundaries for the lifetime vs decay energy dependence for the true $2n$ emission. An upper limit of $\sim 1\mathrm{keV}$ for the decay energy of the unbound ${}^{26}\mathrm{O}$ is inferred based on the recent experimental lifetime value.

We outline a general method for computing nuclear capture reactions on the lattice. The method consists of two major parts. In this study we detail the second part which consists of calculating an effective two-body capture reaction on the lattice at finite volume. We solve this problem by calculating the two-point Green’s function using an infrared regulator and the capture amplitude to a two-body bound state. We demonstrate the details of this method by calculating on the lattice the leading $M1$ contribution to the radiative neutron capture on proton at low energies using pionless effective field theory. We find good agreement with exact continuum results. The approach we outline here can be used in a wide range of applications including few-body reactions in cold atomic systems and hadronic reactions in lattice quantum chromodynamics.

We present the first quantum Monte Carlo (QMC) calculations with chiral effective field theory (EFT) interactions. To achieve this, we remove all sources of nonlocality, which hamper the inclusion in QMC calculations, in nuclear forces to next-to-next-to-leading order. We perform auxiliary-field diffusion Monte Carlo (AFDMC) calculations for the neutron matter energy up to saturation density based on local leading-order, next-to-leading order, and next-to-next-to-leading order nucleon-nucleon interactions. Our results exhibit a systematic order-by-order convergence in chiral EFT and provide nonperturbative benchmarks with theoretical uncertainties. For the softer interactions, perturbative calculations are in excellent agreement with the AFDMC results. This work paves the way for QMC calculations with systematic chiral EFT interactions for nuclei and nuclear matter, for testing the perturbativeness of different orders, and allows for matching to lattice QCD results by varying the pion mass.

The jet fragmentation function is measured with direct photon-hadron correlations in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The $p_T$ of the photon is an excellent approximation to the initial $p_T$ of the jet and the ratio $z_T=p_T^h/p_T^{\gamma }$ is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in $\mathrm{Au}+\mathrm{Au}$ collisions while a photon isolation cut is applied in $p+p$. $I_{\mathrm{AA}}$, the ratio of hadron yield opposite the photon in $\mathrm{Au}+\mathrm{Au}$ to that in $p+p$, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high $z_T$. The associated hadron yield at low $z_T$ is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.

We have isolated ${\overline{\nu }}_{\mu }$ charged-current quasielastic (QE) interactions occurring in the segmented scintillator tracking region of the MINERvA detector running in the NuMI neutrino beam at Fermilab. We measure the flux-averaged differential cross section, $d\sigma /d{Q}^2$, and compare to several theoretical models of QE scattering. Good agreement is obtained with a model where the nucleon axial mass, $M_A$, is set to $0.99\mathrm{GeV}/c^2$ but the nucleon vector form factors are modified to account for the observed enhancement, relative to the free nucleon case, of the cross section for the exchange of transversely polarized photons in electron-nucleus scattering. Our data at higher $Q^2$ favor this interpretation over an alternative in which the axial mass is increased.

We report a study of ${\nu }_{\mu }$ charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a ${\mu }^{-}$ and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, $d\sigma /d{Q}^2$, and study the low energy particle content of the final state. Deviations are found between the measured $d\sigma /d{Q}^2$ and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state.

We calculate the bremsstrahlung photon spectrum emitted from dynamically evolving “quarkyonic” matter and compare this spectrum with that of a high chemical potential quark-gluon plasma as well as to a hadron gas. We find that the transverse momentum distribution and the harmonic coefficient is markedly different in the three cases. The transverse momentum distribution of quarkyonic matter can be fit with an exponential but is markedly steeper than the distribution expected for the quark-gluon plasma or a hadron gas, even at the lower temperatures expected in the critical point region. The quarkyonic elliptic flow coefficient fluctuates randomly from event to event and within the same event at different transverse momenta. The latter effect, which can be explained by the shape of quark wave functions within quarkyonic matter, might be considered as a quarkyonic matter signature, provided that the initial temperature is low enough that the quarkyonic regime dominates over deconfinement effects and the reaction-plane flow can be separated from the fluctuating component.

A new quantum Monte Carlo approach is proposed to investigate low-lying states of nuclei within the shell model. The formalism relies on a variational symmetry-restored wave function to guide the underlying Brownian motion. Sign or phase problems that usually plague quantum Monte Carlo fermionic simulations are controlled by constraining stochastic paths through a fixed-node-like approximation. Exploratory results in the $sd$ and $pf$ valence spaces with realistic effective interactions are presented. They prove the ability of the scheme to yield nearly exact yrast spectroscopies for both even- and odd-mass nuclei.

Macroscopic parameters as well as precise information on the random force characterizing the Langevin-type description of the nuclear fusion process around the Coulomb barrier are extracted from the microscopic dynamics of individual nucleons by exploiting the numerical simulation of the improved quantum molecular dynamics. It turns out that the dissipation dynamics of the relative motion between two fusing nuclei is caused by a non-Gaussian distribution of the random force. We find that the friction coefficient as well as the time correlation function of the random force takes particularly large values in a region a little bit inside of the Coulomb barrier. A clear non-Markovian effect is observed in the time correlation function of the random force. It is further shown that an emergent dynamics of the fusion process can be described by the generalized Langevin equation with memory effects by appropriately incorporating the microscopic information of individual nucleons through the random force and its time correlation function.

The rate of the ${}^{18}\mathrm{F}(p,\gamma ){}^{19}\mathrm{Ne}$ reaction affects the final abundance of the $\gamma$-ray observable radioisotope ${}^{18}\mathrm{F}$, produced in novae. However, no successful measurement of this reaction exists and the rate used is calculated from incomplete information on the contributing resonances. Of the two resonances thought to play a significant role, one has a radiative width estimated from the assumed analogue state in the mirror nucleus, ${}^{19}\mathrm{F}$. The second does not have an analogue state assignment at all, resulting in an arbitrary radiative width being assumed. Here, we report the first successful direct measurement of the ${}^{18}\mathrm{F}(p,\gamma ){}^{19}\mathrm{Ne}$ reaction. The strength of the 665 keV resonance ($E_x=7.076\mathrm{MeV}$) is found to be over an order of magnitude weaker than currently assumed in nova models. Reaction rate calculations show that this resonance therefore plays no significant role in the destruction of ${}^{18}\mathrm{F}$ at any astrophysical energy.

We derive a relativistic chiral kinetic equation with manifest Lorentz covariance from Wigner functions of spin-$1/2$ massless fermions in a constant background electromagnetic field. It contains vorticity terms and a four-dimensional Euclidean Berry monopole which gives an axial anomaly. By integrating out the zeroth component of the 4-momentum $p$, we reproduce the previous three-dimensional results derived from the Hamiltonian approach, together with the newly derived vorticity terms. The phase space continuity equation has an anomalous source term proportional to the product of electric and magnetic fields ($F_{\sigma \rho }{\tilde{F}}^{\sigma \rho }\sim E_{\sigma }{B}^{\sigma }$). This provides a unified interpretation of the chiral magnetic and vortical effects, chiral anomaly, Berry curvature, and the Berry monopole in the framework of Wigner functions.

We investigate the $\alpha +{}^{16}\mathrm{O}$ cluster structure in the inversion-doublet band ($K^{\pi }=0_1^{\pm }$) states of ${}^{20}\mathrm{Ne}$ with an angular-momentum-projected version of the Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function, which was successful “in its original form” for the description of, e.g., the famous Hoyle state. In contrast with the traditional view on clusters as localized objects, especially in inversion doublets, we find that these single THSR wave functions, which are based on the concept of nonlocalized clustering, can well describe the $K^{\pi }=0_1^{-}$ band and the $K^{\pi }=0_1^{+}$ band. For instance, they have 99.98% and 99.87% squared overlaps for $1^{-}$ and $3^{-}$ states (99.29%, 98.79%, and 97.75% for $0^{+}$, $2^{+}$, and $4^{+}$ states), respectively, with the corresponding exact solution of the $\alpha +{}^{16}\mathrm{O}$ resonating group method. These astounding results shed a completely new light on the physics of low energy nuclear cluster states in nuclei: The clusters are nonlocalized and move around in the whole nuclear volume, only avoiding mutual overlap due to the Pauli blocking effect.

We have measured cross sections for the $\gamma {}^3\mathrm{He}\to pd$ reaction at photon energies of 0.4–1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

Intermediate-energy Coulomb excitation measurements are performed on the $N\ge 40$ neutron-rich nuclei ${}^{66,68}\mathrm{Fe}$ and ${}^{64}\mathrm{Cr}$. The reduced transition matrix elements providing a direct measure of the quadrupole collectivity $B(E2;2_1^{+}\to 0_1^{+})$ are determined for the first time in ${}^{68}\mathrm{Fe}_{42}$ and ${}^{64}\mathrm{Cr}_{40}$ and confirm a previous recoil distance method lifetime measurement in ${}^{66}\mathrm{Fe}_{40}$. The results are compared to state-of-the-art large-scale shell-model calculations within the full $fpgd$ neutron orbital model space using the Lenzi-Nowacki-Poves-Sieja effective interaction and confirm the results of the calculations that show these nuclei are well deformed.

We formulate the in-medium similarity renormalization group (IM-SRG) for open-shell nuclei using a multireference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multireference IM-SRG (MR-IM-SRG) is used to perform the first ab initio study of all even oxygen isotopes with chiral nucleon-nucleon and three-nucleon interactions, from the proton to the neutron drip lines. We obtain an excellent reproduction of experimental ground-state energies with quantified uncertainties, which is validated by results from the importance-truncated no-core shell model and the coupled cluster method. The agreement between conceptually different many-body approaches and experiment highlights the predictive power of current chiral two- and three-nucleon interactions, and establishes the MR-IM-SRG as a promising new tool for ab initio calculations of medium-mass nuclei far from shell closures.

In recent experiments at the velocity filter Separator for Heavy Ion reaction Products (SHIP) (GSI, Darmstadt), an extended and improved set of $\alpha$-decay data for more than 20 of the most neutron-deficient isotopes in the region from lead to thorium was obtained. The combined analysis of this newly available $\alpha$-decay data, of which the ${}^{186}\mathrm{Po}$ decay is reported here, allowed us for the first time to clearly show that crossing the $Z=82$ shell to higher proton numbers strongly accelerates the $\alpha$ decay. From the experimental data, the $\alpha$-particle formation probabilities are deduced following the Universal Decay Law approach. The formation probabilities are discussed in the framework of the pairing force acting among the protons and the neutrons forming the $\alpha$ particle. A striking resemblance between the phenomenological pairing gap deduced from experimental binding energies and the formation probabilities is noted. These findings support the conjecture that both the $N=126$ and $Z=82$ shell closures strongly influence the $\alpha$-formation probability.

We study a relativistic plasma containing charged chiral fermions in an external electric field. We show that with the presence of both vector and axial charge densities, the electric field can induce an axial current along its direction and thus cause chirality separation. We call it the chiral electric separation effect (CESE). On a very general basis, we argue that the strength of CESE is proportional to ${\mu }_V{\mu }_A$ with ${\mu }_V$ and ${\mu }_A$ the chemical potentials for vector charge and axial charge. We then explicitly calculate this CESE conductivity coefficient in thermal QED at leading-log order. The CESE can manifest a new gapless wave mode propagating along the electric field. Potential observable effects of CESE in heavy-ion collisions are also discussed.