We present the first ab initio calculations for $p$-shell hypernuclei including hyperon-nucleon-nucleon (YNN) contributions induced by a similarity renormalization group transformation of the initial hyperon-nucleon interaction. The transformation including the YNN terms conserves the spectrum of the Hamiltonian while drastically improving model-space convergence of the importance-truncated no-core model, allowing a precise extraction of binding and excitation energies. Results using a hyperon-nucleon interaction at leading order in chiral effective field theory for lower- to mid-$p$-shell hypernuclei show a good reproduction of experimental excitation energies while hyperon separation energies are typically overestimated. The induced YNN contributions are strongly repulsive and we show that they are related to a decoupling of the $\mathrm{\Sigma }$ hyperons from the hypernuclear system, i.e., a suppression of the $\mathrm{\Lambda }\text{−}\mathrm{\Sigma }$ conversion terms in the Hamiltonian. This is linked to the so-called hyperon puzzle in neutron-star physics and provides a basic mechanism for the explanation of strong $\mathrm{\Lambda }\mathrm{NN}$ three-baryon forces.

We utilize various ab initio approaches to search for a low-lying resonance in the four-neutron ($4n$) system using the JISP16 realistic $NN$ interaction. Our most accurate prediction is obtained using a $J$-matrix extension of the no-core shell model and suggests a $4n$ resonant state at an energy near $E_r=0.8\mathrm{MeV}$ with a width of approximately $\mathrm{\Gamma }=1.4\mathrm{MeV}$.

Masses of ${}^{52g,52m}\mathrm{Co}$ were measured for the first time with an accuracy of $\sim 10\mathrm{keV}$, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous $\beta \text{−}\gamma$ measurements of ${}^{52}\mathrm{Ni}$, the $T=2$, $J^{\pi }=0^{+}$ isobaric analog state (IAS) in ${}^{52}\mathrm{Co}$ was newly assigned, questioning the conventional identification of IASs from the $\beta$-delayed proton emissions. Using our energy of the IAS in ${}^{52}\mathrm{Co}$, the masses of the $T=2$ multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in ${}^{52}\mathrm{Co}$ decays predominantly via $\gamma$ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.

The ${}^{19}\mathrm{Ne}(p,\gamma ){}^{20}\mathrm{Na}$ reaction is the second step of a reaction chain which breaks out from the hot CNO cycle, following the ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ reaction at the onset of x-ray burst events. We investigate the spectrum of the lowest proton-unbound states in ${}^{20}\mathrm{Na}$ in an effort to resolve contradictions in spin-parity assignments and extract reliable information about the thermal reaction rate. The proton-transfer reaction ${}^{19}\mathrm{Ne}(d,n){}^{20}\mathrm{Na}$ is measured with a beam of the radioactive isotope ${}^{19}\mathrm{Ne}$ at an energy around the Coulomb barrier and in inverse kinematics. We observe three proton resonances with the ${}^{19}\mathrm{Ne}$ ground state, at 0.44, 0.66, and 0.82 MeV c.m. energies, which are assigned $3^{+}$, $1^{+}$, and ($0^{+}$), respectively. In addition, we identify two resonances with the first excited state in ${}^{19}\mathrm{Ne}$, one at 0.20 MeV and one, tentatively, at 0.54 MeV. These observations allow us for the first time to experimentally quantify the astrophysical reaction rate on an excited nuclear state. Our experiment shows an efficient path for thermal proton capture in ${}^{19}\mathrm{Ne}(p,\gamma ){}^{20}\mathrm{Na}$, which proceeds through ground state and excited-state capture in almost equal parts and eliminates the possibility for this reaction to create a bottleneck in the breakout from the hot CNO cycle.

We introduce a new mechanism for the chiral magnetic effect that does not require an initial chirality imbalance. The chiral magnetic current is generated by reconnections of magnetic flux that change the magnetic helicity of the system. The resulting current is entirely determined by the change of magnetic helicity, and it is quantized.

Doubly magic nuclei have a simple structure and are the cornerstones for entire regions of the nuclear chart. Theoretical insights into the supposedly doubly magic ${}^{78}\mathrm{Ni}$ and its neighbors are challenging because of the extreme neutron-to-proton ratio and the proximity of the continuum. We predict the $J^{\pi }=2_1^{+}$ state in ${}^{78}\mathrm{Ni}$ from a correlation with the $J^{\pi }=2_1^{+}$ state in ${}^{48}\mathrm{Ca}$ using chiral nucleon-nucleon and three-nucleon interactions. Our results confirm that ${}^{78}\mathrm{Ni}$ is doubly magic, and the predicted low-lying states of ${}^{79,80}\mathrm{Ni}$ open the way for shell-model studies of many more rare isotopes.

The mass ordering of mean transverse momentum $⟨p_T⟩$ and of the Fourier harmonic coefficient $v_2(p_T)$ of azimuthally anisotropic particle distributions in high energy hadron collisions is often interpreted as evidence for the hydrodynamic flow of the matter produced. We investigate an alternative initial state interpretation of this pattern in high-multiplicity proton-proton collisions at the LHC. The QCD Yang-Mills equations describing the dynamics of saturated gluons are solved numerically with initial conditions obtained from the color-glass-condensate-based impact-parameter-dependent glasma model. The gluons are subsequently fragmented into various hadron species employing the well established Lund string fragmentation algorithm of the pythia event generator. We find that this initial state approach reproduces characteristic features of bulk spectra, in particular, the particle mass dependence of $⟨p_T⟩$ and $v_2(p_T)$.

Theoretical models of low-energy ($d$, $p$) single-neutron transfer reactions are a crucial link between experimentation, nuclear structure, and nuclear astrophysical studies. Whereas reaction models that use local optical potentials are insensitive to short-range physics in the deuteron, we show that including the inherent nonlocality of the nucleon-target interactions and realistic deuteron wave functions generates significant sensitivity to high $n\text{−}p$ relative momenta and to the underlying nucleon-nucleon interaction. We quantify this effect upon the deuteron channel distorting potentials within the framework of the adiabatic deuteron breakup model. The implications for calculated ($d$, $p$) cross sections and spectroscopic information deduced from experiments are discussed.

We present a first-principles study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian $SU(N_c)$ and Abelian $U(1)$ gauge fields. Investigating the behavior of vector and axial currents during a sphaleron transition in the presence of an external magnetic field, we demonstrate how the interplay of the chiral magnetic and chiral separation effect leads to the formation of a propagating wave. We further analyze the dependence of the magnitude of the induced vector current and the propagation of the wave on the amount of explicit chiral symmetry breaking due to finite quark masses.

The $\beta$-decay intensity of ${}^{70}\mathrm{Co}$ was measured for the first time using the technique of total absorption spectroscopy. The large $\beta$-decay $Q$ value [12.3(3) MeV] offers a rare opportunity to study $\beta$-decay properties in a broad energy range. Two surprising features were observed in the experimental results, namely, the large fragmentation of the $\beta$ intensity at high energies, as well as the strong competition between $\gamma$ rays and neutrons, up to more than 2 MeV above the neutron-separation energy. The data are compared to two theoretical calculations: the shell model and the quasiparticle random phase approximation (QRPA). Both models seem to be missing a significant strength at high excitation energies. Possible interpretations of this discrepancy are discussed. The shell model is used for a detailed nuclear structure interpretation and helps to explain the observed $\gamma$-neutron competition. The comparison to the QRPA calculations is done as a means to test a model that provides global $\beta$-decay properties for astrophysical calculations. Our work demonstrates the importance of performing detailed comparisons to experimental results, beyond the simple half-life comparisons. A realistic and robust description of the $\beta$-decay intensity is crucial for our understanding of nuclear structure as well as of $r$-process nucleosynthesis.

The ${}^{17}\mathrm{O}(p,\alpha ){}^{14}\mathrm{N}$ reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as ${}^{17}\mathrm{O}$ and ${}^{18}\mathrm{F}$, which can provide constraints on astrophysical models. A new direct determination of the $E_R=64.5\mathrm{keV}$ resonance strength performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) accelerator has led to the most accurate value to date $\omega \gamma =10.0\pm 1.4_{\mathrm{stat}}\pm 0.7_{\mathrm{syst}}\mathrm{neV}$, thanks to a significant background reduction underground and generally improved experimental conditions. The (bare) proton partial width of the corresponding state at $E_x=5672\mathrm{keV}$ in ${}^{18}\mathrm{F}$ is ${\mathrm{\Gamma }}_p=35\pm 5_{\mathrm{stat}}\pm 3_{\mathrm{syst}}\mathrm{neV}$. This width is about a factor of 2 higher than previously estimated, thus leading to a factor of 2 increase in the ${}^{17}\mathrm{O}(p,\alpha ){}^{14}\mathrm{N}$ reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower ${}^{17}\mathrm{O}/{}^{16}\mathrm{O}$ ratios, with important implications on the interpretation of astrophysical observables from these stars.

In recent measurements of the scissors mode in radiative decay experiments, transition strengths were observed that were double that expected from theory and systematics well established from measurements on the radiative excitation channel, that is, using nuclear resonance fluorescence (NRF). Additional strength as measured with NRF can only be present as heretofore unobserved branching or fragmentation of the scissors mode. Such possibilities were investigated in a transmission NRF measurement on the deformed, odd-mass ${}^{181}\mathrm{Ta}$, using a quasimonoenergetic $\gamma$-ray beam at two beam energies. This measurement further influences applications using transmission NRF to assay or detect odd-mass fissile isotopes. A large branching, $\approx 75\%$, of small resonances to excited states was discovered. In contrast, previous studies using NRF of the scissors-mode strength in odd-mass nuclei assumed no branching existed. The presently observed branching, combined with the observed highly fragmented elastic strength, could reconcile the scissors-mode strength observed in NRF measurements with the expectations for enhanced scissors-mode strength from radiative decay experiments.

The double polarization observable $E$ and the helicity dependent cross sections ${\sigma }_{1/2}$ and ${\sigma }_{3/2}$ were measured for $\eta$ photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost $4\pi$ detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from $\eta \to 2\gamma$ and $\eta \to 3{\pi }^0$. The results show that the narrow structure previously observed in $\eta$ photoproduction from the neutron is only apparent in ${\sigma }_{1/2}$ and hence, most likely related to a spin-$1/2$ amplitude. Nucleon resonances that contribute to this partial wave in $\eta$ production are only $N1/2^{-}$ ($S_{11}$) and $N1/2^{+}$ ($P_{11}$). Furthermore, the extracted Legendre coefficients of the angular distributions for ${\sigma }_{1/2}$ are in good agreement with recent reaction model predictions assuming a narrow resonance in the $P_{11}$ wave as the origin of this structure.

Proton radii of ${}^{12–19}\mathrm{C}$ densities derived from first accurate charge changing cross section measurements at $900A\mathrm{MeV}$ with a carbon target are reported. A thick neutron surface evolves from $\sim 0.5\mathrm{fm}$ in ${}^{15}\mathrm{C}$ to $\sim 1\mathrm{fm}$ in ${}^{19}\mathrm{C}$. The halo radius in ${}^{19}\mathrm{C}$ is found to be $6.4\pm 0.7\mathrm{fm}$ as large as ${}^{11}\mathrm{Li}$. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

We discuss the effect of a strong magnetic field on the chemical freeze-out points in ultrarelativistic heavy-ion collisions. As a result of inverse magnetic catalysis or magnetic inhibition, the crossover onset to hot and dense matter out of quarks and gluons should be shifted to a lower temperature. To quantify this shift we employ the hadron resonance gas model and an empirical condition for the chemical freeze-out. We point out that the charged particle abundances are significantly affected by the magnetic field so that the electric charge fluctuation is largely enhanced, especially at high baryon density. The charge conservation partially cancels the enhancement, but our calculation shows that the electric charge fluctuation could serve as a magnetometer. We find that the fluctuation exhibits a crossover behavior rapidly increased for $eB\gtrsim (0.4\mathrm{GeV}{)}^2$, while the charge chemical potential has smoother behavior with an increasing magnetic field.