It is suggested that superfluid helium (condensate of ${}^4\mathrm{He}$ atoms) may stimulate nuclear $\alpha$ decay in a situation when an $\alpha$ emitter moves through superfluid helium with fine-tuned velocity, so that the backward-emitted $\alpha$ particle is at rest in the laboratory frame. It is shown that the probability of stimulated $\alpha$ decay in this case may be sizable enough to be detected.

We report $K/\pi$ fluctuations from $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=19.6$, 62.4, 130, and 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. $K/\pi$ fluctuations in central collisions show little dependence on incident energy and are on the same order as those from NA49 at the Super Proton Synchrotron in central $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=12.3$ and 17.3 GeV. We report results for the collision centrality dependence of $K/\pi$ fluctuations and results for charge-separated fluctuations. We observe that the $K/\pi$ fluctuations scale with the charged particle multiplicity density.

We demonstrate that for small values of momentum transfer $Q^2$ the in-medium change of the $G_E/G_M$ form factor ratio for a bound neutron is dominated by the change in the electric charge radius and predict within stated assumptions that the in-medium ratio will increase relative to the free result. This effect will act to increase the predicted cross section for the neutron recoil polarization transfer process ${}^4\mathrm{He}(\overrightarrow{e},e^{\prime }\overrightarrow{n}){}^3\mathrm{He}$. This is in contrast with medium modification effects on the proton $G_E/G_M$ form factor ratio, which act to decrease the predicted cross section for the ${}^4\mathrm{He}(\overrightarrow{e},e^{\prime }\overrightarrow{p}){}^3\mathrm{H}$ reaction. Experiments to measure the in-medium neutron form factors are currently feasible in the range $0.1<Q^2<1{\mathrm{GeV}}^2$.

The first practical method to evolve many-body nuclear forces to softened form using the similarity renormalization group in a harmonic oscillator basis is demonstrated. When applied to ${}^4\mathrm{He}$ calculations, the two- and three-body oscillator matrix elements yield rapid convergence of the ground-state energy with a small net contribution of the induced four-body force.

We have made a new determination of the half-life of the radioactive isotope ${}^{60}\mathrm{Fe}$ using high precision measurements of the number of ${}^{60}\mathrm{Fe}$ atoms and their activity in a sample containing over ${10}^{15}$ ${}^{60}\mathrm{Fe}$ atoms. Our new value for the half-life of ${}^{60}\mathrm{Fe}$ is $(2.62\pm 0.04)\times {10}^6\mathrm{yr}$, significantly above the previously reported value of $(1.49\pm 0.27)\times {10}^6\mathrm{yr}$. Our new measurement for the lifetime of ${}^{60}\mathrm{Fe}$ has significant implications for interpretations of galactic nucleosynthesis, for determinations of formation time scales of solids in the early Solar System, and for the interpretation of live ${}^{60}\mathrm{Fe}$ measurements from supernova-ejecta deposits on Earth.

We explore the phase diagram of Nambu—Jona-Lasinio-type models near the chiral critical point allowing for phases with spatially inhomogeneous chiral condensates. In the chiral limit it turns out that the region in the mean-field phase diagram where those phases are energetically preferred very generically reaches out to the chiral critical point. The preferred inhomogeneous ground state in this vicinity possibly resembles a lattice of domain wall solitons. This raises the question of their relevance for the phase diagram of QCD.

A linear universal decay formula is presented starting from the microscopic mechanism of the charged-particle emission. It relates the half-lives of monopole radioactive decays with the $Q$ values of the outgoing particles as well as the masses and charges of the nuclei involved in the decay. This relation is found to be a generalization of the Geiger-Nuttall law in $\alpha$ radioactivity and explains well all known cluster decays. Predictions on the most likely emissions of various clusters are presented.

The charge distribution of the heaviest fragment detected in the decay of quasiprojectiles produced in intermediate energy heavy-ion collisions has been observed to be bimodal. This feature is expected as a generic signal of phase transition in nonextensive systems. In this Letter, we present new analyses of experimental data from Au on Au collisions at 60, 80, and $100\mathrm{MeV}/\mathrm{\text{nucleon}}$ showing that bimodality is largely independent of the data selection procedure and of entrance channel effects. An estimate of the latent heat of the transition is extracted.

According to experimental data at GSI, the rates of the number of daughter ions, produced by the nuclear $K$ shell electron capture decays of the H-like heavy ions with one electron in the $K$ shell, such as ${}^{140}\mathrm{Pr}^{58+}$, ${}^{142}\mathrm{Pm}^{60+}$, and ${}^{122}\mathrm{I}^{52+}$, are modulated in time with periods $T_{\mathrm{EC}}$ of the order of a few seconds, obeying an $A$ scaling $T_{\mathrm{EC}}=A/20\mathrm{s}$, where $A$ is the mass number of the mother nuclei, and with amplitudes $a_d^{\mathrm{EC}}\sim 0.21$. We show that these data can be explained in terms of the interference of two massive neutrino mass eigenstates. The appearance of the interference term is due to overlap of massive neutrino mass eigenstate energies and of the wave functions of the daughter ions in two-body decay channels, caused by the energy and momentum uncertainties introduced by time differential detection of the daughter ions in GSI experiments.

The coupled-cluster wave function factorizes to a very good approximation into a product of an intrinsic wave function and a Gaussian for the center-of-mass coordinate. The width of the Gaussian is in general not identical to the oscillator length of the underlying single-particle basis. The quality of the separation can be verified by a simple procedure.

The momentum transfer $\Delta k$ required for a photon to scatter from a target and emerge as a ${\rho }^0$ decreases as the photon energy $k$ rises. For $k>3\times {10}^{14}\mathrm{eV}$, $\Delta k$ is small enough that the interaction cannot be localized to a single nucleus. At still higher energies, photons may coherently scatter elastically from bulk matter and emerge as a ${\rho }^0$, in a manner akin to kaon regeneration. Constructive interference from the different nuclei coherently raises the cross section and the interaction probability rises linearly with energy. At energies above ${10}^{23}\mathrm{eV}$, coherent conversion is the dominant process; photons interact predominantly as ${\rho }^0$. We compute the coherent scattering probabilities in slabs of lead, water, and rock, and discuss the implications of the increased hadronic interaction probabilities for photons on ultrahigh energy shower development.

Excited states in ${}^{152}\mathrm{Sm}$ have been investigated with the ${}^{152}\mathrm{Sm}(n,n^{\prime }\gamma )$ reaction. The lowest four negative-parity band structures have been characterized in detail with respect to their absolute decay properties. Specifically, a new $K^{\pi }=0^{-}$ band has been assigned with its $1^{-}$ band head at 1681 keV. This newly observed band has a remarkable similarity in its $E1$ transition rates for decay to the first excited $K^{\pi }=0^{+}$ band at 684 keV to the lowest $K^{\pi }=0^{-}$ band and its decay to the ground-state band. Based on these decay properties, as well as energy considerations, this new band is assigned as a $K^{\pi }=0^{-}$ octupole excitation based on the $K^{\pi }=0_2^{+}$ state. An emerging pattern of repeating excitations built on the $0_2^{+}$ level similar to those built on the ground state may indicate that ${}^{152}\mathrm{Sm}$ is a complex example of shape coexistence rather than a critical point nucleus.

The shear viscosity coefficient and the corresponding relaxation time for causal dissipative hydrodynamics are calculated based on the microscopic formula proposed in T. Koide and T. Kodama [Phys. Rev. E 78, 051107 (2008)]. Here, the exact formula is transformed into a more compact form and applied to evaluate these transport coefficients in the chiral perturbation theory and perturbative QCD. It is shown that in the leading order calculation, the causal shear viscosity coefficient $\eta$ reduces to that of the ordinary Green-Kubo-Nakano formula, and the relaxation time ${\tau }_{\pi }$ is related to $\eta$ and pressure $P$ by a simple relationship, ${\tau }_{\pi }=\eta /P$.

Isospin symmetry breaking has been investigated in mass $A=67$ mirror nuclei through the experimental determination of the $E1$ strengths of analog electromagnetic transitions. Lifetimes of excited states have been measured in ${}^{67}\mathrm{Se}$ and ${}^{67}\mathrm{As}$ with the centroid shift method. Through the comparison of the $B(E1)$ strengths of the mirror $9/2^{+}\to 7/2^{-}$ transitions, the isovector and the isoscalar components of the electromagnetic transition amplitude were extracted. The presence of a large isoscalar component provides evidence for coherent contributions to isospin mixing, probably involving the isovector giant monopole resonance.

We show that backward-forward elliptic anisotropy correlation provides an experimentally accessible observable which distinguishes between collective and noncollective contributions to the observed elliptic anisotropy $v_2$ in relativistic heavy ion collisions. The measurement of this observable will reveal the momentum scale at which collective expansion seizes and where the elliptic anisotropy is dominated by (semi)hard processes.

The $Q$ value of the ${}^{112}\mathrm{Sn}$ double-beta decay was determined by using a Penning trap mass spectrometer. The new atomic-mass difference between ${}^{112}\mathrm{Sn}$ and ${}^{112}\mathrm{Cd}$ of 1919.82(16) keV is 25 times more precise than the previous value of 1919(4) keV. This result removes the possibility of enhanced resonance capture of the neutrinoless double-EC decay to the excited $0^{+}$ state at 1871.00(19) keV in ${}^{112}\mathrm{Cd}$.

We consider several classes of symmetries of the Dirac Hamiltonian in $3+1$ dimensions, with axially deformed scalar and vector potentials. The symmetries include the known pseudospin and spin limits and additional symmetries which occur when the potentials depend on different variables. Supersymmetries are observed within each class and the corresponding charges are identified.

Collisions of actinide nuclei form, during very short times of few ${10}^{-21}\mathrm{s}$, the heaviest ensembles of interacting nucleons available on Earth. Such collisions have been proposed as an alternative way to produce heavy and superheavy elements. They are also used to produce superstrong electric fields by the huge number of interacting protons to test spontaneous positron-electron ($e^{+}{e}^{-}$) pair emission predicted by the quantum electrodynamics theory. The time-dependent Hartree-Fock theory is used to study collision dynamics of two ${}^{238}\mathrm{U}$ atomic nuclei. In particular, the role of nuclear deformation on collision time and on reaction mechanisms such as nucleon transfer is emphasized. The highest collision times ($\sim 4\times {10}^{-21}\mathrm{s}$ at 1200 MeV) should allow experimental signature of spontaneous $e^{+}{e}^{-}$ emission in case of bare uranium ions. Surprisingly, we also observe ternary fission due to purely dynamical effects.

We calculate the total energy deposited into the medium per unit length by fast partons traversing a quark-gluon plasma. The medium excitation due to collisions is taken to be given by the well-known expression for the collisional drag force. The radiative energy loss of the parton contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. We derive a differential equation which governs how the spectrum of radiated gluons is modified when this energy loss is taken into account. This modified spectrum is then used to calculate the additional energy deposition due to the interactions of radiated gluons with the medium. Numerical results are presented for the medium response for the case of two energetic back-to-back partons created in a hard interaction.

The electric-dipole response of ${}^{140}\mathrm{Ce}$ is investigated using the fully consistent relativistic quasiparticle random phase approximation. By analyzing the isospin structure of the $E1$ response, it is shown that the low-energy (pygmy) strength separates into two segments with different isospin character. The more pronounced pygmy structure at lower energy is composed of predominantly isoscalar states with surface-peaked transition densities. At somewhat higher energy the calculated $E1$ strength is primarily of isovector character, as expected for the low-energy tail of the giant dipole resonance. The results are in qualitative agreement with those obtained in recent ($\gamma$, ${\gamma }^{\prime }$) and ($\alpha$, ${\alpha }^{\prime }\gamma$) experiments, and provide a simple explanation for the splitting of low-energy $E1$ strength into two groups of states with different isospin structure and radial dependence of the corresponding transition densities.