The recently measured probabilities of the $\beta$-delayed fission for ${}^{178,180}$Tl are used to deduce the fission-barrier heights of the daughter isotopes ${}^{178,180}$Hg, undergoing low-energy fission. Four alternative $\beta$-decay strength functions and four variants of the statistical model of de-excitation of the daughter nucleus are used to determine the fission-barrier height for ${}^{180}$Hg. Depending on the choice of the model, the deduced fission-barrier heights appear to be between 10$\%$ and 40$\%$ smaller than theoretical estimates. This observation is verified also for fission-barrier heights extracted using the probability of $\beta$-delayed fission of ${}^{178}$Tl. The spread in extracted fission-barrier heights results mainly from uncertainties in the magnitude of the pairing gap at the saddle configuration.

In this paper, we have investigated the interactions of $K^{-}$ in a ${}^4\mathrm{He}$ target using a quantum mechanical approach. For this purpose, we have used time-dependent perturbation theory and Fermi's golden rule to calculate the capture rate of $K^{-}$ by the ${}^4\mathrm{He}$ atom and the rate of internal Auger effect in the $K\alpha e$ atom. The initial distribution of $n,\ell$ states in the $K{\alpha }^{+}$ ion is also calculated. Some detailed analytical and numerical quantum mechanical calculations are performed for several transitions. Our results for the $n,\ell$ distributions in $K{\alpha }_{}^{+}$ ions are necessary to begin a Monte Carlo simulation of the cascade processes in kaonic helium atoms.

Using coupled-cluster theory and interactions from chiral effective field theory, we compute overlap functions for transfer and scattering of low-energy protons on the target nucleus ${}^{40}$Ca. Effects of three-nucleon forces are included phenomenologically as in-medium two-nucleon interactions. Using known asymptotic forms for one-nucleon overlap functions we derive a simple and intuitive way of computing scattering observables such as elastic scattering phase shifts and cross sections. As a first application and proof of principle, we compute phase shifts and differential interaction cross sections at energies of $9.6$ and $12.44$ MeV and compare with experimental data. Our computed diffraction minima are in fair agreement with experimental results, while we tend to overestimate the cross sections at large scattering angles.

Fragments produced in binary splits of an excited projectile-like fragment (PLF${}^{*}$) formed in the reactions ${}^{124}$Xe $+$ ${}^{112,124}$Sn at an incident energy of 50 MeV/$A$ are examined. The dependence of the isotopic composition of light fragments ($4⩽Z_L⩽8$) on rotation angle allows one to explore changes in $N/Z$ on the time scale of the rotational period of the PLF${}^{*}$. Changes in the $N/Z$ of the fragments persist for times as long as 2–3 zs (600–900 fm/$c$). The two-component nature of the time dependence of $\langle N\rangle /Z$ for $Z_L=4$ and the $Z$ dependence are related to differences in the initial configurations and subsequent decay of the PLF${}^{*}$.

By using a covariant isobar model and the latest experimental data we have analyzed the role of the $P_{13}\left(1900\right)$ and $D_{13}\left(2080\right)$ resonances in the kaon photoproduction process $\gamma p\to K^{+}\Lambda$. Special attention has been paid to the region where the second peak in the cross section is located, i.e., at total c.m. energies around $1.9$ GeV. It is found that this peak originates mostly from the $P_{13}\left(1900\right)$ resonance contribution. Although the contribution of the $D_{13}\left(2080\right)$ resonance is not negligible, it is much smaller than that of the $P_{13}\left(1900\right)$ state. Our finding confirms that the $P_{13}\left(1900\right)$ resonance is also important in explaining the beam-recoil double polarization data $C_x$ and $C_z$, provided that the mass and the width of this resonance are 1871 and 131 MeV, respectively.

The$\beta$-decay properties of neutron-rich Cu isotopes produced in proton-induced fission of ${}^{238}$U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The data were collected using high-resolution online mass separation, reacceleration, and digital $\beta \text{−}\gamma$ spectroscopy methods. An improved decay scheme of $N=49$ ${}^{78}$Cu and the first observation of $N=50$ ${}^{79}$Cu $\beta$-delayed neutron decay followed by a gamma transition are reported. Spin and parity (5${}^{-}$) are deduced for ${}^{78gs}$Cu. The $\beta$-delayed neutron branching ratios ($P_{\beta n}$) for the ${}^{77}$Cu and ${}^{79}$Cu precursors are analyzed with the help of nuclear structure models.

Hydrodynamics is known to well describe matter created in high-energy heavy-ion collisions. Large depositions of energy by passing jets should create not only the sound waves, already discussed in the literature, but also shock waves of finite amplitude. This paper is an introduction to relativistic shocks, which go through elementary energy and momentum continuity arguments, to weak shocks treated in the Navier-Stokes approximation to out-of-equilibrium settings of anti de Sitter/conformal field theory. While we have not yet found numerical solutions to corresponding Einstein equations, we have found a variational approximation to the sum of their squares. Our general conclusion is that deviations from Lublinsky-Shuryak and Navier-Stokes hydrodynamical shock profiles are surprisingly small, even for strong shocks. We end with a list of open questions which the exact solution should be able to answer.

Reconstructed jets in heavy ion collisions are a crucial tool for understanding the quark-gluon plasma. The separation of jets from the underlying event is necessary particularly in central heavy ion reactions in order to quantify medium modifications of the parton shower and the response of the surrounding medium itself. There have been many methods proposed and implemented for studying the underlying event substructure in proton-proton and heavy ion collisions. In this paper, we detail a method for understanding underlying event contributions in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV utilizing the HIJING event generator. This method, extended from previous work by the ATLAS collaboration, provides a well-defined association of “truth jets” from the fragmentation of hard partons with “reconstructed jets” using the anti-$k_T$ algorithm. Results presented here are based on an analysis of 750M minimum bias HIJING events. We find that there is a substantial range of jet energies and radius parameters where jets are well separated from the background fluctuations (often termed “fake jets”) that make jet measurements at the BNL Relativistic Heavy Ion Collider a compelling physics program.

Neutrino emission rate from baryonic matter in neutron stars via weak neutral vector interaction is computed up to order $O\left(v_F^6\right)$, where $v_F$ is the Fermi velocity in units of speed of light. The vector current polarization tensors are evaluated with full vertices which include resummed series in the particle-hole channel. The neutrino emissivity is enhanced compared to the $O\left(v_F^4\right)$ order up to $10\%$ for values $v_F\le 0.4$ characteristic of baryons in compact stars.

We analyze the nuclear matter correlation properties in terms of the pair correlation function. To this aim we systematically compare the results for the variational method in the lowest-order constrained variational (LOCV) approximation and for the Bruekner-Hartree-Fock (BHF) scheme. A formal link between the Jastrow correlation factor of LOCV and the defect function (DF) of BHF is established and it is shown under which conditions and approximations the two approaches are equivalent. From the numerical comparison it turns out that the two correlation functions are quite close, which indicates in particular that the DF is approximately local and momentum independent. The equations of state (EOS) of nuclear matter in the two approaches are also compared. It is found that once the three-body forces (TBF) are introduced, the two EOS are fairly close, while the agreement between the correlation functions holds with or without TBF.

The problem of possible application of an ultracold-neutron (UCN) trap as a detector of dark-matter particles with long-range radius of forces has been considered. Transmission of small recoil energy in scattering is a characteristic of long-range forces. The main advantage of the ultracold-neutron technique lies in the possibility of detecting recoil energy as small as ${10}^{-7}$ eV. Here are presented constraints on the interaction potential parameters, $U\left(r\right)=a^{}{r}^{-1}{e}^{-r/\lambda }$, for dark-matter particles and neutrons, as well as on the density value of long-range dark matter on the Earth. The possible mechanism of accumulation of long-range dark matter on the Earth surface is considered and the factor of density increase on the Earth surface is evaluated. The results of the first experiment on search of astronomical day variation of ultracold-neutron storage time are under discussion.

In ${}^{30}$Mg, existing data for $B$($E$2) strengths connecting the ground and excited 0${}^{+}$ states to the first 2${}^{+}$ state have been used, together with earlier shell-model predictions of normal and intruder $E$2 strengths, to estimate the intruder-normal state mixing in the 0${}^{+}$ and 2${}^{+}$ states. Resulting mixing is small, as expected, and for the ground state my value of 0.11(7) has a larger uncertainty, but is in quantitative agreement with the estimate of 0.0319(76) obtained earlier from the measured $E$0 strength connecting the 0${}^{+}$ states.

We extend the standard Friedrichs model with an extra term that includes time-dependent interactions. The time dependence of the poles of the reduced resolvent of the model is explicitly calculated. It is found that these poles behave as analytical functions of the added time-dependent interaction. The present results are compared with the ones reported by Kälbermann, concerning the assisted tunnelling of $\alpha$ particles.

We derive the distribution of energy and momentum transmitted from a primary fast parton and its medium-induced bremsstrahlung gluons to a thermalized quark-gluon plasma. Our calculation takes into account the important and thus far neglected effects of quantum interference between the resulting color currents. We use our result to obtain the rate at which energy is absorbed by the medium as a function of time to leading logarithmic accuracy. We find that the quantum color interference persists for time scales relevant to heavy ion phenomenology. We further couple the newly derived source of energy and momentum deposition to linearized hydrodynamics to obtain the bulk medium response to realistic parton propagation and splitting in the quark-gluon plasma. We find that because of the characteristic large angle in-medium gluon emission and the multiple sources of energy deposition in a parton shower, formation of well defined Mach cones by energetic jets in heavy ion reactions is not likely.

We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via $e^{+}{e}^{-}$ decays, from $\sqrt{s}=200$ GeV $p+p$ collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10$\%$ over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted $\omega \to e^{+}{e}^{-}$ invariant yields are consistent with previous measurements. The mid-rapidity yields ($dN/dy$) of $\phi$ and $J/\psi$ are extracted through their di-electron decay channels and are consistent with the previous measurements of $\phi \to K^{+}{K}^{-}$ and $J/\psi \to e^{+}{e}^{-}$. Our results suggest a new upper limit of the branching ratio of the $\eta \to e^{+}{e}^{-}$ of $1.7\times {10}^{-5}$ at the 90$\%$ confidence level.

We redefine the surface tension coefficient for a nuclear Fermi-liquid drop with a finite diffuse layer. Following the Gibbs-Tolman concept, we introduce the equimolar radius $R_e$ of the droplet surface at which the surface tension is applied and the radius of tension surface $R_s$ which provides the minimum of the surface tension coefficient $\sigma$. This procedure allows us to derive both the surface tension and the corresponding curvature correction (Tolman length) correctly for the curved and diffuse interface. We point out that the curvature correction depends significantly on the finite diffuse interface. We show that Tolman's length $\xi$ is negative for a nuclear Fermi-liquid drop. The value of the Tolman length is only slightly sensitive to the Skyrme force parametrization and equals $\xi =-0.36$ fm.

Background: Recent experiments on $\beta$-delayed fission in the mercury-lead region and the discovery of asymmetric fission in ${}^{180}$Hg [A. N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010)] have stimulated theoretical interest in the mechanism of fission in heavy nuclei.

Purpose: We study fission modes and fusion valleys in ${}^{180}$Hg and ${}^{198}$Hg to reveal the role of shell effects in the prescission region and explain the experimentally observed fragment mass asymmetry and its variation with $A$.

Methods: We use the self-consistent nuclear density functional theory employing Skyrme and Gogny energy density functionals.

Results: The potential energy surfaces in multidimensional space of collective coordinates, including elongation, triaxiality, reflection-asymmetry, and necking, are calculated for ${}^{180}$Hg and ${}^{198}$Hg. The asymmetric fission valleys—well separated from fusion valleys associated with nearly spherical fragments—are found in both cases. The density distributions at scission configurations are studied and related to the experimentally observed mass splits.

Conclusions: The energy density functionals SkM${}^{*}$ and D1S give a very consistent description of the fission process in ${}^{180}$Hg and ${}^{198}$Hg. We predict a transition from asymmetric fission in ${}^{180}$Hg toward a more symmetric distribution of fission fragments in ${}^{198}$Hg. For ${}^{180}$Hg, both models yield ${}^{100}$Ru/${}^{80}$Kr as the most probable split. For ${}^{198}$Hg, the most likely split is ${}^{108}$Ru/${}^{90}$Kr in HFB-D1S and ${}^{110}$Ru/${}^{88}$Kr in HFB-SkM${}^{*}$.

We explore the relation between proton and nucleon number fluctuations in the final state in relativistic heavy ion collisions. It is shown that the correlations between the isospins of nucleons in the final state are almost negligible over a wide range of collision energy. This leads to a factorization of the distribution function of the proton, the neutron, and their antiparticles in the final state with binomial distribution functions. Using the factorization, we derive formulas to determine nucleon number cumulants, which are not direct experimental observables, from proton number fluctuations, which are experimentally observable in event-by-event analyses. With a simple treatment for strange baryons, the nucleon number cumulants are further promoted to the baryon number ones. Experimental determination of the baryon number cumulants makes it possible to compare various theoretical studies directly with experiments. The effects of nonzero isospin density on this formula are addressed quantitatively. It is shown that the effects are well suppressed over a wide energy range.

High-spin states in doubly odd ${}^{88}$Y have been investigated using the ${}^{82}$Se(${}^{11}$B, 5$n$) reaction at beam energies of 48 and 52 MeV. On the basis of the $\gamma$-$\gamma$ coincidence relationships, the level scheme of ${}^{88}$Y has been extended up to an excitation energy of 9.5 MeV at spin 21$\hslash$. About 20 new levels and 30 new transitions have been added into the level scheme, and spin-parity assignments have been made to most of the newly proposed levels. In order to better understand the nuclear structure of ${}^{88}$Y, semiempirical shell-model calculations were carried out considering a valence space formed by the proton 1$p_{1/2}$, 1$p_{3/2}$, 0$f_{5/2}$, 0$g_{9/2}$ and neutron 0$g_{9/2}$ orbitals.