The influence of the presence of hyperons in dense hadronic matter on the quantum nucleation of quark matter is examined at low temperatures relevant to neutron star cores. We calculate the equation of state and the composition of matter before and after deconfinement by using a relativistic mean-field theory and an MIT bag model, respectively; the case in which hyperons are present in the hadronic system is considered, together with the case of the system without hyperons. We find that strangeness contained in hyperons acts to reduce a density jump at deconfinement as well as a lepton fraction in the hadronic phase. As a result of these reductions, a quark matter droplet being in a virtual or real state has its effective mass lightened and its electric charge diminished into nearly zero. The Coulomb screening of leptons on the droplet charge, which has significance to the droplet growth after nucleation in the absence of hyperons, is thus shown to be of little consequence. If the effective droplet mass is small enough to become comparable to the height of the potential barrier, the effect of relativity brings about an exponential increase in the rate of droplet formation via quantum tunneling, whereas the role played by energy dissipation in decelerating the droplet formation, dominant for matter without hyperons, becomes of less importance. Independently of the presence of hyperons, the dynamical compressibility of the hadronic phase is unlikely to affect the quantum nucleation of quark matter at temperatures found in neutron star interiors. For matter with and without hyperons, we estimate the overpressure needed to form the first droplet in the star during the compression due to stellar spin-down or mass accretion from a companion star. The temperature at which a crossover from the quantum nucleation to the Arrhenius-type thermal nucleation takes place is shown to be large compared with the temperature of matter in the core. We also determine the range of the bag-model parameters such as the bag constant, the QCD fine structure constant, and the strange quark mass where quark matter is expected to occur in the star.

We have calculated the incident photon power density $P_2$ for which the two-step induced emission rate from an isomeric nucleus becomes equal to the natural isomeric decay rate. We have analyzed two-step transitions for isomeric nuclei with a half-life greater than 10 min, for which there is an intermediate state of known energy, spin and half-life, for which the intermediate state is connected by a known $\gamma$-ray transition to the isomeric state and to at least another intermediate state, and for which the relative intensities of the transitions to lower states are known. For the isomeric nucleus ${}^{166m}\mathrm{Ho},$ which has a $1200\hspace{0.5em}y$ isomeric state at 5.98 keV, we have found a value of $P_2=6.3\mathrm{}\times {10}^7\hspace{0.5em}{\mathrm{W}\mathrm{\hspace{0.5em}}\mathrm{cm}}^{-2},$ the intermediate state being the 263.8 keV level. We have found power densities $P_2$ of the order of ${10}^{10}\hspace{0.5em}{\mathrm{W}\mathrm{\hspace{0.5em}}\mathrm{cm}}^{-2}$ for several other isomeric nuclei.

The lifetime of the 2750 keV level in ${}^{37}\mathrm{K}$ was measured using the Doppler shift attenuation method. The result, together with the previously determined ratio of the partial width ratio ${\Gamma }_{\gamma }/{\Gamma }_p,$ allows verification of an absolute measurement of the corresponding resonance strength in the ${}^{36}\mathrm{Ar}(p,\gamma )$ reaction channel. This confirms the strong reaction rate for ${}^{36}\mathrm{Ar}(p,\gamma {)}^{37}\mathrm{K},$ which will cause rapid depletion of ${}^{36}\mathrm{Ar}$ at explosive hydrogen burning conditions.

The (0ν, EC, EC) double β decay of ${}^{54}\mathrm{Fe}$ was investigated. An upper limit on the half-life $T>\mathrm{}4.4\mathrm{}\times {10}^{20}\mathrm{yr}$ (at 68% confidence level) was derived.

The previously measured decay of the ground state of ${}^{12}\mathrm{O}$ was reanalyzed based on new experimental and theoretical results for the ground state of ${}^{11}\mathrm{N}.$ In the previous analysis no evidence for diproton emission was found and the measured large decay width was inconsistent with sequential proton decay via the intermediate system of ${}^{11}\mathrm{N}.$ The recent results on ${}^{11}\mathrm{N}$ show evidence that the ground state of ${}^{11}\mathrm{N}$ is at substantially lower energy allowing for a consistent explanation of the two-proton decay of ${}^{12}\mathrm{O}$ in terms of sequential proton emission.

The original data for precise determinations of the ${}^{10}\mathrm{B}{\mathrm{}(p,n)\mathrm{}}^{10}\mathrm{C}$ and ${}^{14}\mathrm{N}{\mathrm{}(p,n)\mathrm{}}^{14}\mathrm{O}$ threshold energies have been reanalyzed to fully incorporate the effects of proton beam energy spread, nonuniform proton energy loss in the targets, and atomic ionization. The results have been used to give Q values for the $0^{+}$ to $0^{+},$ $T=1\mathrm{}$ superallowed positron decays of ${}^{10}\mathrm{C}$ and ${}^{14}\mathrm{O}.$

This paper is an addendum to our previous communications on the measurement of the ${}^1\mathrm{H}(\gamma ,{\pi }^0)$ reaction in the threshold region. We present the coefficients of angular distribution, not described previously, and comment in particular on the asymmetry coefficient B.

Excitation functions of the ${}^{89}\mathrm{Y}{(n,n}^{\prime }\gamma {)}^{89}{\mathrm{Y}}^m$ and ${}^{89}\mathrm{Y}(n,\alpha \gamma {)}^{86}{\mathrm{Rb}}^m$ reactions were measured over the neutron energy range of 6.2 to 14.7 MeV, using the activation technique in combination with off-line γ-ray spectrometry. Neutrons in the energy range of 6 to 12.4 MeV were produced using the ${}^2\mathrm{H}{\mathrm{}(d,n)\mathrm{}}^3\mathrm{He}$ reaction on a ${\mathrm{D}}_2$ gas target and in the region of 14 MeV at a $D-T$ generator. The half-life of ${}^{89}{\mathrm{Y}}^m$ was redetermined and found to be $15.28\pm 0.17\mathrm{s},$ i.e., slightly shorter than the literature value of 16.09 s. Statistical model calculations taking into account precompound effects were performed for the strong ${}^{89}\mathrm{Y}{(n,n}^{\prime }\gamma {)}^{89}{\mathrm{Y}}^m$ channel as well as for the weak ${}^{89}\mathrm{Y}(n,\alpha \gamma {)}^{86}{\mathrm{Rb}}^m$ process. The experimental data for both the reactions are well described by the calculation over the whole investigated energy range. For the ${}^{89}\mathrm{Y}(n,\alpha \gamma {)}^{86}{\mathrm{Rb}}^{m,g}$ process, the isomeric cross section ratio $[{\sigma }_m/({\sigma }_m+{\sigma }_g\left)\right]$ was deduced. A comparison with the results of nuclear model calculations showed good agreement.

The density functional approach to a nuclear system with pi and rho coupling is framed. We also extend the Hohenberg-Kohn theorem and the self-consistent equations to the arbitrary gauge fields. Particularly, the binding energy of infinite nuclear matter within the nonlinear sigma model is calculated.

The shape of proton rapidity distributions is analyzed in terms of their Gaussian components, and the average rapidity loss is determined in order to estimate the amount of stopping in $\mathrm{C}+\mathrm{C},$ $d+\mathrm{C},$ $\mathrm{C}+\mathrm{Ta},$ and $d+\mathrm{Ta}$ collisions at $4.2A\mathrm{GeV}/c.\mathrm{}$ Three Gaussians correspond to the nuclear transparency and describe well all peripheral and also C+C central collisions. A two-component shape is obtained in case of $d+\mathrm{C}$ and $\mathrm{C}+\mathrm{Ta}$ central collisions. Finally one Gaussian, found in $d+\mathrm{Ta}$ central collisions, corresponds to the full stopping. The calculated values of the average rapidity loss support the qualitative relationship between the number of Gaussian components and the corresponding stopping power. It is observed in central collisions that the average rapidity loss increases with the ratio of the number of target and the number of projectile participants.

The redefined $D$ pair composed of seniority particle operators is introduced in the collective states of nuclei. Its structure amplitude is determined in a self-consistent manner.

We study the space correlations induced by the pairing interaction in a superconductive nucleus. We find that it is possible to have pairs that present short range space correlations when they are described in the full Hilbert space, while the use of a reduced Hilbert space introduces complicated structures in the space correlations. The same types of phenomena are present when a δ function is described in the full or in a reduced Hilbert space.

The form factor $g_{\rho \pi }^{\mathrm{}\left(S\right)\mathrm{}}{(Q}^2)$ of the strange vector current transition matrix element $〈\rho |\overline{s}{\gamma }_{\mu }s|\pi 〉$ is calculated within the chiral quark model. A strange vector current of the constituent U and D quarks is induced by kaon radiative corrections and this mechanism yields the nonvanishing values of $g_{\rho \pi }^{\mathrm{}\left(S\right)\mathrm{}}\mathrm{}\left(0\right).$ The numerical result at the photon point is consistent with the one given by the $\phi$-meson dominance model, but the falloff in the $Q^2$ dependence is faster than the monopole form factor. Mesonic radiative corrections are also examined for the electromagnetic $\rho$-to-$\pi$ and $K^{*}$-to-$K$ transition amplitudes.

Δ-isobar excitation in the nuclear medium yields an effective three-nucleon force. A coupled-channel formulation of nucleon-deuteron scattering with Δ-isobar excitation developed previously is used. The three-particle scattering equations are solved by a separable expansion of the two-baryon transition matrix below the inelastic threshold of pion production. The effect of Δ-isobar excitation on the spin-averaged differential cross section is studied. The discrepancy between theory and experiment in the diffraction minimum is reduced.

A correlated ground state of ${}^{16}\mathrm{O}$ and an $E2\mathrm{}$ giant resonance built on it are calculated using an extended version of the time-dependent Hartree-Fock theory called the time-dependent density-matrix (TDDM) theory. The Skyrme III force is used as an effective interaction for the calculation of both a mean field and two-body correlations. It is found that a TDDM calculation with the Skyrme force gives reasonable ground-state correlations and a large spreading width of the $E2\mathrm{}$ giant resonance.

The x rays of the pionic deuterium 2p-1s transition were measured with a high resolution crystal spectrometer including a cyclotron trap (a magnetic device to increase the pion stopping density) and a CCD (charge-coupled device) detector system. The 1s strong interaction shift ${\epsilon }_{1s}$ and total width ${\Gamma }_{1s}$ were determined from the position and line shape of the x-ray peak. The (complex) pionic deuterium s-wave scattering length $a_{{\pi }^{-}d}$ was deduced. Its real part was related to the pion-nucleon scattering lengths, and the isoscalar coupling constant for ${\pi }^{-}$ absorption was deduced from the imaginary part.

The excitation function for the $4n$ evaporation residue from the ${}^{12}{\mathrm{C}+}^{236}\mathrm{U}$ reaction has been measured for beam energies between 62 and 73 MeV. The shape and magnitude of the residue excitation function is not consistent with appreciable quasifission competition.

Subpicosecond lifetimes of states near the bandhead of an $M1\mathrm{}$ band in ${}^{198}\mathrm{Pb}$ have been measured with the recoil-distance Doppler-shift technique using the Gammasphere array and the Cologne plunger. The deduced $B\left(M1\mathrm{}\right)\mathrm{}$ values are in agreement with the predictions of the tilted axis cranking (TAC) model. Their spin dependence continues the trend set by recently published $B\left(M1\mathrm{}\right)\mathrm{}$ values for the high spin states in this band. The emerging picture gives strong support to the concept of “magnetic rotation,” an alternative mode for the generation of rotational spectra in nuclei.

Noncoplanarity in proton-proton bremsstrahlung is investigated. Significant effects are observed for certain photon polar angles, ${\psi }_{\gamma }.$ Such noncoplanarity effects, not of dynamical origin, are possibly responsible for past disagreements between theory and experiment. The Harvard noncoplanar coordinate system, which avoids kinematic singularities in the cross section, is used in our calculations and is recommended for use in the analysis of experimental data. Alternative methods of presenting cross sections are discussed.

It is shown that there is a double counting in the standard model of $n\mathrm{n̄}$ mixing in the medium, resulting in full cancellation of leading terms. The direct calculation of $n\mathrm{n̄}$ transition followed by annihilation is performed. The lower limit for the free-space $n\mathrm{n̄}$ oscillation time is ${\tau }_{n\mathrm{n̄}}\sim T_{n\mathrm{n̄}}>{10}^{16}\hspace{0.5em}\mathrm{yr},$ where $T_{n\mathrm{n̄}}$ is the lifetime of neutron bound in a nucleus. This limit exceeds the previous one by 16 orders of magnitude.