We have studied the beta spectrum of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ using a unique ${}_{}{}^{14}{}_{}{}^{}\mathrm{doped}$ germanium detector. In 1991 an initial report was made of a distortion in the spectrum that could be explained by the emission of a 17-keV neutrino in approximately 1% of the decays. Further tests have shown that the observed distortion was most likely caused by systematic effects related to the detector’s active guard ring. A new measurement with a smaller data sample shows no sign of this distortion. In addition, we find the Q value of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ decay to be 155.95±0.07(stat.)±0.21(sys.) keV, in disagreement with a previous precision measurement.

There is a theorem that states that there can be no null test of time-reversal invariance (T symmetry) in exclusive reactions; that is, T symmetry does not require any single observable to vanish. This theorem is extended to inclusive reactions. Also, a general argument, that an experimental observable vanishes from T symmetry if a corresponding operator changes sign under time reversal, is shown to be invalid.

A generalized formula of nuclear anapole moment is derived using the current relativistic nuclear approach. The Dirac spin magnetization and the anomalous spin magnetization contributions to anapole moment are shown to be proportional to the second moment of respective magnetizations. The valence nucleon effective ${\mathit{g}}_{\mathit{l}}$(${\mathit{g}}_{\mathit{a}}$) factors in a nucleus are obtained from the different phenomenological generalizations of relativistic nuclear magnetic moment. The unitary transformation approach is used to derive the parity nonconserving (PNC) perturbed wave functions. In the case of ${\mathit{g}}_{\mathit{l}}$ parametrization, the anomalous spin magnetization and pion contributions to anapole moment are nearly two and three times the Dirac magnetization contribution respectively; while for ${\mathit{g}}_{\mathit{a}}$ parametrization, all the three contributions are of the same order of magnitude. Using these calculated values of anapole moment and available atomic structure data from published literature, the ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$ PNC hyperfine amplitudes are calculated. The results are closer to the experimental data, particularly when the measured value of Im ${\mathit{E}}_1^{\mathit{p}\mathit{v}}$/β is used. The optical rotation angles induced by nuclear spin dependent PNC interaction are also calculated.

We examine isospin breaking in the nucleon wave functions due to the u-d quark mass difference and the Coulomb interaction among the quarks, and their consequences on the nucleon electroweak form factors in a nonrelativistic constituent quark model. The mechanically induced isospin breaking in the nucleon wave functions and electroweak form factors are exactly evaluated in this model. We calculate the electromagnetically induced isospin admixtures by using first-order perturbation theory, including the lowest-lying resonance with nucleon quantum numbers but isospin 3/2. We find a small (≤ 1%), but finite correction to the anomalous magnetic moments of the nucleon stemming almost entirely from the quark mass difference, while the static nucleon axial coupling remains uncorrected. Corrections of the same order of magnitude appear in charge, magnetic, and axial radii of the nucleon. The correction to the charge radius in this model is primarily isoscalar, and may be of some significance for the extraction of the strangeness radius from, e.g., elastic forward angle parity violating electron-proton asymmetries, or elastic ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(e,e′) experiments.

We study a Centauro-type phenomenon in high-energy heavy-ion collisions by assuming that pions are produced semiclassically both directly and in pairs through the isovector channel. The leading-particle effect and the factorization property of the scattering amplitude in the impact-parameter space are used to define the classical pion field. We show that the Centauro-type effect is strongly suppressed if a large number of pions are produced in isovector pairs. Our conclusion is supported through the calculation of two pion correlation parameters, ${\mathit{f}}_2^{0\mathrm{-}}$ and ${\mathit{f}}_2^{00}$, as well as ${\mathit{f}}_{2,}$${\mathit{n}}_{\mathrm{-}}^0$ and the average number of neutral pions (〈${\mathit{n}}_0$${\mathrm{〉}}_{\mathit{n}\mathrm{-}}$) a a function of negative pions (${\mathit{n}}_{\mathrm{-}}$) produced.

Detailed shell-model calculations have been performed to study the structure of excited states in neutron deficient T=1, T=3/2, and T=2 nuclei in the mass range A=23–43. Excitation energies, single-particle spectroscopic factors, as well as γ-transition strengths were computed. On the basis of these results new reaction rates were calculated for proton capture on the T=1/2 nucleus ${}_{}{}^{35}{}_{}{}^{}\mathrm{Ar}$, on the odd-odd T=1 nuclei ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{Cl}$, on the even-even T=1 nuclei ${}_{}{}^{26}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{34}{}_{}{}^{}\mathrm{Ar}$, and ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ti}$ and the T=3/2 nuclei ${}_{}{}^{23}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{P}$, ${}_{}{}^{31}{}_{}{}^{}\mathrm{Cl}$, and ${}_{}{}^{35}{}_{}{}^{}\mathrm{K}$. The new reaction rates are compared with the results of statistical model calculations as well as with previous estimates. The consequences of these new rates for the reaction flow and the rp process nucleosynthesis at different stellar temperature and density conditions will be discussed.

We quantitatively determine the effect and the uncertainty on solar neutrino production arising from the screening process. We present predictions for the solar neutrino fluxes and signals obtained with different screening models available in the literature and by using our stellar evolution code. We explain these numerical results in terms of simple laws relating the screening factors with the neutrino fluxes. Furthermore we explore a wider range of models for screening, obtained from the Mitler model by introducing and varying two phenomenological parameters, taking into account effects not included in the Mitler prescription. Screening implies, with respect to a no-screening case, a central temperature reduction of 0.5%, a 2% (8%) increase of ${}_{}{}^7{}_{}{}^{}\mathrm{-}$ ${(}^8$Be-) neutrino flux and a 2% (12%) increase of the gallium (chlorine) signal. We also find that uncertianties due to the screening effect are at the level of 1% for the predicted ${}_{}{}^7{}_{}{}^{}\mathrm{neutrino}$ flux and gallium signal, not exceeding 3% for the ${}_{}{}^8{}_{}{}^{}\mathrm{neutrino}$ flux and the chlorine signal.

The neutron capture cross section of ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ba}$, which was determined recently with the Karlsruhe 4π barium fluoride detector, has been reanalyzed in the low energy region using a shape analysis program. Parameters of 45 resonances were extracted which allow a more reliable determination of the averaged cross section below 20 keV. The results confirm our first analysis and the reported stellar cross sections. Accordingly, the results of the s-process studies based on these data remain unchanged.

We have measured a complete isotope distribution of projectile-like nuclear-charge pickup products, formed by bombarding a ${}_{}{}^{17}{}_{}{}^{}\mathrm{Al}$ target with 790A MeV ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ ions. The shape of the cross-section distribution indicates a dominant influence of evaporation processes during the formation of the final cesium fragments observed, thus masking to a large extent the primary processes involved in the charge exchange. We can show, however, that an intranuclear-cascade-plus-evaporation calculation can reproduce the observed yields, and that the effect of Δ-formation during the first stage of the reaction is visible even in the inclusive cross sections. The same model can explain the strong increase in total charge-pickup cross sections with increasing projectile mass noted previously by other authors. It is therefore not necessary to invoke coherent processes to explain this increase as has been suggested previously.

The cross-section and analyzing power data for the inelastic scattering of polarized protons to the first $2^{+}$ and $4^{+}$ states of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ between 200 MeV and 800 MeV have been analyzed through relativistic Dirac coupled channels calculations. Although considerably better agreement with the data has been obtained compared to previous nonrelativistic Schrödinger calculations, no better determination of the deformation parameters could be obtained. Deformations (both quadrupole and hexadecapole) are almost unchanged over this energy interval and agree with previous results.

The dipole magnetization of a heavy spherical nucleus is studied with macroscopic standpoint. The semiclassical model under consideration focuses on the giant M1 resonance as a result of long wavelength oscillations of the collective magnetization current induced in the surface massive layer of finite depth. The macroscopic picture of the excited collective flow is found to be like that for the torsional elastic vibrations of the peripheral layer against the central spherical region inert with respect to external perturbation. The emphasis is placed on calculation of scaling behavior of integral characteristic parameters of magnetic dipole resonance.

Even though the local density approximation leads to an overestimation of the absolute value of the nuclear level density parameter, we show that this simplifying approximation accurately describes the temperature dependence of Thomas-Fermi calculations of the nuclear level density parameter performed by Shlomo and Natowitz. A simple expression that adequately reproduces the Thomas-Fermi calculations of Shlomo and Natowitz is obtained. Two different definitions of the temperature dependent level density parameter can be adopted. Care must be taken to ensure that level density parameters extracted from experimental data are compared to theoretical calculations made using the appropriate definition.

The electric quadrupole excitation of unstable nuclei with the neutron skin is studied in terms of a Hartree-Fock RPA calculation, taking ${}_{}{}^{28}{}_{}{}^{}\mathrm{O}$ as an example. It is found that there are giant excitation peaks, referred to as giant neutron modes, below the isoscalar giant resonance and these peaks consist of neutron excitations only. Their transient densities are shown to be extended radially in comparison to the isoscalar giant resonance. A strong correlation between B(E2) sum of the giant neutron modes and the numbers of neutrons in the neutron skin is found.

The problem of stable bound states of a system composed of N neutrons and Z negative pions is discussed. Calculations performed within a theoretical model indicate that one needs at least 5 pions and around 8 neutrons in order to get binding. The stability of the system against either pion or neutron emission is investigated, as well as the stability against its possible weak decay modes. Results for several values of N and Z are presented.

We study the nonresonant part of the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$(p,γ${)}^8$B reaction using a three-cluster resonating group model that is variationally converged and virtually complete in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$${+}^3$He+p model space. The importance of using adequate nucleon-nucleon interaction is demonstrated. We find that the low-energy astrophysical S factor is linearly correlated with the quadrupole moment of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$. A range of parameters is found where the most important ${}_{}{}^8{}_{}{}^{}\mathrm{B}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ properties are reproduced simultaneously; the corresponding S factor at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=20 keV is 24.6–26.1 eV b.

We examine η′ photoproduction as a novel tool to study baryon resonances around 2 GeV, of particular interest to the quark shell model, which predicts a number of them. We find important roles of the form factors at the strong vertices, and show that the ${\mathit{N}}^{\mathrm{*}}$(2080) can be probed efficiently by this reaction.

In heavy nuclei there is a parametrical suppression ∼${\mathit{A}}^{\mathrm{-}1/3}$ of T-odd,P-odd matrix elements as compared to T-even,P-odd ones.

In response to a recent paper by Becchetti et al. it is shown that there are several experimental and theoretical evidences about the ${}_{}{}^4{}_{}{}^{}\mathrm{H}$ clustering in lithium nuclei.

I reply to the preceding Comment.

We comment about a recent partial-wave analysis of nucleon-antinucleon scattering data by Timmermans, Rijken, and de Swart [Phys. Rev. C 50, 48 (1994)]. From simple counting arguments, we argue that it is presently impossible to determine the phase parameters.