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The finite-size correction to $\ensuremath{\beta}$ decay plays an important role in determining the expected antineutrino spectra from reactors at a level that is important for the reactor-neutrino anomaly. Here we express the leading-order finite-size correction to allowed $\ensuremath{\beta}$ decay in terms of Zemach moments. We calculate the Zemach moments within a Hartree-Fock model using a Skyrme-like energy density functional. We find that the Zemach moments are increased relative to predictions based on the simple assumption of identical uniform nuclear charge and weak transition densities. However, for allowed ground-state to ground-state transitions in medium and heavy nuclei, the detailed nuclear-structure calculations do not change the finite-size corrections significantly from the simple model predictions, and are only 10\char21{}15% larger than the latter even though the densities differ significantly.

We analyze within a nuclear database framework the shoulder observed in the antineutrino spectra in current reactor experiments. We find that the ENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an analogous shoulder in the aggregate fission beta spectra. In contrast, the JEFF-3.1.1 database does not predict a shoulder for two out of three of the modern reactor neutrino experiments, and the shoulder that is predicted by JEFF-3.1.1 arises from $^{238}$U. We consider several possible origins of the shoulder, and find possible explanations. For example, there could be a problem with the measured aggregate beta spectra, or the harder neutron spectrum at a light-water power reactor could affect the distribution of beta-decaying isotopes. In addition to the fissile actinides, we find that $^{238}$U could also play a significant role in distorting the total antineutrino spectrum. Distinguishing these and quantifying whether there is an anomaly associated with measured reactor neutrino signals will require new short-baseline experiments, both at thermal reactors and at reactors with a sizable epithermal neutron component., Extension of previous version of the same manuscript, including an analysis of the Double Chooz neutrino experiment

We determine the Zemach moments of hydrogen and deuterium for the first time using only the world data on elastic electron-proton and electron-deuteron scattering. Such moments are required for the calculation of the nuclear corrections to the hyperfine structure of these hydrogenic atoms. We compare the resulting HFS predictions to the available high-precision data and provide an estimate of the size of the nuclear polarization corrections necessary to produce agreement between experimental HFS and theoretical calculations., 9 pages, latex - submitted to Physics Letters B

During the final session of the conference participants discussed important questions and issues from the current study of the nuclear few body problem. The discussion was preceded by five very short ''mini-summaries'' (limited to about 5 minutes each) presented by each member of the panel. These ''mini-summaries'' are presented in Sec. 1 below, and the questions and discussion is summarized in Sec. 2. The ''mini-summaries'' are presented in Sec. 1 in the order they were given to the conference.

The chiral two-pion exchange component of the long-range pp interaction is studied in an energy-dependent partial-wave analysis. We demonstrate its presence and importance, and determine the chiral parameters c_i (i=1,3,4). The values agree well with those obtained from pion-nucleon amplitudes., 13 pages, no figures

After a brief review of the role three-nucleon forces play in the few-nucleon systems, the chiral-perturbation-theory approach to these forces is discussed. Construction of the (nominal) leading- and subleading-order Born terms and pion-rescattering graphs contributing to two-pion-exchange three-nucleon forces is reviewed, and comparisons are made of the types of such forces that are used today. It is demonstrated that the short-range $c$-term of the Tucson-Melbourne force is unnatural in terms of power counting and should be dropped. The class of two-pion-exchange three-nucleon forces then becomes rather uniform., 14 pages, latex, 2 postscript figs. -- submitted to Phys. Rev. C -- epsfig.sty required

The electric polarizability and logarithmic mean-excitation energy are calculated for the deuteron using techniques introduced in atomic physics. These results are then used to improve limits on the atomic-deuterium frequency shift due to nuclear polarization in the unretarded dipole limit, as well as confirming previous results., Comment: 7 pages, latex -- To appear in Phys. Rev. C

We examine uncertainties in the analysis of the reactor neutrino anomaly, wherein it is suggested that only about 94% of the emitted antineutrino flux was detected in short baseline experiments. We find that the form of the corrections that lead to the anomaly are very uncertain for the 30% of the flux that arises from forbidden decays. This uncertainty was estimated in four ways, is as large as the size of the anomaly, and is unlikely to be reduced without accurate direct measurements of the antineutrino flux. Given the present lack of detailed knowledge of the structure of the forbidden transitions, it is not possible to convert the measured aggregate fission beta spectra to antineutrino spectra to the accuracy needed to infer an anomaly. Neutrino physics conclusions based on the original anomaly need to be revisited, as do oscillation analyses that assumed that the antineutrino flux is known to better than approximately 4%., Comment: 5 pages, 3 figs., 1 table

We use power-counting arguments as an organizing principle to apply chiral perturbation theory, including an explicit {Delta}, to the {ital pp}{r_arrow}{ital pp}{pi}{sup 0} reaction near threshold. There are two lowest-order leading mechanisms expected to contribute to the amplitude with similar magnitudes: an impulse term, and a {Delta}-excitation mechanism. We examine formally subleading but potentially large mechanisms, including pion-rescattering and short-ranged contributions. We show that the pion-rescattering contribution is enhanced by off-shell effects and has a sign opposite to that of a recent estimate based on a PCAC pion interpolating field. Our result is that the impulse term interferes destructively with the pion-rescattering and {Delta}-excitation terms. In addition, we have modeled the short-ranged interaction using {sigma} and {omega} exchange mechanisms. A recoil correction to the impulse approximation is small. The total amplitude obtained including all of these processes is found to yield cross sections substantially smaller than the measured ones. {copyright} {ital 1996 The American Physical Society.}

Relativistic Hamiltonians are defined as the sum of relativistic one-body kinetic energies, two- and many-body interactions and their boost corrections. We review the calculation of the boost correction of the two-body interaction from commutation relations of the Poincar\'e group and show that its important terms can be easily understood from classical relativistic mechanics. The boost corrections for scalar- and vector-meson-exchange interactions, obtained from relativistic field theory, are shown to be in agreement with the results of the classical calculation. These boost corrections are also shown to be necessary to reproduce the known results of relativistic mean-field theories. We conclude with comments on the relativistic boost operator for the wave function of a nucleus. Some of the results presented in this article are known. We hope that a better understanding of relativistic Hamiltonians and their relation to relativistic field theory is obtained by putting them together with the new relations.

Data on the number of Open Reading Frames (ORFs) coded by genomes from the 3 domains of Life show some notable general features including essential differences between the Prokaryotes and Eukaryotes, with the number of ORFs growing linearly with total genome size for the former, but only logarithmically for the latter. Assuming that the (protein) coding and non-coding fractions of the genome must have different dynamics and that the non-coding fraction must be controlled by a variety of (unspecified) probability distribution functions, we are able to predict that the number of ORFs for Eukaryotes follows a Benford distribution and has a specific logarithmic form. Using the data for 1000+ genomes available to us in early 2010, we find excellent fits to the data over several orders of magnitude, in the linear regime for the Prokaryote data, and the full non-linear form for the Eukaryote data. In their region of overlap the salient features are statistically congruent, which allows us to: interpret the difference between Prokaryotes and Eukaryotes as the manifestation of the increased demand in the biological functions required for the larger Eukaryotes, estimate some minimal genome sizes, and predict a maximal Prokaryote genome size on the order of 8-12 megabasepairs. These results naturally allow a mathematical interpretation in terms of maximal entropy and, therefore, most efficient information transmission., 23 pages, 1 figure (eps)

The amplitude for pion photo- and electroproduction from finite nuclei is constructed in a model that ignores rescattering of the pion. A consistent expansion in inverse powers of the nucleon mass is performed, which generates effective one-body and two-body nuclear operators. The former agree with the Blomqvist-Laget effective operators, while the latter are new and arise from binding-induced and binding-modified emission. Current conservation is applied to this set of operators and they are cast separately into manifestly gaugeinvariant forms. A simple approximation to the complicated two-body terms is constructed, which shares many of the features of the latter.

Triton properties are calculated using new nucleon-nucleon potentials, which were fit to the world nucleon-nucleon data. All potentials are charge dependent and explicitly incorporate the mass difference between the charged and neutral pions. Three of these models have a nearly optimal chi**2 per degree of freedom and can therefore be considered as alternative partial wave analyses, which in quality can almost compete with the Nijmegen partial-wave analysis. The triton binding energy obtained with three local models (Nijm II, Reid93, AV18) can be summarized as 7.62 +_ 0.01 MeV, which is nearly 900 keV lower than experiment. The non-local model Nijm I binds by 7.72 MeV., Comment: 11 pages RevTex and 1 fig in PS, THEF-NYM-93-04

We examine the role of kinematical variables and analyticity in the derivation of low-energy theorems for pion photo- and electroproduction. Other expansion schemes are compared to the low-energy theorem. We illustrate this with a recent calculation of these processes in chiral perturbation theory. The possibility to test the low-energy theorem experimentally is discussed.

The electric dipole polarizabilities of $^3$H, $^3$He, and $^4$He are calculated directly using the Schr\"odinger equation with the latest generation of two- and three-nucleon interactions. These polarizabilities are necessary in order to obtain accurate nuclear-polarization corrections for transitions involving S-waves in one- and two-electron atoms. Our results are compared to previous results, and it is shown that direct calculations of the electric polarizability of $^4$He using modern nuclear potentials are smaller than published values calculated using experimental photoabsorption data. The status of this topic is assessed in the context of precise measurements of transitions in one- and two-electron atoms., Comment: 6 pages, 3 figures

Faddeev-type configuration-space three-body scattering equations are solved for selected two-body- and two-body-plus-three-body-potential model Hamiltonians to obtain absolute predictions for the nucleon-deuteron scattering lengths $^{2}$${\mathit{a}}_{\mathit{n}\mathit{d}}$,${\phantom{\rule{0ex}{0ex}}}^{4}$${\mathit{a}}_{\mathit{n}\mathit{d}}$, $^{2}$${\mathit{a}}_{\mathit{p}\mathit{d}}$, and $^{4}$${\mathit{a}}_{\mathit{p}\mathit{d}}$. Convergence for these zero-energy scattering parameters as a function of the number of NN-potential partial waves included in the calculation is attained for the first time. Kohn variational estimates provide a measure of the precision of our numerical results. The nd predictions agree well with the measured values. The pd predictions differ substantially from accepted experimental values which are extrapolated from measurements made above 400 keV.

Nuclear transition rates in \ensuremath{\mu}-catalyzed p-d fusion have been calculated using numerically converged $^{3}\mathrm{He}$ bound-state and p-d scattering wave functions for the first time. The transition rates for M1 radiative capture in both quartet and doublet initial states have been computed using a model of meson-exchange currents which reproduces the thermal n-d capture cross section, and are in excellent agreement with experiment. The muon internal-conversion rate is in very good agreement with a recent reanalysis of old bubble-chamber measurements. Furthermore, our nonvanishing quartet capture rate resolves the anomaly in the Wolfenstein-Gerstein effect.

The lowest-known excited state in nuclei is the 7.6 eV isomer of 229Th. This energy is within the range of laser-based investigations that could allow accurate measurements of possible temporal variation of this energy splitting. This in turn could probe temporal variation of the fine-structure constant or other parameters in the nuclear Hamiltonian. We investigate the sensitivity of this transition energy to these quantities. We find that the two states are predicted to have identical deformations and thus the same Coulomb energies within the accuracy of the model (viz., within roughly 30 keV). We therefore find no enhanced sensitivity to variation of the fine-structure constant. In the case of the strong interaction the energy splitting is found to have a complicated dependence on several parameters of the interaction, which makes an accurate prediction of sensitivity to temporal changes of fundamental constants problematical. Neither the strong- nor Coulomb-interaction contributions to the energy splitting of this doublet can be constrained within an accuracy better than a few tens of keV, so that only upper limits can be set on the possible sensitivity to temporal variations of the fundamental constants., 4 pages, 2 figures

A permanent electric dipole moment (EDM) of a physical system requires time-reversal (T) and parity (P) violation. Experimental programs are currently pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of fundamental theoretical interest. Here we calculate the magnitude of the PT-violating EDM of 3He and the expected sensitivity of such a measurement to the underlying PT-violating interactions. Assuming that the coupling constants are of comparable magnitude for pi-, rho-, and omega-exchanges, we find that the pion-exchange contribution dominates. Our results suggest that a measurement of the 3He EDM is complementary to the planned neutron and deuteron experiments, and could provide a powerful constraint for the theoretical models of the pion-nucleon PT-violating interaction., 6 pages, 1 figure

Simple formulas for the neutron and proton polarizations in polarized $^{3}\mathrm{He}$ targets are derived assuming (1) quasielastic final states; (2) no final-state interactions; (3) no meson-exchange currents; (4) large momentum transfers; (5) factorizability of $^{3}\mathrm{He}$ SU(4) response-function components. Numerical results from a wide variety of bound-state solutions of the Faddeev equations are presented. It is found that this simple model predicts the polarization of neutrons in a fully polarized $^{3}\mathrm{He}$ target to be 87%, while protons should have a slight residual polarization of -2.7%. Numerical studies show that this model works very well for quasielastic electron scattering.

The impulse-approximation and pion-exchange current contributions to the radiative capture of thermal neutrons by deuterium have been calculated using initial- and final-state wave functions generated by solving the configuration-space Faddeev equations for several nucleon-nucleon and nucleon-nucleon-plus-three-body-force hamiltonian models. Numerical results are compared with previously published total cross section data and with recent measurements of the M1 photon polarization and the spin-quartet capture fraction.

Configuration-space Faddeev-type scattering equations are solved for selected two-body and two-body-plus-three-body potential model hamiltonians to obtain absolute (converged) predictions for the 2 a nd , 4 a nd , 2 a pd , and 4 a pb scattering lengths. Our nd predictions agree well with the measured values. Our pd predictions differ substantially from accepted experimental values.

Recent experiments observed unexpectedly strong interference between the E1-E1 and M1-M1 2\ensuremath{\gamma} decay modes of the ${0}^{+}$ (6.05 MeV) state in $^{16}\mathrm{O}$. We present the results of a detailed calculation which evaluates the two-photon amplitude between realistic nonspurious many-body wave functions derived from a large basis SU(3) shell-model calculation, including up to 5\ensuremath{\Elzxh}\ensuremath{\omega} of excitation. It is found that, as a result of strong cancellation between contributions to the transition polarizability from the giant dipole states built on the closed shell and the deformed (6.05 MeV) ${0}^{+}$ state, the 2E1 matrix element is greatly suppressed. Since the standard one-body M1 operator cannot excite the closed shell, strong cancellations are not seen in this case. The resulting 2M1 decay mode becomes competitive with the 2E1 decay, although it is still underestimated by the calculations.

There exist in nature a few nuclear isomers with very low (eV) excitation energies, and the combination of low energy and narrow width makes them possible candidates for laser-based investigations. The best candidate is the lowest-energy excited state known in nuclear physics, the 7.6(5) eV isomer of $^{229}$Th. A recent study suggests that a measurement of the temporal variation of the excitation energy of this isomer would have 5-6 orders of magnitude enhanced sensitivity to a variation of the fine structure constant ($\alpha \cong 1/137.036$) or of a strong interaction parameter ($m_q/\Lambda_{QCD}$). We reexamine the physics involved in these arguments. By invoking the Feynman-Hellmann Theorem we argue that there is no expectation of significantly enhanced sensitivity to a variation in the fine structure constant (beyond that obtained from experimental considerations such as the low energy and narrow width of the isomer). A similar argument applies to the strong interaction, but evaluating the shift due to temporal variations of the underlying parameters of the strong interaction may be beyond current nuclear structure techniques., Comment: 4 Pages, no figures

We determine the third Zemach moment of hydrogen (_(2)) using only the world data on elastic electron-proton scattering. This moment dominates the O (Z alpha)^5 hadronic correction to the Lamb shift in muonic atoms. The resulting moment, _(2) = 2.71(13) fm^3, is somewhat larger than previously inferred values based on models. The contribution of that moment to the muonic hydrogen 2S level is -0.0247(12) meV., Comment: 3 pages, no figures, revtex - submitted to Physical Review A

Hyperfine intervals in light hydrogenic atoms and ions are among the most accurately measured quantities in physics. The theory of QED corrections has recently advanced to the point that uncalculated terms for hydrogenic atoms and ions are probably smaller than 0.1 parts per million (ppm), and the experiments are even more accurate. The difference of the experiments and QED theory is interpreted as the effect on the hyperfine interaction of the (finite) nuclear charge and magnetization distributions, and this difference varies from tens to hundreds of ppm. We have calculated the dominant component of the 1s hyperfine interval for deuterium, tritium and singly ionized helium, using modern second-generation potentials to compute the nuclear component of the hyperfine splitting for the deuteron and the trinucleon systems. The calculated nuclear corrections are within 3% of the experimental values for deuterium and tritium, but are about 20% discrepant for singly ionized helium. The nuclear corrections for the trinucleon systems can be qualitatively understood by invoking SU(4) symmetry., Comment: 26 pages, 1 figure, latex - submitted to Physical Review C

We strongly disagree with the procedure used in a recent paper to extract the Zemach moment for hydrogen., 1 page, 2 figures, revtex - submitted to Physical Review Letters

The scalar, vector, and tensor components of the (generalized) deuteron electric polarizability are calculated, as well as their logarithmic modifications. Several of these quantities arise in the treatment of the nuclear corrections to the deuterium Lamb shift and the deuterium hyperfine structure. A variety of second-generation potential models are used and a (subjective) error is assigned to the calculations. The zero-range approximation is used to analyze a subset of the results, and a simple relativistic version of this approximation is developed., Comment: 14 pages, LaTex - submitted to Physical Review C

Leading-order three-nucleon forces that violate isospin symmetry are calculated in Chiral Perturbation Theory. The effect of the charge-symmetry-breaking three-nucleon force is investigated in the trinucleon systems using Faddeev calculations. We find that the contribution of this force to the 3He - 3H binding-energy difference is approximately 5 keV., 14 pages, 3 figures

A new method is developed for treating the effect of the neutron-proton mass difference in isospin-violating nuclear forces. Previous treatments utilized an awkward subtraction scheme to generate these forces. A field redefinition is used to remove that mass difference from the Lagrangian (and hence from asymptotic nucleon states) and replace its effect by effective interactions. Previous calculations of static Class II charge-independence-breaking and Class III charge-symmetry-breaking potentials are verified using the new scheme, which is also used to calculate Class IV nuclear forces. Two-body forces of the latter type are found to be identical to previously obtained results. A novel three-body force is also found. Problems involving Galilean invariance with Class IV one-pion-exchange forces are identified and resolved., Comment: 20 pages, 2 figures, latex - submitted to Physical Review C

Alternative definitions of the Born approximation and the distorted-wave Born approximation within the framework of the configuration-space Faddeev equations are explored. The most natural definition does not correspond to the Born approximation derived from the Schroedinger equation, even though the exact T-matrices for both formalisms are equivalent. The Schroedinger form is optimal, although it is shown that the differences are numerically unimportant. The DWBA corresponding to the Faddeev equations is not channel symmetric, although numerically this is unimportant for the p-d (Coulomb) case. Convergence of the Born approximation partial-wave series is briefly investigated for p-d and n-d scattering below breakup threshold., Comment: 10 pages, latex - submitted to Few-Body Systems

The eigenphase shifts and mixing parameters for elastic p-d scattering below the deuteron-breakup threshold are calculated for the AV14 two-body potential using two different numerical methods. The excellent agreement confirms that it is possible to perform accurate numerical studies of p-d scattering as well as n-d scattering for low energies. The numerical results can be considered as benchmarks for future calculations.

A new method for solving the configuration-space Faddeev equations for elastic p-d scattering below the deuteron-breakup threshold is described. Numerical solutions that demonstrate the convergence and accuracy of the method are given. The number of channels and the value of the matching radius required to obtain an accurate solution are also investigated. These calculations demonstrate that this method can efficiently solve the large matrix equations required for the three-body scattering problem., Comment: 11 pages, latex - FBSart.cls required

We examine the time-reversal-violating nuclear ``Schiff moment'' that induces electric dipole moments in atoms. After presenting a self-contained derivation of the form of the Schiff operator, we show that the distribution of Schiff strength, an important ingredient in the ground-state Schiff moment, is very different from the electric-dipole-strength distribution, with the Schiff moment receiving no strength from the giant dipole resonance in the Goldhaber-Teller model. We then present shell-model calculations in light nuclei that confirm the negligible role of the dipole resonance and show the Schiff strength to be strongly correlated with low-lying octupole strength. Next, we turn to heavy nuclei, examining recent arguments for the strong enhancement of Schiff moments in octupole-deformed nuclei over that of 199Hg, for example. We concur that there is a significant enhancement while pointing to effects neglected in previous work (both in the octupole-deformed nuclides and 199Hg) that may reduce it somewhat, and emphasizing the need for microscopic calculations to resolve the issue. Finally, we show that static octupole deformation is not essential for the development of collective Schiff moments; nuclei with strong octupole vibrations have them as well, and some could be exploited by experiment., Comment: 25 pages, 4 figures embedded in text

Charge-independence breaking due to the pion-mass difference in the (chiral) two-pion-exchange nucleon-nucleon force is investigated. A general argument based on symmetries is presented that relates the charge-symmetric part of that force to the proton-proton case. The static potential linear in that mass difference is worked out as an explicit example by means of Feynman diagrams, and this confirms the general argument., 10 pages, latex, 1 figure -- epsfig.sty required -- To appear in Phys. Rev. C

Off-shell aspects of the one-pion-exchange potential and their relationship to different forms of the nonstatic (subleading-order) chiral two-pion-exchange nucleon-nucleon potential are discussed. Various types of off-shell behavior are categorized and numerous examples are given. Recently derived potentials based on chiral approaches are supplemented by a rather general form of the two-pion-exchange potential derived using old-fashioned methods. The latter is closely related to a general form of one-pion-exchange relativistic corrections and nonstatic two-pion-exchange three-nucleon forces developed long ago., 16 pages, latex -- Phys. Rev. C (to appear) -- Published version

We include two new three-nucleon-force terms of pion-range - short-range form in our momentum-space calculations for the three-nucleon continuum. These two terms are expected by chiral perturbation theory to be non-negligible. We study the effects of these terms in elastic neutron-deuteron scattering and pay special attention to the neutron vector analyzing power $A_y$., Comment: 27 pages, latex, 8 figures - fbsart11.sty required - Submitted to Few-Body Systems - Dedicated to the 60th birthday of Walter Gl\"ockle

Recent improvements in the determination of the running of the fine-structure constant also allow an update of the hadronic vacuum-polarization contribution to the Lamb shift. We find a shift of -3.40(7) kHz to the 1S level of hydrogen. We also comment on the contribution of this effect to the determination by elastic electron scattering of the r.m.s. radii of nuclei., Comment: 7 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty required

The nucleon-deuteron analyzing power $A_y$ in elastic nucleon-deuteron scattering poses a longstanding puzzle. At energies $E_{lab}$ below approximately 30 MeV $A_y$ cannot be described by any realistic NN force. The inclusion of existing three-nucleon forces does not improve the situation. Because of recent questions about the $^3P_J$ NN phases, we examine whether reasonable changes in the NN force can resolve the puzzle. In order to do this we investigate the effect on the $^3P_J$ waves produced by changes in different parts of the potential (viz., the central force, tensor force, etc.), as well as on the 2-body observables and on $A_y$. We find that it is not possible with reasonable changes in the NN potential to increase the 3-body $A_y$ and at the same time to keep the 2-body observables unchanged. We therefore conclude that the $A_y$ puzzle is likely to be solved by new three-nucleon forces, such as those of spin-orbit type, which have not yet been taken into account., Comment: 35 pages in REVTeX, 1 figure in postscript and 3 figures in PiCTeX

Nuclear-size corrections of order $(Z \alpha)^5$ and $(Z \alpha)^6$ to the S-state levels of hydrogenic atoms are considered. These nuclear-elastic contributions are somewhat smaller than the polarizability (nuclear-inelastic) corrections for deuterium, but are of comparable or larger size for the hydrogen case. For deuterium the (attractive) nonrelativistic $(Z \alpha)^5$ correction to the 2S-1S transition is 0.49 kHz, while the (repulsive) relativistic $(Z \alpha)^6$ contribution is -3.40 kHz. For the proton the corresponding corrections are 0.03 kHz and -0.61 kHz, respectively. The $(Z \alpha)^5$ contribution largely cancels the Coulomb-retardation part of the nuclear-polarization correction., Comment: 7 pages, latex -- Submitted to Phys. Rev. A

Darwin-Foldy nuclear-size corrections in electronic atoms and nuclear radii are discussed from the nuclear-physics perspective. Interpretation of precise isotope-shift measurements is formalism dependent, and care must be exercised in interpreting these results and those obtained from relativistic electron scattering from nuclei. We strongly advocate that the entire nuclear-charge operator be used in calculating nuclear-size corrections in atoms, rather than relegating portions of it to the non-radiative recoil corrections. A preliminary examination of the intrinsic deuteron radius obtained from isotope-shift measurements suggests the presence of small meson-exchange currents (exotic binding contributions of relativistic order) in the nuclear charge operator, which contribute approximately 1/2%., Comment: 17 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty required

Weinberg's dimensional power counting for nuclei is reprised in this primer. The role of QCD and chiral symmetry in constructing effective Lagrangians is discussed. The two-scale hypothesis of Manohar and Georgi is combined with power counting in amplitudes to shed light on the scales of nuclear kinetic and potential energies, the size of strong-interaction coupling constants, the size of meson-exchange currents, and the relative sizes of $N$-nucleon forces. Numerous examples are worked out and compared to conventional nuclear models., 38 pages, latex, 10 figures -- submitted to Few-Body Systems -- epsfig.sty and fbssuppl.sty required

In a previous paper, we calculated the fully quantum-mechanical cross section for electromagnetic excitation during peripheral heavy-ion collisions. Here, we examine the sensitivity of that cross section to the detailed structure of the projectile and target nuclei. At the transition energies relevant to nuclear physics, we find the cross section to be weakly dependent on the projectile charge radius, and to be sensitive to only the leading momentum-transfer dependence of the target transition form factors. We exploit these facts to derive a quantum-mechanical ``equivalent-photon spectrum'' valid in the long-wavelength limit. This improved spectrum includes the effects of projectile size, the finite longitudinal momentum transfer required by kinematics, and the response of the target nucleus to the off-shell photon., Comment: 19 pages, 5 figures

Benchmark solutions for three-nucleon breakup amplitudes in {ital n}-{ital d} scattering have been produced by two groups separately using momentum space and configuration space techniques. These results have been obtained at two energies for both spin doublet and quartet configurations for an {ital s}-wave potential model and are in excellent agreement.

We calculate the lowest-order contribution to the cross section for simultaneous excitation of projectile and target nuclei in relativistic heavy ion collisions. This process is, to leading order, non-classical and adds incoherently to the well-studied semi-classical Weizs\"acker-Williams cross section. While the leading contribution to the cross section is down by only $1/Z_P$ from the semiclassical process, and consequently of potential importance for understanding data from light projectiles, we find that phase space considerations render the cross section utterly negligible., Comment: 9 pages, LA-UR-94-2470

Various forms of the long-wavelength, nonrelativistic nuclear Compton amplitude are discussed. Simple manipulations allow the usual low-energy theorem for the amplitude to be cast into a manifestly gauge-invariant form, which facilitates interpretation.

Benchmark solutions for {ital n}-{ital d} scattering using a single model interaction have been produced by five different groups using different methods. These {ital s}-wave results have been obtained at three energies for both quartet and doublet scattering.

The effect of unequal neutron and proton masses on the binding-energy difference of $^{3}\mathrm{He}$ and $^{3}\mathrm{H}$ is calculated using a wide variety of nuclear models. We find that this charge-symmetry-breaking mechanism contributes 14(2) keV to the 764 keV difference. We also demonstrate the importance of the mixed-symmetry wave function components in making the contribution of this mechanism fairly small, but rather model dependent.

The derivation of the low energy theorem for threshold photoproduction of neutral pions on a nucleon is reconsidered. Instead of considering explicitly the Born terms, as done in earlier derivations, a more general class of diagrams is separated from the total amplitude. Gauge invariance is imposed on the operator level and the partial conservation of the axial-vector current constraint is incorporated. Besides recovering the older results in this approach, relations for the off-shell behavior of the strong and electromagnetic vertices are derived.

Shortcomings of a momentum-space treatment of strong absorption, as discussed in the preceding Comment, are only of concern at low projectile energies, {gamma}{lt}1.5. At intermediate and high energies, for which the quantum-mechanical equivalent-photon spectrum is intended, the quantum-mechanical cross sections are reduced relative to the semiclassical results whether one treats strong effects via a momentum-space or an impact-parameter (spatial) cutoff. At these energies the origin of the discrepancy between the predictions of fully quantum-mechanical and the semiclassical calculations cannot be traced to differences in the treatment of strong-interaction effects. Rather, they arise from quantum effects neglected in the semiclassical calculations. {copyright} {ital 1997} {ital The American Physical Society}