Table of contents

Comments of the work of W. Plessas and W. Schweiger (see ibid., vol.7, no.8, p.1019-28, 1981), in which analytic expressions were given for the proton-proton Coulomb-modified nuclear T matrix associated with the Graz separable interaction. The authors point out that these (lengthy) expressions can be simplified substantially, and present new formulas that are much shorter.

The ³He(p, pi ⁺)⁴He reaction has been measured at three different energies close to threshold. The laboratory angular range covered varies between 20 degrees and 110 degrees at 201 MeV, 20 degrees and 70 degrees at 190 MeV and 20 degrees and 40 degrees at 180 MeV. The forward cross sections are of the order of a few mu b sr^-1.

It is shown that the contribution of the induced scalar interaction through relativistic form factor coefficients is very important. This interaction affects the spectrum shape factor, to a first approximation, in the same way as the Fierz interference term, contrary to a previous assumption. A limit on the strength of f_s of order 1/M is set.

Discusses the consequences for the recently derived lower bounds on the percentage D state of the deuteron, P_D, of (i) recent further measurements of the asymptotic D- to S-state ratio of the deuteron, eta , (ii) the experimental value of the root-mean-square radius of the deuteron, r_d, recently deduced from low-energy electron scattering data and constrained by the experimental values of eta and a recent quark-model prediction for the neutron electric form factor, G_En, and (iii) the contribution to the experimental value of the quadrupole moment of the deuteron, Q_D, from meson-exchange currents, relativistic effects and isobar components of the deuteron wavefunction.

A model calculation shows that the coupling of the elastic channel to the inelastic ones reached through strongly excited collective levels affects the real part of the optical potential considerably around the Coulomb barrier.

For pt.I see J.Phys. A, vol.13, no.9, p.2903-11 (1980). A rigorous dimensional analysis of subtracted-out Feynman integrands is carried out as functions of external and internal momenta as well as of the masses in the theory. The analysis is very general and gives sufficient conditions for determining the asymptotic behaviour of renormalised Feynman amplitudes, in Euclidean space, when some (or all) of the external momenta become large, some (or all) of the external momenta become small, some of the external momenta remain non-asymptotic and even when some of the masses are led to go to zero. All these variables are led to 'approach' their asymptotic values, in general, at different rates.

A general dimensional analysis is applied to derive, in Euclidean space, the asymptotic behaviour of renormalised (subtracted-out) Feynman amplitudes A. The maximising subspaces for the bond of A are constructed and an explicit expression for the behaviour of A is given including both power and logarithmic asymptotic coefficients. The analysis provides rules for obtaining the asymptotic expression for A when some (or all) of the external momenta become large, some (or all) become small, and some of the masses are led to approach zero. Examples are then worked out as illustrations of these rules.

It is demonstrated how the contribution of hard bremsstrahlung to the total cross section can be integrated analytically for many weak interaction processes.

The author evaluates unitary corrections to the Cheng-Dashen method for the evaluation of sigma terms for both the pi N and the KN systems. Results agree with previous estimates of the effect in the pi N system, and predict smaller effects than previously expected in the KN system.

The absolute normalisation of backward pi N scattering experiments is studied using a phenomenological Regge model. Data below 20 GeV/c are fitted with various choices of absolute normalisation and model extrapolations are made to Fermilab and Serpukhov energies and compared with data.

The part of the static nuclear axial polarisability arising from the nucleonic excitations is derived from the low-energy expansion of the pi N amplitude. It is shown that the contribution of the Delta intermediate state, though dominant, does not saturate the nucleonic response. A similar effect, though more pronounced, is known to occur for the magnetic susceptibility.

Partial transition rates and the gamma -ray spectrum for the radiative pion capture reaction on ¹⁶O have been evaluated using the gauge-invariant effective Hamiltonian which also contains the nucleonic Fermi motion effects. Compared with the results obtained for the conventional effective Hamiltonian, a 15-25% reduction in the yield of the gamma -ray spectrum is observed. This is almost completely related to a new energy term and kinematic renormalisation of the constants of the effective Hamiltonian results in essential changes in the weak partial transitions.

An analytical formula for the overlap integrals in the case of the non-canonical basis of Bargmann and Moshinsky (1961) has been obtained. These integrals are tabulated for mu =0, 1, 2, 3, 4 and lambda > mu . The overlap integrals are used for the construction (by means of the Hilbert-Schmidt procedure) of an orthonormal basis. The transformation coefficients are tabulated for mu =0, 1, 2, 3 and lambda > mu .

The matrix elements of the generators of SU(3) and of the basic O(3) scalars in the enveloping algebra of SU(3) have been calculated between the states of (i) the noncanonical basis of Bargmann and Moshinsky (1961), and (ii) the orthonormalised (by means of the Hilbert-Schmidt procedure) basis. The analytical expressions for the matrix elements are given in tabular form for mu =0, 1, 2, 3 and lambda > mu . The results obtained are of some physical interest in building the algebraic SU(3) model of heavy deformed even-even nuclei.

It is suggested that measurement of the proton polarisation and analysing power for the elastic scattering ⁷Li(p,p)⁷Li should provide a sensitive test of time reversal invariance. It is possible that the 441 keV resonance could be a suitable energy region for study; alternatively measurements at higher energies and at selected angles should be suitable.

A systematic study of the dependence of fusion cross sections on the strength of the friction force has been performed by carrying out classical dynamical trajectory calculations for a number of heavy-ion target-projectile systems. On comparing the calculations with the available experimental data on fusion excitation functions for few typical light-heavy-ion systems, it was seen that in the high-energy region, where the fusion cross sections depend sensitively on the strength of the friction force, there appears to be a trend in the data, that is not easily explained by a simple linear velocity-dependent friction force. However, even in this region, the paucity of experimental data prevents one from drawing any definite conclusions.

Angular distributions for the ²H(d,n)³He reaction have been calculated for incident deuteron energies between 19.5 keV and 349 keV. Model calculations are performed using the generalised R-matrix methodology of Lane and Robson (1966) and additional distorted wave Born approximation terms to describe the long-range spatial contribution to the cross section. Model results are consistent with the experimental prediction of Galloway and Hall (1980) which suggests that D waves become important to a proper description of the cross section at about 290 keV. However, the model indicates that D waves make non-negligible contributions to the cross section even below this energy.

The radioactive decay of ¹¹⁰Ag^m+g has been studied extensively using gamma-gamma coincidence and sum-coincidence spectrometers. Levels at 2078.8, 2250.7, 2287.7, 2433.1, 2539.6, 2659.9, 2706, 2793.4, 2842.5 and 2876.8 keV previously proposed on energy sum considerations are proved by these techniques. For the first time the gamma rays of 120.3, 133.4, 341.4 and 356.4 keV are interpreted. The existence of a new level at 2356.2 keV is proposed. An interpretation is suggested for known gamma rays of 120.3, 133.4, 341.4 and 356.4 keV as well as for new transitions of about 648, 714.9, 1465.6 and 1698.5 keV. The spins of a few levels of ¹¹⁰Cd are discussed on the basis of present models.

The ¹⁷⁵Lu(n, gamma )^176mLu capture cross section has been measured relative to gold at astrophysical energies. The branching ratio derived is inconsistent with an earlier measurement and rules out the chronometric role of the long-lived ^176gLu for s-process synthesis. Instead, it is apparent that thermal equilibrium of the ground and isomeric states occurs in stellar interiors on a timescale less than the 3.64 h half-life of the isomeric state.

The rate of subcores in cosmic-ray air showers has been measured near sea level with a close-packed 35 m² array of spark chambers. A large transition effect was observed from wood beams in the original roof. After the first year, the spark chambers were affixed directly to a new styrofoam sandwich roof of thickness 20 cm (2.2 g cm^-2) in order to minimise transition effects. The measured rate is 0.038+or-0.01 per shower of size N>or=10⁵ particles for subcores of size n₂₅>or=50, where n₂₅ is the net number of subcore particles within a circle of radius 25 cm. The dependence on subscore size goes approximately as n₂₅^-3.4. The higher rates of subcores reported in other experiments are probably due to transition effects. If p_t is calculated by assuming subcore production by pi ⁰'s, the authors find no cases of p₁>5 GeV/c. The problem of abstracting realistic information from the subcore data in order to test theories of high-energy interactions at 10¹⁵ eV is treated. Simulation results that predict significant improvement in data acquisition at higher altitudes are presented.

A measurement of the elongation rate, the rate of change of the depth of shower maximum with energy, has been made in air showers initiated by cosmic-ray primaries with energy in the range 2*10¹⁷-10²⁰ eV. The measurement is based on the study of the rise times of over 13000 pulses recorded from the four 34 m² water Cerenkov detectors of the Haverah Park array and on an application of the elongation rate theorem. The elongation rate is determined to be 70+or-5 g cm^-2 per decade, averaged over the whole energy range, while for 35 events of primary energy greater than 5*10¹⁸ eV the corresponding value is 40+or-20 g cm^-2 per decade. These results are independent of assumptions about features of high-energy interactions. The changes in mass composition, consistent with the authors' measurement and with different assumptions about nuclear interactions, are derived.