[en] A next-to-leading order analysis of inelastic electroproduction of charm is performed using an interpolating scheme which maps smoothly onto massless QCD evolution at large Q² and photon-gluon fusion at small Q². This scheme allows a systematic inclusion of quark mass effects, as well as possible non-perturbative, or intrinsic, charm contributions. We find no conclusive evidence in favor of an intrinsic charm component in the nucleon, although several data points which disagree with perturbative QCD expectations will need to be checked by future experiments

[en] We derive the formal expressions needed to discuss the change of the twist-two parton distribution functions when a hadron is placed in a medium with relativistic scalar and vector mean fields

[en] The renormalization group is extended to cases where several heavy particles are decoupled at the same time. This involves large logarithms which are scale-invariant and so cannot be eliminated by a change of renormalization scheme. A set of scale-invariant running couplings, one for each heavy particle, is constructed without reference to intermediate thresholds. The entire heavy-quark correction to the axial charge of the weak neutral current is derived to next-to-leading order, and checked in leading order by evaluating diagrams explicitly. The mechanism for canceling contributions from the top and bottom quarks in the equal-mass limit is surprisingly non-trivial

[en] Quark mass effects are included in the calculation of polarized structure functions. In particular, the validity of fixed order perturbation theory and of massless evolution is studied in the framework of heavy quark structure functions. The polarized version of the ACOT and MRRS interpolating schemes for the evolution of massive quark distributions is also developed and studied. The different behaviours of the various approaches in x and Q² are shown. (orig.)

[en] Quark mass effects are included in the calculation of polarized structure functions. In particular, the validity of the photon gluon fusion approximation compared to massless evolution is studied in the framework of heavy quarks structure functions. A third framework which interpolates the two previous schemes is then developed and a comparative study between the three is made, suggesting that the massless approach for heavy quarks is a good approximation already at relatively low values of Q². (author)

[en] Quark mass effects are included in the calculation of polarized structure functions. In particular, the validity of the photon gluon fusion approximation compared to massless evolution is studied in the framework of heavy quarks structure functions. A third framework which interpolates the two previous schemes is then developed and a comparative study between the three is made, suggesting that the massless approach for heavy quarks is a good approximation already at relatively low values of Q². Copyright (1999) World Scientific Publishing Co. Pte. Ltd

[en] A brief review covering a number of topics on the subject of spin structure of the proton is presented

[en] There has recently been surprising progress in understanding the spin and flavor dependence of deep inelastic structure functions in terms of the same physics needed in the simple quark models used for hadronic spectroscopy. However, the corresponding scale is usually very low, casting doubt on the use of leading order QCD evolution. We show that the conclusions are not significantly altered if one goes to next-to-leading order. In particular, the excellent agreement with unpolarized and polarized valence quark distributions is retained. (author) 53 refs

[en] An overview of present calculations involving the proton spin structure function is given. It is shown that a significant part of the discrepancy between the data and the Ellis-Jaffe sum-rule may arise through the axial anomaly if the gluons within the proton are strongly polarized. While a quark model, such as the MIT bag, does not include the anomaly, and therefore cannot be expected to reproduce the spin structure function, it does give a rather good description of recent data which is anomaly free, such as the distribution of polarized, valence up-quarks in the proton. The corresponding leading twist parton distribution was established in leading and next-to-leading order QCD evolution to the scale of the experiments. 35 refs., 1 fig

No abstract available