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Neutrino- and antineutrino-nucleon scattering into hadrons is analyzed and related to electron-nucleon scattering according to a scaling model which has been recently proposed. The electromagnetic and weak structure functions are determined and explicitly given in terms of the πN total cross sections. Predictions are made in good agreement with experiments.

The infrared corrections to the Drell-Yan process are studied to all orders in QCD. Our results show that higher-order terms slightly modify the first-order corrections in the range of τ experimentally accessible in proton-proton collisions. Accurate measurements with pion and kaon beams should, however, reveal the increase with τ of the soft corrections.

With use of the coherent-state formalism, general expressions are presented for arbitrary massless quark and gluon jet cross sections. Also, normalized probability distributions are given for the jet transverse momentum which take due account of correlations imposed by the momentum conservation. These results are used to discuss successfully the SPEAR data of Hanson et al. (1979) between 3 and 7.8 GeV. (9 refs).

Electron-positron annihilation into hadrons, photoproduction, total and singly inclusive electro-production are discussed in the framework of a scaling model of electromagnetic interactions in which the photon is coupled to a continuum of hadronic states whose properties are established consistently. The model makes use of the concept of the shrinkage of the size of the particle with its mass. The exhibition of scaling properties in e.m. interactions demands a similar scaling behaviour of strong interactions. Predictions are made which are in good agreement with experiments.

Electromagnetic and finite-width effects are discussed for % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWexLMBb50ujb% qeguuDJXwAKbacfaGae8xCaeNaf8xCaeNbaebaaaa!3DB9! $$q\bar q$$ jets produced in e+e− annihilation near the Z0 pole. Angular asymmetries are also considered for inclusively produced π+ and K+ with large fractional momenta.

The problem of mass singularities is studied using the formalism of coherent states. The introduction of new states which account for both soft and hard radiation effects provides one with matrix elements which are free from infra-red and mass singularities at the leading logarithmic approximation. In QED our results coincide with those obtained from the renormalization group equations. The generalization to QCD agrees with perturbative calculations and provides a simple framework for evaluating the finite corrections to hard processes.

Motivated by the remarkably good agreement in the descriptions of deep inelastic processes and some radiative meson decays by the quark model and the method of infinite vector-meson saturation, we argue in general that these two approaches are equivalent. We explicit the nature of this equivalence by endowing vector-mesondominated vertices with the asymptotics implied by quark current algebra. With this leverage we obtain satisfactory predictions forSU3 meson decays, including those for which the quark model by itself fails, excepting the ρ → πγ decay. Applied to the radiative decays of the new mesons, this scheme avoids the difficulties of nonrelativistic calculations and predicts considerably smaller widths.

A complete analysis of EM radiative corrections to Bhabha scattering near the Z 0 is presented Compact analytic formulae are given which include exact one-loop results and soft-and-collinear photon effects resummed to all orders. Detection of back-to-back e + e − pairs can be therefore used as a high precision monitor of luminosity at LEP/SLC energies.

Radiative decays of tensor and axial mesons are considered in the framework of a previously proposed scheme, where the basic currents ofSU4 are dominated by vector mesons and exhibit a quark structure asymptotically. Agreement is found with previousSU3 estimates. The decay rates for ψ′ → γχ1,2 also agree with experiments and nonrelativistic estimates. Conversely, the χ1,2 → γJ/ψ widths have been found smaller by about a factor of two than those obtained in the n.r. bound-state picture. Our results are also compared with those previously obtained for the χ0-meson.

A representation for the Pomeranchon exchange and the multiple scattering corrections is suggested, which contains crossing symmetry, asymptotic Regge behaviour, and obeys the duality requirement of a non resonating background. A very good description of the proton-proton elastic scattering is obtained in the diffraction, intermediate and large angle regions.

Normalized probability distributions are presented for (massless) quark and gluon jet longitudinal momenta which take due account of correlations imposed by momentum conservation. A general algorithm is introduced to analyze the experimental data in terms of QCD parameters only.

It is shown that the weak amplitude must also be radiatively corrected for a satisfactory analysis of the neutral current in e + e − → μ + μ − . Radiative asymmetry can be of possible help in isolating the weak effect provided the symmetric cross section can be measured to ≳ 1% accuracy at PEP/PETRA energies.

A new precise measurement of σ (e+e−→ hadrons) at low energy is suggested, of particular relevance for the theoretical prediction ofaμ. The method proposed consists in collidingo((10÷100) MeV) electrons from a superconducting linac witho((1÷2) GeV) positrons of a conventional storage ring.

A “leading log” analysis of radiative corrections to inclusive ep scattering at HERA energies is presented. Neutral current weak interactions are considered at the level of the Born cross section as well as of the modifications of vertex and vacuum polarization parts. The leading log approximation has been also improved in the single hard and multiple soft photon emission by appropriate kinematical considerations. Some numerical results are presented for polarized electron and positron beams.

We evaluate the full o(αs3) cross sections for the processes g+g→g+X and g+g→q+X, relevant for jet production at large pT at very high energies. Some phenomenological applications of our results at Sp p S and Tevatron energies are also presented.

The methods of coherent states and of structure functions in QED are considered in detail for a precise evaluation of the radiative effects at LEP/SLC. They are explicitly shown to give identical results for the exponentiated infrared factors and the o( α ) terms corresponding to the initial and final state radiation. Then the combined use of both techniques further improves the theoretical predictions to an accuracy better than 1%-including interference effects-and provides simple analytical formulae of immediate phenomenological application.

It is shown that if M H ≈O(100 GeV) the production of the Higgs boson via the gluon fusion mechanism, and the subsequent decay into a heavy Q Q pair cannot be revealed by looking at the jet-jet invariant mass, due to initial state gluon bremsstrahlung.

The study of the relative transverse momentum distributions of back-to-back jets produced at the\(\bar p\) collider is suggested to provide a clean test of gluon-gluon dynamics.

New expressions are presented for radiative corrections to colliding beam experiments in presence of narrow resonances, including interference effects. These are applied to ψ (3.1) and ψ (3.7) to obtain the values ( Γ e Γ h / Γ )=(4.0±0.2) keV for ψ (3.1) and (2.8 ± 0.3) keV for ψ (3.7).

A recently proposed scheme for radiative decays of mesons with vector meson dominated vertices and the asymptotics implied by quark current algebra is applied to scalar meson decays. The reactions ϵ → γγ, χ → γγ, ψ′ → χγ and χ → ψγ are considered in detail. Results are in good agreement with experiments.

From simple quark model arguments and assuming a quadratic η − η ′ mixing we predict the radiative decays of the vector and pseudoscalar mesons, in good agreement with experiments. Our results strongly favour the new determination of the η → γγ partial width.

A recently proposed approach to the problem of infrared and mass singularities in QCD, based on the formalism of coherent states, is extended to discuss massless quark and gluon jets. Our results include all leading (In δ) terms as well as finite terms in the energy loss ϵ, in addition to the usual In ϵ associated with In δ. Our formulae agree with explicit perturbative calculations, whenever available. Explicit expressions for the total $K_T$ distributions are given which take into account transverse-momentum conservation. Predictions are also made for the $Q^2$ dependence of the mean $K_T^2$ for quark and gluon jets. Our jet $k_T$ distributions are extrapolated for low $K_T$ and shown to describe with good accuracy the data for eē → qq̄ → hadrons. Numerical predictions are also presented for the forthcoming PETRA, PEP and LEP machines.

A previously proposed analysis of radiative decays of 0 ++ mesons is reexamined. New estimates are given for the widths of χ → γγ and ψ → χγ .

Absolute p ⊥ -distributions for Drell-Yan pairs produced in π N and pN collisions are studied in perturbative QCD and found in excellent agreement with data. Soft gluon effects, implented by exact kinematics considerations, play a very important role in the analysis. A moderate value of the parton intrinsic 〈 p 2 ⊥ 〉 ≈ 0.4 GeV 2 is found.

The hadronic contribution to the muon anomalous magnetic moment is calculated using recent results from colliding beam experiments; a value of (68 ± 9) × 10 −9 is obtained.

A model for all the Pomeranchuk terms is constructed by taking into account some general properties associated to the leading vacuum singularity. It gives a very good description of the p p , pp total and differential cross sections and provides an accurate determination of the Pomeranchuk parameters.

A model describing the radiative P→γγ, V→Pγ, P→PPγ and the strong V→PPP decays is proposed. The amplitudes for processes with a three-particle final state are approximated by finite dispersion relations and the coupling constants are related by the quark model. Predictions derived from usual VMD are only in qualitative agreement with experiments. Better agreement is achieved by extending VMD with the inclusion of further vector mesons.

An intuitive picture for understanding scaling in hadronic as well as non hadronic processes is proposed which makes use of shrinkage of the size of the particle with its mass. An explicit model in agreement with experiment is also discussed.

Production of massive lepton pairs in hadronic collisions is discussed in a model recently proposed by us (with E. Etim) (1972) which shows scaling for strong as well as e.m. processes and an increase in the average transverse momentum with the mass. This model is applied to obtain approximately a p/sub perpendicular to //sup -4/ decrease with transverse momentum, p/sub perpendicular to /, in inclusive hadronic distribution functions. (7 refs).

A model of scale invariance for both deep inelastic scattering and e + e − annihilation incorporating an infinite number of vector mesons is proposed. Structure functions are calculated explicitly in good agreement with experiments. Precocious scaling arises naturally in the model.