A report is presented of recent experimental and theoretical progress in studies of the production of massive lepton pairs in hadronic collisions. Among the topics discussed are deviations from scaling, the status of the proofs of factorization in the parton model, higher-order terms in the QCD expansion, the discrepancy between measured and predicted yields (K factor), high-twist terms, soft gluon effects, and transverse momentum distributions.

The hadroproduction of lepton pairs with mass Q and finite transverse momentum Q{sub T} is described in perturbative QCD by the same partonic subprocesses as prompt photon production. The authors demonstrate that, like prompt photon production, lepton pair production is dominated by quark-gluon scattering in the region Q{sub T}> Q/2. This feature leads to sensitivity to the gluon density in kinematical regimes accessible in collider and fixed target experiments, and it provides a new independent method for constraining the gluon density.

Giving an accurate account of the concepts, theorems and their justification, this book is a systematic treatment of perturbative QCD. It relates the concepts to experimental data, giving strong motivations for the methods. Ideal for graduate students starting their work in high-energy physics, it will also interest experienced researchers.

Recent experimental data and theoretical developments on the production of lepton pairs in hadron collisions are reviewed. With emphasis on the interplay between theory and experiment, the relevance of theoretical calculations to the data available at present energies is critically examined. The Drell--Yan mechanism is found to be phenomenologically dominant provided that the parton distribution functions contain effects of gluon radiation in a narrow cone. Explicit QCD perturbative calculations of the non-Drell--Yan type yield results that are apparently important at large transverse momenta, but are contradicated by subsequent data at 400 GeV and below. A consistent picture in the parton model is sketched. Further experiments to probe the basic mechanism are suggested. 83 references.

In this paper, the authors summarize recent work in which they demonstrate that the Compton subprocess, q + g 2![gamma]* + q also dominates the Drell-Yan cross section in polarized and unpolarized proton-proton reactions for values of the transverse momentum Q{sub T} of the pair that are larger than roughly half of the pair mass Q, Q{sub T}> Q/2. The Drell-Yan process is therefore a valuable, heretofore overlooked, independent source of constraints on the spin-averaged and spin-dependent gluon densities. Although the Drell-Yan cross section is smaller than the prompt photon cross section, massive lepton pair production is cleaner theoretically since long-range fragmentation contributions are absent as are the experimental and theoretical complications associated with isolation of the real photon. Moreover, the dynamics of spin-dependence in hard-scattering processes is a sufficiently complex topic, and its understanding at an early stage in its development, that several defensible approaches for extracting polarized parton densities deserve to be pursued with the expectation that consistent results must emerge.

A review is presented of recent experimental and theoretical progress in studies of the production of massive lepton pairs in hadronic collisions. I begin with the classical Drell-Yan annihilation model and its predictions. Subsequently, I discuss deviations from scaling, the status of the proofs of factorization in the parton model, higher-order terms in the perturbative QCD expansion, the discrepancy between measured and predicted yields (K factor), high-twist terms, soft gluon effects, transverse-momentum distributions, implications for weak vector boson (W/sup + -/ and Z°) yields and production properties, nuclear A dependence effects, correlations of the lepton pair with hadrons in the final state, and angular distributions in the lepton-pair rest frame.

The top quark pair production and decay into leptons with at least one being a [tau] lepton is studied in the framework of the CDF experiment at the Tevatron proton antiproton collider at Fermilab (USA). The selection requires an electron or a muon produced either by the [tau] lepton decay or by a W decay. The analysis uses the complete Run II data set i.e. 9.0 fb-1, selected by one trigger based on a low transverse momentum electron or muon plus one isolated charged track. The top quark pair production cross section at 1.96 TeV is measured at 8.2 ± 1.7+1.2-1.1 ± 0.5 pb, and the top branching ratio into [tau] lepton is measured at 0.120 ± 0.027+0.022 -0.019 ± 0.007 with statistical, systematics and luminosity uncertainties. These are up to date the most accurate results in this top decay channel and are in good agreement with the results obtained using other decay channels of the top at the Tevatron. The branching ratio is also measured separating the single lepton from the two leptons events with a log likelihood method. This is the first time these two signatures are separately identified. With a fit to data along the log-likelihood variable an alternative measurement of the branching ratio is made: 0.098 ± 0.022(stat:) ± 0.014(syst:); it is in good agreement with the expectations of the Standard Model (with lepton universality) within the experimental uncertainties. The branching ratio is constrained to be less than 0.159 at 95% con dence level. This limit translates into a limit of a top branching ratio into a potential charged Higgs boson.