We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations — parton-level fixed order, shower-matched, merged — in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e − collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.

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The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations

We have studied the three quark system in a relativized version of the quark potential model with chromodynamics. With parameters consistent with those of an analogous study of meson spectroscopy we obtain a successful description of the spectrum of baryons. The model naturally explains the apparent absence of spin‐orbit interactions in baryons.

Baryons in a relativized quark model with chromodynamics

The task of quantizing general relativity raises serious questions about the meaning of the present formulation and interpretation of quantum mechanics when applied to so fundamental a structure as the space-time geometry itself. This paper seeks to clarify the foundations of quantum mechanics. It presents a reformulation of quantum theory in a form believed suitable for application to general relativity. The aim is not to deny or contradict the conventional formulation of quantum theory, which has demonstrated its usefulness in an overwhelming variety of problems, but rather to supply a new, more general and complete formulation, from which the conventional interpretation can be deduced. The relationship of this new formulation to the older formulation is therefore that of a metatheory to a theory, that is, it is an underlying theory in which the nature and consistency, as well as the realm of applicability, of the older theory can be investigated and clarified.

"relative State" Formulation of Quantum Mechanics

We review the techniques necessary for the calculation of virtual electroweak and soft photonic corrections at the one-loop level. In particular we describe renormalization, calculation of one-loop integrals and evaluation of one-loop Feynman amplitudes. We summarize many explicit results of general relevance. We give the Feynman rules and the explicit form of the counter terms of the electroweak standard model, we list analytical expressions for scalar one-loop integrals and reduction of tensor integrals, we present the decomposition of the invariant matrix element for processes with two external fermions and we give the analytic form of soft photonic corrections. These techniques are applied to physical processes with external W-bosons. We present the full set of analytical formulae and the corresponding numerical results for the decay width of the W-boson and the top quark. We discuss the cross section for the production of W-bosons in e^{+}e^{-}-annihilaton including all O(alpha) radiative corrections and finite width effects. Improved Born approximations for these processes are given.

Techniques for the calculation of electroweak radiative corrections at the one-loop level and results for W-physics at LEP200

Fragmentation of transversely polarized quarks probed in transverse momentum distributions

An Introduction to Quarks and Partons. By F.E. Close. Pp.481. (Academic: London, New York and San Francisco, 1979.) £26.40; $54.50.

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Elementary particle theory

Polarization and angular distributions in the decay sequence {ital t}{r arrow}{ital bW}{sup +},{ital W}{sup +}{r arrow}{ital l}{sup +}{nu}{sub {ital l}} are discussed for the standard model. Top quarks from {ital e}{sup +}{ital e{minus}}{r arrow}{ital t{bar t}} are predicted to have large polarization but, even if not, the parity-violating effects in this decay chain are large and will test closely the detailed spin structure of the electroweak interactions involving the top quark. A means of analyzing {ital {bar t}t} decays following {ital {bar t}t} production in hadronic interactions is developed, leading to an illuminating construction. Its application is illustrated by the analysis of the candidate for top-antitop pair creation in {ital {bar p}p} collisions found by the Collider Detector at Fermilab (CDF) at 1.8 TeV center-of-mass energy. If this is really {ital {bar t}t} production, then the top-quark mass would be 125{sub {minus}11}{sup +19} GeV/{ital c}{sup 2}.

Decay and polarization properties of the top quark

Phenomenological study of s-shell hypernuclei with ΛN and ΛNN potentials

The existence of the H particle, the dihyperon predicted by Jaffe, would bring into question the existence of double hypernuclei. We review the two double hypernucleus events published in the literature. We include an independent report, hitherto unpublished, which was made on the $\Lambda\Lambda^{10}$Be event in 1963 and clarifies the salient features of the event; this report reaffirms its published interpretation. We have made a simple calculation of the energy spectrum for $\Xi^-$ hyperons produced with K$^-$ beams in past emulsion experiments, with a result which accounts adequately for the paucity of reported double hypernucleus events. We outline a hybrid emulsion experiment that would locate $\Xi^-$ hyperon interactions efficiently and could thereby greatly improve our knowledge of double hypernuclei.

Richard Henry Dalitz

Papers

Elementary particle theory

Decay and polarization properties of the top quark

Phenomenological study of s-shell hypernuclei with ΛN and ΛNN potentials

The Identified $\Lambda\Lambda$-Hypernuclei and the Predicted H-Particle

Baryon spectroscopy and the quark shell model (I). The framework, basic formulae, and matrix-elements