2/20/2023 0 Comments Qm courier![]() Also discussed is the Pomeranchuk theorem relating particle-particle to particle-antiparticle asymptotic cross-section growth, but, surprisingly, no attention is drawn to the optics-diffraction motivation for the key assumption in the proof of this “theorem”. The essential ideas of dispersion relations, Muller’s generalization of the optical theorem to inclusive reactions and the key, rigorous theorems on permissible growth with energy of cross-sections are presented. to the diffractive aspects of hard interactions. Here the emphasis is on those aspects of theory and experiment that are directly relevant to the present-day resurgence of interest in diffraction – i.e. The second part of the book surveys concisely the old soft diffraction from the “golden age” of Regge theory. ![]() A chapter on relativistic kinematics introduces the concepts of rapidity and rapidity gaps, the latter being the current focus of intense experimental study in lepton-hadron deep inelastic scattering (DIS). It also includes a discussion of the eikonal approximation, which plays a major role in later chapters, when attempting to understand the high-energy behaviour of very complex QCD Feynman diagrams. The first offers a rapid but clear survey of scattering theory in both classical wave optics and non-relativistic QM. There are three main sections to this book. It manages to succinctly introduce all the important ideas in the Regge theory of diffraction (now referred to as soft diffraction) and attempts to connect these to the recent developments in hard diffraction and its interpretation in the framework of QCD. It is for these lost generations, and, of course, for the present generation of elementary particle physicists that this volume will be of great value. Unfortunately, the concepts and language of Regge theory have largely fallen into disuse, so that several generations of young physicists, whose education had a lacuna in this field, now find themselves working on experiments in which such concepts are of importance. ![]() So we should not be surprised to learn that there is a connection between certain aspects of deep inelastic reactions and Regge concepts, and that the relatively new field of hard diffraction opens up the possibility of a bridge between Regge theory and QCD (leading, one hopes, to an understanding of Regge theory in the language of QCD). Consequently, a huge effort has gone into the study of such deep inelastic reactions.īut history, according to the Italian philosopher Vico, is supposed to be cyclical. ![]() Because of its property of asymptotic freedom, QCD was able to predict interesting correlations between experimental data in certain kinematical regions characterized by a hard scale. The discovery of the partonic structure of hadrons and the advent of quantum chromodynamics (QCD) led to a dramatic change in the thrust of experimental high-energy physics, away from the study of elastic and diffractive scattering. (A non-physicist spouse, upon being introduced to Tulio Regge at a party in the 1960s, is reported to have said: “Ah, Mr Pole, I have heard so much about you.”) Terms like Regge pole, pomeron and reggeon became household words. This led to the theory of Regge poles, which enjoyed enormous success in correlating the data on many reactions, though it also experienced some failures. This new idea was the concept of complex angular momentum in non-relativistic QM (now a vital component in any serious book on QM) and its connection with the behaviour of relativistic scattering amplitudes at high energy. Being essentially non-perturbative processes, theory could not provide a really detailed description of elastic and diffractive scattering, but it did introduce a new idea that is truly fundamental. Given the wave-particle duality of quantum mechanics (QM), diffraction continued to be an important concept in non-relativistic QM scattering, and later in the study of elementary particle scattering using relativistic S-matrix theory.įor some decades after 1950, a vast experimental and theoretical effort went into the study of high-energy elastic and diffractive scattering of elementary particles, culminating in the largely unexpected discovery that cross-sections grow with energy. By Vincenzo Barone and Enrico Predazzi, Springer Verlag 2002, ISBN 3540421076, €74.95 plus local VAT.ĭiffraction has played a fundamental role in physics for centuries, beginning with the realization of the wave nature of light.
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