<<

Nature Vol. 283 17 January 1980 315 BOOK REVIEWS Elementary theory R.H. Dalitz

EVEN a decade ago, it was apparent that the An Introduction to and Partons. considerable detail, bringing out their and , previously regarded By F.E. Close. Pp.481. (Academic: connection with simple field theories. as elementary constituents of the atomic London, New York and San Francisco, There are brief discussions of scale nuclei, were actually composite. Very 1979.) £26.40; $54.50. invariance in - many excited states were known for them at high , of neutral and many also for the and the those when this book was finalised. currents appropriate to the unified electro­ . The numbers of these Nevertheless, the book will be much wel­ magnetic-weak , and of the excited hadronic states formed definite comed, especially by students, for it is the observed scaling violations, now believed patterns, recognised to correspond to a only recent introduction available at book to reflect for the 'molecular model' for the , each length. It does not proceed to expound the underlying field theory. The parton model consisting of three of the quarks subject deductively, from basic principles, is extended by introducing hypothesised by Gell-Mann and Zweig but is better described as a discursive review fragmentation functions, used to analyse some years before, each consisting surveying the state of the art in this field of and predict spectra and their of a quark and an antiquark. Each pattern in mid-1978. It tends to give results angular dependence in various high- corresponded to a definite excitation of without derivation, although then analy­ reactions. This leads on to a discussion of their internal and orbital . sing the result to give some intuitive under­ large momentum-transfer phenomena in Independently, the data on deep-inelastic standing of its origin and meaning, a pro­ hadron-hadron collisions and to quark electron- had shown cedure having great value for any isolated counting rules for their asymptotic forms. rather directly that contained reader. Specific models such as 'Drell-Yan' and point-Jik(; , which Feynman Following a brief introduction to set the 'constituent-interchange', are introduced termed 'partons'. With later experiments scene, the book consists of three parts. The and compared with the data. on deep-inelastic v ... µ- and l7 - µ + first part begins with SU(N) symmetries for The third part first sketches briefly the reactions on nucleons, these data showed N quark flavours, initially for N = 2 and electromagnetic-weak and QCD gauge that partons and quarks appeared to be then for N = 3. This SU(3)symmetryis then theories, analysing the qualitative features identical, having the same spin, baryon extended to an SU (6) symmetry in the space of the one--exchange potential number and values (½ and -¼ times SU(3) x SU(2)6 , where o denotes Pauli between quarks. The major topic is the the proton charge). This quark-parton spin. In this framework the charmed quark c and its role in the 'new picture of the hadrons is now generally classifies hadrons according to the product particles', such as the ip/ J and ip' mesons accepted. SU(6) x 0(3). Since Pauli spin is non­ discovered in 1974, and the D and F mesons The quarks are 'point-like' for distances relativistic, this classification cannot refer established subsequently. Quite a detailed down to 10-16 cm, at least, so that they are to a fundamental symmetry; its use today is discussion is given of the bound states of our present-day candidates for the title motivated only by the quark model and is Charmonium (c-c), the 'hydrogen ' of 'elementary particles'. However, quarks for convenience, allowing the systematic the 'new particle' physics; all of its come in a number of kinds, with differing procedures of group theory to be used for properties are well accounted for by QCD, attributes, known as 'flavours'. There are economic calculation and tabulation. In assuming that this can be shown to imply N = 5 flavours established today, the general, the observed hadrons correspond confinement. The heaviness of the c quark corresponding quarks being labelled to mixed representations of SU(6) x 0(3). (about 1.5 proton ) justifies a non­ u,d,s,c and b, in order of , and the The -elements, for the most relativistic Schrodinger treatment and the discovery of further flavours is expected. important transitions, are shown to hyperfine structure of the spectrum arises The experiments also showed that nucleons correspond to the group SU(6)w, so its from the one-gluon-exchange potential. contain neutral objects; these are now algebra is discussed in considerable detail, Electric y-transitions occur between believed to be the quanta of a 'gluon field' making the usual distinction between its S and P states with rates in accord with which binds the quarks and antiquarks into SU(6) for currents and SU(6) for hadron these Schrodinger calculations. The long the hadron. Finally, in order to give the constituents and leading to the general lifetimes of the ip/J and ip' states are due to patterns observed, the Pauli principle Melosh expression for electromagnetic the asymptotic freedom of QCD. The one­ required that each quark have three transition amplitudes. Various selection gluon-exchange potential and the quark possible states, each now labelled by a rules are noted, compared with the data masses are then used to account for all of colour, and each indistinguishable through and analysed to show how they work. For the mass splittings between and within the the hadronic, electromagnetic and weak hadronic decay processes, the transition various charge multiplets observed within 3 we know. This corresponds to 'Vacuum ... P 0(qq)' is introduced, and particular SU(6) x 0(3) mesonic and an exact 'colour symmetry' and we now the resulting amplitudes are related with baryonic supermultiplets. There are also believe that the gluon field may be the SU(6)w- Some review is given of attempts chapters dealing with the 'bag model' for gauge field for 'colour', just as the to include relativistic effects in quark­ hadrons and the possibility of bound field is the gauge field for charge. This model calculations. multiquark systems. The former is entitled is now known as quantum The second part is devoted to partons "Quarks confined to a sphere"; despite its chromodynamics (QCD). It is a tightly and their phenomenology. The notion of very general formulation, the bag model constrained theory, almost unique in form, levels of scaling is introduced, and traced program has been implemented to date and it is the theory at the centre of attention (for inelastic electron scattering) from the only for the case with a rigid spherical bag. today. nuclear to the quark-parton level. The The book closes with gauge theories for Following QCD, elementary particle parton distributions in nucleons are 'grand unification', where quarks and theory is now undergoing rapid changes deduced from the various leptonic deep­ are assigned to common multiplets and our views today differ greatly from inelastic reaction data and discussed in and the lepto-quark gauge fields are

© 1980 Publishing Group 316 Nature Vol. 283 17 January 1980 extraordinarily heavy, with masses of the interactions, violated only by the quark order of 10·10g. These theories mostly mass values. Little is said about 'confine­ Primary imply that the proton should decay ment', the central unresolved question for spontaneously (for example, to e + + n°) QCD; indeed, the book says rather little energy resources and have led to a number of experimental about QCD, beyond implications of the proposals to push up the present limit one-gluon-exchange potentials. The book (t 1030 years) on the proton lifetime. has come too soon to include the recent D.O. Hall This is a book for the quark-model developments in baryon spectroscopy due practitioner. It gives all the prescriptions to Isgur and Karl, which have brought Biological Energy Resources. By M. and rules; they are analysed thoroughly but much order concerning A* and r:;• states. It Slesser and C. Lewis. Pp.192. (E. & F. are not always derived (nor even necessarily would have greater value for students N.Spon: London, 1979.) £8.50. all consistent). It says something about today if it had more about the funda­ every idea current today, although some in mentals and applications of gauge theories, TODAY about one-seventh (or possibly much more detail than others. The book is especially for QCD, since the book would more) of the world's primary energy is somewhat uneven in its treatment, being then have appeared forward-looking; its derived from biomass - this is equivalent strongest and most detailed in the areas present emphasis is on theoretical aspects to 19 million barrels of oil a day (which is where the author's own contributions lie from the past, which may be expected to twice the Saudi Arabian oil production and (photo-excitation of excited and change in the near future. But this is equal to the US daily oil use). However, polarised -hadron interactions). It perhaps the fate of any book in this field of because most of this biomass energy use also has a somewhat dated air, since our physics, where exploration is moving fast; occurs in the developing countries (and picture of elementary has it is easy and unfair to make this judgement there predominantly in rural areas) and been changing rapidly. It is now a general in retrospect. There is no doubt that every because it seldom enters the official belief that the quarks (u,d) are almost physics library should possess this book, statistics, it has, until recently, been massless, whereas most hadron spectro­ for there is much to be found on its pages virtually ignored by planners, politicians scopy still assumes non-relativistic which it is not easy to find elsewhere. D and aid agencies alike. A combination of for the quarks in hadrons. The SU(N) the "energy crisis" and desertification symmetries discussed here are now con­ R.H. Dalitz is Royal Society Research Professor problems has focussed the attention of sidered accidental, the true symmetry being in the Department of at the both developing and developed countries the flavour independence of quark-gluon University of Oxford, UK. on the importance and potential of 'biological energy resources'. This aptly titled book is a must for anyone interested in the basics ofbioenergy The book begins (chapter 1) with a brief and its conversion, and more especially in Chondrocytes description of the morphological and the energetics and economics of biomass and their chemical differences between various types systems. The concepts of energy ratios, net of cartilage. Chapter 2 gives an adequate energy yield, net utilisable energy matrix account of the ultrastructural morphology production, and gross energy requirement of the chondrocyte, the effect of hormones are well presented, and a number of case on the chondrocyte and the antigenicity of studies are thoroughly discussed. It is chondrocytes. Chapter 3 deals with the clearly pointed out that intensification of F.N. Ghadially morphology and of the matrix natural ecosystems for biomass energy components. In this excellent chapter we requires both capital inputs and better Biology of Cartilage Cells. By R.A. are treated to quite a detailed account of management - but local industry, skills Stockwell. Pp.329. (Cambridge University collagen structure and synthesis, elastic and energy self-reliance can be built up. Press: London, New York and Melbourne, fibres and elastogenesis, and the structure Such energy systems are applicable to 1979.) £25. of proteoglycans. However, the varying extents in diverse conditions morphology of proteoglycans (that is, around the world and must be tailored to THIS book is a welcome addition to the matrix particles) is barely discernible in the suit local conditions. literature on cartilage. It is not a book electron micrographs presented. Chapters The chapter on economics of biomass about the chondrocyte only, as the title 4 and 5 deal with the metabolism and systems touches on net present value, might lead one to believe; quite detailed nutrition of chondrocytes. Chapters 6 and energy payback times, and economic accounts of the morphology and chemistry 7 deal with chrondrocyte differentiation costings. It considers some specific of various components of the matrix are and proliferation. The book ends (chapter examples like ethanol production and included as well as other topics such as the 8) with a discourse on degenerative biogas generation, and compares costs nutrition and permeability of cartilage and changes, age - associated changes, and a with other energy sources. These costs are the nature of the articular surface. All this section on calcification in which an up-to­ changing so rapidly it seems imperative to is successfully accomplished in what the date account of matrix vesicles and their update one's analyses and comparisons author modestly refers to as a "short role in cartilage calcification is presented. annually to take account of accelerating book", but the concise style of writing has In summary, this book provides a brief costs. permitted the inclusion of a volume of review of existing knowledge about the It is a good book and very timely. But factual data which one usually associates chondrocyte and surrounding matrix. It is please could authors and/or publishers try with much larger works. The well selected up to date, well written and packed with to list references that can be traced - references and a carefully prepared index factual data. In my opinion this book conference proceedings references are enhance the value of this work. should be of value not only to research useless unless the accurate source is given It is difficult to fault the text in any major workers as suggested by the author, but and organizations who publish booklets, respect. The photomicrographs are rather also to rheumatologists, orthopaedic and so on, have their addresses given. In small in size but of good quality; the same, surgeons and postgraduate students such a rapidly developing field with wide however, cannot be said of the electron (residents) interested in cartilage. sources of interest it is important to be able micrographs, which are of a variable to trace the information. D quality. In contrast to this the line drawings F.N. Ghadially is Professor and Joint-Head of are superb, and the graphs and tables are Pathology at the University of Saskatchewan, D.O. Hall is Professor of Biology at King's well planned and informative. Saskatoon, Saskatchewan. College, University of London, UK.

© 1980 Nature Publishing Group