Archibald W. Hendry

The quark model

The quark model is reviewed in a version which includes three colours and at least five quark flavours. Methods are discussed which are applicable to any number of flavours, provided the underlying symmetry is SU(n). The relation between quark bound states and hadron spectroscopy is discussed, and sum rules are given for baryon magnetic moments and hadron mass splittings. Quark-parton models of high-energy hadron-hadron and lepton-hadron scattering are treated. It is concluded that the quark model has been on the whole very successful in accounting for the properties and interactions of hadrons in a qualitative way.

Ratio of the nucleon structure function F2 for heavy nuclei and free nucleons

Abstract An intuitive nuclear wave function is used to show that the so-called European Muon Collaboration Effect can be accounted for by nucleons having a somewhat larger effective size when bound in nuclear matter than when free. In spite of its crudeness, the same model also gives a not unreasonable nucleon structure function F 2 ( x ) for intermediate x -values.

Dependence on atomic weight of the ratio of the structure function for bound and free nucleons

SummaryWe account for the mainA dependence of the ratio of the structure functionF2 for bound and free nucleons in terms of a model in which bound nucleons have a slightly larger size and smaller effective mass than free nucleons.RiassuntoSi rende conto della dipendenza piú importante dal numero atomicoA del rapporto della funzione di strutturaF2 per nucleoni legati e liberi per mezzo di un modello in cui i nucleoni legati hanno una dimensione leggermente maggiore ed una massa effettiva leggermente inferiore a quelle dei nucleoni liberi.

Decays of high spin Δ∗ and N∗ resonances in the quark model

Starting with a set of harmonic oscillator wavefunctions, we calculate partial decay rates of excited Δ∗ and N∗ states into a nucleon with single pion emission. Good agreement with values estimated from data is obtained for N ≤ 6, thus indicating that the simple quark model is reasonable over a much wider range than expected. The calculated decay rates of the even higher states depend more sensitively on the finer details of the nucleon wavefunction.

Pion-nucleon scattering up to 10 Gev/c

Abstract Pion-nucleon data in the momentum range 1.6 to 10 GeV/c are analyzed. As an intermediate step in the analysis, an impact parameter model, which describes the data primarily in terms of diffractive and peripheral contributions, is used. Many of the resulting partial wave amplitudes show strong resonance-like behavior. The masses, widths and elasticities of resonances with spins j = 7 2 ,…, 21 2 are estimated.

Slopes, coherence and compositeness in high-energy collisions with nuclei

SummaryWe examine some recent data on high-energy collisions in volving nuclei. All the main features can he readily understood in terms of various degrees of coherence among the constituents.RiassuntoSi esaminano dati recenti di collisioni ad alte energie su nuclei. Tutte le principali caratteristiche di tali dati si spiegano agevolmente in funzione dei vari gradi di coerenza fra i costituenti.РЕжУМЕМы ИсслЕДУЕМ НЕкОтОР ыЕ НЕДАВНИЕ ЁкспЕРИМЕНтАльНыЕ Д АННыЕ пО сОУДАРЕНИьМ пРИ ВысО кИх ЁНЕРгИьх с ьДРАМИ. ВсЕ ОсНОВНыЕ хАРАктЕРИс тИкИ сОУДАРЕНИИ МОжНО лЕгкО пОНьть В т ЕРМИНАх РАжлИЧНых ст ЕпЕНЕИ кОгЕРЕНтНОстИ МЕжДУ сОстАВНыМИ ЧАстьМИ.

Structure of A NN ( 90

It is suggested that, just as the differential cross section at 90/sup 0/ for proton-proton elastic scattering oscillates, so does the spin-correlation parameter A/sub N/N at 90/sup 0/. The oscillations appear to be around the quark-model value of 1/3, with a periodicity corresponding to an interaction radius of about 0.8 fm.

On the Veneziano formulation of pion-nucleon scattering

Abstract Igis extension of Venezianos model to pion-nucleon charge-exchange scattering is examined. We find that it is possible to obtain a good fit to the forward scattering data, but are unable to fit simultaneously both forward and backward directions. The uniqueness of the formulae is discussed.

PION PHOTOPRODUCTION UP TO MEDIUM ENERGIES

Abstract Pion photoproduction is studied using the N/D method with pole approximations for the left-hand cuts. The cross-sections arising from the J = 3 2 magnetic and electric dipoles are calculated, and resonances obtained corresponding to the first two photoproduction resonances. The results are strongly dependent on pion-nucleon scattering; various other features are discussed.

Newton's Apple

Isaac Newton may have seen an apple fall, but it was Robert Hooke who had a better idea of where it would land. No one really knows whether or not Isaac Newton actually saw an apple fall in his garden. Supposedly it took place in 1666, but it was a tale he told in his old age more than 60 years later, a time when his memory was failing and his recollections of events did not always match known facts. However, one thing is certain—falling objects were to play a key part in Newtons eventual understanding of how objects move.