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Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1975"


Journal ArticleDOI
TL;DR: In this article, the Zweig rule for meson decays and the decays of the Ψ-resonances are discussed, depending on the various possibilities for the spectrum of the glue mesons.
Abstract: On the basis of the quark-gluon field theory we discuss the dynamical manifestations of gluons in hadron physics. Especially we concentrate on the Zweig rule for meson decays and the decays of the Ψ-resonances. Depending on the various possibilities for the spectrum of the glue mesons, we describe both the glue annihilation and the mixing mechanism for the Zweig-rule-violating meson decays. Furthermore we discuss the break-down of PCAC for the pseudoscalar analogue of the Ψ-meson and the importance of the glue mixing term for the mass spectrum of the pseudoscalar mesons.

209 citations


Journal ArticleDOI
TL;DR: In this paper, an iterative procedure is presented to exactly calculate the two-body distribution function of an infinite fermion system described by a Jastrow wave function of general product form.
Abstract: An iterative procedure is presented to exactly calculate the two-body distribution function of an infinite fermion system described by a Jastrow wave function of general product form. In the approximation of neglecting the elementary diagrams the procedure leads to integral equations which are the analogues of the well-known hypernetted-chain equation for the boson case. Preliminary numerical calculations have been performed for the ground state of nuclear matter using central, hard-core Open image in new window potentials; the results obtained seem to indicate the necessity of using the fermion HNC approximation even at nuclear densities.

156 citations


Journal ArticleDOI
R. Tarrach1
TL;DR: A complete set of independent gauge-invariant and Lorentz-covariant tensors which carry the maximal amount of kinematics and which are either even or odd under the discrete symmetries and crossing is given for virtual-photon scattering off polarized nucleons.
Abstract: A complete set of independent gauge-invariant and Lorentz-covariant tensors which carry the maximal amount of kinematics and which are either even or odd under the discrete symmetries and crossing is given for virtual-photon scattering off polarized nucleons. The remaining kinematics is explicitly shown in the amplitudes. A great variety of different processes of physical interest may be described with this set by taking the adequate limits. The possible connections among these different limits are now open.

114 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the anomalous properties of partial wave amplitudes of the conformal groupOD,2, (D not necessarily integer) in configuration space, and the presence of Euclidean singularities in the Wilson expansion in conformai invariant field theories.
Abstract: Analyticity properties of partial-wave amplitudes of the conformal groupOD,2, (D not necessarily integer) in configuration space are investigated. The presence of Euclidean singularities in the Wilson expansion in conformai invariant field theories is discussed, especially in connection with the program of formulating dynamical bootstrap conditions coming from the requirement of causality. The exceptional case ofD = 2 is discussed in detail.

95 citations


Journal ArticleDOI
TL;DR: In this article, the Coulomb partial-wave series is extended to potentials made up of a Coulomb potential plus an arbitrary short-range part Vs.r(r).
Abstract: An earlier study of the Coulomb partial-wave series and of the connection between screened and unscreened Coulomb potentials is extended to potentials made up of a Coulomb potential plus an arbitrary short-range part Vs.r(r). The partial-wave series for the contribution of Vs.r is shown to converge pointwise, for all θ, provided Vs.r is O(r-3-8) asr → ∞.

72 citations


Journal ArticleDOI
Abstract: Exceptional realizations of the Lorentz group are given via the exceptional Jordan algebra of Jordan, von Neumann and Wigner. The exceptionalSL2,C multiplets generate an intrinsically nonassociative algebra and have built in non-Abelian charge space properties. Considering these multiplets as the basis of a superspace it is shown how to give realizations of exceptional supersymmetry groups which incorporate important charge-space groups in a nontrivial way and which are different from the usual Clifford algebraic supersymmetry groups. Possible applications to the leptonic world are indicated.

65 citations


Journal ArticleDOI
TL;DR: In this article, it is shown that an additional term is required which grows in importance with energy, which corresponds to a singularity atJ = 1 in the complex angular-momentum plane.
Abstract: The experimental data on the charge exchange differential cross-section and on the difference of the π+p and π−p total cross-sections in the rangep L =5 GeV/c to 200 GeV/c are shown to be incompatible with conventional Regge asymptotic behaviour. It is shown that an additional term is required which grows in importance with energy. The precise form of the new term cannot be ascertained, but it is shown that it corresponds to a singularity atJ =1 in the complex-angular-momentum plane. Amongst the possible types of additional term there are two which are aesthetically favoured and which have been closely analysed. These correspond to i) a non-Regge behaviour associated with the maximal growth permitted in axiomatic field theory; ii) a «hyper-Regge» term,i.e. an odd-signatured Regge pole, the analogue of the pomeron pole, with interceptα =1 att =0. Very striking predictions, in particular for the charge exchange polarization, follow as a consequence of the non-Regge or hyper-Regge asymptotic behaviour of the crossing-odd amplitude.

65 citations


Journal ArticleDOI
TL;DR: In this paper, the perturbation theory graphs and divergences in supersymmetric Lagrangian models are studied by using superfield techniques, and it is shown that in superΦ3-theory very little effort is needed to arrive at the single infinite (wave function) renormalization counter-term, while in super Φ4theory the method indicates the counter-Lagrangians needed at the one-loop level and possibly beyond.
Abstract: The perturbation theory graphs and divergences in supersymmetric Lagrangian models are studied by using superfield techniques. In superΦ3-theory very little effort is needed to arrive at the single infinite (wave function) renormalization counter-term, while inΦ4-theory the method indicates the counter-Lagrangians needed at the one-loop level and possibly beyond.

64 citations


Journal ArticleDOI
TL;DR: In this paper, the quantum-mechanical problem of the nonlinear oscillator with the Lagrangian L = 1/2 [x2-k0x2)/(l-λx2] is solved exactly and the energy levels and eigenfunctions are obtained completely.
Abstract: The quantum-mechanical problem of the nonlinear oscillator with the Lagrangian L= 1/2 [x2-k0x2)/(l-λx2)] is solved exactly and the energy levels and eigenfunctions are obtained completely. This model (whenk0=0) is the zero-space-dimensional isoscalar analogue of the nonlinearSU2⊗ SU2 chirally invariant Lagrangian in the Gasiorowicz-Geffen co-ordinates and may also be considered as a modified version of the anharmonic-oscillator and Lee-Zumino models. The bound-state energy levels are found to have a linear dependence on the coupling parameter, in sharp contrast to the case of the familiar oscillator With quartic anharmonicity where the energy, as a function of λ, has complicated singularities at λ = 0. We investigate how far certain standard approximation procedures reproduce the exact results. The Bohr-Sommerfeld quantization procedure is found to reproduce the form of the boundstate energy levels correctly. Interestingly a perturbation-theoretic treatment also reproduces the correct results at least up to the order (λ2) to which we have carried our calculations.

60 citations


Journal ArticleDOI
TL;DR: In this article, the lowest-order massive scalar loop corrections to the graviton propagator were evaluated using the technique of dimensional regularization, and the quantum corrections were then in agreement with the Slavnov-Ward identities.
Abstract: The lowest-order massive scalar loop corrections to the graviton propagator are evaluated using the technique of dimensional regularization. It is shown how to handle a particularly troublesome massive tadpole diagram by adding an appropriate cosmological counter-term. The quantum corrections are then in agreement with the Slavnov-Ward identities. The finite part can be extracted and the divergent part cancelled by suitable generally covariant counter-terms. An extensive comparison is made with previous calculations of the graviton, photon and neutrino one-loop corrections to the graviton propagator. The problem of renormalizability is also discussed.

58 citations


Journal ArticleDOI
TL;DR: In this article, the authors generalize the Maxwell equations in terms of four-potentials for both ordinary and faster-than-light charges, and give a physical meaning to the complex electromagnetic fourpotential.
Abstract: Within « extended relativity » we generalize the Maxwell equations in terms of four-potentials for both ordinary and faster-than-light charges. We succeed in giving a physical meaning to the complex electromagnetic four-potential (and to complex electromagnetic four-current, tensor and field), and in giving a new interpretation to the Cabibbo-Ferrari relation for magnetic monopoles.

Journal ArticleDOI
TL;DR: In this paper, a generalization of low-energy theorems is given to obtain the Compton-scattering amplitude on nuclei up to energies smaller than the excitation of nucleons.
Abstract: A generalization of low-energy theorems is given to obtain the Compton-scattering amplitude on nuclei up to energies smaller than the excitation of nucleons. By means of this technique the presence of seagull terms coming from exchange forces is predicted and the consistency of their contribution is demonstrated in the framework of subtracted dispersion relations.

Journal ArticleDOI
TL;DR: In this article, the energy spectra of light nuclides produced in the interaction of 600 MeV protons on various targets (Be, C, Na, Al, Ca, Fe, Au) have been measured at several laboratory angles (30°, 45°, 75°, 105°) by means of ΔE-E telescopes (semiconductor and scintillator detectors).
Abstract: The energy spectra of light nuclides ( 1 1 H, 1 2 H, 1 3 H, 2 3 He, 2 4 He) produced in the interaction of 600 MeV protons on various targets (Be, C, Na, Al, Ca, Fe, Au) have been measured at several laboratory angles (30°, 45°, 75°, 105°), by means of ΔE-E telescopes (semiconductor and scintillator detectors). The spectra are fitted with calculated curves derived both from a two-step model and a thermodynamical model of the p-nucleus interaction. Two ranges of nuclear temperature are found: the first one (about (20÷30) MeV) describes the high-energy part of the spectra, the second one (a few MeV) describes the low-energy part (de-excitation of the residual nucleus). These fits are used for the integration over energies and angles, which allows the computation of the total cross-sections and of the fragmentation probabilities. These probabilities are necessary for the study of2H and3He production in the propagation of galactic cosmic rays and their interaction with interstellar matter. We find that the 〈CNO〉 contribution for the production of cosmic He nuclei is not negligible and must be added to the4He contribution. The mean interstellar path length is about 4 g·cm−2. The results obtained with Na and Ca targets should present a biophysical interest.

Journal ArticleDOI
TL;DR: In this article, it was shown that under superluminal Lorentz transformations some physical quantities that are real in one frame of reference appear in the other to be imaginary.
Abstract: Some misconceptions concerning tachyons are corrected and it is shown that under superluminal Lorentz transformations some physical quantities that are real in one frame of reference appear in the other to be imaginary. Transfer of electromagnetic radiation between two worlds, each of which judged the other to be composed of tachyon matter, would then cause some of the physical quantities of each world to become complex quantities.

Journal ArticleDOI
TL;DR: In this article, the authors compared the results corresponding to a semi-crystallic structure characterized by correlated density fluctuations of the four spin-isospin nucleon types, with those corresponding to the standard Fermi gas homogeneous and isotropic nuclear-matter structure.
Abstract: Variational computations of the binding energy per particle for various models of nuclear matter are reported The main purpose is to compare the results corresponding to a «semi-crystallic» structure characterized by correlated density fluctuations of the four spin-isospin nucleon types, with those corresponding to the standard «Fermi gas» homogeneous and isotropic nuclear-matter structure It is found that, in some cases, the semicrystallic configuration yields more overall attraction (actually less overall repulsion) than the Fermi-gas case, already at (mean) nuclear densities equal to the central density of ordinary (heavy) nuclei This effect becomes more pronounced at higher (mean) nuclear densities; it can, in most cases, be attributed, at least in part, to the tensor component of the nuclear interaction, that averages to zero in the Fermi-gas case, and yields instead an attractive contribution in configurations with appropriately correlated density fluctuations of the four spin-isospin nucleon states All computations are based on realistic one-boson exchange nucleon-nucleon potentials The correlations associated with the strongly repulsive character of the nucleon-nucleon interaction at short range have not been properly accounted for The results of this paper have therefore no immediate phenomenological implications; whether the effect displayed here is preserved when the repulsive core of the nucleon-nucleon interaction is properly taken into account (both in the computations with and without density fluctuations) remains an open question

Journal ArticleDOI
TL;DR: The variation with energy and with Feynman's variablex of the production of ψ and ψ’ is a sensitive test of their production mechanism as discussed by the authors, and a simple parton model predicts that at relatively low energies production nearx=0 is strongly favored and that the invariant crosssection atx = 0 increases by two orders of magnitude between BNL and ISR energies.
Abstract: The variation with energy and with Feynman’s variablex of the production of ψ and ψ’ is a sensitive test of their production mechanism. A simple parton model predicts that at relatively low energies production nearx=0 is strongly favoured and that the invariant crosssection atx=0 increases by two orders of magnitude between BNL and ISR energies. A sharp increase is also predicted for the ratio of ψ or ψ’ production to the nonresonant lepton pair background.

Journal ArticleDOI
TL;DR: In this paper, the phase shifts obtained from angular distributions have been analyzed in terms of multichannel multilevel R-matrix formalism, and Ambiguities arising from this procedure are discussed.
Abstract: Elastic scattering of alpha-particles from12C has been experimentally studied for16O excitation energies between 9.4 and 14.7 MeV. The phase shifts obtained from angular distributions have been analysed in terms of multichannel multilevelR-matrix formalism. Ambiguities arising from this procedure are discussed.

Journal ArticleDOI
TL;DR: In this article, the α-spectrum is mainly due to the pre-compound emission mechanism, except for the nuclei near lead, where a strong component of direct effect is found.
Abstract: Energy spectra of α-particles emitted under bombardment of (20÷30) MeV protons have been studied in many nuclei of masses ranging from 150 to 210. It is found that the α-spectrum is mainly due to the pre-compound emission mechanism, except for the nuclei near lead, where a strong component of direct effect is found. As the pre-compound emission mechanism here considered assumes the pre-formation of α-like clusters in the target nucleus, the reduction of this effect in nuclei near lead is attributed to a reduction of the α cluster pre-formation coefficient. In the frame of the pre-compound theory, the α cluster pre-formation coefficient is extracted from the absolute values of the reaction cross-section and compared with other results.

Journal ArticleDOI
TL;DR: In this article, it was shown that the fourth-rank vacuum polarization tensor can be built up in general, in terms of seventeen linearly independent explicitly gauge-invariant polynomial tensors.
Abstract: We have shown that expansions for the fourth-rank vacuum polarization tensor for a virtual four-photon system can be built up in general, in terms of seventeen linearly independent explicitly gauge-invariant polynomial tensors. A special choice of the tensor basis corresponds to the one obtained by Karplus and Neuman. We have also dealt with the real four-photon system. An expression for the tensor amplitude which describes this process has been found in general, in terms of five linearly independent manifestly gauge-invariant polynomial tensors. Both in the case of massive and real photons, we have investigated the kinematical singularities of the scalar amplitudes relative to the chosen tensor bases. For the real case we have also obtained the low-energy limits of the helicity amplitudes in the centre-of-mass system. Finally, we have looked for the effective Lagrangian densities related to the helicity amplitudes in the low-energy region.

Journal ArticleDOI
TL;DR: In this article, a relativistic kinetic theory for massless particles is developed in which expressions for the transport coefficients in terms of the cross-section are found for a neutrino gas of temperature T.
Abstract: A relativistic kinetic theory for massless particles is developed in which expressions for the transport coefficients in terms of the cross-section are found. Applied to a neutrino gas of temperatureT one obtains for the heat conductivityλ and the shear viscosityη the expressionsλ=5·1057T−2 andη=9.3·1035T−1 (cgs units). The volume viscosity vanishes.

Journal ArticleDOI
TL;DR: In this article, a Lorentz-covariant quantization of non-Abelian gauge theories is performed by using the canonical formalism, and the Faddeev-Popov ghost is shown to be a consequence of two requirements: i) the vector states describing physical and longitudinal vector mesons should be orthogonal and ii) there should be no transition between physical and unphysical modes.
Abstract: A Lorentz-covariant quantization of non-Abelian gauge theories is performed by using the canonical formalism. The Faddeev-Popov ghost is shown to be a consequence of two requirements: i) the vector states describing physical and longitudinal vector mesons should be orthogonal and ii) there should be no transition between physical and unphysical modes. The Slavnov-Taylor identities are derived. The metric of the vector space is studied.

Journal ArticleDOI
TL;DR: In this article, a technique for constructing Feynman graphs directly from superfields rather than from the constituent fields is presented, using as an example the theory of a scalar multiplet.
Abstract: A technique is presented for constructing Feynman graphs directly from superfields rather than from the constituent fields. Using as an example the theory of a scalar multiplet, we show how such a technique simplifies a discussion of the divergences for multiloop diagrams.

Journal ArticleDOI
TL;DR: In this paper, a more primitive method of measuring the velocity, by means of traps, is described; it is essentially the experimental method, and the connection between momentum and velocity is then derived, for the velocity measured in this way, from the displacement invariance principle.
Abstract: The significance of the energy-momentum conservation laws, as consequences of the general invariance principles, is much enhanced if the momentum, and hence the energy, can be coupled, still by means of the invariance principles, to some directly observable quantity. If the positions of particles can be measured in the quantum-mechanical sense, and if the corresponding operator satisfies the obvious invariance requirements, the velocity can also be ascertained and its relation to the momentum four-vector can easily be derived from the displacement invariances. Serious doubts have been cast, however, on the measurability of the position. Hence, a more primitive method of measuring the velocity, by means of « traps » is described; it is essentially the experimental method. The connection between momentum and velocity is then derived, for the velocity measured in this way, from the displacement invariance principle.

Journal ArticleDOI
C. Peterson1, L. Sollin1
TL;DR: In this paper, high-energy models for πN backward scattering are investigated with respect to consistency with low-energy data using CMSR. But they are restricted to appear in the s-channel physical region.
Abstract: High-energy models for πN backward scattering are investigated with respect to consistency with low-energy data using CMSR. As low-energyt-channel input, ππ phase shifts are used below the KK threshold and narrow-width approximations for higher meson poles. Real parts are restricted to appear in thes-channel physical region. A pole model with a double zero in Nα and a « geometrical delta » model reproduce the data on πN → πN and NN → ππ when the parameters are determined by CMSR.

Journal ArticleDOI
TL;DR: In this article, the authors discuss the consequences of the Bernstein, Dashen and Ma formalism of statistical mechanics concerning the definition of the mass spectrum and the level density for interacting gas.
Abstract: In this paper we discuss some consequences of the Bernstein, Dashen and Ma formalism of statistical mechanics, concerning the definition of the mass spectrum and the level density for interacting gas A recipe for constructing the relativistic level density ofN interacting quantum particles is provided Comparison with the bootstrap equation leads to a dynamical interpretation of the Yellin coefficients

Journal ArticleDOI
TL;DR: In this paper, a quark-diquark model of baryons is generalized to include charmed baryon within the framework of the broken-symmetry groupsSU8 andSU8 ×O3.
Abstract: A quark-diquark model of baryons is generalized to include charmed baryons within the framework of the broken-symmetry groupsSU8 andSU8 ×O3. Mass relations are obtained for the baryons belonging to the lowest-lying level ofSU8, and some qualitative features of the higher levels are given.

Journal ArticleDOI
TL;DR: In this article, the scattering of neutrinos off real or virtual photons is examined in the gauge theories of weak interactions, and finite amplitudes of orderGα are calculated in the fourth-order perturbation for various models.
Abstract: The scattering of neutrinos off real or virtual photons is examined in the gauge theories of weak interactions. Finite amplitudes of orderGα are calculated in the fourth-order perturbation for various models.

Journal ArticleDOI
TL;DR: In this article, it is shown how it is possible to construct a Lagrangian which contains a fundamental length, by selecting a class of motions of the string, which gives rise to a spin tower of zeromass particles.
Abstract: With the aid of the ideas suggested by the string model, the possibility of describing nonhadrons by a geometrical approach is studied. It is shown how it is possible to construct a Lagrangian which contains a fundamental length, by selecting a class of motions of the string. The quantization of the model gives rise to a spin tower of zeromass particles. The interaction among these states is realized in analogy with the theory of Mandelstam for the interacting strings. The vertices for the lower spin states are studied in some detail. It is shown that in order to get the correct electromagnetic and gravitational interactions the fundamental length √α′ must be of the order of 10−33 cm. This choice of √α′ gives a very great value for the three-scalar coupling constant. This fact allows some speculation on the possibility to interpret these scalars as the constituents of the hadrons.

Journal ArticleDOI
TL;DR: In this article, the lowest hyperspherical harmonic was used to find the wave function for the 1−, isospin-3/2 state reached by E1 transitions and the Ballot-Beiner-Fabre wave function was used for the 3He ground state.
Abstract: We use the lowest hyperspherical harmonic to find the wave function for the 1−, isospin-3/2 state reached byE1 transitions. The Ballot-Beiner-Fabre wave function is used for the3He ground state. Our calculated cross-section is in agreement with Fetisov’s measurements of photodisintegration into three nucleons for photon energy from 18 to 85 MeV, but we find too low a cross-section below 18 MeV.

Journal ArticleDOI
TL;DR: In this paper, a nonlinear spinor theory for a 2-component Weyl spinor field with anomalous dimension 1/2 is formulated which is invariant under (local) gauge transformations and the full 15-parameter conformal group.
Abstract: A nonlinear spinor theory for a 2-component Weyl spinor field with anomalous dimension 1/2 is formulated which is invariant under (local) gauge transformations and the full 15-parameter conformal group. In this formulation a first attempt is made to incorporate all recent developments in this context: 1) establishment of gauge invariance without additional vector fields by virtue of bilinear forms of a subcanonical spinor field of dimension 1/2, 2) construction of a canonical framework for the subcanonical spinor field by introducing subsidiary fields and by a corresponding extension of the unphysical state space, 3) verification of conformal invariance in the enlarged framework. The present theory appears, in a certain sense, as a canonical imbedding of a nonlinear spinor theory of the Heisenberg type. In the present formulation the spinor theory can be approached by conventional approximation methods. The lowest Bethe-Salpeter approximation for boson states yields nondivergent results for masses and coupling constants but requires a mass scale which is introduced by the assumption of a dilatation asymmetric vacuum. The theory can be readily generalized to include higher internal symmetries and in this form may be appropriate for a fundamental theory of elementary particles.