Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1983"
TL;DR: The correlation between the two leading protons in the range 0.4⩽x < 0.9 is measured to be below ± 1%, at the highest ISR energy as discussed by the authors.
Abstract: The correlations between the two «leading» protons in thex-range 0.4⩽x<0.9 are measured to be below ±1%, at the highest ISR energy.
37 citations
TL;DR: Some QCD-inspired spectral function sum rules are discussed in this article, in view of the most recent experimental results on scalar and pseudoscalar mesons, and estimates of the weak-decay amplitudes of 0− radial excitations, of the current quark mass ratiomg/md and the quark vacuum condensate ratio are performed.
Abstract: Some QCD-inspired spectral function sum rules are discussed, in view of the most recent experimental results on scalar and pseudoscalar mesons. Estimates are performed of the weak-decay amplitudes of 0− radial excitations, of the current quark mass ratiomg/md and of the quark vacuum condensate ratio\(\langle \bar \psi _s \psi _s \rangle /\langle \bar \psi _u \psi _u \rangle \).
35 citations
TL;DR: In this paper, a functional formulation of Euclidean quantum field theory based on a complete equivalence with classical statistical mechanics is described, which allows us to control in a simple way the invariance properties of the integration measure.
Abstract: This paper describes a functional formulation of Euclidean quantum field theory, based on a complete equivalence with classical statistical mechanics. One introduces an extra time variable and sets up a canonical scheme with new Lagrangian and Hamiltonian functions. The generating functional is then defined as the Gibbs average over the ensemble. This allows us, in particular, to control in a simple way the invariance properties of the integration measure. In several cases of physical interest it is seen that the invariance requirement leads to extra determinantal factors in the integration volume and, therefore, to a set of improved Feynman rules. In particular, enforcing dilatation invariance for the generating functional is shown to lead to a nonzero background,i.e. to spontaneous breaking of the symmetry. The application of the method to constrained systems is discussed in detail and in the case of Yang-Mills theories the Faddeev-Popov prescription for quantization is reproduced with remarkable simplicity. A discussion of the functional quantization of gravity is also offered.
26 citations
TL;DR: In this article, the relativistic pair current and contributions of nucleon isobars are evaluated in the constituent quark model and the magnetic form factor of the deuteron and the charge form factors of 3He and 3H are modifed significantly.
Abstract: The relativistic pair current and contributions of nucleon isobars are evaluated in the constituent-quark model Isovector charge and isoscalar current contributions change substantially compared to previous calculations The magnetic form factor of the deuteron and the charge form factors of3He and3H are modifed significantly and the previously predicted large differences in the form factors of3He and3H are considerably reduced
21 citations
TL;DR: In this article, the symmetric quark model with hyperfine interaction is applied to the electromagnetic elastic and transition form factors of low-lying baryons, and the results provide a reasonable and consistent treatment of baryon e.m. properties for not too high q2 values and allow a direct evaluation of two-nucleon current operators.
Abstract: The symmetric quark model with hyperfine interaction is applied to the electromagnetic elastic and transition form factors of low-lying baryons. The results provide a reasonable and consistent treatment of baryon e.m. properties for not too highq2 values and allow a direct evaluation of two-nucleon current operators. However, the model fails in the region in which nucleon structure effects seem to be important for the description of e.m. form factors of light nuclei. An alternative model, based on a three-body quark interaction, is, therefore, proposed.
20 citations
TL;DR: In this article, the relativistic quark model was used to model the radiative decays π→eνγ and K→ eνγ, and the model was extended to the K-decays.
Abstract: We comment about the relativistic quark model approach to the radiative decays π→eνγ and K→eνγ.
19 citations
TL;DR: In this paper, the flux of hadrons with energies greater than 0.7 GeV produced in muon-generated nuclear cascades is estimated for various depths, based on measurements made at a depth of 550 m w.r.t.
Abstract: The flux of hadrons with energies greater than 0.7 GeV produced in muon-generated nuclear cascades is estimated for various depths. The estimation is based on our measurements made at a depth of 550 m w.e. and on the presently available accelerator data. The results show the hadron background to be essential for proton decay experiments up to 8000 m w.e.
17 citations
TL;DR: In this paper, a branching ratio of 3.2±0.8 is derived for the proton electromagnetic form factor at the threshold of the timelike region and a value ofG atq2=3.61 (GeV/c)2 corresponding topp−≃300 MeV/ c is also evaluated with the hypothesis |GE|=|GM|=G, by using e+e− pairs produced byp-p annihilation in flight.
Abstract: In an experiment performed at the CERN PS withp- at rest, 45 collinear e+e− pairs with electron energy >700 MeV have been observed. A branching ratioBee−=Γ(p-p → e+e−)/Γ(pp- total)=(3.2±0.8) · 10−7 is measured. A value of |GE|=|GM|=G=0.51±0.06 is derived for the proton electromagnetic form factor at the threshold of the timelike region. A value ofG atq2=3.61 (GeV/c)2 corresponding topp−≃300 MeV/c is also evaluated with the hypothesis |GE|=|GM|=G, by using e+e− pairs produced byp-p annihilation in flight. In the same experiment 47 acoplanar electron pairs have been observed which can be attributed to the reactionp-p → V0(e+e−)+π0. The analysis of the data supports the existence of 2 heavy vector mesons identified with the ρ′(1250) and ρ″(1600).
14 citations
TL;DR: In this article, it was suggested that the monopole may have a light mass, which gives the possibility to avoid a conflict between cosmology and grand unification theory, and thus avoids the need for a supernova.
Abstract: In this paper, we suggest that the monopole may have a light mass, which gives the possibility to avoid a conflict between cosmology and grand unification theory.
14 citations
TL;DR: Antisymmetry and orthogonality effects in single-particle models of (γ, p) reactions are formally discussed and numerical calculations for the reaction16O(γ,p)15N are presented.
Abstract: Antisymmetry and orthogonality effects in single-particle models of (γ, p) reactions are formally discussed and numerical calculations for the reaction16O(γ, p)15N are presented
13 citations
TL;DR: In this article, the role of mesonic and isobar degrees of freedom in various electromagnetic processes is reviewed for light nuclei, and special emphasis is laid on the deuteron, which allows the cleanest answers within the non-relativistic framework.
Abstract: The role of mesonic and isobar degrees of freedom in various electromagnetic processes is reviewed for light nuclei. Special emphasis is laid on the deuteron, which allows the cleanest answers within the non-relativistic framework. The origin of the photonuclear enhancement with respect to both exchange forces and exchange currents is discussed in detail.
TL;DR: In this paper, the neutrinoless double beta-decay of 76Ge (Jπ = 0+) leading to the first excited state of 76Se was studied and a lower bound of T 1/2 > 2 · 1021 y, at 68% confidence level, has been obtained.
Abstract: We have attempted to look for the neutrinoless double beta-decay of76Ge (Jπ = 0+) leading to the first excited state (Jπ = 2+) of76Se. By using a multicoincidence set-up between a Ge(Li) detector and seven NaI detectors, a lower limitT1/2 > 2 · 1021 y, at 68% confidence level, has been obtained. The current theoretical situation for the76Ge double-beta-decay half-life has been also reviewed.
TL;DR: In this article, the isotopic enrichment induced by laser radiation in flow systems is described, and up to 95.6% of the 13C was obtained by starting from a sample of CF3Br in which the13C was in the natural abundance of 1.12%.
Abstract: Experiments of isotopic enrichment induced by laser radiation in flow systems are described. Quantitative separation up to 95.6% of the13C was obtained by starting from a sample of CF3Br in which the13C was in the natural abundance of 1.12%.
TL;DR: In this paper, the light-quark masses are calculated on the basis of finite energy sum rules and a model for the π-meson radial excitation mass spectrum is proposed.
Abstract: The light-quark masses are calculated on the basis of finiteenergy sum rules. The obtained result (m
u+m
d (1 GeV) ≅20 MeV) allows us to estimate the ratiom
b/m
s≈20 which should be compared with the prediction of theSU
5 model of grand unificationm
b/m
s=17. We estimate a value of the π′-meson residue and propose a model for the π-meson radial excitation mass spectrum. In particular, we obtain a mass of the second π-meson excitationm
π
2
(2)=2m
π′
2
, in agreement with the experimental data.
TL;DR: In this paper, the scaling function F(y) should be defined in terms of a new scaling variabley1 which takes explicitly into account the effects from finite nuclear masses and nucleon binding; in the asymptotic limity1 goes over into the usual scaling variableY0=Mω/q−q/2.
Abstract: y-scaling in quasi-elastic electron scattering from nuclei is discussed paying particular attention to the question of the definition of the scaling variable. By analysing recent experimental data on12C, it is shown that the scaling functionF(y) should be defined in terms of a new scaling variabley1 which takes explicitly into account the effects from finite nuclear masses and nucleon binding; in the asymptotic limity1 goes over into the usual scaling variabley0=Mω/q−q/2. Some open problems concerningy-scaling in3He are also discussed.
TL;DR: In this article, the authors analyzed neutral-pion photoproduction between 1.3 and 2.1 GeV and at four different angles in terms of the four complex amplitudes by using the optimal formalism.
Abstract: Data for neutral-pion photoproduction between 1.3 and 2.1 GeV and at four different angles are analyzed in terms of the four complex amplitudes, by using the optimal formalism. Although the sets of data are incomplete for a complete determination of these amplitudes, with the help of the optimal formalism one can find frames in which the incomplete sets of data yield an accurate determination of most of the amplitude parameters. The results show many interesting features which can be considered as clues toward finding the proper dynamics of such a reaction. Among these features we see evidence that it is possible to find an amplitude formalism in whichall four complex amplitudes determined from the data have the same phase (and hence can all be considered real).
TL;DR: In this paper, the energy shifts of the electronic X-ray lines of the lead isotopes 204, 206, 207 and 208 have been measured with high precision and the theoretical results agree quite well with the measured shifts.
Abstract: Energy shifts of the electronic
$$K_{\alpha _1 } $$
X-ray lines of the lead isotopes 204, 206, 207 and 208 have been measured with high precision. Theoretical values for δ〈r
2〉 and δ〈r
4〉 have been computed in the framework of a microscopic model for a number of lead isotopes. The theoretical results agree quite well with the measured shifts. The present data are compared with previous X-ray shift data, with muonic data, with shifts resulting from a combined evaluation of electron scattering and muonic data and with atomic optical data.
TL;DR: In this article, the reaction mechanism in photoabsorption of light nuclei below pion threshold in the frame of a selfconsistent RPA theory with a Skyrme force was discussed.
Abstract: In the present paper, we discuss the reaction mechanism in photoabsorption of light nuclei below pion threshold in the frame of a self-consistent RPA theory with a Skyrme force. The role of both exchange currents in electromagnetic operators and two-body correlations in the nuclear wave function has been studied in the RPA formalism. Exchange currents in RPA calculations are related to the nucleon effective mass in the Hartree-Fock field. Comparison is made between the RPA formalism and the Gari and Hebach theory. The relative contribution of exchange currents and nuclear correlations to the photoreaction of16O is evaluated from proton threshold up to 80 MeV.E1 andE2 multipoles are included in the calculation.
TL;DR: In this article, the low transverse-momentum region of pions is investigated in interactions of 50 GeV/c π-with nuclear emulsion placed in a strong magnetic field.
Abstract: The low-transverse-momentum region of pions is investigated in interactions of 50 GeV/c π-with nuclear emulsion placed in a strong magnetic field. The existence of a sharp peak in the transverse-momentum distribution of charged secondary pions is explained on the basis of the quark recombination model. This sharp peak in the region ofPT2 ≤ is due to the recombination of quarks and antiquarks from the sea. The atomic-number dependence of thePT2 distribution is also investigated.
TL;DR: In this paper, closed systems of approximate Dyson-Schwinger equations for the gluon propagator are investigated, in which, the simplest Slavnov-Taylor identity is respected.
Abstract: Closed systems of approximate Dyson-Schwinger equations for the gluon propagator are investigated, in which, the simplest Slavnov-Taylor identity is respected. It is rendered plausible that the model of Baker, Ball and Zachariasen, which does yield a confining singularity, cannot consistently dispense with the dependence on the gauge parameter. A spectral model of Delbourgo is shown to violate the Slavnov-Taylor identity in an unacceptable manner. An improved spectral model is in troduced.
TL;DR: In this article, the relativistic theory for few-nucleon systems developed by Giockle and Muller is transformed into the light front formalism, and the 10 generators of the Poincare group are derived in pure particle space up to lowest order in the coupling.
Abstract: The relativistic theory for few-nucleon systems developed by Giockle and Muller is transformed into the light front formalism. For a model of scalar particles exchanging scalar mesons the 10 generators of the Poincare group are derived in pure particle space up to lowest order in the coupling. Because of the impossibility of a complete partial-wave decomposition on the light front, only bound states can be calculated numerically. This is done for the two-body system. The results differ from those at an instant because of the omission of higher-order terms.
TL;DR: A review of recent works on the unified treatment of photoreactions at intermediate energies and quasi-elastic electron scattering is presented in this paper, where the theoretical framework based on the assumption of the direct knock-out is critically presented and some selected results are compared with the data to show the necessity of further investigation.
Abstract: A review is presented of recent works on the unified treatment of photoreactions at intermediate energies and quasi-elastic electron scattering. The theoretical framework based on the assumption of the direct knock-out is critically presented and some selected results are compared with the data to show the necessity of further investigation.
TL;DR: Using DWBA form factors with Tassie transition densities, this paper extracted the electric multipole strength forL≤4 residing in 28 discrete states and in the inelastic continuum below 22.5 MeV of excitation.
Abstract: Inelastic electron scattering of 124 and 180 MeV electrons from58Ni has been measured for momentum transfers of 0.4 fm−1≤q≤1.2 fm−1 with an energy resolution of 110 keV. Using DWBA form factors with Tassie transition densities, we have extracted the electric multipole strength forL≤4 residing in 28 discrete states and in the inelastic continuum below 22.5 MeV of excitation.
TL;DR: The reciprocity principle of Born, when used in the context of the phase-space representation of relativistic quantum mechanics, suggests a Yukawa-like equation whose eigenfunctions properly describe the baryon mass spectrum.
Abstract: The reciprocity principle of Born, when used in the context of the phase-space representation of relativistic quantum mechanics, suggests a Yukawa-like equation whose eigenfunctions properly describe the baryon mass spectrum. Good numerical agreement with experimental data is established by introducing internal SU
3 symmetry, which when broken leads to a satisfactory quantitative description of the well-known linear baryon Regge trajectories.
TL;DR: In this paper, a consistent multidimensional perturbation scheme is investigated in terms of a collective variable, which is a parameter that traces the classical path, and other variables which describe the fluctuations away from this path.
Abstract: The construction of a consistent multidimensional perturbation scheme is investigated in terms of a collective variable, which is a parameter that traces the classical path, and other variables which describe the fluctuations away from this path. The perturbation scheme is considered in the context of classical and quantum mechanics, and the corresponding fluctuation and Schrodinger equations are considered with respect to either a fixed frame of reference or a moving frame which travels along the classical path. The role played byDirac constraints in the canonical transformations is examined. Finally the lowest-order quantum corrections to the classical energy are calculated.
TL;DR: The possibility of using electron cooling in the LEAR ring, operating as a p-p-collider between 0.6 and 2.0 GeV/c, is investigated in this article.
Abstract: The possibility of using electron cooling in the LEAR ring, operating as a p-p- collider between 0.6 and 2.0 GeV/c, is investigated. Cooling times at different energies and expected luminosities are evaluated. The project of an electron source ((100÷700) keV, 10A d.c.,j==5·103 A/m2) with high-efficiency energy recovery is proposed. Problems regarding cathode, optics, beam qualities and diagnostic methods are tackled.
Journal Article•
TL;DR: In this article, the manifestly gauge-invariant Lagrangian of the system in which a real scalar field (matter field) is interacting with itself and Weyl's gauge field is studied.
Abstract: Using the manifestly gauge-invariant Lagrangian of the system in which a real scalar field (matter field) is interacting with itself and Weyl’s gauge field, we study the equations of matter field and Weyl’s gauge field, and discuss the self-interacting term of matter field.
TL;DR: In this paper, a chain-of-partition-labeled approach to N-body scattering is developed, which is based on a natural decomposition of partition interactions into chain elementary components.
Abstract: A new chain-of-partition-labelled approach toN-body scattering is developed, which is based on a natural decomposition of partition interactions into chain elementary components This distribution property only demands an elementary decomposition of the unity In terms of the elementary interactions we introduce elementary chain Hamiltonians and resolvents through standard definitions, and successively we provide dynamical equations without resorting to any recurrence relation or analogical procedure In the present direct attack to theN-body problem a great compactness is achieved, in virtue of the employment of matrix operators defined in the full-chain space Under this unifying perspective we can revisit all the current chain-labelled equations and we find out that they are particular realizations, corresponding to different choices of the unknowns, of a unique simple Lippmann-Schwinger-type structure which emerges from the very beginning in our chain formalism as the basic dynamical law
TL;DR: In this paper, the authors transform the driven-neutron-oscillation problem into a form similar to a magnetic resonance problem in an internal space, and obtain an approximate analytical solution in the neighborhood of the resonances.
Abstract: We transform the driven-neutron-oscillation problem into a form similar to a magnetic-resonance problem in an internal space, and obtain an approximate analytical solution in the neighborhood of the resonances. The results are in good agreement with the numerical work of Arndt, Prasad and Riazuddin. We find that the n probability is quite insensitive to variations in magnetic-field strength and driving frequency when near a resonance maximum, the only critical aspect being the alignment between the static and oscillating fields.