Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1994"
TL;DR: In this paper, the systematics of deuteron-like two-meson bound states, deusons, are discussed, including the tensor potential and the deformation of the P-wave.
Abstract: The systematics of deuteronlike two-meson bound states,deusons, is discussed. Previous arguments that many of the present non-\(q\bar q\) states are such states are elaborated including, in particular, the tensor potential. For pseudoscalar states the important observation is made that the centrifugal barrier from theP-wave can be overcome by the 1/r2 and 1/r3 terms of the tensor potential. In the heavy-meson sector one-pion exchange alone is strong enough to form at least deuteronlike\(B\bar B^* \) and\(B^* \bar B^* \) composites bound by approximately 50 MeV, while\(D\bar D^* \) and\(D^* \bar D^* \) states are expected near the threshold.
66 citations
TL;DR: In this article, a ''background blind'' bubble chamber, which is exclusively sensitive to nuclear recoils and which is operated in a quasi-continuous mode, is described for an improved search of dark-matter candidates.
Abstract: A «background blind» bubble chamber, which is exclusively sensitive to nuclear recoils and which is operated in a quasi-continuous mode is described for an improved search of dark-matter candidates. The detection principle is based on the metastability of superheated liquids, which can be tuned such that the detector becomes insensitive to ordinary α, β, γ-radiation.
39 citations
TL;DR: The phase structure of the four-fermion model under the action of an external chromomagnetic fieldH, temperatureT and a chemical potential Μ has been studied in three dimensions as mentioned in this paper.
Abstract: The phase structure of the four-fermion model (1) under the action of an external chromomagnetic fieldH, temperatureT and a chemical potential Μ has been studied in three dimensions. It has been shown that: 1) the conditionsH ⊋ 0,T, Μ = 0 lead unavoidably to a spontaneous breakdown of the chiral invariance; 2) the chiral symmetry can be restored at sufficiently largeT or Μ values. The expressions for the critical temperature and quark mass in the range of large and small external field values have been derived.
33 citations
TL;DR: In this article, evidence for a 50 W anomalous heat production in a hydrogen-loaded nickel rod was reported. But this was not the case for the case of a single rod.
Abstract: SummaryEvidence for a 50 W anomalous heat production in a hydrogen-loaded nickel rod is reported.
31 citations
TL;DR: In this paper, the connection between torsion, a necessary geometrical feature of the space-time when gravity is considered in the realm of elementary-particle physics as, for instance, in the early universe, and some property of string theory is shown.
Abstract: It is shown the connection between torsion, which is a necessary geometrical feature of the space-time when gravity is considered in the realm of elementary-particle physics as, for instance, in the early universe, and some property of string theory. We emphasize also the role of torsion when one tries to quantize the gravitational field, that is to quantize the space-time itself. Finally it is shown that through the time-temperature uncertainty relation it is possible to arrive at the notion of a minimum acceleration that can be important in connection with observations involving galaxies.
26 citations
TL;DR: All theoretical attempts that concentrate only on few-body interactions, both electromagnetic and nuclear, are probably insufficient to explain Pd-hydrides phenomena, and good indications are found that theories describing collective, coherent interactions among elementary constituents leading tomacroscopic quantum-mechanical effects belong to the class of possible theories of those phenomena.
Abstract: We review some of the key facts in the phenomenology of Pd-hydrides usually referred to as «cold fusion». We conclude that all theoretical attempts that concentrate only on few-body interactions, both electromagnetic and nuclear, are probably insufficient to explain such phenomena. On the other hand we find good indications that theories describing collective, coherent interactions among elementary constituents leading tomacroscopic quantum-mechanical effects belong to the class of possible theories of those phenomena.
19 citations
TL;DR: In this article, the excitation functions of α-induced reactions were measured with stacked-foil technique and high-resolution Ge(Li) spectroscopy method for projectile energiesE≤50 MeV.
Abstract: Excitation functions of the reactions181Ta(α,xn) and209Bi(α,xn) have been measured with stacked-foil technique and high-resolution Ge(Li) spectroscopy method for projectile energiesE≤50 MeV. The excitation functions for the production of184Re,183Re,182Re and181Re from α-induced reactions on181Ta;210At and209At from α-induced reactions on209Bi are presented. The α-induced reactions on209Bi were measured for the first time with better accuracy than earlier measurements, which were done with ionization chamber some thirty years ago. The experimental data were compared with theoretical calculations considering equilibrium as well as pre-equilibrium mechanisms according to the hybrid model of Blann. The high-energy part of the excitation functions is dominated by the non-equilibrium reaction mechanism. The initial exciton numbern0=4 (4p 0h) gives fairly good agreement with presently measured results.
18 citations
TL;DR: In this article, relativistic microscopic impulse approximation calculations and Dirac coupled-channel calculations have been performed to analyse cross-sections and analysing powers data for elastic and inelastic scatterings of 800 MeV polarized protons from some low-lying states in 12C and 16O.
Abstract: Dirac microscopic impulse approximation calculations and Dirac coupled-channel calculations have been performed to analyse cross-sections and analysing powers data for elastic and inelastic scatterings of 800 MeV polarized protons from some low-lying states in12C and16O. Fairly good agreement between the relativistic microscopic impulse approximation calculations and the data has been obtained, however somewhat better agreement has been obtained with Dirac coupled-channel collective-model calculations for all these states investigated.
18 citations
TL;DR: In this article, a quasi-potential relativistic equation for two scalar particles of arbitrary masses is presented for the electromagnetic interaction, and the exact solutions are considered in several limits.
Abstract: A novel quasi-potential relativistic equation for two scalar particles of arbitrary masses is presented. The derivation is demonstrated in detail. For the electromagnetic interaction, the equation has the form of the one-particle Schrodinger equation. The interaction is introduced by the minimal substitution. The exact solutions are considered in several limits: non-relativistic, equal masses, one particle at rest and ultrarelativistic. The problem of interaction retardation is discussed.
16 citations
TL;DR: In this paper, the authors present a systematic study and statistically significant results of different types of correlations, in angles, rapidities and rapidity intervals, between various charged secondary particles produced in inelastic interactions of relativistic nuclei with emulsion at (4.1-4.5) GeV/c.
Abstract: We present a systematic study and statistically significant results of different types of correlations, in angles, rapidities and rapidity intervals, between various charged secondary particles produced in inelastic interactions of relativistic nuclei with emulsion at (4.1–4.5) A GeV/c. All types of particles are found to be emitted asymmetrically in the azimuthal plane. This asymmetry increases with the decrease of impact parameter. The two-particle correlation function is found to be positive except in the extreme projectile fragmentation region. Particles from different kinematical regions are emitted back-to-back in the azimuthal plane. A multiparticle correlation is observed between created particles as well as target fragments. This assumes production of clusters. These clusters seem to be formed during the decolouring process. Investigations are being carried out to reveal the characteristics of these clusters.
16 citations
TL;DR: A feasibility study has been carried out for high-precision measurements of two-photon reactions leading to hadrons at the DAΦNE electron-positron collider as mentioned in this paper.
Abstract: A feasibility study has been carried out for high-precision measurements of two-photon reactions leading to hadrons at the DAΦNE electron-positron collider. This new facility will operate at a c.m. energy of 1.02 GeV and up to a maximum of 1.5 GeV. It will have a luminosity ofL⋍5·1032 cm−2s−1, 100 times larger than the present available e+e− colliders. DAΦNE offers an excellent opportunity to study γγ reactions at low energy with high statistics, using the KLOE detector equipped with electron tagging facilities as described in this report. Among the various topics that one may address in these studies, we concentrate on the following: 1) Precision measurements of the polarizabilities of charged and neutral pions via the two-photon reactions γγ→ππ. These will allow tests of chiral theories and chiral perturbation techniques, as well as other theoretical approaches. 2) Measurements for the first time of the azimuthal correlations of the γγ→ππ and other two-photon reactions. These provide new tests of the validity of chiral and other theories. 3) Formation of theC=+1 light pseudoscalar mesons, π0, η and η′. This allows the study of the\(q\bar q\) and possibly gluonic inner structure of these mesons. For the π0 its measured radiative width will also improve the currently known lifetime. 4) The possibility to realize a double tagging at DAΦNE will allow reliable measurements of the currently little known total γγ→hadrons cross-section below 1 GeV, to be compared with several models. The physics program described abovecannot be realized without tagging the two-photon reactions to suppress the background from e+e− annihilation channels and other sources.
TL;DR: In this article, the Paris- and Bonn-B two-nucleon interactions were used to calculate the final p-d scattering state of the proton-deuteron break-up.
Abstract: Electron-induced proton-deuteron break-up of3 He is calculated using solutions of the 3N Faddeev equations for3He and the final p-d scattering state. The Paris- and Bonn-B two-nucleon interactions are employed. We study the importance of final-state interaction effects. Recent NIKHEF data are fairly well described.
TL;DR: In this article, a self-consistent definition of quantum free particle on a generic curved manifold naturally emerges by restricting the dynamics to submanifolds of co-dimension one.
Abstract: A self-consistent definition of quantum free particle on a generic curved manifold naturally emerges by restricting the dynamics to submanifolds of co-dimension one.
TL;DR: In this paper, a review of recent optical experiments is presented, including a discussion on suitable indicators which characterize the different regimes as well as the modelling of the various phenomena, and possible applications to quantum mechanics are sketched.
Abstract: Pattern formation and competition occurs in a non-linear extended dynamical system if dissipation allows for attracting sets, independently of initial conditions. Most reported patterns are still dependent on boundary conditions. This dependency disappears in chemical Turing patterns emerging from reaction-diffusion dynamics. Also in diffraction-diffusion dynamics, as the one ruling an optical field coupled to a polarizable medium, similar phenomena can occur. A review of recent optical experiments is presented, including a discussion on suitable indicators which characterize the different regimes as well as the modelling of the various phenomena. Furthermore possible applications to quantum mechanics are sketched.
TL;DR: The oscillator-like interaction is introduced in the equation for a particle of arbitrary spin, given by Dirac and re-written in matrix form by Dowker as mentioned in this paper, which is the basis for our work.
Abstract: The oscillator-like interaction is introduced in the equation for a particle of arbitrary spin, given by Dirac and re-written in matrix form by Dowker.
TL;DR: In this article, the theoretical predictions of perturbative quantum chromodynamics (QCD) for the quantities R, Rτ and ΓhadronicZ0.34−0.05+0.04 were considered.
Abstract: We consider the theoretical predictions of perturbative quantum chromodynamics (QCD) for the quantities\(R_{e^ + e^ - } \),Rτ and ΓhadronicZ0. Using αs(Mτ)=0.34−0.05+0.04, we find that αs (34 GeV)=0.140−0.008+0.006 in agreement with the value extracted from experiment, αs (34 Gev)=0.148(22), and αs (MZ)=0.119(5), in excellent agreement with the experimental value from LEP, αs(MZ)=0.120(7). We show that using only the above value for αs(Mτ) as input andno free parameters we can predict αs(μ) forMτ⩽μ⩽200 GeV. Our result is in agreement with all known experimental values. Thus it can be seen that αs truly runs, in agreement with perturbative QCD.
TL;DR: In this article, the structure of the hadron spectrum is discussed in connection with the main phenomena of non-perturbative QCD: confinement and chiral symmetry breaking (CSB).
Abstract: The structure of the hadron spectrum is discussed in connection with the main phenomena of non-perturbative QCD: confinement and chiral symmetry breaking (CSB). In the higher part of the spectrum (M⩾2 GeV) spin and chiral effects are unimportant; the spectrum of\(q - \bar q\) system is described by an effective Hamiltonian deduced from QCD. The Hamiltonian reduces to the relativistic quark potential model or to the open string model in two opposite limits. Hybrids are shown to appear naturally in the theory and enter into multiplets which are compared to the experiment and to the bosonic string theory. The phenomenon of conspiracy of the spectrum of radial excited states producing the operator product expansion is discussed. The lower part of the spectrum (M < 2 GeV) is influenced by spin and chiral effects. CSB and the chiral quark mass are deduced for the vacuum containing instantons and confining background. The main points are summarized in the conclusion.
TL;DR: In this article, four models for the pomeron contribution to the forward elastic amplitudes for MN and NN interactions are compared and a very good fit of experimental data is obtained within the framework of Regge approach.
Abstract: Four models for the pomeron contribution to the forward elastic amplitudes for MN and NN interactions are compared. A very good fit of experimental data is obtained within the framework of Regge approach. It is found that available experimental data att = 0 do not seem to indicate a growth of the total cross-sections faster than the first power in logarithm of the energy.
TL;DR: In this paper, the authors discuss scalar mesons, emphasizing those which do not carry manifest flavour quantum numbers and point out the properties of these mesons are still poorly understood.
Abstract: We discuss scalar mesons, emphasizing those which do not carry manifest flavour quantum numbers. The properties of these mesons are still very poorly understood. Some of them probably do not have the usual two-quark (quark-antiquark) structure, but may be mixed with glueball states or other exotics. We discuss simple models for these mesons and point out which measurements can shed light on their composition.
TL;DR: In this paper, different descriptions of the S = 0 particle with oscillator-like interaction are considered and the results are in conformity with the paper of S. Bruce and P. Minning (Nuovo Cimento A,106, 711 (1993)).
Abstract: Different descriptions of theS=0 particle with oscillatorlike interaction are considered. The results are in conformity with the paper of S. Bruce and P. Minning (Nuovo Cimento A,106, 711 (1993)).
TL;DR: In this paper, the main experimental results on some significant physical quantities obtained in He−Li collisions at 45A GeV/c are presented and the experiments have been performed at the Syncrophasotron from JINR Dubna, in the frame of the SKM 200 Collaboration.
Abstract: In this paper the main experimental results on some significant physical quantities obtained in He−Li collisions at 45A GeV/c are presented The experiments have been performed at the Syncrophasotron from JINR Dubna, in the frame of the SKM 200 Collaboration
ENEA1
TL;DR: In this paper, a measurement of gamma-ray spectra emitted after neutron capture ins-andp-wave resonances of53Cr, in the range 2-50 keV, was described.
Abstract: A measurement is described of gamma-ray spectra emitted after neutron capture ins- andp-wave resonances of53Cr, in the range 2–50 keV. The observed decay scheme concerns 38 excited levels of54Cr, with energies up to 5.6 MeV. New information is obtained on the multiplicity of gamma cascades, on the spin and parity of54Cr levels, and on the spin of neutron resonances of53Cr. PartialE1 andM1 radiative widths are obtained for transition energies from 4.1 to 9.7 MeV. The overall energy behaviour ofE1 reduced widths is in rough agreement with a Lorentzian shape, but the average intensity is higher than expected from photo-neutron data. The measured averageE1 strength is =(8.7±±0.8)·10−15, MeV−5. Fluctuations around this average are non-random, showing the existence of an intermediate structure. ReducedE1 widths are strongly correlated with the reduced neutron widths in the whole energy interval. An indication is found for a correlation between reducedE1 widths and spectroscopic factors of54Cr levels. The measured averageM1 strength =(5.9±0.7)·10−9 MeV−3 appears to be energy-independent as in the single-particle model.
TL;DR: A simple model for the idiotypic network among antibodies and its relevance for the maintenance of immunological memory is studied and the problem of computing the memory capacity of such a model is considered.
Abstract: In this paper, after a telegraphic introduction to modern immunology, we present a simple model for the idiotypic network among antibodies and we study its relevance for the maintenance of immunological memory. We also consider the problem of computing the memory capacity of such a model.
TL;DR: In this paper, the pd break-up cross-sections for different kinematically complete configurations have been measured atEplab = 22.7 MeV and compared with predictions of the Argonne AV14, Bonn B, Nijmegen and Paris potentials.
Abstract: The pd break-up cross-sections for different kinematically complete configurations have been measured atEplab = 22.7 MeV. The data are compared with predictions of the Argonne AV14, Bonn B, Nijmegen and Paris potentials. Clear discrepancies between theory and experimental data have been found, which cannot be explained by angular resolutions of the experimental set-up.
TL;DR: In this paper, a measurement of the neutron spin-dependent structure function g1n(x) over a range inx from 0.03 to 0.6 and withQ2>1 (GeV/c)2 are presented.
Abstract: Results from a measurement of the neutron spin-dependent structure functiong1n(x) over a range inx from 0.03 to 0.6 and withQ2>1 (GeV/c)2 are presented. The experiment consisted of scattering a longitudinally polarized electron beam from the Stanford Linear Accelerator off a polarized3He target and detecting scattered electrons in two magnetic spectrometers. The results are interpreted in the quark-parton model and used to test the Bjorken sum rule.
TL;DR: In this paper, the dual superconductor mechanism of confinement for pure SU(2) lattice gauge theory in the maximally Abelian gauge was investigated and the dual Meissner effect was shown to satisfy the dual London equation.
Abstract: We investigate the dual superconductor mechanism of confinement for pureSU(2) lattice gauge theory in the maximally Abelian gauge. We focus on the dual Meissner effect. We find that the transverse distribution of the longitudinal chromoelectric field due to a static quark-antiquark pair satisfies the dual London equation. Moreover we show that the size of the flux tube scales according to asymptotic freedom.
TL;DR: Experiment WA91 searches for non-\(q\bar q\) mesons produced in the central region in the reaction pp→pf(X0)ps at 450 GeV/c using the CERN Omega Spectrometer as discussed by the authors.
Abstract: Experiment WA91 searches for non-\(q\bar q\) mesons produced in the central region in the reaction pp→pf(X0)ps at 450 GeV/c using the CERN Omega Spectrometer. WA91 is a continuation of the WA76 experiment which has studied this reaction using beams of 85 and 300 GeV/c. Preliminary results from experiment WA91 are presented. In particular the X(1450) and X(1900) observed for the first time in the π+π-π+π- channel of the WA76 experiment at 300 GeV/c are confirmed by the WA91 data.
TL;DR: In this article, the authors extended the hyperspherical variables method to the analytical calculation of the angular integral of the box graph and discussed the applications of their results to analytical calculations of the QED contribution to the electrong−2 of the set of three-loop triple-cross vertex graphs.
Abstract: We have extended the hyperspherical variables method to the analytical calculation of the angular integral of the box graph. We discuss the applications of our results to the analytical calculation of the QED contribution to the electrong−2 of the set of three-loop triple-cross vertex graphs.
ENEA1
TL;DR: In this paper, it was shown that the exponential parametrization of the Cabibbo-Kobayashi-Maskawa matrix can be used to derive the elements of the Wolfenstein matrix.
Abstract: It is shown that the exponential parametrization allows the derivation of the elements of the Cabibbo-Kobayashi-Maskawa matrix using a single parameter. The Wolfenstein form is recovered as a particular case of the exponential representation. It is also shown that the method can be straight-forwardly extended to arbitrary quark generations.
TL;DR: The first measurement of the neutron form factors in the timelike region has been produced by studying the e+e-⟹¯¯¯¯¯¯\bar nn\\\\\\\\¯¯¯¯¯¯ reaction at variousE¯¯¯¯c. m. at the ADONE storage ring as discussed by the authors.
Abstract: The first measurement of the neutron form factors in the timelike region has been produced by studying the e+e-⟹
$$\bar nn$$
reaction at variousE
c. m. at the ADONE storage ring. Results at 2.0 GeV and 2.1 GeV, based on the analysis of one third of the data on tape, are reported here.