Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1982"

Multiquark scattering and large- p T jet production in hadronic collisions

Abstract: The role of multiple quark scattering subprocesses in large-pT jet production from high-energy hadron-hadron collisions is discussed. In particular, the connection with multiconstituent distributions is emphasized.

On the shape of tachyons

Abstract: We study some aspects of the experimental behaviour of tachyons, in particular by finding out their « apparent » shape. A Superluminal particle, which in its own rest frame is spherical or ellipsoidal (and with an infinite lifetime), would « appear » to a laboratory frame as occupying the whole region of space bound by a double cone and a twosheeted hyperboloid. Such a structure (the tachyon « shape ») rigidly travels with the speed of the tachyon. However, if the Superluminal particle has a finite lifetimein its rest frame, then in the laboratory frame it gets afinite space extension. As a by-product, we are able to interpret physically the imaginary units entering—as is well known—the transverse co-ordinates in the Superluminal Lorentz transformations. The various particular or limiting cases of the tachyon shape are thoroughly considered. Finally, some brief considerations concerning possible experiments to look for tachyons are added.

Massless second-order tetradic spin-3 and higher-helicity bosons

Abstract: The unique, uniform, second-order formulation of massless bosons of helicity ≥3 is presented here in terms of tetradic fields. The actions we find are shown to coincide both with the first-order (tetradic) formulation of Vasiliev and with the symmetric second-order description of Fronsdal. We carefully analyse the gravitational coupling of the spin-3 field and find that tetradic spin-3 matter presents the same translational consistency problem as symmetric matter does. Further, in the curved tetradic case the generalized Lorentz invariance can be restored by the addition of nonminimal terms.

Detailed investigation on 800 TeV jet interaction

Abstract: A gamma-ray family JF1af1 with energy of ΣEγ∼260 TeV was observed in the emulsion chamber on board the Super Sonic Concorde. By using the geometrical method, it was found that the interaction vertex was located within the surroundings of the Concorde. The large slant distance 3.24−0.28+0.40 m enabled one successfully to separate the shower cores generated by even highest-energy gamma-rays in the forward region. The event showed the characteristic features of a very-high-energy interaction: high multiplicity ∼150, high gamma-ray density in rapidity scale ∼50 and presence of a high transverse-momentum component with =0.60−1.10+0.12 GeV/c having frequency of one tenth of the total. Comparisons were made with other extremely-high-multiplicity events observed so far at high energies.

Contractions of Group Representations. 3.

Abstract: SummaryWe illustrate in this paper the technique of contracted representations, introduced in two previous papers, by which the representations of non-semi-simple Lie groups can be constructed in a simpler way than by means of the usual technique of induced representations. As relevant examples, we obtain the representations of the Poincaré group, of the extended Galilei group and of the harmonic-oscillator group.RiassuntoCon l’illustrazione di alcune applicazioni, si conclude con questo articolo la presentazione della tecnica delle rappresentazioni contratte, alternativa alla tecnica delle rappresentazioni indotte per ottenere le rappresentazioni dei gruppi di Lie non semisemplici. Si ricavano dalle rappresentazioni dei gruppi pseudo ortogonali quelle dei gruppi di Poincaré, di Galileo esteso e dell’oscillatore armonico.РезюмеВ этой работе демонст рируется техника сокращенных предста влений, разработанна я в предыдущей статье, с помощью которой пре дставлен предыдущей статье, с п омощью которой предс тавления не полу-прос тьых груии Ли могут бы ть сконструированы б олее просто, чем с помо щью обычной техники полу-простьых груии Л и могут быть сконстру ированы более просто, чем с помощью обычной техники приведенных представлений. Мы пол учаем представления группы Пуанкаре, прот яженной группы Галил ея и гру более просто, чем с пом ощью обычной техники приведенных предста влений. Мы получаем пр едставления группы П уанкаре, протяженной группы Галилея и груп пы гармонического ос циллятора. приведенных предста влений. Мы получаем пр едставления группы П уанкаре, протяженной группы Галилея и груп пы гармонического ос циллятора. группы Пуанкаре, прот яженной группы Галил ея и группы гармониче ского осциллятора. гармонического осци ллятора.

Observation of the decay η → π0γγ

Abstract: The rare radiative decay η → π0γγ has been effectively observed and studied at the 70 GeV IHEP accelerator with the hodoscope spectrometer GAMS-2000. The branching ratio for this decay is found to be Br(η → π0γγ) = (9.5 ± 2.3)-10-4.

BBS algebra of theSU2/1 electroweak ghost-gauge theory

Abstract: We review the status and predictions of the SU2/1 model of electroweak interactions. We then construct an extended BRS algebra of the ghost-antighost symmetric type, including an ‘ anti-BRS ’ operator, as introduced by Curci and Ferrari and by Ojima. The algebra is closed and completely geometrical. It corresponds to the structural equation of a P2(M, G x G) double bundle. The grading by ghost number and the natural grading of the supergroup are combined (the ‘ fork ’ mechanism) so as to ensure that only ghost-charged states be endowed with wrong statistics. The theory predicts a single isospinor Higgs-Goldstone scalar, precisely fitting the minimal standard model.

Orthodoxvs. unorthodoxB\bar B widths of diquoniumswidths of diquoniums

Abstract: The quantitative status of the $$B\bar B$$ widths of true diquoniums as predicted by various models is critically analysed. It is shown that—contrary to a recent claim—unorthodox values of ≃10 MeV for the $${\mathcal{N}}\bar {\mathcal{N}}$$ widths remain the most plausible ones in the framework of the3 P 0 model.

Glueballs' masses in the bag model

Abstract: The masses of low-lying glueballs with quantum numbersJPC=0++ andJPC=0−+ are calculated within the framework of the MIT bag model.

Experimental study on the elastic-scattering processes of muonic hydrogen and deuterium against protons and deuterons

Abstract: We have measured the elastic-scattering cross-sections of muonic hydrogen and deuterium atoms against protons and deuterons, respectively. The results are δdd = (8.0 ± 2.0).10-20 cm2 (referring to μp atoms in the singlet state) and δpp = (1.49 ± 0.14).10-20 cm2. For (μp)1s atoms formed in gaseous hydrogen, renewed predictions are given on the lifetime τT of the triplet states as a function of pressure.

The structure of strong interactions in anisotropic chromodynamics@@@Структура сильных взаимодействий в анизотропной хромодинамикс: II. - The meson spectrum@@@II: Мезонный спектр

Abstract: SummaryWe have applied anisotropic chromodynamics (ACD) to a calculation of the first approximation of the meson ( % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWexLMBb50ujb% qeguuDJXwAKbacfaGae8xCaeNaf8xCaeNbaebaaaa!3DB9! $$q\bar q$$ spectrum. We show that ACD affords a consistent and remarkably successful description of this spectrum in terms of 5 parameters only: 4 quark masses and the « string tension » µ. We can clearly delineate which higher-order effects should act, and how, in order to produce a systematic and accurate account of the parameters of all known mesons including their decay properties.RiassuntoSiè applicata la cromodinamica anisotropa (ACD) al calcolo della prima approssimazione allo spettro dei mesoni (stati % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWexLMBb50ujb% qeguuDJXwAKbacfaGae8xCaeNaf8xCaeNbaebaaaa!3DB9! $$q\bar q$$ ). Si mostra che 1’ACD produce una descizione dello spettro estremamente accurata con un numero di parametri minimo: 4 masse dei quark e una « tensione della corda » μ. Siè pure in grado di delineare quali siano gli ordini di approssimazione e in ehe modo essi potranno, in una fase successiva del calcolo, portare ad un perfetto accordo sperimentale.РезюмеМы используем анизотропную хромодинамику для вычисления мезонного спектра в первом приближении. Мы показываем, что анизотропная хромодинамика позволяет согласованно и довольно успешно описать такой спектр в терминах только пяти параметров: четырех масс кварков и «натяжения струны» μ. Мы можем обрисовать, как включить эффекты более высоких порядков и как произвести систематический и точный учет параметров для всех известных мезонов, включая их свойства распада.

Central heavy-ion collisions with emulsion at 4.2 GeV/c per incident nucleon

Abstract: Multiplicity and angular distributions of particles produced in central collisions between12C ions and emulsion nuclei were studied at momentum 4.2 GeV/c per incident nucleon. The investigated data represent the most central collisions which had ever been studied yet. Events of central collisions are defined, here, as those having no projectile charged fragments, even a singly charged one, emitted within 3° of the beam direction. The analysis of the experimental data shows agreement with the limiting-fragmentation hypothesis. The multiple production of particles in central collisions is not in disagreement with the assumption of a superposition of nucleon-nucleon collisions. The angular distributions of target fragmentation particles, grey and black particle tracks corresponding to proton kinetic energies 27

Induced quantum gravity from heat kernel expansion

Abstract: The asymptotic expansion of the heat kernel is employed to derive the Einstein action from the matter effective action. The advantages of this approach are discussed. We point out some problems arising when scalar fields, nonminimally coupled to the background geometry, are used as fundamental pregeometric objects.

Measurement of\((D^ + \bar D)\) charm meson pair production in (pp) interactions at √s=62 GeV.charm meson pair production in (pp) interactions at √s=62 GeV.

Abstract: The charm meson D+ is observed in (pp) interactions at 62 GeV centre-of-mass energy, in association with its antimeson, D− or\(\bar D^o \). The cross-section for\((D^ + \bar D)\) pair production is evaluated according to various hypotheses on the production mechanisms. The value of the cross-section is found to be ∼300 μb when both the D+ and the\(\bar D\) are assumed to be «centrally» produced.

A detailed study of vs. E had andm 1,2 at different $$\left( {\sqrt 8 } \right)_{pp} $$ in (pp) interactionsin (pp) interactions

Abstract: By using (pp) interactions at three different c.m. energies,\(\left( {\sqrt 8 } \right)_{pp} \)=30, 44, 62 GeV, it is shown that the average charged-particle multiplicity vs. the invariant mass of the hadronic systemm1,2 has the same behaviour as it hasvs. 2Ehad. Moreover, in both cases is shown to be nearly independent of\(\left( {\sqrt 8 } \right)_{pp} \) and in good agreement with the average charged-particle multiplicity measured in the (e+e−) annihilation.

The inclusive momentum distribution in (pp) reactions, compared with low-energy (e+e−) data in the range$$\left( {\sqrt s } \right)_{e^ + e^ - } = (3.0 \div 7.8) GeV$$

Abstract: By using the method of removing the leading protons, the inclusive fractional-momentum distributions of particles produced in low-pT (pp) interactions have been measured for effective hadronic energies,Ehad, available for particle production, in the range corresponding to the very low (e+e−) c.m. energies\(\left( {\sqrt s } \right)_{e^ + e^ - } = (3.0 \div 7.8) GeV\). The results are in good agreement with (e+e−) data. This shows that the similarity with (e+e−), already found at higherEhad, extends to the lowest energy range in (e+e−). The experiment was performed at (√s)pp=30 GeV, in the CERN Intersecting Storage Rings, by using the Split-Field Magnet Facility.

The structure of strong interactions in anisotropic chromodynamics

Abstract: We discuss the structure of strong interactions emerging from quark-confining anisotropic chromodynamics (ACD). We show that i) the finite-energy states (the hadrons) are described by quarks, arranged in colour singlets, and moving in linear configurations; ii) a natural perturbative structure emerges which fully supports the ideas of the quark model; and iii) the meson\((q\bar q)\) spectrum is given by a Schrodinger-like equation with relativistic kinematics and a «potential» increasing linearly with the relative distance.

A Lagrangian approach to the no-interaction theorem

Abstract: A proof of the no-interaction theorem is given in the framework of Lagrangian mechanics. It appears to be simpler than the proofs in the framework of Hamiltonian mechanics.

Surface waves in α-nuclei elastic scattering

Abstract: We develop in detail a theory of surface waves, excited by the grazing rays in the elastic scattering of α-particles on nuclei, working within the framework of the short-wave-length approximation. The nuclearinteraction region is schematized as an absorbing sphere surrounded by a nearly transparent shell: the surface waves, which are excited at the edge of the interaction region and propagate along it, can take one or more shortcuts. In this way we can explain the large-angle elastic scattering of α-particles on16O,28Si and40Ca from ∼ 20 to ∼ 60 MeV. Indeed the theory is tested by fitting the differential cross-sections of these scattering processes. The nuclear-interaction radii can be extracted from our phenomenological analysis.

Exactly solvable model of relativistic wave equations and meson spectra

Abstract: The Kemmer-Fermi-Yang bound-state equation, which is an equal-time relativistic wave equation for a two-body system of Dirac particles, is solved exactly for the case in which the potential is of squarewell type. Energy eigenvalue equations for a quark-antiquark system with normalJP (JP=0+, 1−, 2+,…) and abnormalJP (JP=0−, 1+, 2−,…) are derived. Meson spectra are studied as functions of the quark mass. In particular, the mixing between normal-JP states withL=J−1 andL=J+1 is studied in detail. It is pointed out that there may be large mixing between3(J−1)J and3(J+1)J in light normal-JP mesons. And it is also demonstrated that the lowest trajectory is not always the same one in the large-quark-mass limit and in the small-quark-mass limit.

Dynamical unification of fermions and gauge bosons for internal symmetry and gravity

Abstract: Internal-symmetry gauge bosons and the tetrad fields of gravity with their respective nontrivial local transformation behaviour are constructed by more basic gauge fermions A physically sensible mass scale Λ2 for a parametrization for the small-distance behaviour of the theory is closely related to Newton’s and Sommerfeld’s constants Local invariances determine uniquely the renormalizable gauge fermion self-interactions The very quantization can be interpreted as a dynamical breakdown of a local spin rotation invariance and leads to spin-spin four-fennion interaction in a dynamical Higgs mechanism

Indecomposable representations ofA 2 (su 3 ,su 2,1 ) and representations induced by them

Abstract: Indecomposable representations are investigated for the case of the simple complex Lie algebraA2 (the complexification ofsu3 andsu2,1). The matrix elements are explicitly determined for the elementary representations, and the extremal vectors which characterize invariant subspaces are given in explicit form. Quotient spaces are used to derive other representations from the elementary representations, including the finite-dimensional irreducible representations, the infinite-dimensional irreducible representations which are bounded above, as well as new types of indecomposable representations. Again, the matrix elements for these representations are given in explicit form. In the appendix the same program is carried out for the simple complex lie algebraA1 (the complexification ofsu2 andsu1,1) as an example. The branching of the elementary representations, as well as of the representations derived from the elementary representations, is analyzed with respect to two subalgebras of the typeA1. Again, theA1 extremal vectors are obtained in explicit form.

Experimental study of polarization in the reaction\bar pp \to \bar pp at 0.7 GeV/cat 0.7 GeV/c

Abstract: The polarization for the\(\bar pp\) elastic scattering was measured as a function of the centre-of-mass angle of scattering between 17° and 90° at the average incident momentum of 0.7 GeV/c by using doublescattering events in a bubble chamber. The average value of the polarization was found to be 0.23 ± 0.05. The angular dependence of the polarization obtained in this experiment was interpreted by the strong absorptive potential model for\(\bar {\mathcal{N}}{\mathcal{N}}\) interactions recently proposed.

Baryon and Lepton Nonconservation in Supersymmetric Models

Abstract: The possible baryon- and lepton-nonconserving effective interactions among ordinary particles are analysed in the frame ofSU 3×SU2×U1supersymmetric models. Operators of lower dimensionalities than in ordinary GUTs are generally allowed in the supersymmetric schemes of Dimopoulos and Georgi type, in which a discrete symmetry is imposed to guaranteeB andL conservation in renormalizable terms. Operators of the same dimensionalities as in GUTs are obtained, instead, in the schemes of the type considered by Weinberg and by Sakai and Yanagida, where eitherR-invariance or an extraU 1 gauge factor is assumed. However, the different terms lead in most cases, with the exception of the ΔB=ΔL proton decay, to unobservable rates for physical processes, unless Higgs supermultiplets are introduced at an intermediate mass scale.

Curvature and symmetry breaking: An induced-action approach

Abstract: We recover the general form of the one-loop effective potential for aλφ4 theory, nonminimally coupled to a constant-curvature background geometry, in the low-energy limit,i.e. for small curvature. Renormalization is carried out and the massless limit of the renormalized theory is performed. Then we study the symmetry properties of the vacuum state according to the value of the nonminimal coupling constant ξ and the sign of the curvature.

Time-of-flight telescope for mass identification of heavy ions

Abstract: A time-of-flight telescope, employing microchannel plate electron multipliers as start detector and a silicon surface barrier as stop detector, is presented. The measured intrinsic time resolution is 160 ps FWHM for262Cf α-particles and 235 ps FWHM for252Cf fission fragments selected in the energy rangeE = (79÷80) MeV. The contribution of each fragment mass is estimated to be 120 ps. The measured detection efficiencies are ≿95%, depending on ion masses.

A new measurement of the muon transfer rate from muonic hydrogen to argon

Abstract: We have studied the transfer reaction μp+Ar→μAr*+p occurring in gases (P=(2÷4) atm). The transfer rate has been measured by detecting theX-rays from the electromagnetic cascade of μAr*. We obtain\(\Lambda _{1S}^{{\rm A}r} = \left( {3.67 \pm 0.72} \right) \cdot 10^{ - 11} s^{ - 1} \), in agreement with previous measurements performed with the same technique.

Experimental study on low-energy2H(α, α)2H elastic scattering

Abstract: A series of differential cross-sections of α-d elastic scattering was measured, in small energy steps betweenE α L =6 and 14 MeV, and analysed in terms of the phase-shift formalism. The theoretical prediction following from Faddeev-type calculations was compared with the present data. A multichannel multilevelR-matrix analysis was then performed with special emphasis on the 2+ and 1+ levels of6Li; the dependence of the level parameters on the boundary conditions was investigated. The role of the α-d tensor interaction was found to be much smaller than theoretically estimated.

Saturation of the Froissart bound by crossing symmetric and unitary amplitudes

Abstract: A class of amplitudes is constructed that saturates the Froissart bound and satisfies crossing symmetry and all inelastic unitarity inequalities.