Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1974"
TL;DR: In this article, an unusual perturbation theory anomaly is pointed out in the case of the one-loop neutrino contribution to the graviton propagator and the photon contribution.
Abstract: An unusual perturbation theory anomaly is pointed out. If there exists a trace identity valid in an arbitrary number of dimensions, then employing dimensional regularization can result in an amplitude satisfying the identity in an arbitrary number of dimensions, but the finite part of the amplitude violating it in four dimensions. An example given here is the one-loop neutrino contribution to the graviton propagator. Anomalous behaviour, of a different origin, also occurs in the one-loop photon contribution. Both kinds of anomaly can be removed at the expense of introducingn-dimensional, rather than 4-dimensional, counterterms.
311 citations
TL;DR: In this paper, the authors investigated the possibility that the experimentally determined lifetime τ be different from the theoretical lifetime 1/γ for undisturbed evolution of the unstable quantum system and showed that such a difference, together with a variation of τ with the different experimental set-ups, could be revealed by properly choosing some specific unstable systems and properly devised measuring apparatuses.
Abstract: Within the description of the experimental determination of the decay law recently proposed we investigate the possibility that the experimentally determined lifetime τ be different from the theoretical lifetime 1/γ for undisturbed evolution of the unstable quantum system. It is shown that in some specific examples the deviation of τ from 1/γ is competitive with the accuracy of the experiment. It is made plausible that such a difference, together with a variation of τ with the different experimental set-ups, could be revealed by properly choosing some specific unstable systems and properly devised measuring apparatuses.
106 citations
TL;DR: Conformal covariant Green's functions and operator product expansions for more than two operators are discussed in this paper, and asymptotic expressions derived extension inD-dimensional space-time is studied and the peculiar role ofD=2, both group-theoretically and as connected to infinite-momentum frames, is pointed out.
Abstract: Conformal covariant Green's functions and operator-product expansions for more than two operators are discussed Analyticity properties are investigated and asymptotic expressions derived Extension inD-dimensional space-time is studied and the peculiar role ofD=2, both group-theoretically and as connected to infinite-momentum frames, is pointed out The role of shadow singularities in relation to Euclidean metrics is discussed
97 citations
TL;DR: Anomalous Ward identities arise when the Lagrangian in 2l-dimensional space-time is not invariant under the symmetry transformation in question withl arbitrary as mentioned in this paper, and the anomalous symmetry-breaking terms have associated a factor 2l−4 and disappear at the classical level in four dimensions.
Abstract: Anomalous Ward identities arise when the Lagrangian in 2l-dimensional space-time is not invariant under the symmetry transformation in question withl arbitrary. (The anomalous symmetry-breaking terms have associated a factor 2l–4 and disappear at the classical level in four dimensions.) In particular, the axial anomaly is connected with the chiral breaking due to the fermion kinetic energy and the canonical trace anomaly is a consequence of dilatation non-invariance of any interaction.
78 citations
TL;DR: The picture of Brodsky and Farrar for scattering processes at large transverse momentum is formulated in softened field theory as discussed by the authors, where a modest softening of the quark-quark-gluon vertex is introduced to suppress unwanted logarithm in the formalism.
Abstract: The picture of Brodsky and Farrar for scattering processes at large transverse momentum is formulated in softened field theory. A modest softening of the quark-quark-gluon vertex is introduced to suppress unwanted logarithms in the formalism. It is shown that the electromagnetic form factors of the proton and the pion yield asymptotically behaviours which agree with the result of simple dimensional counting. The threshold behaviours of the deep inelastic structure functions are calculated for the proton and the pion to give ∼ (1 −ω)3 and ∼ (1 −ω)2, respectively. Thus the Drell-Yan-West relation holds in the case of the proton target but is violated in the case of the pion target. It is also proved that the asymptotic behaviours of wide-angel elastic ππ and pp scattering naively predicted by dimensional counting and conjectured by Brodsky and Farrar on the basis of simple Born diagrams are actually the next-to-leading-order terms. The highest-order terms come from a certain set of diagrams that Landshoff studied.
76 citations
TL;DR: In this paper, it was shown that the Hermitian energy operator can be defined in the Hilbert space of continuous L2-functions, and that it is canonically conjugate to the total energy and satisfies the Ehrenfest principle and Galilei invariance.
Abstract: Within aspace-time description of nonrelativistic quantum objects in terms of wave packets, one may simply consider (for every fixed spatial point\(\bar x\): see eq. (5)) the «wave-packets»\(F(t,\bar x) = \int d Ef(E,\bar x)\), that we shall assume to have as weight functions the vectors of the functional spaceP defined as follows. The spaceP is the space of continuousL2-functions i) defined over the (total) energy interval 0
75 citations
TL;DR: In this paper, the antiproton-neutron annihilation cross-section has been determined at 9 values of the antipproton energy together with the differential crosssection dσ/dt for scattering events.
Abstract: About 45000 interactions of antiprotons of kinetic energy between 57 and 170 MeV have been measured in a deuterium bubble chamber. Total and annihilation cross-sections have been determined at 9 values of the antiproton energy together with the differential crosssection dσ/dt for scattering events. In spite of the peculiar behaviour of the deuteron target at these low energies a reliable measure of the antiproton-neutron annihilation cross-section has been obtained.
71 citations
TL;DR: In this paper, a cluster expansion for an infinite system of bosons or fermions is presented together with a diagrammatic representation and simple rules for writing the various terms, and the expansion is shown to be linked and irreducible.
Abstract: A cluster expansion for an infinite system of bosons or fermions is presented together with a diagrammatic representation and simple rules for writing the various terms. The expansion is shown to be linked and irreducible. The explicit expression so obtained is convenient for performing partial summations of terms associated with different orders of the expansion.
66 citations
TL;DR: In this paper, a technique is developed by which general multiloop amplitudes in additive dual-resonance models can be calculated, with spurious states propagating internally in the loops, however the result shows the same automorphic structure as has been found in the Veneziano model.
Abstract: A technique is developed by which general multiloop amplitudes in additive dual-resonance models can be calculated, with spurious states propagating internally in the loops, however The result shows the same automorphic structure as has been found in the Veneziano model The case of the Neveu-Schwarz model is considered in more detail
49 citations
CERN1
TL;DR: In this article, the authors studied the problem of an interacting string and showed that the probability of emission of n photons off the string reproduces the dual amplitude of the conventional model with "photons" as external particles.
Abstract: In this paper we study the problem of an interacting string. In the case of an open string the interaction is introduced by adding in the Lagrangian an additional term which describes the interaction of the string with an external «photonlike» field. The interaction is acting only at the ends of the string to keep the invariance of the Lagrangian under reparametrization. The equation of motion of the string is exactly solved in the case of a monochromatic external field. All the spectrum properties already known in the case of a free string are left unchanged by the interaction. In addition we show that the probability of emission ofn «photons» off the string reproduces the dual amplitude of the conventional model with «photons» as external particles. In the case of a closed string the interaction is obtained by introducing in the free Lagrangian a four-dimensional metric tensorgμν(x) associated with a curved space as in the theory of general relativity. Also in this case the equation of motion of the string in an external «gravitational» field are exactly solved for a monochromatic «graviton» field. All the main features of the Shapiro-Virasoro model are then reproduced starting from this description of a closed string.
43 citations
TL;DR: In this article, the quantum mechanics of the relativistic material point is discussed in the light of some recent ideas developed for the study of the interacting string model, and the interaction among the particles is introduced in a geometrical way, but also show how to interpret such an interaction as due to an external field.
Abstract: The quantum mechanics of the relativistic material point is discussed in the light of some recent ideas, developed for the study of the interacting string model. In accordance with these ideas the interaction among the particles is introduced in a geometrical way, but we also show how to interpret such an interaction as due to an external field. The same considerations are briefly applied to the string model.
TL;DR: In this article, the vertex operators associated with the transverse states of DRM are explicitly written and the couplings of three excited transversal states are explicitly computed, as well as the vertex operator couplings.
Abstract: The vertex operators associated with the transverse states of DRM are explicitly written. As an application of this result the couplings of three excited «transverse» states are explicitly computed.
TL;DR: In this paper, the quantum theory of a neutral scalar field with interactions Lagrangian was studied in the static ultra-local approximation which can be obtained by crossing out the kinematical term in the Hamiltonian.
Abstract: We study the quantum theory of a neutral scalar field with interactions Lagrangian\(g\varphi ^4 \) in the static ultra-local approximation which can be obtained by crossing out the kinematical term in the Hamiltonian. The model is exactly solvable and we study in details the behaviour ofG2(xy) as a function of the coupling constant.
TL;DR: In this article, the (p, n) reaction cross-sections of 51V,56Fe and 65Cu have been measured, for incident-proton energies ranging from 10 to 45 MeV, in steps of 2 MeV.
Abstract: The (p, n) reaction cross-sections of51V,56Fe and65Cu have been measured, for incident-proton energies ranging from 10 to 45 MeV, in steps of 2 MeV. The excitation curves exhibit the usual changes in slope consistent with the expectation that the high-energy tails are mainly due to pre-equilibrium neutron emission. These changes occur for proton energies around 20 MeV, a value in accord with the result previously obtained for reactions of the same type in heavier nuclei. A detailed analysis of the excitation curves has been performed under the hypothesis of incoherent addition of the contributions from compound-nucleus evaporation and pre-equilibrium emission. It is concluded that calculations, based, for the pre-equilibrium contribution, on the exciton model, can give results in satisfactory agreement with the experiment even for nuclei with mass numbers as low asA≃50.
TL;DR: In this article, Lambda and neutral-kaon production is studied in K−p interactions at 3.93 and 14.3 GeV/c, respectively, yielding mainly backward lambdas.
Abstract: Lambda and neutral-kaon production is studied in K−p interactions at 3.93 and 14.3 GeV/c. Topological inclusive cross-sections are given at both energies. Invariant cross-sections for lambdas and neutral kaons are presented as a function of the Feynmanx-variable and are found to decrease in magnitude and vary their shapes with energy. The\(AK\overline K \) production, which represents (9±2)% and (29±3)% of the lambda inclusive cross-section at 3.93 GeV/c and 14.3 GeV/c respectively, yields mainly backward lambdas. The shapes of the transverse-momentum invariant distributions vary withx, but are roughly independent of energy. The lambda polarization is studied as a function ofx at both incident momenta: for fast lambdas it is negative, as observed in reactions where nucleon exchange is dominant.
TL;DR: In this article, it was shown that scalar-meson four-point Green's functions are free of infinities, provided that the scalar mesons do not couple to any fermions in the model and there is no directλϕ4-term in the Lagrangian.
Abstract: In a gauge theory of scalar mesons interacting with gauge vector particles, we show that scalar-meson four-point Green’s functions are free of infinities, provided that i) the scalar mesons do not couple to any fermions in the model and ii) there is no directλϕ4-term in the Lagrangian. The proof relies on a «gauge approximation» technique which systematically exploits the information provided by Ward-Takahashi identities. For non-Abelian gauge theories, the significance of this result is that a large class of scalar multiplets which can induce spontaneous symmetry breaking do not affect the issue of asymptotic freedom. In order to exploit the information of Ward-Takahashi identities we use the «axial gauge», in which there are no fictitious scalar particles and the identities assume their naive form, withZ1 =Z2 for all matter and gauge fields.
TL;DR: In this article, the authors present a systematic comparison of the predictions of the Polya-Eggenberger formula with a new collection of 25 experiments, to be added to the 22 discussed in the first paper.
Abstract: After a short introduction in which we briefly summarize the different motivations which lead so many people to the Polya-Eggenberger formula for multiplicity distributions, we present a systematic comparison of the predictions of the formula with a new collection of 25 experiments, to be added to the 22 discussed in the first paper of this series. The general trend for normal reactions already found is confirmed. The possible description of the\(\bar p\)p data on multiplicity distributions in terms of the same phenomenological formula is also pointed out.
TL;DR: In this article, a spinor field of subcanonical dimension 1/2 appearing as constituent field in a scale and gauge-invariant nonlinear spinor fields theory can be imbedded in a conventional Lagrange field theory with third-order derivatives.
Abstract: A spinor field of subcanonical dimension 1/2 appearing as constituent field in a scale- and gauge-invariant nonlinear spinor field theory can be imbedded in a conventional Lagrange field theory with third-order derivatives. In this framework and by restricting the investigations to the corresponding «free» case the «currents», in particular the current proper, the energy-momentum tensor, the spin tensor and the dilatation current, can be constructed in classical analogy and quantization can be introduced along conventional lines. The theory can be cast into canonical form by introducing two additional spinor fields which are related to first- and second-order derivatives of the original field by Euler equations. The subcanonical spinor field theory appears as a certain projection of the canonical theory which has to be interpreted as a projection on the underlying state space in order to preserve the algebraic relations. The currents and as a consequence their commutators are not uniquely determined by their generator properties. To identify them with physical currents, additional conditions connected with the positive-definite metric of the physical subspace have to be required which single out the formal «Noether currents» of the canonical version of the theory as the only physically acceptable ones. As a consequence the leading singularities of the current commutator on the light-cone are found to agree with those of the Dirac, theory whereas the disconnected part contains a factor of three.
TL;DR: In this paper, a solvable model in four spacetime dimensions is given that has a solution with the following properties: the theory is gauge invariant and this symmetry is spontaneously broken, however there is no massive vector field in the solution.
Abstract: The Higgs model is briefly reviewed and in this model the Goldstone theorem is discussed and the mechanism by which the gauge vector field becomes massive. The properties of the four-momentum and of the metric are studied. In particular it is found that the translations are not unitarily implemented. A solvable model in four spacetime dimensions is given that has a solution with the following properties: the theory is gauge invariant and this symmetry is spontaneously broken, however there is no massive vector field in the solution.
TL;DR: In this paper, threshold photo-and electroproduction of neutral pions off nucleons are analyzed in terms of the higher equal-time commutator, evaluated in the Gell-Mann, Oakes and Renner model.
Abstract: Threshold photo- and electroproduction of neutral pions off nucleons are analysed in terms of the higher equal-time commutator 〈N|[∂
ν
A
ν
,
V
e.m.|N〉, evaluated in the (
$$3,\bar 3$$
)⊕(
$$\bar 3,3$$
) model of Gell-Mann, Oakes and Renner. We discuss in particular the role of the chiral-symmetry-breaking parameters. Comparison with other, independent approaches leads to a size of the « proton-quark » mass consistent with the notion of approximateSU
2×SU
2 symmetry of hadrons.
TL;DR: In this article, spin motion equations in a rotating rest frame in which the particle's velocity and acceleration vectors are instantaneously at rest are derived and used to calculate the corrections due to betatron oscillations to theg - 2 frequency in weak focusing storage devices.
Abstract: Spin motion equations in a rotating rest frame in which the particle’s velocity and acceleration vectors are instantaneously at rest are derived These equations are used to calculate the corrections due to betatron oscillations to theg - 2 frequency in weak focusing storage devices The corrections are found up to second order in the (nonlinear) focusing field Nonresonant and resonant solutions are derived and both magnetic and electric focusing fields are treated Quantitative estimates are also given of depolarization effects near resonance
TL;DR: In this article, a dimension-selecting duality principle for electrodynamics and for relativistic strings is proposed, with the added constraints of general covariance and shock-free wave propagation.
Abstract: We propose a dimension-selecting duality principle for electrodynamics and for hadrodynamics of relativistic strings. Dual theories are identical in formal structure to Maxwell's electrodynamics. Maximal dual systems must be two dimensional, with as their simplest examples all the strings of dual-resonance models. Minimal dual systems are realized by Born-Infeld electrodynamics in four dimensions. From these two infinite classes of theories, the added constraints of general covariance and shock-free wave propagation single out uniquely two exceptional systems. One is the Nambu string, the other is the original Born Lagrangian admitting Nambu-string solutions in its strong-field limit. Our analysis stresses the physics and naturalness of string structures in gauge theories. It leads to a geometro-dynamical interpretation of the duality principle.
TL;DR: In this paper, an exact Gell-Mann-Goldberger (GG) formula for the two-body off-energy-shellt-matrix is derived, and it is explicitly shown that in the case of the Coulomb plus Yamaguchi potential such an extension cannot even be considered as an approximation.
Abstract: An exact Gell-Mann-Goldberger (GG) formula for the two-body off-energy-shellt-matrix is derived. It follows that the simple extension of the matrix elements in the usual on-shell GG formula, which has so far been used in the literature, is not exact. It is explicitly shown that in the case of the Coulomb plus Yamaguchi potential such an extension cannot even be considered as an approximation.
TL;DR: In this article, the momentum-dependent contribution to the one-loop planar and nonplanar amplitudes for both fermions and mesons was calculated in a unified way.
Abstract: Using some recent techniques of Mandelstam for the Neveu-Schwarz-Ramond model we calculate the momentum-dependent contribution to the one-loop planar and nonplanar amplitudes for both fermions and mesons in a unified way and thus obtain a better understanding of previous results, together with some new results on fermion loops.
TL;DR: In this article, the authors studied the behavior of fermion fields which arise as bound states in these theories and proposed a way to incorporate vacuum asymmetries like violation of scale invariance and isospin.
Abstract: Renormalizable field theories of locally coupled fermion fields can be formulated with subcanonical fields. The canonical formulation of theories with subcanonical fields is given. We study the behaviour of gauge fields which arise as bound states in these theories and propose a way to incorporate vacuum asymmetries (and as a consequence more degrees of freedom for low energies) like violation of scale invariance and isospin.
TL;DR: In this paper, the cross-sections of quasi-two-body reactions produced in K−proton interactions at 13 different energies in the centre-of-mass energy range 1.915 to 2.168 GeV were given.
Abstract: We give the cross-sections of quasi-two-body reactions produced in K−-proton interactions at 13 different energies in the centreof-mass energy range 1.915 to 2.168 GeV.
TL;DR: In this paper, the problem of representing scattering data given on the boundary of the analyticity domain by analytic functions satisfying unitarity is investigated, and the optimal representation inL2-norm is shown to be the solution of a constrained convex optimization problem in some Hilbert space of analytic functions.
Abstract: The problem of representing scattering data given on the boundary of the analyticity domain by analytic functions satisfying unitarity is investigated. The optimal representation inL2-norm is shown to be the solution of a constrained convex optimization problem in some Hilbert space of analytic functions. A duality optimization theorem based on the generalized Lagrange multiplier technique is applied for solving this problem. The method is found to easily accommodate unequal errors on the real and imaginary parts of the amplitude and the case of data given along a limited part of the boundary.
TL;DR: In this article, the authors measured the cross-section of the double charge exchange with a high-pressure helium streamer chamber triggered by a scintillation counter hodoscope.
Abstract: The cross-section for the\(\pi ^ + + ^4 He \to \pi ^ - + 4p\) reaction has been measured with a high-pressure helium streamer chamber triggered by a scintillation counter hodoscope. Measurements were made for angles between 25° and 165°. Supposing the angular distribution of the secondary meson to be isotropic, we obtained the following total cross-section for the double charge exchange:\(\sigma _{tot} = \left( {0.30 \pm 0.15} \right) \cdot 10^{ - 27} cm^2 \). The obtained value turned out to be somewhat smaller than expected from calculations using the pair correlation model.
TL;DR: In this article, it was shown how the Thirring model with its anomalies can be treated by dimensional regularization, and the model was shown to be a regularization model for the regularization problem.
Abstract: It is shown how the Thirring model with its anomalies can be treated by dimensional regularization.
TL;DR: In this paper, Lagrangian theories involving higher-order derivatives are reconsidered and conservation laws derived according to Noether and Bessel-Hagen are stated in a compact form.
Abstract: Lagrangian theories involving higher-order derivatives are reconsidered. Such theories appear of great interest as an imbedding for field theories with fields of subcanonical dimension, likee.g. the Heisenberg nonlinear spinor theory, for which local interactions are less singular than in the canonical case. The conservation laws derived according to Noether and Bessel-Hagen are stated in a compact form. Quantization is introduced without making use of the canonical formalism.