Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1973"
TL;DR: In this paper, a version of an equation derived by Ersak was studied to obtain rigorous bounds on the rate of change of the integrity of a normalized state, and the bounds were shown to be tight.
Abstract: A version of an equation derived by Ersak is studied to obtain rigorous bounds on the rate of change of the integrity of a normalized state.
198 citations
TL;DR: In this paper, a new PCAC law was proposed to identify axial vectors and pseudoscalars as antisymmetric 3-component and 4-component tensors in space-time of arbitrary dimensions.
Abstract: Identifying axial vectors and pseudoscalars as antisymmetric 3-component and 4-component tensors in space-time of arbitrary dimensions, we discover a new PCAC law:\(\partial [_{K\bar \psi } \Gamma _L \Gamma _M \Gamma _{N]} = \)\( = 2mi\bar \psi \Gamma _{[K} \Gamma _L \Gamma _M \Gamma _{N]} \psi - \frac{1}{5}i\bar \psi (\overleftrightarrow {i\partial }^J + 2eA^J )\Gamma _{[J} \Gamma _K \Gamma _L \Gamma _M \Gamma _{N]} \psi = \), where the extra term on the right-hand side does not exist in 4 dimensions. However, when we do descend to 4 dimensions after dimensional regularization it is precisely the axial vector anomaly. In a parallel calculation we have also shown how to obtain the anomaly in the matrix elements of the trace of the stress tensor.
164 citations
TL;DR: In this article, it was shown that the decay law is exponential and that the measurement process is a localization of the decay products and that, consequently, the unstable system is reduced to a unique quantum state.
Abstract: By assuming that in every actual decay process the unstable system is subject to repeated processes of measurement which ascertain whether the system is decayed or not, we prove that the decay law is exponential, obtaining a consistent reconciliation of the quantum and the classical statistical descriptions of decay experiments. We also show that the measurement process is a localization of the decay products and that, consequently, the unstable system is reduced to a unique quantum state. We are able to give, within the framework of ordinary quantum mechanics, a natural definition of the wave function of the unstable system.
80 citations
TL;DR: In this article, a generalized sigma model is proposed for the axial current divergence of the free spinor Lagrangian, where the divergence is converted into the sum of two distinct pion fields, and the first pion field couples with the fermion and the second pion couples through the anomalous kinetic energy interaction.
Abstract: In a space-time of arbitrary even dimension neither the mass term nor the kinetic-energy term of the free spinor Lagrangian is chirally invariant. We construct a generalized sigma-model whereby the divergence of the axial current is converted into the sum of two distinct pion fields. The first pion couples in the conventional manner with the fermion whereas the second pion couples through the anomalous kineticenergy interaction
$$\bar \psi \overleftrightarrow \partial ^J \Gamma _{[J} \Gamma _K \Gamma _L \Gamma _M \Gamma _{N]} \tau \psi $$
. This second coupling disappears from all tree graphs as we descend to four dimensions, but through closed fermion loops is responsible for all the anomalous meson interactions. The 〈AAA〉 and 〈VAAA〉 anomalies are thereby calculated in terms of the 〈VVA〉 anomaly.
72 citations
TL;DR: An optical spark-chamber counter experiment at Adone, the Italian colliding electron-positron ring, has succeeded in measuring the cross-section for the process e+e−→p\(\bar p) near threshold as mentioned in this paper.
Abstract: An optical spark-chamber counter experiment at Adone, the Italian colliding electron-positron ring, has succeeded in measuring the cross-section for the process e+e−→p\(\bar p\) near threshold (Ec.m.=2.1 GeV). The result isσ(e+e−→p\(\bar p\))=(0.91±0.22) nb.
63 citations
TL;DR: An underground experiment where a Ge(Li) diode is used both as source and as detector of the lepton nonconserving neutrinoless ββ decay of76Ge is reported in this paper.
Abstract: An underground experiment where a Ge(Li) diode is used both as source and as detector of the lepton nonconserving neutrinoless ββ decay of76Ge is reported A 685 cm3 active volume Ge(Li) heavily shielded against local radioactivity has been operated for about 4400 h of effective running time in a laboratory situated in the Mont Blanc tunnel (4200 m of water equivalent) No evidence for neutrinoless decay was found with an upper limit on the lifetime of τ0v>5·1021 years at 68% confidence level This result, together with those of other experiments on different nuclei, is discussed in connection with the present theories on lepton nonconservation, and a limit on the lepton nonconserving amplitude is obtained
56 citations
TL;DR: In this paper, a new groupG of Lorentz transformations in four dimensions, generalized also for Superluminal frames, is introduced and particularly studied in its physical implications, where the meanings of inertial frame, equivalence, principle of relativity, covariance may be correspondingly extended.
Abstract: A new groupG of Lorentz transformations (LT) in four dimensions, generalized also for Superluminal frames, is introduced and particularly studied in its physical implications. With the help of a « principle of duality »—implied byG—between subluminal and Superluminal frames, the meanings of « inertial frame », « equivalence », « principle of relativity », « covariance » may be correspondingly extended. A biunivocal correspondence exists between bradyonic and tachyonic velocities, which we find to be a particular conformal mapping (inversion). Since the groupG consists of generic rotations in space-time, it includes,e.g., also the total-inversion operation (PT). Moreover (for a non « charge »-free universe), it is shown that our generalized special relativity requires covariance underCPT. A « tachyonization principle » is formulated, on the basis of which relativistic physical laws (of mechanics and electrodynamics, at least) can be easily extended to tachyons. Many simple applications are performed of the generalized LT’s (velocity composition law, comparison of the length and time units, Doppler effect, refraction index, …), either useful to clarify our problem or interesting in astrophysics.
47 citations
TL;DR: In this article, about 1500 absorption events of π+ in flight (∼ 130 MeV of kinetic energy) have been studied in a propane bubble chamber, and the events have been analyzed according to their charged-prong multiplicity.
Abstract: About 1500 absorption events of π+ in flight (∼ 130 MeV of kinetic energy) have been studied in a propane bubble chamber. The corresponding cross-section is (189 ± 19) mb/C nucleus, about one half of the total inelastic cross-section. The absorption on two nucleons with low excitation of the residual nucleus seems to be responsible for 10% of the σtot abs only, while the capture by an α-cluster seems to be more important (∼40% of the total). The events have been analysed according to their charged-prong multiplicity. Data concerning two-prong events agree with the theoretical predictions calculated by assuming the dominance of the reaction π+(np)→pp and by using the impulse approximation model; however a large fraction of them (∼40%) is due to the absorption on an α-cluster: π+(α)→ppd with very-low-energy transfer to the deuteron. Three-prong events have been interpreted as due to the process π+(α)→pppn and qualitative agreement between data and theory has been found. Some data on many-prong events are also reported.
45 citations
TL;DR: In this article, generalized partial wave dispersion relations on hyperbolic curves in the Mandelstam plane are derived for elastic pion-nucleon scattering, where the left-hand cut contribution is explicitly given by convergent partial wave series in the crossed channels.
Abstract: After reviewing the commonly used dispersion relations, a systematic investigation of more generalized dispersion relations on parametrized curves in the Mandelstam plane fors-u crossing-symmetric amplitudes is made with the aim of obtaining dispersion relations which receive contributions from all three channels, however, in such a way that knowledge of the absorptive parts is only required in regions well inside the various Lehmann ellipses. In addition we require that the dispersion relations receive no contributions from kinematic singularities arising from the parametrization and that they allow partial-wave projections to be made in a relatively simple manner. It is found that dispersion relations on hyperbolic curves in the Mandelstam plane are a natural solution of the problem. The dispersion relations are written in a remarkably simple form similar to the usual fixed-t dispersion relation but with an additionalt-channel contribution. As an interesting application, we derive generalized partial-wave dispersion relations for elastic pion-nucleon scattering, where the left-hand cut contribution is explicitly given by convergent partial-wave series in the crossed channels.
42 citations
TL;DR: In this article, the dynamic assumptions of the statistical generalization of the one-dimensional multi-peripheral bootstrap model proposed by the present author are discussed by means of an optical analogy.
Abstract: The dynamic assumptions of the statistical generalization of the one-dimensional multiperipheral bootstrap model proposed by the present author are discussed by means of an optical analogy. No dramatic contradictions are found between the experimental indications on scaling and correlation parameters and the predictions of the model.
41 citations
CERN1
TL;DR: In this article, the statistical model and the thermodynamic model were formulated for multihadron production in e+e− annihilation and asymptotic results for both approaches, with particular attention to critical features subject to experimental test, were derived for storage ring center of mass energies from 2 to 6 GeV.
Abstract: The statistical model and the thermodynamic (statistical bootstrap) model are formulated for multihadron production in e+e− annihilation Asymptotic results are derived for both approaches, with particular attention to critical features subject to experimental test Quantitative predictions of multiplicities, average secondary energies and inclusive single-particle distributions are presented for storage ring centre-of-mass energies from 2 to 6 GeV
TL;DR: In this paper, the mathematical properties of the Dirac equation in over-critical external potentials are investigated, where the 1/r Coulomb potential is treated as the limitR → 0 of cut-off CPs.
Abstract: The mathematical properties of the solutions of the Dirac equation in over-critical external potentials are investigated. The 1/r Coulomb potential is treated as the limitR → 0 of cut-off Coulomb potentials (R is the cut-off parameter). The results are interpreted in terms of quantum electrodynamics. A number of new physical phenomena occur in quantum electrodynamics of strong fields. One of the most interesting ones is the autoionization of positrons (energyless creation of electron-positron pairs) in over-critical external fields.
TL;DR: In this paper, a multihadron production by electron-positron colliding beams has been investigated for total center-of-mass energies ranging from 1.2 to 2.4 GeV.
Abstract: Multihadron production by electron-positron colliding beams has been investigated for total centre-of-mass energies ranging from 1.2 to 2.4 GeV. The total cross-section, σtot ≡ σ(e+e−→π+π−+ + anything), is of the order of σμμ ≡ σ(e+e−→μ+μ−), with a threshold near 1 GeV. Partial cross-sections for the various channels are also derived. The cross-section of the specific channel e+e−→π+π−π+π− exhibits an energy dependence which is suggestive of a heavier vector meson, ρ' (mρ,≈ 1.6 GeV,Гρ, ≈ 350 Mev), having the same quantum numbers as the ρ-meson. An upper limit is given for the coupling constantfρ′ (fρ′/4π<18, wherefρ′=mρ′2e/gγρ′). Final states withG+ parity are found to be much more abundant than those withG− parity. The average multiplicity (charged plus neutral final-state pions) is found to be betweet 4 and 5 over all the energy range explored.
TL;DR: The Neveu-Schwarz model is revealed as possessing the same Koba-Nielsen structure as the original dual-resonance model in a formalism where the KobaNielsen variables are extended by the incoporation of anticommuting variables as discussed by the authors.
Abstract: The Neveu-Schwarz model is revealed as possessing the same Koba-Nielsen structure as the original dual-resonance model in a formalism where the Koba-Nielsen variables are extended by the incoporation of anticommuting variables.
TL;DR: In this paper, the production cross-sections for all the nucleon resonances of the harmonic-oscillator baryon spectrum with massM < 1750 MeV were calculated.
Abstract: The cross-section for neutrino excitation of a nucleon resonance can be expressed by three partial cross-sectionsσR, σL andσS. These are directly given in terms of matrix elements of the weak currents. Taking the current matrix elements from a relativistic quark model, we calculate the production cross-sections for all the nucleon resonances of the harmonic-oscillator baryon spectrum with massM < 1750 MeV. It is found that outside the forward direction whereσS dominates,σR andσS are small compared withσL in the whole resonance region considered. The calculated cross-section and density matrix elements for the P33(1236) resonance are in good agreement with the recent Argonne experiment.
TL;DR: In this article, the elastic scattering of 12C ions on 12C target nuclei has been studied in the center-of-mass energy range between 13.5 and 37.5 MeV at energy intervals of 250 keV, and at center of mass angles of 50°, 60°, 70°, 80° and 90°, respectively.
Abstract: The elastic scattering of12C ions on12C target nuclei has been studied in the center-of-mass energy range between 13.5 and 37.5 MeV at energy intervals of 250 keV, and at center-of-mass angles of 50°, 60°, 70°, 80° and 90°, respectively. Marked structure has been found in these excitation functions: a gross structure with characteristic width ∼3 MeV, and a structure with intermediate width systematically increasing from ∼200 keV to ∼1.5 MeV in the energy range studied. The experimental energy resolution in use was not adequately high to resolve very fine statistical fluctuation structure if present.
TL;DR: In this paper, the dependence of the calculated cross-sections on the model parameters has been studied systematically, and Ambiguities in the optical-potential parameter determinations have also been investigated.
Abstract: Elastic-scattering excitation functions for14N on14N (partially obtained with a new heavy-ion gas target system) are reported for center-of-mass angles of 50°, 60°, 70°, 80° and 90° in the energy range 17≤Ec.m.≤30 MeV. Comparative optical-model analyses of the16O-16O,14N-14N and12C-12C data have been carried out; the dependence of the calculated cross-sections on the model parameters has been studied systematically. Ambiguities in the optical-potential parameter determinations have also been investigated. The extracted Wood-Saxon parameters are as follows.
Open image in new window
TL;DR: In this paper, the vertex for ground-state emission successfully converts all the Virasoro fermion operators into meson ones and vice versa, which is more than is guaranteed by duality.
Abstract: Techniques are developed for handling the vertex for fermion emission in Ramond’s model. These are used to show the vertex for ground-state emission successfully converts all the Virasoro fermion gauge operators into meson ones andvice versa. This is more than is guaranteed by duality. Further it is proved that the vertex converts fermionFN gauges into sums ofGm ones. Unfortunately the more important converse result fails to hold.
TL;DR: In this paper, it was shown that if a heavy lepton exists and is universally coupled only to ordinary leptons, its mass must be heavier than 1.4 GeV.
Abstract: A further search for heavy leptons at the ADONE e+e− storage ring has revealed no events. This establishes, with 95% confidence, that, if a heavy lepton exists and is universally coupled only to ordinary leptons, its mass must be heavier than 1.4 GeV. If it is also coupled to the hadrons, its mass must be greater than 1 GeV, again with 95% confidence.
TL;DR: In this article, it is shown that the adiabatic switching procedure allows a proper treatment of infra-red divergences, without introducing any fictitious photon mass, and a method of carrying out explicitly the calculation, which does not create dishomogeneity in evaluating the contributions from two-and three-body intermediate states.
Abstract: It is shown, discussing the explicit case of further order vacuum polarization, that the adiabatic switching procedure allows a proper treatment of infra-red divergences, without introducing any fictitious photon mass. The new approach suggests a method of carrying out explicitly the calculation, which does not create dishomogeneity in evaluating the contributions from two- and three-body intermediate states.
TL;DR: In this article, the first results of an experiment at the CERN intersecting storage rings, which measured the total cross-section in proton-proton collisions, were presented.
Abstract: We present the first results of an experiment at the CERN intersecting storage rings, which measures the total cross-section in proton-proton collisions. The equivalent laboratory momenta are 291, 496, 1068 and 1480 GeV/c. We have made a direct measurement of αT as the ratio between the total interaction rate and the machine luminosity. The present paper gives a detailed description of the experimental apparatus and of the analysis procedure. We find that αT increases by about 10% in the energy region studied.
TL;DR: The final results of an experimental investigation of the reaction γ+n→p+π− performed with a deuterium bubble chamber at the 1 GeV Frascati electrosynchrotron are presented in this paper.
Abstract: The final results of an experimental investigation of the reaction γ+n→p+π− performed with a deuterium bubble chamber at the 1 GeV Frascati electrosynchrotron are presented. Total and differential cross-sections on neutrons are extracted by means of the spectator model, the reliability of which has been checked by numerous tests and is extensively discussed. The problems of a possible isotensor component in the electromagnetic current, the time-reversal invariance of the electromagnetic interactions and the photoproduction of the Roper resonance are considered in detail.
TL;DR: The properties of the experimental data on the hypercharge exchange reactions πN→KΣ, KΛ and πΛ in the region (4÷16) GeV/c are surveyed, with attention to line-reversal inequalities, reaction energy dependences in terms of effective trajectories, phase-energy properties, and SU3 for exchanges.
Abstract: The properties of the experimental data on the hypercharge-exchange reactions πN→KΣ, KΛ and\(\bar K\)N→πΣ, πΛ in the region (4÷16) GeV/c are surveyed, with attention to line-reversal inequalities, reaction energy dependences in terms of effective trajectories, phase-energy properties, andSU3 for exchanges. We determine thes-channel helicity nonflip amplitudes at 4 and 14 GeV/c, assuming an exchange degenerate\(K_V^* - K_T^* \) Regge-pole approximation for the flip amplitudes. In the impact-parameter representation only the imaginary parts of the πN→KY nonflip amplitudes (or in terms of exchanges Im\(K_V^* \)) are found to be peripheral. All other nonflip amplitude components are central. AnSU3 comparison is made with K−p→νΛ, ν'Λ data.
TL;DR: In this paper, a comparison of recent measurements of the absolute vertical intensities of muons in the momentum range (0.2÷10) GeV/c is presented.
Abstract: A comparison of recent measurements of the absolute vertical intensities of muons in the momentum range (0.2÷10) GeV/c is presented. The results are consistent—within an error of 8%—with a form spectrum normalized at the standard momentum of 1 GeV/c to the value of 3.09·10−3 cm−2 sr−1 s−1 (GeV/c)−1. All parameters having influence on the accuracy of absolute measurements are discussed.
TL;DR: In this article, the structure of the interactions between the proton and the electron in the weak-field limit has been studied assuming general covariance and assuming that the interactions involve no higher derivatives than those appearing in the free Dirac and gravitational Lagrangians.
Abstract: Assuming general covariance, we discuss the structure of gravitational interactions between the proton and the electron. There are 15 (3) different couplings between a massive spin-1/2 particle (a two-component neutrino) and the gravitational field, provided that interactions involve no higher derivatives than those appearing in the free Dirac and gravitational Lagrangians. In the weak-field limit the interactions may be divided into 4 classes: (C, P, T)=(+,+,+), (+,−,−), (−,+,−) and (−,−,+). Any deviation from Einstein's theory entails an asymmetric energy-momentum tensor, hence involving hypotheticalmassless, spinless particles, represented by a skewsymmetric tensor field whose source is the spin of the proton and the electron. We also discuss possible effects of this particle on the hyperfine structure of the hydrogen atom.
TL;DR: In this article, the pion photoproduction from three-body nuclei in the energy region of the first pion-nucleon resonance is calculated in the impulse approximation, including an estimation of the rescattering terms, and compared to recent experimental results.
Abstract: The pion photoproduction from three-body nuclei in the energy region of the first pion-nucleon resonance is calculated in the impulse approximation, including an estimation of the rescattering terms, and compared to recent experimental results. It is shown that the proper kinematics and the inclusion of theS′ andD states into the three-body nuclear wave function explains fairly well the position of the pion-nucleus resonance and the behaviour of the cross-section at fixed momentum transfer for the whole investigated region. The calculations are performed for several types of nuclear wave functions. The results are sensitive to the value of theD-state radius. The stability of the calculated curves with respect to the choice of the amplitude for the pion photo-production on nucleon is tested. At fixed angle, the measured cross-section disagrees with the bare impulse approximation calculations for higher values of the momentum transfer. In this case, the influence of the rescattering terms is discussed.
CERN1
Abstract: We investigate ambiguities in reconstructing a unitary elastic amplitude at fixed energy given the differential cross-section when one assumes analyticity in the cos ϕ plane Strong hints are given that not more than a twofold nontrivial ambiguity is present This is demonstrated for genuine entire functions of finite order Moreover it is found that within a class of amplitudes which includes polynomials as well as entire functions of order zero, i) the difference between the two amplitudes with the same cross-section must be a polynomial, ii) if the cross-section is smaller than 138 (4π/k2) there is no ambiguity Indications are given on directions for future work
TL;DR: In this article, the (π+, π+p) reaction is investigated by means of a propane bubble chamber and the results compared with the predictions of the impulse approximation model (IAM): the agreement is generally good.
Abstract: The (π+,\(\pi \mathcal{N}\)) reactions at ∼130 MeV (kinetic energy) have been investigated by means of a propane bubble chamber. About 250 events of quasi-elastic scattering on bound protons of thep ands shells have been analysed and the results compared with the predictions of the impulse approximation model (IAM): the agreement is generally good. We obtained the following results: the best values for the parameterA appearing in the harmonic-oscillator form factors areAp=(160±10) MeV/c andAs=(300±30) MeV/c forp- ands-shell protons respectively; the total cross-section for the (π+, π+p) reaction is (66±10) mb and the ratio between the cross-sections for the separation of ap- or as-proton is 1.5±0.2. About 100 charge exchange events have been collected; the corresponding cross-section is (36±5) mb, while the estimedσ for (π+, π0p) is (18±3) mb. In the limit of the statistics it seems that also this reaction can be explained on the basis of the IAM. Data concerning the reactions (π+, π+n) based on ∼100 events show some discrepancies with the IAM predictions which cannot be easily explained by the poor statistics and by the difficulties of the experimental analysis. The ratio between the cross-sections for separation of a p and of a n is 1.7±0.2.
TL;DR: In this paper, some basic properties of renormalized coupling constants are discussed in the framework of spontaneously broken gauge symmetries and two possible solutions are suggested for the problem of infra-red divergences.
Abstract: Some basic properties of renormalized coupling constants are discussed in the framework of spontaneously broken gauge symmetries. It is pointed out that conventional definitions lead to some difficulties connected with infra-red divergences and two possible solutions are suggested. The ultraviolet divergent contributions to the lowest-order particular examples, how these divergent terms cancel in the interrelations between renormalized coupling constants and masses. The specific calcula-tions are carried out in the unitary gauge of theSU2xU1 gauges model, using thev-dimensional regularization method.
TL;DR: In this article, an experiment on neutron production by cosmic-ray muons has been carried out at the depth of 4300 m w.e.t., the target is a 35 cm layer of Pb and the neutron detector with twenty-eight BF3 counters has an average efficiency of 2·10−3.
Abstract: An experiment on neutron production by cosmic-ray muons has been carried out at the depth of 4300 m w.e. The target is a 35 cm layer of Pb and the neutron detector with twenty-eightBF3 counters has an average efficiency of 2·10−3. The results on the muon interaction cross-section\(\bar m\sigma \) and on the mean multiplicity at production\(\bar m\) are compared with other data at lower energies (magnetic spectrographs and underrock) and with the expectation from the conventional nuclear and electromagnetic processes of muons of mean energy (250÷300) GeV.