Neutral Vector Meson Research Articles

Observation of the (e +e −)-decay modes of neutral vector mesons

The (e +e −) decay rates of vector mesons have been measured using spark chambers and Čerenkov gamma-spectrometers.

Phenomenological Analysis of the Photoproduction of Neutral Vector Mesons and Strange Particles

Branching ratios for photoproduction of vector mesons and strange particles are discussed. The one-pion-exchange mechanism cannot explain the observed ratio between $\ensuremath{\rho}$ and $\ensuremath{\omega}$ photoproduction cross sections. Various versions of pseudoelastic mechanisms are studied and it is shown that although they correctly predict the large $\ensuremath{\rho}:\ensuremath{\omega}$ production ratio, they cannot account for the extremely small preliminary cross section for $\ensuremath{\phi}$ production. It is shown that no combination of one-pion exchange and the diffraction mechanism with exact or broken $\mathrm{SU}(3)$ can explain the low $\ensuremath{\phi}$ production rate. The multiperipheral model may explain the low $\ensuremath{\phi}$ production, but predicts the wrong $\ensuremath{\rho}:\ensuremath{\omega}$ production ratio. Various possible sources of this discrepancy are studied and experimental tests are discussed which can distinguish between the different proposed theories. A large number of new predictions based on exact or broken $\mathrm{SU}(3)$ symmetry are derived and compared with experiment.

Classical Scattering of Neutral Mesons. II

In Paper I, the scattering of neutral scalar and vector mesons by nucleons was calculated on the basis of a classical action-at-a-distance theory and compared with the corresponding field-theoretical results. In both theories the postulated vector and tensor coupling terms of the vector mesons with the nucleons were analogous to those of electrodynamics. Recently, a more general form of interaction was proposed; for monopole singularities it introduces a pseudovector coupling term which does not satisfy an equation of continuity. In this paper, the scattering of neutral spin-1 mesons by heavy particles is calculated using all three coupling terms, on the basis of the field-theoretical as well as the action-at-a-distance equations of motion of the particles. Cross sections due to the pseudovector coupling alone are examined in detail. Unlike the results of Paper I, the new field-theoretical and action-at-a-distance results show significant differences; furthermore, the behavior of the cross sections is found to depend critically on the magnitudes of the physical constants characterizing the meson field and the particles, exhibiting various resonance-like features.

Possible Charge-Conjugation Noninvariance in the Photoproduction of NeutralρMesons

We examine theoretically the dominant features of the experimental data on the reaction $\ensuremath{\gamma}+p\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}+p$ which have recently been presented by the Cambridge Electron Accelerator bubble-chamber collaboration. In accord with the experimentalists' conclusions, we find that (a) the exchange of a single ${\ensuremath{\pi}}^{0}$ does not seem to play an important role in the production mechanism, perhaps merely because of a relatively small value for the ${\ensuremath{\rho}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ vertex; (b) a diffraction production mechanism may play a significant role in the production of ${\ensuremath{\rho}}^{0}$ at near-forward angles. However, for photon laboratory energies between 1.8 and 6 BeV, about 40% of the ${\ensuremath{\rho}}^{0}$ are produced at center-of-mass angles $\ensuremath{\theta}$ with $cos\ensuremath{\theta}<0.85$. We address ourselves to the question of whether the exchange of a neutral vector meson, in particular the ${\ensuremath{\omega}}^{0}$, can be playing a significant role in the production mechanism; perhaps a dominant role for ${\ensuremath{\rho}}^{0}$ produced at other than near forward angles. The ${\ensuremath{\rho}}^{0}{\ensuremath{\omega}}^{0}\ensuremath{\gamma}$ vertex violates charge-conjugation invariance and time-reversal invariance. We find that the present data on (1) the forward differential cross section as a function of photon energy, (2) the production angular distribution and total cross section at about 5 BeV, and (3) the behavior of the ${\ensuremath{\rho}}^{0}$ density matrix elements as functions of production angle and photon energy, are completely consistent with the results from the exchange of an ${\ensuremath{\omega}}^{0}$, with a $C$-violating transition magnetic moment at the ${\ensuremath{\rho}}^{0}{\ensuremath{\omega}}^{0}\ensuremath{\gamma}$ vertex of the order of unity, in units of $\frac{e\ensuremath{\hbar}}{2m\ensuremath{\rho}}$. It appears that further experiments to elucidate the behavior of the density matrix elements as functions of production angle, in particular at the larger production angles, could detect a variation that is possibly characteristic of the ${\ensuremath{\omega}}^{0}$-exchange mechanism. When our results correspond to some aspect of the data which can also be correlated with diffraction production, we say only that the data are consistent with $C$ noninvariance. When our results give rise to some striking aspect which is not an evident feature of diffraction production, we say only that that $C$ noninvariance provides one possible interpretation should the data exhibit this aspect. In the Appendix, we note a model in which $C$ noninvariance in the electromagnetic interaction of neutral vector mesons manifests itself in certain processes through $C$ noninvariant and isotopic-spin-violating vertices among hadrones, which are of order $\ensuremath{\alpha}$.

On gauge invariance in quantum electrodynamics

Abstract Results of simple calculations in the usual perturbation expansion in quantum electrodynamics appear to be in contradiction with gauge invariance. We point out why certain divergent integrals which are assumed or “shown” to be zero are really not required to vanish. This argument is applicable to such diverse problems as vacuum polarization in quantum electrodynamics and the renormalizability of the theory of a neutral vector meson interacting with a conserved fermion current. In general terms, we show that more caution has to be exercised when four-divergences are neglected in a Lagrangian density.

C-parity violation and neutral particles production in colliding electron-position beams

The possibility is considered of the production of a neutral vector meson pair via one virtual photon in electron-positron annihilation.

Model ofCViolation in Semistrong Interactions

A simple model of $C$ violation in semistrong interactions is proposed. The basic semistrong interaction is an "equal" mixture of $C$-invariant and -noninvariant parts. The former part is the coupling between two neutral vector mesons (Sakurai's interaction), and the latter is the coupling between neutral vector and scalar mesons. The nature of this particular interaction and the possible experimental consequences are discussed. The small ${{K}_{2}}^{0}\ensuremath{\rightarrow}2\ensuremath{\pi}$ decay rate can be consistent with our model. Also the $\ensuremath{\rho}\ensuremath{\eta}\ensuremath{\pi}$ coupling and the $C$-violating effect in the ${\ensuremath{\Sigma}}^{0}\ensuremath{\rightarrow}\ensuremath{\Lambda}{e}^{+}{e}^{\ensuremath{-}}$ decay are calculated.

Gauge Independence and Path Independence

Quantum electrodynamics is formulated in a gauge-independent as well as path-independent way. The theory is manifestly Lorentz covariant. It can be obtained from the path-dependent electrodynamics of Mandelstam by an averaging process. The commutation relations and propagators in this gauge-independent formulation correspond to those of the Landau gauge in the conventional theory, giving this gauge a fundamental significance. The method is also applied to the gauge-invariant theory of neutral vector mesons with nonvanishing mass interacting with a conserved current. The resulting theory is gauge-independent and describes a pure spin-1 particle, the spin-0 contributions being identically zero.

Production ofN11Resonance and Properties of the Neutral Vector Mesons

Production of<i>N</i>₁₁Resonance and Properties of the Neutral Vector Mesons

Interaction of isotopic gauge fields with photons

The quantization of the following systems of interacting fields is studied: i) Yang-Mills isotopic gauge field interacting with the electromagnetic field; ii) partially isotopic gauge-invariant field (with nonvanishing mass terms and arbitrary anomalous moment type couplings); and iii) its interaction with the electromagnetic field (with arbitrary anomalous magnetic moment couplings). By assuming the isotopic charge to be small, the perturbativeS-matrix theory is formulated for each of the three problems. The field system i) is renormalizable, but ii) and iii) are not. The interaction with the electromagnetic field by consistent couplings does not completely destroy the isotopic gauge invariance of the Yang-Mills field, but rather leads to an extended invariance of the whole system of two interacting fields with respect to a 4-dimensional gauge group called the combined charge-isotopic gauge group, which can still be generalized to include any number of kinds of « photons ». This extended gauge invariance enables us to take Lorentz gauge for both the electromagnetic and the isotopic gauge-invariant field and also permits a global covariant formalism for dealing with the subsidiary conditions of all the component zero-mass vector fields. In both problems ii) and iii), all anomalous moment interactions give rise to noncovariant high-orderS-matrix elements and to « extra-high-order » divergences, but these difficulties all disappear in a certain particular case; the results of the two problems may be applied to analysing the interaction among charged and neutral vector mesons of isospin one considered as isotopic gauge bosons and also their interaction with photons.

Experimental Restrictions on Ne'eman's Fifth Interaction

Recently, Ne'eman has proposed a "fifth interaction" between the strangeness current and a neutral vector meson $\ensuremath{\chi}$, for the purpose of breaking SU(3) symmetry. We show that a $\ensuremath{\chi}$ mass less than $2{m}_{\ensuremath{\pi}}$ would be inconsistent with a variety of experiments, including $K$-mesonic atoms, the long-range $\mathrm{pp}$ potential, ${K}_{1}$ regeneration from a ${K}_{2}$ beam, the Lamb shift, modern refinements of the Cavendish "ice-bucket" experiment, and the absence of ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}+\ensuremath{\chi}$ and $\ensuremath{\chi}\ensuremath{\rightarrow}{e}^{+}+{e}^{\ensuremath{-}}$. The remaining possibility, that ${m}_{\ensuremath{\chi}}$ exceeds $2{m}_{\ensuremath{\pi}}$, is discussed briefly.

Note on the magnetic moments of baryons

We show that the magnetic-moment relations of Coleman and Glashow are unaffected by ω-ϕ mixing and the ρ — ϕ mass difference, provided that the neutral vector mesons ρ0, ω and ϕ dominate the Pauli form factors of the baryons and that the coupling constants of the vector meson octet are given by unitary symmetry.

Asymptotic Behavior of Feynman Integrals with Spin

Some general features are investigated of the dependence of the asymptotic behavior of Feynman integrals upon factors in the numerator of the integrand resulting from particles with spin. These results are used to analyze the high-energy behavior of ladder diagrams for spin-12 nucleons interacting with neutral vector mesons. The leading contribution is shown to consist of terms corresponding to a reggeised nucleon together with certain other terms. The expected cancellation of these other terms by terms associated with a well-defined class of crossed diagrams is verified in detail for the sixth-order case. Finally, other significant diagrams, different from the ladders and their associated crossed diagrams, are investigated and it is shown that they only provide higher-order corrections to the trajectory of the reggeised nucleon.

Green’s functions of vector theories

Green’s functions of neutral vector meson theories are discussed in a Bloch-Nordsieck-like approximation. In the Green’s functions theB-field is traced in detail.

Some Remarks onωandϕMeson Widths andR-Conjugation Invariance in Strong Interaction

It is pointed out that partial widths of two neutral vector mesons, $\ensuremath{\omega}$ and $\ensuremath{\phi}$, into three pions provide some information for or against $R$-conjugation invariance in strong interaction. A particular model is considered in detail, in which $\ensuremath{\omega}$ and $\ensuremath{\phi}$ mesons are $R$ conjugation invariantly associated with baryonic charge and hypercharge currents, respectively. This model is shown to explain consistently various phenomena involved in production and decay processes of these vector mesons.

Unitary Symmetry and Electromagnetic Self-Energies of Neutral Vector Mesons

Unitary Symmetry and Electromagnetic Self-Energies of Neutral Vector Mesons

A vector-spinor bootstrap as an identity

It has been shown in the first non-trivial approximation that the Langrangian field theory of spin 1/2 fermions and neutral vector mesons interacting through a conserved current has the apparently miraculous property that the spinor particle lies on a Regge trajectory. We would like to point out here that this feature of the spinor-vector field if it is in fact exactly true, also has interesting implications when phrased in terms of S-matrix theory, in which it is assumed that there are no elementary objects and that all particles are created by a bootstrap mechanism.

The Gauge-Invariant Theory of Neutral Vector Meson in Analogy with that of Quantum Electrodynamics

The strong analogy between the neutral vector meson theory and quantum electrodynamics is well known. It is shown/), 2 ) in particular that the two theo­ ries coalesce in the limit of the vector meson mass tending to zero. This and many other similarities of the two theories are due to a type of gauge invariance that the neutral vector meson theory is shown to possess in common with that of electrodynamics. Recently a gauge-invariant formulation of quantum electrodynamics has been given by Mandelstam, 3 ) who used fields rather than potentials. The interactions of the charged and electromagnetic fields are brought in through the path­ dependence of the charged fields. This has the advantage over the conventional formulation that no indefinite metric or unphysical states are introduced in the theory. The purpose of this paper is to present a formulation of the neutral vector meson theory in analogy with the gauge-invariant theory of quantum elec­ trodynamics, proposed by Mandelstam and then to obtain the latte1' from the former by making the vector meson mass vanish. This will be achieved if we could show that i) the theory is consistent with the fact that no longi­ tudinal or scalar photons are observed and ii) the field equations for the expec- · tation values go over to the Maxwell equations. In the next section we introduce the notations of the vector meson theory. Then we employ the Stueckelberg formalism to show the type of gauge-invariance under which the theory is invariant. In § 3 we present the new formulati_on of the vector meson theory and finally show its close connection with that of the gauge-invariant theory of electrodynamics given by Mandelstam.

Consequences of a fundamental length in very-high-energy scattering

We show that a fundamental length provides the mechanism in quantum field theory to produce the effects noticed in very-high-energy scattering. In the very-high-energy large momentum-transfer (s, |t|≫λ−2, λ≡fundamental length) approximation already semi-quantitative agreement with the following features is obtained. 1) Detailed shape of the elastic scattering curves, including: very sharp forward (and sometimes backward) « diffraction » peaks with universal exponential tails int (oru), the « flattening » and huge experimental « shrinking of the diffraction peak » with energy of the p-p curves, the weak « flattening » and absence of « shrinking » of the π-p curves. 2) Asymptotic constancy of total cross-sections, asymptotic equality of σe1(π−-p) and σe1(π+-p), the rough relation σe1(π-p)≈1/2 σe1(p-p). One characteristic of λ≠0 is the rapid vanishing of higher-order corrections at high energies and of radiative corrections at large momentum transfers. With λ=0, this is not so, the sharp peaking and exponential tails disappear, and the « shrinking » of the p-p peak is far too small. An essential « dynamical » assumption is that a neutral vector meson may be exchanged. These experiments indicate λ ≈10−14cm; the vector meson mass is not yet clear. The fundamental-length field theory used (5–7) requires an explicit dependence of theS-operator on themeasuring frame (frame in which the experiment is performed); it is believed that any relativistically invariant, etc. fundamental-length theory requires this generalization of field theory. This « kinematical » fundamental-length-theoretic and the « dynamical » Regge pole explanations of very-high-energy scattering are compared point by point; they are clearly distinguishable at ultrahigh momentum transfers. A λ≠0 implies changed asymptotic properties of analytic amplitudes (essential singularities at infinity), thus changes in the physical conclusions derived from dispersion relations.

Intermediate vector mesons and unitary symmetry

A theory is formulated of the weak interaction in connection with the unitary symmetry model by introducing charged and neutral intermediate vector mesons. It is assumed that weak baryonic currents or the interaction are components of some unitary octet and that the resulting effective interaction of nonleptonic, strangeness-violating processes is also a component of another unitary octet. Four distinct vector mesons are used to satisfy the theory. (R.E.U.)