On <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> pair production by colliding electromagnetic pulses

Electron-positron pair production from vacuum in an electromagnetic field created by two counterpropagating focused laser pulses interacting with each other is analyzed. The dependence of the number of produced pairs on the intensity of a laser pulse and the focusing parameter is studied with a realistic three-dimensional model of the electromagnetic field of the focused wave, which is an exact solution of the Maxwell equations. It has been shown that e⁺e^? pair production can be experimentally observed when the intensity of each beam is I～10²⁶ W/cm², which is two orders of magnitude lower than that for a single pulse.     

Long-range potentials and the electromagnetic polarizabilities

The long-range spin and velocity independent forces of electromagnetic origin which act between any two systems are studied for those cases in which no forces of this type exist to order e². It is shown that they are uniquely determined by the charge, magnetic moment, and polarizabilities of both systems, not only to the dominant order r^?n, but also to the next one r^?(n+1). These potentials provide the link between Compton scattering polarizabilities (response to real photons) and classically defined polarizabilities (response to static electromagnetic field). The two definitions are shown to be equivalent for neutral spinless systems; the problems arising for a neutral particle with magnetic moment are studied in detail. The r^?(n+1) terms have no classical counterpart, since they are due to the relativistic quantum propagation of the system which carries charge or magnetic moment. The results are of general validity with analyticity, crossing, unitarity, and gauge invariance as only inputs. The most general conclusion is that the polarizabilities represent electromagnetic properties of a system at order e², as the charge and magnetic moment do at order e. Thus they give the strength of the response to electric and magnetic fields, independently of the specific characteristics of the electromagnetic agent.     

Three-jet distributions ine + e − annihilation: Electromagnetic and weak production

Hard gluon bremsstrahlung off quarks ine ⁺ e ^? annihilation is expected to produce three-jet events. The angular distributions of the jets are calculated for electromagnetic and weak production in the high energy region (Z resonance decay included). Numerical estimates are presented for the vectoraxialvector interference terms within the Weinberg-Salam theory. We discuss (i) angular correlations between jets, (ii) semiinclusive pion distributions and (iii) we comment on angular asymmetries of leptons originating from heavy quark decays.     

New resonance-polariton Bose-quasiparticles enhances optical transmission into nanoholes in metal films

We argue the existence of fundamental particles in nature, neutral Light-Particles with spin 1, and rest mass m=1.8⋅¹⁰−4me, in addition to electrons, neutrons and protons. We call these particles Light Bosons because they create the electromagnetic field which represents Planck's gas of massless photons together with a gas of Light-Particles in the condensate. In this respect, the condensed Light-Particles, having no magnetic field, represent the constant electric field. In this context, we predict an existence of polariton-plasmon Bose-quasiparticles with effective masses ml≈¹⁰−6me and mr=0.5me, which are induced by interaction of the plasmon field and the resonance Frölich-Schafroth charged bosons with electromagnetic wave in metal. Also, we prove that the enhancement optical transmission into nanoholes in metal films and Surface Enhanced Raman Spectroscopy are provided by a new resonance-polariton Bose-quasiparticles but not model of surface plasmon-polariton. In this Letter, the quantization Fresnel's equations is presented which confirms that Light-Particles in the condensate are concentrated near on the wall of grooves in metallic grating and, in turn, represent as the constant electric field which provides the launching of the surface Frölich-Schafroth bosons on the surface metal holes.     

A possibility of asymptotic freedom without non-Abelian gauge theories

We discuss solutions of the renormalization group equations for a Yukawa field theory. For an increasing effective boson mass we find that the leading terms in the vertex functions in the high-energy region are given by diagrams which contain no internal boson lines. In e⁺e^? annihilation into hadrons we get the parton model formula R(s) = Σ_iQ_i², whereas in the deep inelastic e^?p scattering the simple parton model behaviour is modified by the (in general) non-canonical dimension of the quark field.     

Confined phase of electroweak theory and the e+e− peaks observed in large-Z heavy-ion collisions

We discuss the speculations that the e⁺e⁻ peaks seen in large-Z heavy-ion collisions are evidence for a confined phase of an effective theory similar to strongly-coupled QED. It has been suggested that the observed radiation arises from the decay of nontopological solitons in this confined phase. (In this work we develop a scenario in which a photon condensate is formed in a finite region of space. We show that the existence of such a condensate will lead to the confinement of electrons and positrons.) However, as has been recently pointed out by Peccei, Solà and Wetterich, a new phase of QED requires that the nonlinear effects in the effective Lagrangian for the electromagnetic field become large. We describe how this might come about, within the context of electroweak theory with two Higgs doublets.     

Strings in a conformally invariant theory of gravitation and electromagnetism

A recently proposed unified theory of gravitation and electromagnetism is studied in the weak field approximation and conformally flat gauge. It requires the photon to have a mass real or imaginary (Meissner effect) depending on the sign of the cosmological constant λ, and proportional to λ^{$\text{1}\text{2}$}. Thus the range of the electromagnetic interaction must be greater than ～2 × 10²⁷ cm. The electromagnetic field is entirely of topological origin, strings are present in the theory and the flux of the electromagnetic field is quantized. A classical normalization condition for the potential makes the flux quantum equal to ± e, while the fine structure constant provides a scale for the rate of change in the length of a vector displaced around a closed path linking the flux.     

Quantum effects in radiation on short bunches

The radiation caused by particles of one bunch in the collective electromagnetic field of the short oncoming bunch is studied. Quantum effects are calculated for the spectrum of radiated photons. Using this spectrum, the dependence of the relative energy loss δ on a quantum parameter K is discussed. It is shown that the behaviour of δ changes considerably with the increase of that parameter. In the classical regime (K ? 1) the energy loss is proportional to the incoming particle energy, while in the extreme quantum regime (K ? 1) the energy loss becomes a constant. The coherent e⁺e^? pair production for γe colliders as cross-channel to CBS is considered.     

The post-post-Newtonian problem in classical electromagnetic theory

We find the Lagrangian to order c^?4 for two charged bodies (with $\text{e}{}_1\text{m}{}_1\text{=}\text{e}{}_2\text{m}{}_2$) in electromagnetic theory. This Lagrangian contains acceleration terms in its final form and we show why it is incorrect to eliminate these terms by using the equationsof motion in the Lagrangian as was done by Golubenkov and Smorodinskii, and by Landau and Lifshitz. We find the center of inertia and show that the potential energy term does not split equally between particles 1 and 2 as it does in the Darwin Lagrangian (Lagrangian to order c^?2). In addition to the infinite self-energy terms in the electromagnetic energy-momentum tensor, which are eliminated using Gupta's method, some new type of divergent terms are found in the moment of electromagnetic field energy and in the electromagnetic field momentum which cancel in the final conservation law for the center of inertia.     

The characteristic surfaces of a classical spin-3/2 field in an Einstein-Maxwell background

It is shown that the anomalous characteristic surfaces of the Rarita-Schwinger equation minimally coupled to an electromagnetic field can be eliminated by including the gravitational field provided that the charge e and mass m satisfy m = e/√3G.     

Proof of comparable K-pair and π-pair production from time-like photons of 1.5, 1.6, and 1.7 GeV and determination of the K-meson electromagnetic form factor

The observation of 21 K⁺K^? pairs in 38 hadron pair events produced at 1.5, 1.6, and 1.7 GeV total centre-of-mass energies in e⁺e^? annihilations, establishes that time-like photons produce K pairs and π pairs with comparable rates in this energy range. The K-meson electromagnetic form factor at a mean s-value of 2.4 GeV² is measured to be |F_K| = 0.50±0.08. The number of e⁺e^? pairs observed in the same angular and energy range is 5148.     

Electron-positron bremsstrahlung at ADONE. A new limit for the existence of a heavy electron

A new measurement of the cross section for the reaction e⁺e^? → e⁺e^?γ has been performed at the ADONE storage ring, using a wide angle electromagnetic detector together with tagging counters for detecting small-angle electrons. The results are in agreement with the QED predictons. New limits for the mass and coupling constant (e¹, eγ) of a heavy electron, e¹, have been established.     

Physics with high energy electron-positron colliding beams with the MARK J detector

This report reviews the experimental investigation of high energy e⁺e^? interactions by the MARK J collaboration at PETRA, the electron-positron colliding beam accelerator at DESY in Hamburg, Germany. The physics objectives include studies of several purely electromagnetic processes and hadronic final states, which further our knowledge of the nature of the fundamental constituents and of their strong, electromagnetic and weak interactions. Before discussing the physics results, the main features and the principal components of the MARK J detector are discussed in terms of design, function, and performance. Several aspects of the on-line data collection and the off-line analysis are also outlined. Results are presented on tests of quantum electrodynamics using e⁺e^? → e⁺e^?, μ⁺μ^? and τ⁺τ^?, on the measurement of R, the ratio of the hadronic to the point-like muon pair cross section, on the search for new quark flavors, on the discovery of three jet events arising from the radiation of hard noncollinear gluons as predicted by quantum chromodynamics, and on the determination of the strong coupling constant α_s.     

Reducible scale invariance at short distances

It is proven that, using reducible scale invariance at short distances, conformal symmetry implies canonical (Bjorken) scaling, provided diagonal dimensions of dilatation multiplets occuring in the operator product expansion of two electromagnetic currents have the canonical value l_n = 2 + n. If the electromagnetic current itself belongs to such multiplets then the hadron production cross section in e⁺e^? annihilation falls off faster than $\text{1}\text{s}$ at asymptotic energy.     

Magnetic field induced multi-component QED3 and quantum Hall effect

Dynamics of two dimensional electrons under the strong perpendicular magnetic field is shown to be described by a multi-component fermion theory. The electric conductance has a remarkable property known as the quantum Hall effect. The Hall conductance is quantized in units ofe ²/h in the gap region and in the localized state region. The proof of exactness is presented in general cases using quantum field theory.     

Electromagnetic transition form factors of Λ → <Emphasis Type="Italic">ne</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> weak dilepton decay

Weak radiative decay Λ → ne⁺e^? depends in general on four independent electromagnetic transition form factors. These form factors can be fixed in an extended model of dominance of vector mesons, where the asymptotic behavior of form factors is in agreement with quark counting rules. The dependence of the branching ratio of the Λ → ne⁺e^? decay on the relative weight of four electromagnetic form factors is investigated.     

Determination of the longitudinal and the transverse part in π+ electroproduction

We report on an experiment where the different contributions from the transverse and longitudinal polarization of the virtual photon are measured separately for the reaction e^?p→e^?π⁺n. The data taken above the resonance region at small ∣t∣ values in the q² range of ∣q²∣ < 0.5 GeV² show a clear dominance of the longitudinal part of the cross section and are well described by a generalized Born-term model. Using this model the electromagnetic form factor of the pion is determined. At q² = ?0.35 GeV² one gets F_π = 0.598 ± 0.021.     

Photon production in Au+Au collisions at \sqrt {s_{NN} } = 130 GeV

We report raw photon, neutral pion and eta measurements at RHIC. Photons in the energy range from 100MeV ? 4GeV were detected by reconstructing e ⁺ e ^? pair production, γ+Z→e ⁺+e ^?+Z, with the STAR Time Projection Chamber (TPC). Along with the photon detection technique we discuss the purity of the photon candidates and measurements of hadronic decays via their electromagnetic decay channels. The π⁰→γ and η→γγ decay channels are addressed.     

Study of electron-positron collisions at the highest PETRA energy

We report on the results of the study of e⁺e^? collisions at the highest PETRA energy of √s = 31.57 GeV, using the 4π sr, electromagnetic and calorimetric detector Mark J. Based on 88 hadron events, and an integrated luminosity of 243 nb^?1 we obtain R = σ(e⁺e^? → hadrons)/σ(e⁺e^? → μ⁺μ^?) = 4.0 ± 0.5 (statistical) ± 6 (systematic). The R value, the measured thrust distribution and average spherocity show no evidence for the production of new quark flavors.