Critical Schwinger pair production

We investigate Schwinger pair production in spatially inhomogeneous electric backgrounds. A critical point for the onset of pair production can be approached by fields that marginally provide sufficient electrostatic energy for an off-shell long-range electron-positron fluctuation to become a real pair. Close to this critical point, we observe features of universality which are analogous to continuous phase transitions in critical phenomena with the pair-production rate serving as an order parameter: electric backgrounds can be subdivided into universality classes and the onset of pair production exhibits characteristic scaling laws. An appropriate design of the electric background field can interpolate between power-law scaling, essential BKT-type scaling and a power-law scaling with log corrections. The corresponding critical exponents only depend on the large-scale features of the electric background, whereas the microscopic details of the background play the role of irrelevant perturbations not affecting criticality.Comment: 6 pages, 1 figur

Diffractive charged meson pair production

We investigate the possibility to measure the nonforward gluon distribution function by means of diffractively produced \pi^+\pi^- and K^+K^- pairs in polarized lepton nucleon scattering. The resulting cross sections are small and are dominated by the gluonic contribution. We find relatively large spin asymmetries, both for \pi^+\pi^- and for K^+K^- pairs.Comment: 15 pages, version with changed kinematical cuts, to be pubished in Phys.Lett.

Exlusive charmed meson pair production

The experimental data of BELLE Collaboration on the exclusive charmed meson pair production in the process of monophotonic $e^+e^-$-annihilation ($e^+e^-\to \gamma^* \to D\bar D$) has been studied. It has been shown that these data is described satisfactorily in the frame work of constituent quark model. Our studies have demonstrated that the central production process $e^+e^-\to e^+e^-\gamma\gamma \to e^+e^-D\bar D +X$ and the process of monophotonic $e^+e^-$-annihilation yield comparable numbers of the charmed meson pairs.Comment: 15 pages, 7 figures, RevTeX

Schwinger pair production in AdS2

We analyze the pair production of charged particles in two-dimensional Anti-de Sitter space (AdS_2) with a constant, uniform electric field. We compute the production rate both at a semi-classical level, viewing Schwinger pair production as a tunneling event, and at the full quantum level, by extracting the imaginary part of the one-loop amplitude. In contrast to the usual Schwinger pair production in flat space, pair production in AdS_2 requires a sufficiently large electric field E^2> M^2+1/4 in order to overcome the confining effect of the AdS geometry -- put in another way, the presence of an electric field E raises the Breitenlohner-Freedman bound to M^2 > -1/4 + E^2. For E greater than this threshold, the vacuum is unstable to production of charged pairs in the bulk. We expect our results to be helpful in constructing supersymmetric AdS_2 X S^2 perturbative string vacua, which enter in the near-horizon limit of extremal charged black holes. Although the generalized Breitenlohner-Freedman bound is obeyed in these cases, production of BPS particles at threshold is possible and relevant for AdS_2 fragmentation.Comment: 23 pages, 4 figures, v2:important revision, discussion of one-loop amplitude extended, several references adde

e+e−e^+e^- Pair Production from 10 GeV to 10 ZeV

At very high energies, pair production ($\gamma\to e^+e^-$) exhibits many interesting features. The momentum transfer from the target is very small, so the reaction probes the macroscopic properties of the target, rather than individual nuclei. Interference between interactions with different atoms reduces the pair production cross section considerably below the Bethe-Heitler values. At very high energies, photonuclear interactions may outnumber pair production. In contrast, in crystals, the interaction amplitudes may add coherently, greatly increasing the cross sections. Pair production in matter-free magnetic fields is also possible. The highest energy pair production occurs at high energy particle colliders. This article will compare pair production in these very different regimes.Comment: 37 pages with 9 figures. Invited Review for "Radiation Physics and Chemistry" Version for publication, incorporating comments by the referee, and by Gerhard Baur and Roman Le

Catalysis of Schwinger Vacuum Pair Production

We propose a new catalysis mechanism for non-perturbative vacuum electron-positron pair production, by superimposing a plane-wave X-ray probe beam with a strongly focused optical laser pulse, such as is planned at the Extreme Light Infrastructure (ELI) facility. We compute the absorption coefficient arising from vacuum polarization effects for photons below threshold in a strong electric field. This set-up should facilitate the (first) observation of this non-perturbative QED effect with planned light sources such as ELI yielding an envisioned intensity of order 10^{26}W/cm^2.Comment: 4 pages, 2 figures; v2 clarifications and references adde