New particles in strong fields?

Abstract

Abstract. The recent search for new particles in the MeV mass range is reviewed. The most relevant experiments, most notably the GSI positron experiments, are described and their results are combined to restrict the properties of the hypothetical particles. The theoretical analyses of these and a large number of other experiments are presented in detail. Finally some special candidates for new particles such as the axion and localised complex vacuum excitations are discussed. I discuss a number of ideas and suggestions which merit further investigation. With respect to the GSI experiments it is concluded that it is very unlikely that the observed e+-e-coincidences indicate the existence of new particles.

Can extended objects explain the GSI e+ e? lines?

“…9 Nuclear pair conversion processes (A*~ A +e-+ e +) appear to be excluded from 7-ray and electron spectra, Doppler shift analysis, and A-independence. 9 Lines at 620, 750 and 810 keV sum energy have been observed by the EPOS collaboration. Lines at about 560, 640, and 800 keV have been observed by the ORANGE collaboration.…”

“…9 The line positions appear to fall into several groups between 250 and 440 keV; their width is about 70 keV, if all positron emission angles are covered. This value corresponds to the Doppler width of a sharp line emitted by a source moving with center-of-mass velocity.…”

“…+b; 23.20.Nx This is the characteristics of a two-body decay of a (slowly moving) particle-like object X~ § +e-with mass in the 1.8 MeV region. This has led to a large diversity of models and speculations on the nature of the object X ~ [9]. Meanwhile the situation has become even more complex since several line structures have been found which do not all confirm with the two-body decay scenario [10,11].…”

Photon-photon interaction in axial channeling

“…For the SSM we have qAo(p)= V(p) and after multiplication with yO, ( 2 ) simplifies to First we substitute the corresponding expression in a" a" a, for the Cartesian operator y .V. Our second step is to make a nonunitary transformation of the resulting equation.…”

“…Thus one has to conclude that the nonperturbative nonlinear effects of QED are presently hardly tested at all. There even has been much speculation about exotic nonperturbative effects in connection with the sharp electron-positron resonances observed at the Gesellschaft für Schwerionenforschung (Darmstadt); for a review see [2] and references therein. While none of these speculations should be taken too seriously they show how little is known about this sector of QED.…”