ABSTRACT
Experimental results for the radiative energy loss of 149, 207, and 287 GeV electrons in a thin Ir target are presented. From the data we conclude that at high energies the radiation length increases in accordance with the Landau-Pomeranchuk-Migdal (LPM) theory and thus electrons become more penetrating the higher the energy. The increase of the radiation length as a result of the LPM effect has a significant impact on the behavior of high-energy electromagnetic showers.
ABSTRACT
A strong increase of inclusive nuclear-charge pickup cross sections, forming 83Bi from 158A GeV 82Pb ions, is observed in comparison to similar measurements at 10.6A GeV. From the dependence of these cross sections on target atomic number, this increase is attributed to the electromagnetic process of pion production by equivalent photons. The observed cross sections can be reproduced quantitatively using the recently developed RELDIS code.
ABSTRACT
Although some authors have claimed that the effect is not detectable, we show experimentally for the first time that as the quantum parameter chi grows beyond 1, an increasingly large part of the hard radiation emitted arises from the spin of the electron. Results for the energy loss of electrons in the energy range 35-243 GeV incident on a W single crystal are presented. Close to the axial direction the strong electromagnetic fields induce a radiative energy loss which is significantly enhanced compared to incidence on an amorphous target. In such continuously strong fields, the radiation process is highly nonperturbative for ultrarelativistic particles and a full quantum description is needed. The remarkable effect of spin flips and the energy loss is connected to the presence of a field comparable in magnitude to the Schwinger critical field, E0 = m(2)c(3)/ePlanck's over 2pi, in the rest frame of the emitting electron.
