Particle theory

Abstract:

The magnetic field strength in the radio-emitting shell of the supernova remnant Cassiopeia-A should be greater than $8 \times 10^{-5} G$ if the bremsstrahlung by the electrons responsible for the non-thermal radio emission is not to exceed the upper limits to the gamma-ray emissivity set by the recent observations. This field strength is shown to be too large to be generated by a mere compression of the interstellar field by the supernova shock but must arise due to magnetohydrodynamic instabilities in the expanding shell. Gamma-ray generation through inverse-Compton scattering of photons in the surrounding H II region is also briefly discussed.

Abstract:

We point out that over an experimentally important kinematic region lepton pair production arises from the annihilation of a quark and antiquark within the same hadron. This renders incorrect the conventional extraction of structure functions from data in this region. Instead it now becomes possible to obtain information on the correlation between a quark and antiquark within the same proton. We carefully quantify this kinematic region of interest and illustrate it with a discussion of the validity of some recent structure function analyses. © 1980.