Search for parity violation in cosmic rays

We study a possible parity-violating area near the high-energy sources of photons. Such a violation might occur as a result of the condensation of a pseudoscalar background. We show that if this condensate has a large density gradient, then photons with a positive chirality decay into $e^+e^-$ pairs. This process consequently reduces the number of positively polarized photons and can increase the portion of positrons in cosmic rays.