On pair content of quasar jets

We use X-ray observations of blazars to infer that jets in quasars contain many more e(+)/e(-) pairs than protons, but dynamically, they are still dominated by protons. In particular, we show that pure pair jets can be excluded, as they overproduce soft X-ray radiation; likewise, pure proton-electron jets can be excluded, as they produce too little nonthermal X-ray radiation. We demonstrate that jets which initially consist of protons / electron plasma can be pair loaded due to interactions with 100 - 300 keV photons produced in the hot accretion disc coronae.