A search for ultra-high energy photons with energies above 1 EeV is performed using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode. An unprecedented separation power between photon and hadron primaries is achieved by combining measurements of the longitudinal air-shower development with the particle content at ground measured by the fluorescence and surfac...

Previous researches on high-energy neutrino events from gamma-ray bursters (GRBs) suggest a speed variation v(E)=c(1±E/ELV?) with ELV?=(6.4±1.5)×1017 GeV, together an intrinsic time difference ?tin=(?2.8±0.7)×102 s, which means that neutrinos come out about 300 s earlier than low-energy photons in the source reference system. Considering possibility pre-bursts of may be accompanied by photons, ...

A possible reason for the emission of soft photons in high energy pp-collisions is discussed.

A search for ultra-high energy photons with energies above 1 EeV is performed using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode. An unprecedented separation power between photon and hadron primaries is achieved by combining measurements of the longitudinal air-shower development with the particle content at ground measured by the fluorescence and surfac...

Gamma-ray bursts (GRBs) and their afterglows at high redshifts have been widely believed to be detectable. Here we analyze a new feature of the MeV spectra of high-redshift GRBs, which is unlikely to appear in low-redshift GRBs. We generally discuss high-energy emission above a few decades of GeV due to synchrotron self-Compton scattering in the internal shock model. Our discussion seems to be ...