Measurement of the production of high-mass. gamma. gamma. ,. pi. sup 0. pi. sup 0 , and. gamma. pi. sup 0 pairs in. pi. sup minus p ,. pi. sup + p , and pp collisions at 300 GeV/ c

The NA24 experiment at CERN investigated inclusive {gamma}{gamma}, {pi}{sup 0}{pi}{sup 0}, and {gamma}{pi}{sup 0} final states in the mass range between 4 and 9 GeV/{ital c}{sup 2} produced in {pi}{sup {minus}}{ital p}, {pi}{sup +}{ital p}, and {ital pp} reactions at a c.m.-system energy {radical}{ital s} =23.7 GeV. The {pi}{sup 0}{pi}{sup 0} cross sections agree well with expectations of the quark-parton model. For {gamma}{pi}{sup 0} production in {pi}{sup {minus}}{ital p} and {ital pp} reactions, a clear signal is observed and cross sections are shown. The production of {gamma}{gamma} events was observed with a statistical significance of 2.9{sigma} in {pi}{sup {minus}}{ital p} reactions. The cross section is in agreement with a higher-order QCD prediction.