EVIDENCE FOR TWO NEUTRAL PIONS

Abstract

Experimental results from π-, K-, Σ- capture, [Formula: see text] and [Formula: see text] annihilations in liquid H2 show that the fraction of captures and annihilations from atomic P states is less than 5% in agreement with theoretical expectations. However, an anomalously large fraction from P states by a factor of ten is inferred from the branching ratios for the reactions [Formula: see text] and [Formula: see text] at rest in liquid H2 and liquid D2 respectively. One explanation for this inconsistenct is that the reaction [Formula: see text] is occurring from an atomic S state of protnium, which is possible if the two π0's are not identical. It should be noted that a second neutral pion (with different lifetime and decay properties) was observed in antinucleon-nucleon reactions in a 1964 experiment. We describe two experimental tests, one to determine whether [Formula: see text] can occur from an atomic S state, and another to search for the π0π0 decay mode of neutral vector mesons with JPC = 1--.