THE pentaquark, an oversized subatomic particle that has challenged physicists since its reported discovery two years ago, does not exist after all, according to a sensitive experiment designed to look for it.
The existence of pentaquarks was hypothesised in 1997 by Russian researchers at the Petersburg Nuclear Physics Institute in St Petersburg. Unlike the ordinary protons and neutrons in atomic nuclei, which consist of three of the elementary particles called quarks, the pentaquark contains five. The Russians convinced a team of experimental physicists at a Japanese particle accelerator to look for the particle debris expected when pentaquarks decay, and in…
