An experiment to investigate the existence of charged particles of mass ~550 m_e

Abstract

Evidence suggesting the existence of charged particles of mass ~550 m_e has been reported by Alikhanian, Sostakovic, Dadaian, Fedorov and Deriagin. A search has been made for these particles in a photographic emulsion stack exposed for five months at an altitude of 11 000 ft, λ= 24° N at Khillanmarg (Kashmir). The central plate of the stack was scanned for all tracks, with dip angles <45°, due to particle’s brought to rest within it. A total of 5790 tracks was obtained in this scan. Of these tracks, 2613 were due to particles, with ranges <5 mm, emerging from nuclear disintegrations; these were not considered further. Mass measurements were carried out on the remaining 3177 tracks by the grain density vs. residual range method; the range interval involved is (3÷40) g/cm². The 3177 tracks investigated were found to be due to 1018 μ-mesons, 168 π-mesons and 1991 particles of mass ≥850 m_e. No particle with a mass estimated to be between 390 m_e and 850 m_e has been observed. Five such particles are to be expected on the abundance of ~½ % compared to μ-mesons (in the same range interval) quoted by Alikhanian et al. The question of the existence of such particles is discussed in the light of this and other experiments.