A Re-evaluation of Evidence for Light Neutral Bosons in Nuclear Emulsions

TL;DR

This paper re-analyzes electron-positron pair-production data from emulsion detectors to investigate potential light neutral bosons, finding possible signals with varying significance and very small production cross-sections.

Contribution

It provides a consistent re-evaluation of previous data, suggesting evidence for light neutral bosons with specific mass ranges and lifetimes, using a conservative background model.

Findings

Possible neutral bosons with masses 3-20 MeV/c^2 identified

Statistical significance of signals varies from 2 to 8 sigma

Production cross-section is over 1,000 times smaller than pion production

Abstract

Electron-positron pair-production data obtained by bombardment of emulsion detectors with either cosmic rays or projectiles with mass between one and 207 and kinetic energies between 18 GeV and 32 TeV have been re-analysed using a consistent and conservative model of the background from electromagnetic pair conversion. The combined data yield a spectrum of putative neutral bosons decaying to e+e- pairs, with masses between 3 and 20 MeV/c^2 and femtosecond lifetimes. The statistical significance against background for these "X-bosons" varies between 2 and 8 sigma. The cross-section for direct production of X-bosons increases slowly with projectile energy, remaining over 1,000 times smaller the the pion production cross-section.