Production of new particles in heavy-ion collisions

Abstract

Experimentally observed sharp lines in the positron-emission spectra resulting from low-energy heavy-ion collisions are interpreted in terms of the production and subsequent decay of a neutral, pseudoscalar particle. This particle has a mass of about 1.6 MeV and a lifetime of about 1.3 x 10" 13 sec.

On the Possibility of New Particle Production in Heavy-Ion Collisions

“…for an axion of mass 1.65 MeV, X is either 4.4 x 10~2 or 22 assuming three generations of quarks and taking the ratio of u and d quark current algebra masses to be 0.56. The latter X value yields too long a lifetime (~1CT 5 sec) to be compatible with experiments, 10 while the former value gives a lifetime of about 10"" 12 sec, in agreement with the electron anomalous magnetic moment considerations.…”

“…corrections, 1^ one concludes that this contribution would not have been observed if gg ~ lO" 1 *. 10 Since this particle predominantly decays into electron-positron pairs, its lifetime can then be calculated to bẽ 10~1 3 sec 10 which is well within the previously mentioned bounds.…”

“…However, essentially all axion searches performed prior to 1986 are not sensitive to a particle decaying as fast as 10~1 3 sec. 10 ' 20 '…”

“…In this talk, I consider an alternative hypothesis, namely two-body decay of a particle, 10 >* * which would explain the constancy of the peak energy. I also discuss the consequences of such a hypothesis and recent theoretical and experimental work motivated by it.…”

Searching for Axionlike Particles with Ultraperipheral Heavy-Ion Collisions

“…1) and with mass in the range 5 to 100 GeV. (See [12][13][14] for early proposals related to MeV-scale particles in low energy heavy ion collisions.) Relatively light pseudoscalar bosons are natural ingredients in a large class of models which invoke the breaking of approximate symmetries.…”