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Heavy-Particle Production by Cosmic Rays (1979) |
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A. Stable Heavy Leptons
Charged heavy leptons will interact mainly electromagnetically. The range of such stable heavy leptons after production should therefore be about
Heavy leptons should mostly be produced nearly at rest in the center-of-mass system. Their mean energy in the earth's frame would therefore be about 
since the 
production rate is largest when the incident cosmic ray has an energy 
. Hence their range (in water) should be about 
. Lighter 
will therefore stop in the oceans (the 
forming ``water'' and the 
perhaps ``ammonium'' ions). Heavier ones will stop deep in the earth; they might be found in lava. The abundance of light in ocean water should be given in terms of the flux 
[Eq. (7)] by (9)
Since terrestrial searches may reach a sensitivity of one new particle in 
nucleons (of sea water) (10) they should be sensitive to new stable heavy leptons with masses up to about 20 GeV.
B. Heavy Hadrons
Heavy hadrons would undergo secondary interactions in the atmosphere after production. The strong interactions of possible heavy hadrons are essentially unknown; we expect their cross sections to be similar to those of light hadrons. (11) We estimate that 
mb at high energies and that the average inelasticity (
) of an 
collision is about 0.3, and expect these guesses to be correct to within a factor of 2.
Semistable heavy hadrons (with lifetimes 
sec) could only be detected in delayed-particle cosmic-ray experiments (1) , (12) (see Sec. IV); stable ones are, however, also amenable to direct terrestrial searches. The mean range of stable hadrons of energy 
is given very approximately by
where 
is their interaction length. Heavy hadrons, like heavy leptons, tend to be produced nearly at rest in the center-of-mass system [typically the fractional longitudinal momentum (
) distribution for heavy hadrons produced far above threshold is exp(
)], so that their mean energy in the earth's frame is about 
. Using this and the above-mentioned estimates for 
and , we find that 
in water, equivalent to about five times the atmospheric depth. Neutral and negatively charged heavy hadrons should be captured in nuclei when they stop, but positive ones should capture an electron to form a hydrogenlike atom (as do positive pions). The concentration of possible heavy hadrons in the form of ocean water would therefore be approximately
so that terrestrial searches in sea water could detect stable heavy hadrons with masses up to 
GeV. Searches might also be considered in substances such as ocean sediments and moon rock in which the concentration of these particles would not have been so diluted (the concentration of a 10 GeV stable heavy hadron in a core from 
10 m below the lunar surface could be as great as one in 
nucleons).
