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Articles Particle Physics Heavy-particle Production by Cosmic Rays (1979)
Heavy-particle Production by Cosmic Rays (1979) |
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The basic principle of a delayed-particle cosmic-ray experiment (1) , (12) is to search for particles which traverse the apparatus after the main part of an air shower has passed. Two measurements are usually made on these particles: their delay relative to the shower front and the energy that they deposit.
We consider an experiment under 8000 kg m
of the atmosphere, and with an effective area of 1 
, and we specialize our discussion to the production of hadrons; heavy leptons would probably be produced at a rate too small to be detected by present experiments and would deposit insufficient energy to register in a calorimeter. Very-high-energy primary cosmic-ray protons tend to interact within the top 1000 kg m of the atmosphere, about 15-20 km above the experiment, so any heavy hadrons produced will interact on average about twice before reaching the apparatus. They will as a result have an average energy of 
GeV at that point, with, however, a considerable spread about this mean value. (13) If, instead of our previous estimates of 
and 
we took 
to interact like a kaon, it would have an average energy of 
GeV, a possibility which we consider to be a lower bound. Since a particle with 
will be delayed by a time 
h(km) 
nsec relative to a particle with 
over a distance 
, the delay time for heavy hadrons would be 
nsec. This result is, however, sensitive both to the average energy and to : we find empirically that 
with only slight dependence on . (The apparent correlation between 
and 
should, incidentally, be washed out by fluctuations.) Since we expect heavy hadrons to be produced with 
(and therefore within the shower cone), an experiment with perfect detection efficiency might then observe 
heavy hadrons per year. (14) Thus, for example, if there is a stable hadron (15) with a mass of around 5 GeV then the experiment considered above should observe 
such particles per year; their average delay time should be about 20 nsec and their energy around 100 GeV. Even if this particle has a lifetime 
sec, it should still enter the apparatus at a detectable rate. Note that the detection of such a long-lived particle, if identified with a meson containing the 
quark, would rule out the Kobayashi-Maskawa six-quark CP-violation model. (16)
