I. Introduction

Numerous unified models of elementary particles suggest that there may exist species of hadrons or charged leptons other than those already known. It is entirely possible that some of these new particles may be stable or nearly stable ( sec). Present accelerator experiments indicate that no such particles exist with masses less than about 4 GeV (1); the next generation of accelerators should extend this search through their capability of pair-producing particles with masses of up to 15 GeV. At least in the immediate future, more massive particles can be found only if they are remnants from the early universe or are produced by interactions of cosmic rays. Only absolutely stable heavy particles produced in the early universe would have survived to the present, and conventional models of the early universe indicate (2) that such particles should be readily observable in forthcoming static terrestrial searches. Even if no heavy particles were created in the presumably high temperatures of the early universe, a small terrestrial abundance could still result from the interactions of cosmic rays with the earth's atmosphere. Stable or nearly stable heavy particles produced in this way might also be directly detectable in cosmic-ray experiments.

In this paper we consider various features of the production of possible heavy (nearly) stable particles by cosmic rays. We also discuss some of their properties. Throughout this paper we aim to provide only order-of-magnitude estimates since significantly more accurate predictions would require a knowledge of cosmic rays and particle interactions not yet available.

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