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Astronomical

If an astronomical strangelet were to hit the atmosphere, it would result in a shower of high energy particles. Several experiments originally conceived to detect cosmic tex2html_wrap_inline560 rays have sensitivity to such a shower. As an upper limit on the expected flux, assume that all of the dark matter consists of strangelets. The density of dark matter in our region of space is about tex2html_wrap_inline562 g/cm tex2html_wrap_inline460 . Strangelets of radius .01 to 10 cm would then have a number density of tex2html_wrap_inline566 cm tex2html_wrap_inline568 . The typical collision velocity would be that of the sun's velocity due to galactic rotation, about tex2html_wrap_inline570 cm/sec. This results in a limit on the flux reaching the earth of tex2html_wrap_inline572 cm tex2html_wrap_inline574 sec tex2html_wrap_inline576 , depending on size.

One such experiment was originally intended to search for pulsars in the crab nebula. It ran for 112 hours, and was set to trigger on events lasting tex2html_wrap_inline578 seconds. A reanalysis of the data to search for strangelet events required a `burst' of 12 events to arrive within tex2html_wrap_inline580 seconds. This corresponds to the transit time of a strangelet through the part of the atmosphere from which events could be detected. Producing 12 events from random fluctuations would require a fluctuation of tex2html_wrap_inline582 . From this analysis the upper limit on the flux of strangelets is tex2html_wrap_inline584 cm tex2html_wrap_inline574 sec tex2html_wrap_inline576 , for strangelets ranging from tex2html_wrap_inline590 g. This is below the upper limit from the quick estimate above.

Each of the other experiments have sensitivities to strangelets of a particular size, covering an overall range from tex2html_wrap_inline592 g to 250 g. Each places a limit on the total flux of strangelets of a given mass. When compared with the upper limit from the estimate above, the experiments are virtually all consistent with that limit. Experiments designed specifically for strangelet detection should be able to place much stricter limits.


next up previous
Next: Terrestrial Up: Detection of natural sources Previous: Detection of natural sources

Joshua Holden
Sun May 17 15:37:00 EDT 1998