Underground particle hunts
The dark matter experiments described in “Mining for missing matter” (SN: 8/28/10, p. 22) sound almost identical to those looking for neutrinos. Both are placed deep underground to help screen out background radiation, especially neutrons. How do particle hunters differentiate between neutrino hits and those by the putative dark matter particles? Also, the article makes it sound like investigators think there is only one type of [exotic] dark matter particle. Why is that when there is an entire zoo of normal matter particles and forces?
James Smith, San Jose, Calif.
Neutrinos, for the most part, would deposit much more energy than that expected for dark matter particles, though a few rare types of neutrino interactions could produce signals similar to those of dark matter particles. The sizes of the detectors have been very different