I should clarify one point, though. We expect that charm particles will be created when cosmic ray protons or nuclei smash into the upper atmosphere. There's no good way to tell when it happens, because there are so many particles in the resulting shower. So what we do is extrapolate the curves we find from fixed target and collider experiments (where we can usually tell) out to the cosmic ray primary energies.
Backing up a bit: the cosmic ray primary is the one that comes from where-ever and hits the upper atmosphere: usually a proton, sometimes another nucleus. The primary has the highest energy, of course. The secondary particles share that energy, and then they interact with other atmospheric nuclei to produce more (lower energy) secondaries and on and on until they range out, are absorbed in nuclei, or decay. The stuff that hits the ground is almost all muons from the decay of particles produced in the showers.
If the extrapolation is wrong, our estimate for how many high-energy muons we should get from that initial primary-cosmic-nucleus hitting a nitrogen nucleus will be wrong, because we won't have the rate of charm quarks in the first generation of secondary particles and subsequent decay into relatively high energy muons right. And the decay of one of those very high energy muons would generally produce a high energy neutrino.
But, as Halzen points out, if we discover that we have the wrong rate, that tells us something interesting about charm physics.
I am not leaking anything by saying that Bert and Ernie are not the only interesting events, but they are (so far) the highest energy, and the first ones discovered.
You might wonder why the group gave the events names. It is in the culture, in a manner of speaking. There are 86 "strings" with detectors (DOM) strung on them: a total of 5160. OK, quick: does DOM number 54-02 need to be rebooted, or was it 54-20? Early on (before I arrived) someone (Krasberg?) figured out that people remembered names better than strings of numbers, so each DOM has a location (string and position on the string), a serial number, and a name (Cayenne_pepper, Porter, Chardonnay, Demophobia, Thalassophobia, Claestorp, Apache_tribe, and so on). The extension of this idea to rare and interesting events I leave as an exercise to the reader.
2 comments:
Are you drawing the circle around the bullet hole?
Hardly. You should hear the debates.
The only thing that is likely to firmly answer the question is to have enough statistics to let us unambiguously point at some astronomical object and say "this many neutrinos came from that object, that many are background" That means being able to see the energy spectrum for on-source and off-source regions of the sky, and compare them. The spectra should be different, and the difference will tell us something about the production mechanisms of atmospheric and extra-solar neutrinos. If the background atmospheric neutrino spectrum doesn't match the theory, we'll be able to say whether the charm production cross section rises faster with energy than expected. It won't be as accurate as results from a super-super collider experiment would be, but such a beast isn't affordable (and would take way too long to build).
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