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Cosmic Rays From Galactic Black Holes
dork writes in with word of a study that contradicts, at least for the highest-energy events, the recent conclusion that cosmic rays are probably formed in supernova remnants. The Pierre Auger Observatory in Argentina has announced that active galactic nuclei are the most likely candidates for the source of the highest-energy cosmic rays that hit Earth. The researchers found that the sources of these highly energetic events are not distributed uniformly across the sky, linking their origins to the locations of nearby galaxies hosting active nuclei in their centers. These galaxies are thought to be powered by supermassive black holes that are devouring large amounts of matter. The exact mechanism of how particles get accelerated to energies 100 million times higher than achievable by the most powerful particle accelerators on Earth is still unknown. The observatory has made 1% of its events available through a public online event display."
Cosmic rays can provide some interesting information for physicists.
In fact, since the particle accelerator for the LHC has not yet turned on, the only real "data" to speak of is cosmic rays passing through the detectors. It's great background noise to make sure everything is working.
However, it's not as good as an accelerator for a couple of reasons:
1) Most interesting particles are the decay products of a collision, not necessarily in cosmic rays.
2) Repeatability. While protons in the LHC may collide at 100Hz or so, cosmic rays are a little less predictable.
3) Statistics. To show the existence of a new particle, you need statistics at 5-sigma. This might require tens or hundreds of thousands of recorded events of a certain signature in order to be considered reliable. You simply can't get that from cosmic rays.
(3) is why some results from the Tevatron are just now getting interesting - the device has simply been running long enough to make the discovery of the Higgs a remote possibility because of the sheer number of days running and events recorded. Because the energies of the LHC are going to be much higher and at a greater rate, the Higgs search should be much faster on that machine.
(I am not a particle physicist. I just work for them.)
Most interesting particles are the decay products of a collision, not necessarily in cosmic rays.
The problem here is one of energy. Cosmic rays do actually "collide" with the ATLAS detector but the energy available is far, far lower than current colliders plus most of the cosmic rays are muons which mean that they only rarely have a real collision.
Repeatability. While protons in the LHC may collide at 100Hz or so, cosmic rays are a little less predictable.
You are a few orders of magnitude off here. The LHC proton bunches collide at 40MHz and there are roughly 20 collisions per crossing at nominal intensity. In fact the bunches collide so rapidly that the particles from the preceding collision have not actually escaped the detector by the time the next bunch crossing occurs. On the other had, at the surface, one cosmic ray will pass through 1cm3 every second. Down in the detector pit this is less but what also kills the rate is that we want a direction that will pass through most of the detector.
Statistics. To show the existence of a new particle, you need statistics at 5-sigma. This might require tens or hundreds of thousands of recorded events of a certain signature in order to be considered reliable. You simply can't get that from cosmic rays.
Actually new particles have been found in cosmic rays - that is how the muon (heavier brother of the electron) was discovered in 1935/6 (IIRC). To get to 5-sigma you simply need a lot more signal events than background events. If your backgrounds are very low then you don't need many events at all.
(I am not a particle physicist. I just work for them.)
I am a particle physicist and while I don't know whom you work for or in what capacity - thanks! A lot of people don't realise that while there are a lot of physicists working on theses experiments there are even more technicians, engineers, machine operators etc. behind the scenes making it all possible.
Long ago I read that dust particles from meteors are important to the atmosphere because they nucleate raindrops. I wonder if the heat dumped into the at atmosphere by particles with this amount of energy has an effect on the energy budget of the stratosphere which would be worth modelling.
ISTR it is believed that cosmic rays may trigger lightning bolts, which are quite important to life.
http://blog.nexusuk.org