|WikiProject Physics||(Rated C-class, High-importance)|
|WikiProject California / San Francisco Bay Area||(Rated C-class, Low-importance)|
Their formation requires energy equivalent to a temperature of 10 million °C, and Big Bangs aside, this does not tend to happen naturally. (from the article) -- Isn't the interior of the sun (a "natural" body) at 15 Million Kelvin, which would be high enough? 22.214.171.124 04:50, 17 November 2005 (UTC)
- 10 million C sounds wrong to me. Let me check on this. HEL 16:27, 30 September 2006 (UTC)
- Setting M_P = k_B T I get a temperature of 10 trillion Kelvin (10^13 K). Antiproton freeze-out is going to happen at a somewhat lower temperature (factor of 20, rule of thumb?). HEL 13:29, 2 October 2006 (UTC)
Should I add Template::Antimatter? Its longer than the body text. Chad 07:49, 6 February 2006 (UTC)
- The antiproton article is still in Category: Andromeda (TV series). Since the Andromeda references have been removed, should this category be removed also? HEL 16:38, 8 October 2006 (UTC)
Reverted to Sep 30 2006 version -- negatron is (rarely) used to refer to an electron, never to an antiproton. HEL 13:13, 2 October 2006 (UTC)
Antiproton production in cosmic rays?
We should mention something about antiprotons in cosmic rays. If I remember right, they have been detected in cosmic rays by detectors in space. Let me check and find a ref. HEL 13:35, 2 October 2006 (UTC)
- Did it! I added a section on "Occurrence in Nature", about antiproton detection in cosmic rays. It's still a little rough; if anyone wants to improve it I would be grateful. I'm hoping to add more in the future, maybe a bit about discovery, and maybe clean up some kind of non-encyclopedic-sounding style in the intro ("Big Bangs aside"?) HEL 03:39, 7 October 2006 (UTC)
- Good show. Only one piece of editing advice though: don't put linebreaks within paragraphs when you get to the edge of the edit box, just keep typing. When paragraphs are broken up over multiple lines it makes future editing harder and it makes changes more complicated to review with the diff functionality. But again, good job! — Saxifrage ✎ 08:34, 7 October 2006 (UTC)
- Thanks for the tip! I'll be careful in the future. (I typed it up offline in pico which sticks in the linebreaks automatically.) HEL 15:09, 7 October 2006 (UTC)
Burst of energy?
The first sentence states: "any collision with a proton will cause both particles to be annihilated in a burst of energy". Can anyone quantify the form of this energy? By analogy, the annihilation of an electron and a positron produces (I believe) a pair of characteristic 511 keV photons.
- Good question! In any kind of annihilation reaction like that, you get out a selection of whatever is allowed by the total energy and quantum numbers of the initial state. For electron-positron annihilation at low speeds (when you only have 2 x 511 keV of energy available), the only things lighter that you can annihilate into are photons or neutrinos. The pair of photons is by far the dominant mode (to get neutrinos you'd have to annihilate via a W or Z boson; they're heavy so their contribution is very suppressed at these low energies).
- For proton-antiproton annihilation at low speeds you've got 2 x 938 MeV of energy. I would expect the dominant annihilation mode by far would be via the strong interaction. Below the mass of the proton you've got the pions, kaons, eta, rho, and omega (at least). These are all unstable and decay down almost entirely to pions, muons+neutrinos and photons; the charged pions decay to muon+neutrino and the neutral pions decay to photon pairs; the muons finally decay depending on their charge to electron + 2 neutrinos or positron + 2 neutrinos. Unlike the electron-positron annihilation, you would typically get a good handful of final-state particles, so they wouldn't be monoenergetic.
- I'm theorizing all of this; does anyone have more direct experience or references? HEL 20:26, 1 November 2006 (UTC)
The second paragraph says interactions energetic enough to produce antiprotons don't really happen in nature. I think this is false, or if it is true, should be reworded to avoid confusion. Antiprotons are produced in nature all the time, after all.
- You can wish for a consistent naming system, but in reality objects that are discovered early on in a field get well-known names that don't fit into later schemes. It's not Wikipedia's job to try to change this. --Strait (talk) 14:35, 30 November 2011 (UTC)
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