Talk:Positron

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The number is 1.022 Mev, a little over one Mev, not one thousand Mev. pstudier 20:50, 2003 Dec 8 (UTC)

Yes, that was a mistake. - Patrick 00:24, 9 Dec 2003 (UTC)

Correct me if I'm wrong – I'm not a particle physicist – but isn't the positron supposed to have a spin of ±1/2?

No, you mistake the positron for the neutrino. How could the positron have spin +or- half, if so it could never be responsoble for the annihalation of it's anti-particle the electron User:62.253.219.130 11:14, 3 December 2004

Electrons and Positrons both have spin of 1/2. To annihalate, an electron must meet a positron with opposite spin, that is, an electron with spin +1/2 must meet a positron with spin -1/2. This event gives off two photons, each of which have spin of 1. So one photon will have spin of +1 and the other -1. See Spin (physics). pstudier 23:14, 2004 Dec 3 (UTC)

If a particle has "spin" 1/2, this means that the spin quantum number s = 1/2. The spin magnetic quantum number m_s can have values -s, -s+1, ..., s-1, s. Thus, if s = 1/2, m_s can be ±1/2. David 17:41, 8 Jun 2005 (UTC)

Q: The negative spin relates to the negative, or reverse, time factor in the calculations, if I am not completely mistaken. If I am not mistaken, does this mean that the positron is supposed to travel... well, you know... backwards in time?

Contents 1 Publicity 2 Positronic holes? 3 Parity 4 Earlier "discovery"? 5 what 6 Help! 7 Copyright of image

[edit] Publicity

At the Christie Hospital North West Medical Physics Open Evening last night, the speaker was talking about PET scanning and running a slide show, and on one of the slides was, in big(~20cm on a ~1m high screen) letters http://en.wikipedia.org/wiki/Positron. Boffy b 12:35, 2005 Mar 18 (UTC)

[edit] Positronic holes?

While I can't find a source for this (not normally a good sign), I was under the impression that a 'hole' in an otherwise electron-saturated lattice is also sometimes called a positron; Relative to the lattice it has an electropositive charge (zero rather than -1). I also thought this was the (pseudo)scientific explanation of the Asimov/Star Trek android brain - the more the android learns, the less energy it needs to store the information, and a magnetic bottle wouldn't be required inside the machine to prevent the brain from annihilating everything else. Can someone confirm or deny either of these? [I also checked for pseudopositron as the right word for this kind of phenomenon, but there doesn't seem to be anything else on the web using that term.] Cyrek 23:26, 1 June 2006 (UTC)

I think holes in a lattice are called, well, holes. I've never heard of them being called positrons, which would be a very confusing abuse of terminology. However, there is a historical analogy with Dirac's initial model of the positron as a hole in an infinite sea of negative-energy electrons. (This is an old, and no longer accepted, interpretation of the Dirac equation.) The science fiction business about negative energy may be based on that interpretation, but there isn't any particular scientific merit to the technobabble that I can see.

In the future, you might want to post questions at Wikipedia:Reference desk rather than on talk article talk pages, which are (strictly speaking) for discussion of the article itself. -- SCZenz 23:40, 1 June 2006 (UTC)

[edit] Parity

Positron has opposite parity as the electron. I would add this but I know nothing about it other than its true (probably). Fresheneesz 07:34, 9 June 2006 (UTC)

As far as I can recall, electrons are not parity eigenstates. You can only talk about parity of things like pions. -- Xerxes 21:54, 9 June 2006 (UTC)

Hmm, well its beyond me to disagree with you, but my physics teacher mentioned it in passing (not that I trust him..), and this page suggests to me that theres *at least* confusion about this. Fresheneesz 02:06, 10 June 2006 (UTC)

You're interpreting this wrong. The electron field really describes four different particles: the left-handed electron, the right-handed electron, the left-handed positron and the right-handed positron. Parity-reversal exchanges left-handed particles with right-handed ones. Charge-conjugation exchanges electrons with positrons. Due to CPT symmetry, if you apply parity-reversal, charge-conjugation and then flip the arrow of time, all reactions look exactly the same. This implies that left-handed electrons are "like" right-handed positrons. But neither is the parity-flip of the other. -- Xerxes 18:44, 10 June 2006 (UTC)

[edit] Earlier "discovery"?

I find that Eddington in "Further Notes on the Radiative Equilibrium of Stars" (Monthly Notes of the Royal Astronomical Society, 77, p. 611), published in 1917, mentions "positive and negative electrons occasionally anulling each other" as a source of stellar energy. What is this, if not antimatter (or some way-advanced prediction of something like it)? --Tardis 02:07, 10 July 2006 (UTC)

Well, this is something very interesting I didn't know before. There was a lot of speculation about "positive electrons" before Dirac came up with the right equation for them. In addition to the Eddington 1917 ref, I also found an article by Bragg in 1910 speculating about bound positive-negative electron pairs making up X-rays. So I suppose Dirac was just the first to come up with a correct derivation that the positron should exist. I think we should probably add a section discussing incorrect previous theories as well. -- Xerxes 18:22, 10 July 2006 (UTC)

My reading of old books and articles on the electron and electricity helped me to find that a positive electron was sometimes what we now call a proton because electron was, for a while, considered to be an element for a short while.

Bvcrist 20:56, 11 August 2006 (UTC)

[edit] what

Why is half of a scientific article devoted to "The positron in fiction"... Who really cares if the positron was in some dumb anime show. Positron Annihilation Spectroscopy isn't even mentioned in the article. I would rewrite it myself but I don't have any expertise on the subject.

This is why people on the internet shouldn't be allowed to write encylopedias... No matter what the article is about it is going to be packed full of references to shitty cartoons and ghostbusters by some stupid geek. —The preceding unsigned comment was added by 81.152.10.161 (talk • contribs) .

What, are you under the impression that an explanation of Positron Annihilation Spectroscopy was deleted in order to make room for cartoons? Wikipedia is under construction. Melchoir 23:01, 16 September 2006 (UTC)

[edit] Help!

I'm currently studying physics at A2, and have come across what seems to be a logical contradcition. If protons are positively charged and electrons negatively charged, why do the electrons leave the nucleus in Beta decay? Please someone help! 80Turnbull 21:57, 16 November 2006 (UTC)80Turnbull

I added a link. Does that clear anything up? --Tardis 21:13, 17 November 2006 (UTC)

[edit] Copyright of image

The copyright notice of the image "Cloud chamber - visible trace of positron" [1] says that the copyright is expired because more than 70 years have passed since the author's death. Since Anderson died in 1991, this is obviously false. Also, the picture is upside-down. 147.142.160.134 17:57, 13 January 2007 (UTC)