Talk:Positron

Number

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?

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)

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)

I would hate to dissuade someone from asking a clarifying question in an article's discussion page. The function of these discussion pages is to collaborate in improving the article. Sometimes that end is accomplished indirectly by people asking questions about the topic, revealing that the article might be improved or expanded. CosineKitty (talk) 02:45, 20 January 2010 (UTC)

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)

Earlier "discovery"?

Skobeltsyn page says he observed the positron in 1923. This page says 1929. Which date is correct? Marcreif (talk) 12:14, 26 April 2016 (UTC)Marcreif

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)

In this very good articles it is stated (as practically everywhere else) that "Feynman, and earlier Stueckelberg, proposed an interpretation of the positron as an electron moving backward in time,[6] reinterpreting the negative-energy solutions of the Dirac equation. Electrons moving backward in time would have a positive electric charge."

Actually, A.S.Eddington in his Presidential address to the Mathematical Association, delivered on 5 January 1931 (The End of the World: from the Standpoint of Mathematical Physics, Nature, Supplement, no. 3203, 21 March, 1931) said the following. "I was once asked a ribald question: How does an electron (which has not the resource of consciousness) remember which way time is going? Why should it not inadvertently turn around and, so to speak, face time the other way? Does it have to calculate which way entropy is increasing in order to keep itself straight? I am inclined to think that an electron does something of that sort. For an electric charge to face the opposite way in time is the same thing as to change the sign of the charge. So if an electron mistook the way time was going it would turn into a positive charge. Now, it has been one of the troubles of Dr. P.A.M. Dirac that in the mathematical calculations based on his wave equation the electrons do sometimes forget themselves in this way. As he puts it, there is a finite chance of the charge changing sign after an encounter. You must understand that they only do this in the mathematical problem, not in real life".91.55.175.213 (talk) 11:08, 18 October 2013 (UTC)

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)

Don't worry, more "scientific" stuff is about to be added. A page on positron annihilation spectroscopy will also emerge in a few weeks.Positroni (talk) 22:00, 18 May 2008 (UTC)

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)

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)

positron-electron collisions

i am a 16 year old boy at Manchester Grammar School but have a wide knowledge of the sub atomic world. in the Standford Linear Accelerator Center for example accelerating electrons into positrons i have read that this forms pure energy. they cn thn re-matarialize into the same constituents, i.e a positron and an electron. theoretically wouldnt this mean that this cycle can be a continous cycle occuring an infinite number of times as the positron will always encounter an electron and therefore could'nt there be a continual liberation of energy, which we all know is impossible? lastly as the positron-electron energy re-materializes it is said that it can also form a muon and an antimuon. what i cannot comprehend is how it can re-materialize into something that is 200 times (or of that order) bigger than the original mass of the constituents? question by Mark Ramotowski. —The preceding unsigned comment was added by Rambatino (talk • contribs) 23:25, 8 May 2007 (UTC).

At each collision, no more energy is liberated than was there in the first place. The extra energy to make a muon/antimuon pair comes from the large momentum of the colliding electron and positron. energy is conserved, but total mass is not. -- SCZenz 15:18, 27 July 2007 (UTC)

Er, this is a case where energy is not preserved. Energy ($E$) and momentum ($\mathbf {p}$) are not preserved, but the relation $\mathbf {p} \cdot \mathbf {p} -c^{2}E^{2}$ is preserved. Some momentum becomes energy, and so neither energy nor momentum is preserved. (212.247.11.156 (talk) 20:43, 7 October 2009 (UTC))

Thank you for your informative comment, but the relation between two variables can be more complex than a simple linear, and if a relation exists and can be described, you can turn one variable into another, right?

$P=mv$, $E=m(v^{2}):2$, so $E=Pv:2$, Since the relation between Energy and Momentum is linear with variables we know, if we know the Momentum and the Mass, we can calculate the velocity $v=P:m$ and therefore the energy. This means that a large momentum does equal a large energy and that you can describe it in formulas. This is done via Newtonian mechanics, and at high energies electrons have relativistic speeds, but AFAIK momentum and energy can be correlated in a somewhat linear fashion, since General Relativity can be approximated by Newtonian mechanics at low energies.

If it can't, please elaborate with formulae. Braggy (talk;contributions) 14:19, 21 March 2022 (UTC)

Message to the 16 year old poster: Why did you bother to capitalize "Manchester Grammar School" but not your sentences? And why bother with periods? If you want your writing to be as readable as possible, please use traditional punctuation. Obviously Manchester Grammar School doesn't teach grammar. And what is "could'nt"? The apostrophe stands for a missing letter, in this case "o", but you did not mean "couldont" did you? Why "wouldnt"? And your careful capitalization of "Manchester Grammar School" makes a mockery of your cn, thn. Why not save more precious keystrokes by writing "Mnchstr Grmr Skl"? Your posting makes you appear dumb/unintelligent. Sorry, but in this case your mobile phone ABC syntax or "Internetese" medium of communication becomes the message, rather than your deep discussion about nature. — Preceding unsigned comment added by 76.176.184.100 (talk) 16:17, 13 December 2011 (UTC)

Good Article nomination

GA review (see here for criteria)

1. It is reasonably well written.

   a (prose): b (MoS):

2. It is factually accurate and verifiable.

   a (references): b (citations to reliable sources): c (OR):

3. It is broad in its coverage.

   a (major aspects): b (focused):

4. It follows the neutral point of view policy.

   Fair representation without bias:

5. It is stable.

   No edit wars etc.:

6. It is illustrated by images, where possible and appropriate.

   a (images are tagged and non-free images have fair use rationales): b (appropriate use with suitable captions):

7. Overall:

   Pass/Fail:

⋅This article is almost completely unreferenced, does not have a summary introduction separate from the minimal main content, and is dominated by unreferenced trivia, apparently selected on the base that the word "positron" is there somewhere. Needs more on physics, less on entertainment. Jimfbleak (talk) 08:57, 14 December 2007 (UTC)

importance rating

i feel that this is a very important topic, as the experimental discovery of the positron was a huge success for theoretical physics, and believe the positron is an important antiparticle, please revert or discuss if you diagree. It is however a shame the quality of the article does not represent the importance, and hope someone has the time that i dont to improve it 193.60.83.241 (talk) 11:56, 14 May 2008 (UTC)

The article is about to be improved, please be patient.Positroni (talk) 22:01, 18 May 2008 (UTC)

Reassessment?

Is it time to reassess this article for "good article" status? It has been two years... -RadicalOne•^{Contact Me}•_{Chase My Tail} 03:08, 20 January 2010 (UTC)

Funny, I have been looking at this article the last couple of days, and tonight I started digging through all my college physics books looking for some more beef to add here. It seems like a thin coverage of such and important physics topic. CosineKitty (talk) 03:19, 20 January 2010 (UTC)

I agree. -RadicalOne•^{Contact Me}•_{Chase My Tail} 03:37, 20 January 2010 (UTC)

I did a bit of work to the history section tonight. I tried to be WP:BOLD, but hopefully not too much! It would be nice for experts to review my changes for errors or misinterpretations, both in terms of history and physics. I'm concerned my changes may be controversial, though I did my best to base it all on primary sources. CosineKitty (talk) 03:08, 22 January 2010 (UTC)

I know a particle physicist - should I ask her to look it over? She will not mind, I can assure that. -RadicalOne•^{Contact Me}•_{Chase My Tail} 03:16, 22 January 2010 (UTC)

Of course... no need to get permission. Any help improving this would be great! CosineKitty (talk) 15:07, 22 January 2010 (UTC)

She likes it. :) -RadicalOne•^{Contact Me}•_{Chase My Tail} 15:49, 22 January 2010 (UTC)

That is good to hear! I am still concerned that I may have gone too far by interpreting the original Dirac paper. Everywhere else on Wikipedia writes that the Dirac paper "predicts" the existence of the positron. However, the notion of prediction is a complete fabrication when I read the paper, so I used the wording here. However, this may be construed as original research on my part, and my admitted use of "primary" sources is problematic under WP:PRIMARY. Perhaps all the physicists who read that paper at the time saw something obvious that I am missing, leading them to say "wow, there must be some kind of anti-electron", even though I can't find it. I hope someone will come along and give me some good-faith head-butting on this issue, along with reliable sources to back up the prevailing point of view, so that we can end up with an even better article. CosineKitty (talk) 17:38, 24 January 2010 (UTC)

From the background I do have in quantum physics - far from professional, but enough so that I would be watching this article ;) - Dirac appears to have hypothesized the positron not from a modern standpoint but from the hypothetical "sea" that bears his name. In an effort to solve the false vacuum paradox of negative energy, he implied the "sea" must be full an thus not permit everything to settle into the lowest energy state. When one of the particles occupying a "slot" was removed, that space was a positron. Therefore, he appears to have been thinking of the positron not as a unique particle, but merely an electron with negative energy. This is incorrect, and its mathematical impetus "E⁴=m²c⁴" and thus "E²=±mc²" appears to me to be more mathematical manipulation than actual proof. Yes, negative energy exists, but Dirac appears to have been in a bit of a blind alley. -RadicalOne•^{Contact Me}•_{Chase My Tail} 17:54, 24 January 2010 (UTC)

Interesting! And the Dirac sea article seems to be consistent with this interpretation: the sea was based on an aether-like concept. CosineKitty (talk) 23:03, 24 January 2010 (UTC)

That is a good analogy. -RadicalOne•^{Contact Me}•_{Chase My Tail} 23:55, 24 January 2010 (UTC)

I wish I could claim credit for it, though it was stolen from one of the references of the Dirac sea article.  :) Apparently, in the post-Michelson-Morely world, that was a serious hindrance to the idea. CosineKitty (talk) 00:35, 25 January 2010 (UTC)

It would be. One could spend hours getting their tail in knots just trying to justify it. -RadicalOne•^{Contact Me}•_{Chase My Tail} 00:45, 25 January 2010 (UTC)

Dirac really did predict the positron

I have added another step in the story between Dirac's 1929 paper and Anderson's discovery in 1932. I found a paper he wrote in 1931 in which he explicitly predicts the existence of an "anti-electron", that it should have the same mass as the electron, and that it would mutually annihilate with an electron. To avoid problems of WP:PRIMARY, I have included a book reference to corroborate my reading of the original paper. CosineKitty (talk) 02:35, 11 February 2010 (UTC)

That certainly sounds much closer to the real description of a positron. However, I am now left wondering how he got from an electron with negative energy to a new particle altogether. Did he predict other differences (like an equivalent of the not-yet-discovered color charge) or simply an electron with negative electric charge? Maya and I were discussing this over a meal and agree that unless he predicted some of the "flagship" characteristics of antimatter, he came close but from a wrong direction. -RadicalOne•^{Contact Me}•_{Chase My Tail} 02:56, 11 February 2010 (UTC)

Maybe that part needs a little more detail. You might try reading the online version of the 1931 paper from the citation (or this copy works too) and see what you think. He explicitly abandons the idea of the proton being an anti-electron. He says "a hole, if there were one, would be a new kind of particle, unknown to experimental physics, having the same mass and opposite charge to an electron." He also predicts that the anti-electron will annihilate with an electron, which is what clinched it for me. He even goes on to speculate about the possibility of an anti-proton, the proton being only other known subatomic particle at that time. But yes, it would be nice to find some secondary sources that give an interpretation of the Dirac/Oppenheimer discussion. CosineKitty (talk) 12:45, 11 February 2010 (UTC)

Yes, the prediction of annhilation is certainly compelling. However, he appears to remain steadfast in his sea hypothesis, in which an antiparticle is a particle with negative energy (wrong), and that there is a limited number of "slots" for such particles (also wrong). As such, unless a source that discards this baggage is found, I am hesitant - as is Maya - to attribute the prediction of the true positron to Dirac. Dirac was indeed an excellent physicist, and one of high intelligence, but he appears to have fallen out of orbit on this one. -RadicalOne•^{Contact Me}•_{Chase My Tail} 23:18, 11 February 2010 (UTC)

Almost everywhere I look, it is stated as fact that Dirac did predict the positron. I might or might not agree with your reluctance, mostly because I haven't finished my research yet. But regardless of what we think, in the long run we will have to defer to what reliable secondary sources say, otherwise it is original research. It wasn't until recently that I read WP:PRIMARY and realized I am already skating on thin ice with regard to Wikipedia policy when I read the original papers and interpret them. So in the mean time, I'm looking for more books written by established experts in the field about Dirac's work. If I find multiple conflicting points of view, I can balance them here with the "A says X, but B says Y" approach. Here is one possible dissenting voice, though I will need to track down the book and read it.

The negative energy point is interesting because a non-physicist like me thinks (naively perhaps) that the positron+electron reaction would then result in zero energy release; they would both vanish without a trace, as opposed to the pair of gamma photons. But my guess isn't a reliable source as defined by Wikipedia policy. CosineKitty (talk) 01:18, 12 February 2010 (UTC)

What did some of the other giants of quantum physics (Feynman, Pauli, Planck, Weinberg, and the like) have to say on this matter?

The negative energy point would be correct...were quantum physics natural and straightforward. Think of a stationary object. As per $E_{k}={\frac {mv^{2}}{2}}$, its kinetic energy (the kind of energy mentioned in the above paper) is zero. Does that mean it doesn't exist? No. The theory of quantum mechanics, once one understands it, is intutive. Some of the premises, not so much. -RadicalOne•^{Contact Me}•_{Chase My Tail} 01:31, 12 February 2010 (UTC)

Positron acceleration procedure

Is there a reference concerning the positron that explains the positron acceleration procedure? I don't see anything in the article that explains that. How does Fermilab do it?WFPM (talk) 11:39, 21 May 2010 (UTC)

The positron is a charged particle, so it's really no different than accelerating any other charged particle. Headbomb {talk / contribs / physics / books} 21:47, 9 August 2010 (UTC)

The Positron source (at Fermilab), per (National Geographic May.1985), is said to be created from Beryllium (EO4Be9). Thus the source of the Positron from within the atom would have to be from one of the Neutrons. However since it is positively charged, it is not understood how it it is impelled in the opposite direction from the electron by the (electrostatic?) directional acceleration system of the electrons.WFPM (talk) 18:57, 17 August 2010 (UTC)

Blackett and Occhialini

The article should probably mention Patrick Blackett and Giuseppe Occhialini who did secondary results that confirmed and popularised the discovery of the positron, although Anderson is correct credited as the initial discoverer. -93.97.122.93 (talk) 16:57, 28 May 2010 (UTC)

Discovery by a bubble chamber ??

In 1.2 Experimental clues and discovery, it says Dmitri Skobeltsyn used a bubble chamber while the article bubble chamber says it was invented in 1952... I suppose it was a cloud chamber, can you confirm ? —Preceding unsigned comment added by AiméCésar (talk • contribs) 17:55, 9 August 2010 (UTC)

He used a cloud chamber. Fixed and source added. Solarswordsman (talk) 01:57, 11 August 2010 (UTC)

Fractional version of mass

The positron and electron both have a "fractional version" of their mass in the Infobox. The note mentions that this is just another way of writing the decimal value, so it doesn't add any information. I've never heard of it being used and I haven't seen it on any other Wikipedia page, so I don't understand why it is useful to have it. I have no formal education in this area, but I have been reading a lot on the subject, so I expect that most people will not know what this value means for the positron. Can somebody please explain what this information means for the positron and add it to the page, or remove it if there's no reason to have it?     — SkyLined (talk) 07:17, 3 August 2011 (UTC)

I'm not sure I understand what you mean by fractional mass. Can you elaborate? Dauto (talk) 16:02, 3 August 2011 (UTC)

In the infobox, under mass, there are a couple of numbers. One of them has a note explaining "The fractional version's denominator is the inverse of the decimal value (along with its relative standard uncertainty of 4.2×10−10)." From this I assume that number is the fractional version. If you raise that number to the power -1, you get the "normal" value, so it's just a different way of saying the same thing in my opinion.     — SkyLined (talk) 21:07, 3 August 2011 (UTC)

I agree. It's just a different way of saying the same thing. I don't know why it's there. Doesn't hurt anything, I suppose. I wouldn't mind were it removed. Dauto (talk) 23:31, 3 August 2011 (UTC)

After double checking the calculation I realize that that number seems to have a typo. it is the inverse of 5.485799043 instead of 5.4857990943. Note the missing digit. It should be either fixed or removed. Dauto (talk) 23:49, 3 August 2011 (UTC)

Its numerical value is, for obvious reasons, close to the proton-to-electron mass ratio, but I agree that the inverse electron mass in inverse atomic mass units is useless. I would replace it with “1/1836.15267343(11) m_p” rather than removing it altogether, maybe. (This applies to both Positron and Electron.) ― A. di M.​_plé​^dréachtaí 00:17, 5 August 2011 (UTC)

References

Mass discrepancy

The mass in the box on this page needs to be updated to correspond to the same (more recent) source as that of the electron page, since a casual user may look up both positron and electron and think that the two have (very slightly) different masses (as I did before digging into the sources). David.S.Hollman (talk) 14:57, 30 January 2012 (UTC)

Picture caption?

I'm not entirely sure what the caption is referring to; it'd be helpful to have clarification on either the picture itself, or for the caption to be more clear. 86.163.71.158 (talk) 20:51, 6 May 2012 (UTC)

Who observed it first?

Dmitri Skobeltsyn and Chung-Yao Chao are both dated as "1929" for the first observations. Can someone please look into the exact dates, as in month and day, so we can know who really observed it first? DrZygote214 (talk) 23:02, 10 September 2014 (UTC)

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Discovery of positron

Who observed what when has been discussed on this talk page regarding the discovery of the positron. But, in reading this article, it remains puzzling as to why Dmitri Skobeltsyn is not given credit for the discovery of the positron. Did he not do anything with his cloud-chamber observations of 1929? Perhaps not publish them? Anyway, right now, the article confusing on this matter. Attic Salt (talk) 13:57, 5 August 2018 (UTC)