Question regarding particle-pair production [Archive]

vernonner3voltazim

Aug20-04, 04:46 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nAn example of pair production is when a 1.1Mev gamma (approx)\nspontaneously becomes an electron and a positron. I have been\naware for years that this event can only take place where the\ngamma happens to encounter a virtual-particle pair nearby to\nsome ordinary charged particle.\n\nRecently I have been told that this event specifically requires\nthe ordinary charged particle to be an electron (or positron).\nIf a magnetic bottle was filled with protons, and a lot of 1.1Mev\nphotons were directed through the bottle, none of the photons\nwould ever spontaneously convert to an electron/positron pair.\n(But really-potent gammas, about 2Gev, could convert to proton/\nanti-proton pairs, in the vicinity of a protron.)\n\nI find this difficult to accept, that only electrons can\ncatalyze the electron/positron pair-productionn scenario.\nBecause it implies that the electric field around an\nelectron is not the same as the electric field around a\nproton. Virtual particles pop into temporary existence\neverywhere, so ANY where there happens to be a suitable\nelectric field, and a suitable gamma-ray, that is all we\nneed for pair-production. And some patience, of course.\n\nCan somebody here set the record straight? Thanks in advance!\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>An example of pair production is when a 1.1Mev \gamma (approx)
spontaneously becomes an electron and a positron. I have been
aware for years that this event can only take place where the
\gamma happens to encounter a virtual-particle pair nearby to
some ordinary charged particle.

Recently I have been told that this event specifically requires
the ordinary charged particle to be an electron (or positron).
If a magnetic bottle was filled with protons, and a lot of 1.1Mev
photons were directed through the bottle, none of the photons
would ever spontaneously convert to an electron/positron pair.
(But really-potent gammas, about 2Gev, could convert to proton/
anti-proton pairs, in the vicinity of a protron.)

I find this difficult to accept, that only electrons can
catalyze the electron/positron pair-productionn scenario.
Because it implies that the electric field around an
electron is not the same as the electric field around a
proton. Virtual particles pop into temporary existence
everywhere, so ANY where there happens to be a suitable
electric field, and a suitable \gamma-ray, that is all we
need for pair-production. And some patience, of course.

Can somebody here set the record straight? Thanks in advance!

greywolf42

Aug20-04, 10:45 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n"vernonner3voltazim" <vnemitz@pinn.net> wrote in message\nnews:42336979.0408192145.1701c36e@posting .google.com...\n>\n> An example of pair production is when a 1.1Mev gamma (approx)\n> spontaneously becomes an electron and a positron. I have been\n> aware for years that this event can only take place where the\n> gamma happens to encounter a virtual-particle pair nearby to\n> some ordinary charged particle.\n>\n> Recently I have been told that this event specifically requires\n> the ordinary charged particle to be an electron (or positron).\n> If a magnetic bottle was filled with protons, and a lot of 1.1Mev\n> photons were directed through the bottle, none of the photons\n> would ever spontaneously convert to an electron/positron pair.\n> (But really-potent gammas, about 2Gev, could convert to proton/\n> anti-proton pairs, in the vicinity of a protron.)\n>\n> I find this difficult to accept, that only electrons can\n> catalyze the electron/positron pair-productionn scenario.\n> Because it implies that the electric field around an\n> electron is not the same as the electric field around a\n> proton. Virtual particles pop into temporary existence\n> everywhere, so ANY where there happens to be a suitable\n> electric field, and a suitable gamma-ray, that is all we\n> need for pair-production. And some patience, of course.\n>\n> Can somebody here set the record straight? Thanks in advance!\n\nAFAIK, there has never been a documented experimental case of pair\nproduction anywhere but in the immediate vicinity of a charged matter\nparticle. The Stanford E144 experiments claim to have pair production with\nonly virtual particles, but they actually use a high energy electron beam.\nhttp://www.google.com/groups?selm=10e6hhie8m6chb9%40corp.supernews.com\n \nNow, this does not mean that only charged matter particles can cause pair\nproduction. It may mean only that one of the properties of electrons and\nnuclei is needed. Such as a specifically high enough field gradient, or\nsomething else.\n--\ngreywolf42\nubi dubium ibi libertas\n{remove planet for e-mail}\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"vernonner3voltazim" <vnemitz@pinn.net> wrote in message
news:42336979.0408192145.1701c36e@posting.google.c om...
>
> An example of pair production is when a 1.1Mev \gamma (approx)
> spontaneously becomes an electron and a positron. I have been
> aware for years that this event can only take place where the
> \gamma happens to encounter a virtual-particle pair nearby to
> some ordinary charged particle.
>
> Recently I have been told that this event specifically requires
> the ordinary charged particle to be an electron (or positron).
> If a magnetic bottle was filled with protons, and a lot of 1.1Mev
> photons were directed through the bottle, none of the photons
> would ever spontaneously convert to an electron/positron pair.
> (But really-potent gammas, about 2Gev, could convert to proton/
> anti-proton pairs, in the vicinity of a protron.)
>
> I find this difficult to accept, that only electrons can
> catalyze the electron/positron pair-productionn scenario.
> Because it implies that the electric field around an
> electron is not the same as the electric field around a
> proton. Virtual particles pop into temporary existence
> everywhere, so ANY where there happens to be a suitable
> electric field, and a suitable \gamma-ray, that is all we
> need for pair-production. And some patience, of course.
>
> Can somebody here set the record straight? Thanks in advance!

AFAIK, there has never been a documented experimental case of pair
production anywhere but in the immediate vicinity of a charged matter
particle. The Stanford E144 experiments claim to have pair production with
only virtual particles, but they actually use a high energy electron beam.
http://www.google.com/groups?selm=10e6hhie8m6chb9%40corp.supernews.com

Now, this does not mean that only charged matter particles can cause pair
production. It may mean only that one of the properties of electrons and
nuclei is needed. Such as a specifically high enough field gradient, or
something else.
--
greywolf42
ubi dubium ibi libertas
{remove planet for e-mail}

Rufus Anton

Aug23-04, 04:06 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nFirst off, on the theoretical side the pair production by an electric\nfield is known as Schwinger\'s effect and his beautiful pioneering work\n"On Gauge Invariance and Vacuum Polarization" is worth looking at:\nPhys Rev, Vol 82, #5, 664 (Jun 1 1951).\n\nAs to your question: The strongest electric fields experimentally\navailable are those in highly intense laser beams. If anywhere\nexperimentally observable it should be as a nonlinearity in such laser\nbeams. However, Itzykson and Brezin have calculated that even at the\nhighest intensities experimentally accesible the nonlinearity due to\npair production is negligible: Phys Rev D 2, 7, 1191 (Oct 1 1970).\n\nNow this was in the early 70s, so possibly there has been some\nprogress, but I don\'t know about that... Let us know if you find\nsomething.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>First off, on the theoretical side the pair production by an electric
field is known as Schwinger's effect and his beautiful pioneering work
"On Gauge Invariance and Vacuum Polarization" is worth looking at:
Phys Rev, Vol 82, #5, 664 (Jun 1 1951).

As to your question: The strongest electric fields experimentally
available are those in highly intense laser beams. If anywhere
experimentally observable it should be as a nonlinearity in such laser
beams. However, Itzykson and Brezin have calculated that even at the
highest intensities experimentally accesible the nonlinearity due to
pair production is negligible: Phys Rev D 2, 7, 1191 (Oct 1 1970).

Now this was in the early 70s, so possibly there has been some
progress, but I don't know about that... Let us know if you find
something.

Franz Heymann

Aug23-04, 04:06 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n"vernonner3voltazim" <vnemitz@pinn.net> wrote in message\nnews:42336979.0408192145.1701c36e@posting .google.com...\n>\n> An example of pair production is when a 1.1Mev gamma (approx)\n> spontaneously becomes an electron and a positron. I have been\n> aware for years that this event can only take place where the\n> gamma happens to encounter a virtual-particle pair nearby to\n> some ordinary charged particle.\n\n> Recently I have been told that this event specifically requires\n> the ordinary charged particle to be an electron (or positron).\n\nNot so. Whoever told you that doesn\'t know his onions. Any charged\nparticle will do the trick. Gamma ray detectors often use lead\nnucleii as the medium to facilitate pair production. The probability\nof the process in fact depends on the square of the charge of the\ntarget particle.\n\n> If a magnetic bottle was filled with protons, and a lot of 1.1Mev\n> photons were directed through the bottle, none of the photons\n> would ever spontaneously convert to an electron/positron pair.\n\nThat is quite wrong.\n\n> (But really-potent gammas, about 2Gev, could convert to proton/\n> anti-proton pairs, in the vicinity of a protron.)\n\nProton anti-proton pairs may be produced by the electromagnetic\ninteraction in a process exactly like the production of e+e- pairs.\nHowever, p+p- pairs are produced more copiuosly by virtue of the\nstrong interaction. That, however, implies a projectile particle\nother than a photon.\n\n[snip]\n\nFranz\n\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"vernonner3voltazim" <vnemitz@pinn.net> wrote in message
news:42336979.0408192145.1701c36e@posting.google.c om...
>
> An example of pair production is when a 1.1Mev \gamma (approx)
> spontaneously becomes an electron and a positron. I have been
> aware for years that this event can only take place where the
> \gamma happens to encounter a virtual-particle pair nearby to
> some ordinary charged particle.

> Recently I have been told that this event specifically requires
> the ordinary charged particle to be an electron (or positron).

Not so. Whoever told you that doesn't know his onions. Any charged
particle will do the trick. \Gamma ray detectors often use lead
nucleii as the medium to facilitate pair production. The probability
of the process in fact depends on the square of the charge of the
target particle.

> If a magnetic bottle was filled with protons, and a lot of 1.1Mev
> photons were directed through the bottle, none of the photons
> would ever spontaneously convert to an electron/positron pair.

That is quite wrong.

> (But really-potent gammas, about 2Gev, could convert to proton/
> anti-proton pairs, in the vicinity of a protron.)

Proton anti-proton pairs may be produced by the electromagnetic
interaction in a process exactly like the production of e+e- pairs.
However, p+p- pairs are produced more copiuosly by virtue of the
strong interaction. That, however, implies a projectile particle
other than a photon.

[snip]

Franz

Franz Heymann

Aug23-04, 04:06 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n"greywolf42" <mingstb@marssim-ss.com> wrote in message\nnews:10ic4s0rel1ggb5@corp.supernews.com.. .\n\n\n> AFAIK, there has never been a documented experimental case of pair\n> production anywhere but in the immediate vicinity of a charged\n> matter particle.\n\nProton-antiproton pairs may be produced via the strong interaction.\nCharge is not necessary in that case.\n\n[snip]\n\nFranz\n\n\n[Moderator\'s note: Quoted text trimmed by moderator. Please quote reasonably.\nSee http://www-stud.uni-essen.de/~sb0264/HowToPost.html. Thanks. -usc]\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"greywolf42" <mingstb@marssim-ss.com> wrote in message
news:10ic4s0rel1ggb5@corp.supernews.com...

> AFAIK, there has never been a documented experimental case of pair
> production anywhere but in the immediate vicinity of a charged
> matter particle.

Proton-antiproton pairs may be produced via the strong interaction.
Charge is not necessary in that case.

[snip]

Franz

[Moderator's note: Quoted text trimmed by moderator. Please quote reasonably.
See http://www-stud.uni-essen.de/~sb0264/HowToPost.html. Thanks. -usc]

FrediFizzx

Aug24-04, 04:54 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"vernonner3voltazim" <vnemitz@pinn.net> wrote in message\nnews:42336979.0408192145.1701c36e@posting .google.com...\n|\n| An example of pair production is when a 1.1Mev gamma (approx)\n| spontaneously becomes an electron and a positron. I have been\n| aware for years that this event can only take place where the\n| gamma happens to encounter a virtual-particle pair nearby to\n| some ordinary charged particle.\n\nLet\'s take ordinary to mean "real" charged particle.\n\n| Recently I have been told that this event specifically requires\n| the ordinary charged particle to be an electron (or positron).\n| If a magnetic bottle was filled with protons, and a lot of 1.1Mev\n| photons were directed through the bottle, none of the photons\n| would ever spontaneously convert to an electron/positron pair.\n| (But really-potent gammas, about 2Gev, could convert to proton/\n| anti-proton pairs, in the vicinity of a protron.)\n\nIt doesn\'t have to be just electrons or positrons. Protons work also.\n\n| I find this difficult to accept, that only electrons can\n| catalyze the electron/positron pair-productionn scenario.\n| Because it implies that the electric field around an\n| electron is not the same as the electric field around a\n| proton. Virtual particles pop into temporary existence\n| everywhere, so ANY where there happens to be a suitable\n| electric field, and a suitable gamma-ray, that is all we\n| need for pair-production. And some patience, of course.\n\nIt is theorized that a strong enough slowing changing or not changing\nelectric field strength will also create pairs from the vacuum; no real\nfermions involved. There are experiments in the works to test this. See\n"Boiling the Vacuum with an X-Ray Free Electron Laser".\n\nhttp://www.arxiv.org/abs/hep-ph/0304139\n\nYou can also do searches for "x-ray free electron laser" to find the planned\nexperiments.\n\nFrediFizzx\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"vernonner3voltazim" <vnemitz@pinn.net> wrote in message
news:42336979.0408192145.1701c36e@posting.google.c om...
|
| An example of pair production is when a 1.1Mev \gamma (approx)
| spontaneously becomes an electron and a positron. I have been
| aware for years that this event can only take place where the
| \gamma happens to encounter a virtual-particle pair nearby to
| some ordinary charged particle.

Let's take ordinary to mean "real" charged particle.

| Recently I have been told that this event specifically requires
| the ordinary charged particle to be an electron (or positron).
| If a magnetic bottle was filled with protons, and a lot of 1.1Mev
| photons were directed through the bottle, none of the photons
| would ever spontaneously convert to an electron/positron pair.
| (But really-potent gammas, about 2Gev, could convert to proton/
| anti-proton pairs, in the vicinity of a protron.)

It doesn't have to be just electrons or positrons. Protons work also.

| I find this difficult to accept, that only electrons can
| catalyze the electron/positron pair-productionn scenario.
| Because it implies that the electric field around an
| electron is not the same as the electric field around a
| proton. Virtual particles pop into temporary existence
| everywhere, so ANY where there happens to be a suitable
| electric field, and a suitable \gamma-ray, that is all we
| need for pair-production. And some patience, of course.

It is theorized that a strong enough slowing changing or not changing
electric field strength will also create pairs from the vacuum; no real
fermions involved. There are experiments in the works to test this. See
"Boiling the Vacuum with an X-Ray Free Electron Laser".

http://www.arxiv.org/abs/http://www.arxiv.org/abs/hep-ph/0304139

You can also do searches for "x-ray free electron laser" to find the planned
experiments.

FrediFizzx

greywolf42

Aug29-04, 12:54 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"Franz Heymann" <notfranz.heymann@btopenworld.com> wrote in message\nnews:cg5s1u\\$rau\\$2@sparta.btinternet.c om...\n>\n> "greywolf42" <mingstb@marssim-ss.com> wrote in message\n> news:10ic4s0rel1ggb5@corp.supernews.com...\n>\n>\n > > AFAIK, there has never been a documented experimental case of pair\n> > production anywhere but in the immediate vicinity of a charged\n> > matter particle.\n>\n> Proton-antiproton pairs may be produced via the strong interaction.\n> Charge is not necessary in that case.\n\nThank you for the theoretical opinion. However, the issue under discussion\nis experimental validation.\n\n--\ngreywolf42\nubi dubium ibi libertas\n{remove planet for e-mail}\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Franz Heymann" <notfranz.heymann@btopenworld.com> wrote in message
news:cg5s1u$rau$2@sparta.btinternet.com...
>
> "greywolf42" <mingstb@marssim-ss.com> wrote in message
> news:10ic4s0rel1ggb5@corp.supernews.com...
>
>
> > AFAIK, there has never been a documented experimental case of pair
> > production anywhere but in the immediate vicinity of a charged
> > matter particle.
>
> Proton-antiproton pairs may be produced via the strong interaction.
> Charge is not necessary in that case.

Thank you for the theoretical opinion. However, the issue under discussion
is experimental validation.

--
greywolf42
ubi dubium ibi libertas
{remove planet for e-mail}