Can Higher Energy Photons Create Heavier Particle Pairs?

[Chaos' lil bro Order]

1) If an electron/positron pair can be produced by a gamma ray with kT=or>1MeV striking a nucleus, can heavier particle/anti-particle pairs be created by photons with even higher energies?

2) Can a photon with kT>800MeV create a Up/Anit-Up quark pair for example?

Thanks, I am dying to know.

 

[selfAdjoint]

1) If an electron/positron pair can be produced by a gamma ray with kT=or>1MeV striking a nucleus, can heavier particle/anti-particle pairs be created by photons with even higher energies?

Yes, as long as conservation laws are satisfied.

2) Can a photon with kT>800MeV create a Up/Anit-Up quark pair for example?

I believe so.

Thanks, I am dying to know.

Don't kick the bucket just yet!

 

[Astronuc]

The threshold for pair production is 2x rest mass of electron - 1.022 MeV.

In the low MeV range, gamma photons would likely eject protons or neutrons from a nucleus - photoneutron effect. Creation of proton-antiproton would require a photon energy of at least 2x rest mass or about 1876.544 MeV for a proton-anitproton pair. For lower photon energies, I imagine that nucleons or alpha particles would be ejected, rather than quark-antiquark pair production.

However, it maybe more likely that lepton pairs (electron-positron, or muon-antimuon are likely). Nature tends to favor lower energy processes to higher energy processes.

See -

Photoproduction of large-mass lepton pairs at HERA as a probe of the small x structure of the proton
http://www.citebase.org/cgi-bin/citations?id=oai:arXiv.org:hep-ph/9307340

Prompt photon, Drell-Yan and Bethe-Heitler processes in hard photoproduction
http://ppewww.ph.gla.ac.uk/preprints/1996/06/glapre.html8

http://ppewww.ph.gla.ac.uk/preprints/1996/06/glapre/glapre.html

 

[Chaos' lil bro Order]

Thanks Astronuc.

So let me ask you this...

Knowing that the 'Top Quark' has a rest mass of 174 GeV and its corresponding anti-particle the 'Anti-Top Quark' has the same rest mass of 174 GeV. Can we assume that a photon with energy in excess of 348 GeV could produce a 'Top Quark/ Anti-Top Quark' pair?

 

[Astronuc]

Here are some tables of mesons, hadrons and quarks.

I am not sure what a top quark and anti-top quark would form.

I am also not sure how one would form a 348 GeV photon.

It is not clear to me that photons could produce quarks, rather they more likely form leptons, e.g. electron-positron pairs.

 

[Chaos' lil bro Order]

Thanks Astronuc, I appreciate you egoless honesty.

As for the 348GeV photon, the 'Friedmann Equation' can be formatted to predict the time at which the average kT (photon) equalled 348GeV, the result of which is 2.3x10*-11 seconds.

So in essence, the BigBang itself formed the extremely energetic 348GeV photon needed to (theoretically) produce a Top/ Anti-Top Quark pair.

I seem to be at a bottleneck as I've not been able to determine from inquiring around if in fact, particles other than electon/ positrons can be pair produced from photons. I'd appreciate it if you could ask some colleagues to try and find out, since you are in the field and seem like a nice, intelligent fellow.

Thanks again.

 

[arivero]

Knowing that the 'Top Quark' has a rest mass of 174 GeV and its corresponding anti-particle the 'Anti-Top Quark' has the same rest mass of 174 GeV. Can we assume that a photon with energy in excess of 348 GeV could produce a 'Top Quark/ Anti-Top Quark' pair?

Here the answer has a little trick. They can be produced (taking care of preserving linear and angular momentum, of course) but they are so heavy (and strong force so weak) that they will not bind themselves into a meson, as the rest of quarks do.

 

[selfAdjoint]

I wondered about that, since the force already at the charm quark mass is as weak as electromagnetism (cf states of the J/psi meson, alias charmonium).

 

[Chaos' lil bro Order]

arivero

1) So you are saying that this type of pair production (with the obvious conservation of momentum laws) can occur for all quarks right?



2) But, you are also saying that the Top/ anti-Top quark doesn't form a meson because the color force isn't strong enough to bind them right?



3) Finally, tell me if this list of particles that can be pair-produced is complete:

QUARKS: up, down, charm, strange, top bottom

Leptons: electon & e neutrino; muon & muon neutrino; tau & tau neutrino

ARE THERE ANY OTHER PARTICLES THAT CAN BE PAIR-PRODUCED?




Thanks, great posts arivero.

 

[arivero]

arivero
1) So you are saying that this type of pair production (with the obvious conservation of momentum laws) can occur for all quarks right?

Yes, see 3 below.

2) But, you are also saying that the Top/ anti-Top quark doesn't form a meson because the color force isn't strong enough to bind them right?

Exactly, both because the weakness of color and because of the high mass of the top, that causes it to disintegrate faster than the time to do an orbit, if you want to think semiclassically.

3) Finally, tell me if this list of particles that can be pair-produced is complete:

QUARKS: up, down, charm, strange, top, bottom
Leptons: electon , e neutrino; muon , muon neutrino; tau , tau neutrino

ARE THERE ANY OTHER PARTICLES THAT CAN BE PAIR-PRODUCED?

Note that the top has 175 GeV, you need a > 300 GeV photon.

Also note we are speaking of production from gamma, it could have sense to speak of producing pairs from W+ or from gluons, simply preserve charge in the produced particles.

I am in doubt now if there is a W+W- gamma vertex (I think so). Then also W could be produced as a pair. same question about a Z0 Z0 gamma vertex (in principle are orthogonal objects but quantum life is strange), I should check.

 

[Chaos' lil bro Order]

Note that the top has 175 GeV, you need a > 300 GeV photon

How come it requires only 300 GeV as the lower limit if 175 x 2 = 350GeV? Simple typo, or an exotic concept that I am missing?




it could have sense to speak of producing pairs from W+ or from gluons, simply preserve charge in the produced particles.

You are saying that photons aren't the only ones that can pair-produce? You are saying that W+ vector bosons and gluons can also pair-produce?
If so, basically you are saying 3 of the 4 known messenger particles can pair produce, so with this in mind do you think the theoretical graviton could also pair-produce? Hmmm this thread is getting real interesting, real fast!

Awesome posts as usual arivero, thanks.

 

[arivero]

Note that the top has 175 GeV, you need a > 300 GeV photon
How come it requires only 300 GeV as the lower limit if 175 x 2 = 350GeV? Simple typo, or an exotic concept that I am missing?

Consider it a typo. I meant to say > 3E2, which is the sci way of saying "greater than 250-350". Of course 350 is a minumum for pair creation.

You are saying that photons aren't the only ones that can pair-produce? You are saying that W+ vector bosons and gluons can also pair-produce?
If so, basically you are saying 3 of the 4 known messenger particles can pair produce, so with this in mind do you think the theoretical graviton could also pair-produce?

Well the graviton is not inside the standard theory of elementary particles. Actually I do not know how one particle (spin 1/2) can emit one single graviton (spin 2) and preserve angular momentum. Virtual graviton, it must be, forcefully.

As for the rest of the force messengers, yes, and indeer pair creation via gluons is usual mechanism in strong decay. Perhaps the foton one is the purest because it does not carry charge; W+ carries electric charge and thus creates differenty charged particles (electron and antineutrino). Gluons carry colour so they create differently coloured particles (say a red up quark and an antigreen up antiquark.). And then they can not create leptons.

 

[Chaos' lil bro Order]

As for the rest of the force messengers, yes, and indeer pair creation via gluons is usual mechanism in strong decay. Perhaps the foton one is the purest because it does not carry charge; W+ carries electric charge and thus creates differenty charged particles (electron and antineutrino). Gluons carry colour so they create differently coloured particles (say a red up quark and an antigreen up antiquark.). And then they can not create leptons.

So, two Zo Intermediate Vector bosons can annihilate each other and pair-produce?

If so, what would they produce given that their combined Rest energies are so high 92Gev + 92GeV = 184 GeV! The only particle I can think of that comes close to that huge energy is the Top Quark at 174 GeV.


Also, is a gluon massive? I know it mediates the Strong nuclear force between quarks, but does it have mass, or is it like the photon?


Thanks again arivero.

 

[arivero]

So, two Zo Intermediate Vector bosons can annihilate each other and pair-produce?

If so, what would they produce given that their combined Rest energies are so high 92Gev + 92GeV = 184 GeV! The only particle I can think of that comes close to that huge energy is the Top Quark at 174 GeV.

Yeah, but we need to produce two. So nope. Z0 colliding to two tops is not kinematically allowed. Besides to be a second order process, each Z0 g giving one weak fermi coupling factor to the product.

Also, is a gluon massive? I know it mediates the Strong nuclear force between quarks, but does it have mass, or is it like the photon?

No, the gluon is massless. Its short range is due to colour confinement. The pion is massive, and manages the strong force between protons and neutrons.

Thanks again arivero.[/QUOTE]

 

[Chaos' lil bro Order]

arivero

Can you give me an example of what particle(s) two Zo bosons could pair produce?

Also, what could two Gluons pair produce?


Thanks

 

[nrqed]

Can you give me an example of what particle(s) two Zo bosons could pair produce?

Also, what could two Gluons pair produce?


Thanks

You don't even need a *pair*. As single Zo could produced any lepton-antilepton pair or quark-antiquark pair. muon-antimuon, a charm-anti-charm, and on and on...even aney neutrino-antineutrino (whether it's electronic or muonic or tauonic). And since the Zo is massive, you don't even need aninteraction with a nucleus or something else to conserve four-momentum lik eyou need for the photon.

As for a gluon, it can produce any quark-antiquark pair. To lowest order, it cannot produce a lepton-anti lepton pait because these have no color. However, if you go to higher order processes (with loops if you think in terms of Feynman diagrams) then anything is possible, as long as you don't if other stuff is produced. So you could get out of a gluon an electron-positron pair plus other stuff...or almost anything you want!


Pat

 

[Chaos' lil bro Order]

Pat

You don't even need a *pair*. As single Zo could produced any lepton-antilepton pair or quark-antiquark pair. muon-antimuon, a charm-anti-charm, and on and on...even aney neutrino-antineutrino (whether it's electronic or muonic or tauonic). And since the Zo is massive, you don't even need aninteraction with a nucleus or something else to conserve four-momentum lik eyou need for the photon.
Pat

Very interesting Pat, thank you.
So in a nutshell you are saying that the vector bosons can spontaneously create any particle, period, without the need for interaction to do so. My question is how can a Zo boson (M=~92GeV) create a TOP-quark (M=~174GeV)? Is this possible due to the Zo's momentum energy combined with RestMass energy being high enough to produce the TOP? Or perhaps due to the fact that quark RestMass values are only guidelines and not absolute?

Any experiments, references, websites supporting your post would be appreciated. Thanks again Pat.

 

[selfAdjoint]

It's not that the Z0 is a vector boson that enables it to do this, but the fact that it is its own antiparticle, something that is also true of the photon. As to your other question, remember that it's not just the mass of the particle, but its total energy that goes into pair production, if it is moving fast enough its kinetic energy can be as large as you like.

 

[nrqed]

Very interesting Pat, thank you.
So in a nutshell you are saying that the vector bosons can spontaneously create any particle, period, without the need for interaction to do so.

Well, let's be careful. I mean without interaction with any other stuff (like a nearby nucleus). But the decay is due to an interaction (if you think in terms of Feynman diagrams) between the Z_0 and the particles it creates (example, the positron-electron, etc). So there is no need for an interaction with "extra" stuff (in the sense of something extra to the interaction between the Z0 and the particles created)...but there is of course an interaction between the Z0 and the particles created, otherwise the decay would not occur (to lowest order).


Also, you have to be careful about the distinction between lower order processes and higher order processes (in the second case, the pair-anti pair is not directly created but is a byproduct of other processes).

In the lowest order, it is not true that any vector boson can create anything. The Z0 is special in that respect. For example, a photon can't create (in lowest order) a neutrino-antineutrino pair (because they have no electric charge). Likewise, a gluon could not create an electron-positron pair (because they have no color charge). And a W+ could not create any particle-antiparticle pair because the charge would not be conserved. So the Z0 is a bit special because it has no electric charge and it couples to anything with a weak charge which includes all the leptons and quarks.

You would need a table of the Standard Model and the vertices present in the Standard Model. I know many books with that but no good website (they usually don't provide the Feynman rules).

Pat

My question is how can a Zo boson (M=~92GeV) create a TOP-quark (M=~174GeV)? Is this possible due to the Zo's momentum energy combined with RestMass energy being high enough to produce the TOP? Or perhaps due to the fact that quark RestMass values are only guidelines and not absolute?

Your first answer is the correct one. This is just E=mc^2 at work...energy can be converted into mass and vice versa. If the z0 has enough kinetic energy, this, added to its rest mass energy, can be enough to create anything...

 

[Chaos' lil bro Order]

Pat

Wow Pat, you are most intelligent poster ever on PF.

You didn't beat around the bush and you explained it so wonderfully that I could actually understand it. Thanks a million.

Drawing on the fact that the Zo boson can create any lepton or quark because it is its own anti-particle, is it plausible to infer that it was the first particle ever created? By your description, it seems to me that the Zo can produce any two daughter particles known to man, is this a fair statement or not?


P.S. You should be a moderator Pat, PF could use some more like you.
Thanks again.

 

[nrqed]

Wow Pat, you are most intelligent poster ever on PF.

You didn't beat around the bush and you explained it so wonderfully that I could actually understand it. Thanks a million.

Thank you for the praise ! But there are far more intelligent and knowledgeable people around here, believe me! (I can easily think of a dozen names right off the top of my hat, several posting right here in quantum physics). But it's nice when people appreciate...

Drawing on the fact that the Zo boson can create any lepton or quark because it is its own anti-particle, is it plausible to infer that it was the first particle ever created? By your description, it seems to me that the Zo can produce any two daughter particles known to man, is this a fair statement or not?

Note that the point about the Z0 being its own antiparticle (like the photon but unlike gluons) was pointed out by selfAdjoint and this was an excellent point to make...

Well, if you include gluons and photons and other gauge bosons, the Z0 cannot produce those, to lowest order. A Z0 cannot turn into two or more photons, to lowest order or into a gluon-antigluon pair...or into a W+W-...(even if all these reactions conserve the electric charge). In terms of Feynman diagrams it is because there is no vertex involve a Z0 and two photons and so on.

Soon after the Big Bang, there was so much energy around that everything was being created all the time, mostly from high energy photons (photons are usually more readily created than Z0 because they are massless)...You should not think in terms of having one or several initial particles present which then decayed to create all the other particles. You should think in terms of a huge amount of energy present (coming from where, no one knows) and this energy then used to create al sorts of particles. When the energy was *huge*, everything was readily created in huge quantities. When the universe started to cool down, the production of the heaviest particles stopped first (and these quickly decayed to lighter particles) then the creation of light particles stopped and so on...

Hope this makes sense...

P.S. You should be a moderator Pat, PF could use some more like you.
Thanks again.

Thanks (blushing again)...

Pat

 

[pallidin]

A most enjoyable thread.