What, specifically, happens when a proton and an antiproton collide?

What happens depends on the energy of the colliding particles, or maybe it is better to say on their relative momenta. If proton and antiproton collide at low energy (low relative speed) then they essentially see each other as entities, their internal structure does not matter, as the energies are too low (or wavelengths of the particles too long) to resolve it. Therefore at low energies all you may get is annihilation. Contrary to the electron-positron case, the annihilation does not usually result in "pure energy" (photons). Protons are heavy and they have plenty of possible final states, most of them involving mesons (like pions, kaons, rhos, etas...). Those mesons eventually decay, their decay products decay further... If you wait long enough for every unstable product to decay, you'll end up with a bunch of electrons (and positrons), neutrinos and photons.

It is a completely different story, when the colliding particles have high energies (high relative momentum). In this case they can resolve their internal structure and they "see" each other as clouds of quarks, gluons, virtual quark-antiquark pairs, photons... At very high energies the collision time is very short, thus both the proton and the antiproton behave as collections of essentially independent particles. A collision involves usually just one particle from each "cloud", the other particles just continue along their paths. As both clouds contain many different particles, many different collisions may occur: a quark from proton may collide with and antiquark from the antiproton, a quark from either one may collide with a gluon from another one, two gluons may collide, a quark from a proton may collide with a virtual quark (not antiquark) from antiproton... Add to this the different possible combinations of quark types, and you see, that there is a variety of collisions possible.

And the collision between contituents does not end the story either - the scattered particles after the collision usually have unbalaced color charge and as such are not allowed to be seen. They must somehow form color-neutral particles (hadrons) and they do it by creation of additional quark-antiquark pairs, that combine with the scattered particles (an also with the remnants of the colliding particles, that happily fly on along their original paths) to form final state hadrons. Thus a high-energy collision batween a proton and an antiproton is messy indeed and usually produces many final state particles.

www.quora.com...

In particle physics, initial and final state radiation refers to certain kinds of radiative emissions that are not to due[clarification needed] particle annihilation.[1][2] It is important in experimental and theoretical studies of interactions at particle colliders.

en.wikipedia.org...

Ok so even in relation to particle-antiparticle interactions objects with mass survive?

At issue being whether or not the conclusion that mass is actually annihilated as a result of matter-antimatter interactions does in fact violate the Law of Conservation?



To me information cannot be destroyed despite anything we have in some circles defined otherwise.


Any thoughts?

a reply to: Kashai


Extinction Level Event .

Hang onto your hat !

Or ..

We will not notice it's having been; conquering nothing and leaving ... sheepishly.

a reply to: Timely



Ok but matter-antimatter populated the early events in the Universe substantively from a statistical perspective.

Or for that "matter" otherwise....


A point would be that given matter is not annihilated in a matter-antimatter interaction?

Perhaps there is no annihilation at all and so despite such an implication otherwise the information is conserved.


So essentially I am considering that if the mass of the "Empire State Building", were to interact with an equal amount of anti-matter.

The information despite that interaction would still exist.

I really has nothing to do with doom porn but rather is a question related to the information thus....

a reply to: Kashai

That's a really good question.

I think they should toss them into the Hadron Collider and see what happens!

a reply to: Kashai


I think it is a yin/yang nature balance thing.

Balance seems to be key to harmony ...

With more complex particles like protons and neutrons, you can get partial annihilations. Especially if they're humming along when they collide.

a reply to: Bedlam

What if they're just sort of loitering and casually bump into each other?

originally posted by: Phage
a reply to: Bedlam

What if they're just sort of loitering and casually bump into each other?

Well, if a particle and its antiparticle really love each other, they might want to get together in a special way. If they take their time, then it's more likely that they'll both have lots of little baby photons.

But if they rush things, the daddy particle might have premature ejection and not all of the mommy and daddy particle's bits might find each other, leaving behind a legacy of baby particles, photons, and regret.

a reply to: Kashai

I don't think that is a matter/anti matter collision. I think you are describing an electron and positron collision.

As far as I can see, it can yield energy. Are you looking for it yielding a black hole? That would be a LOT of energy.

originally posted by: Phage
a reply to: Bedlam

What if they're just sort of loitering and casually bump into each other?

Arrested for jaywalking, but they don't like it, much.

originally posted by: Bedlam

originally posted by: Phage
a reply to: Bedlam

What if they're just sort of loitering and casually bump into each other?

Well, if a particle and its antiparticle really love each other, they might want to get together in a special way. If they take their time, then it's more likely that they'll both have lots of little baby photons.

But if they rush things, the daddy particle might have premature ejection and not all of the mommy and daddy particle's bits might find each other, leaving behind a legacy of baby particles, photons, and regret.

baby photons hurt my eyes. the one next door is constantly screaming and my ear balls need lobe goggles.

a reply to: reldra


The anti-matter equivalent to an electron is a positron.

I don't know what your problem with proton-antiproton collisions is. What is always conserved is not rest mass of the colliding particles but their total energy E and momentum p. The former is expressed in terms of Einstein's relation between energy E and relativistic mass m : E = mc^2. The latter is given by E^2 = p^2c^2 + (Mc^2)^2, where M is the rest mass of the particle and p is its momentum. At high energies (E>>Mc^2), many inelastic events occur that do not amount to simple quark-antiquark annihilations. But, how many particles materialise from the fireball of the collision, their total energy is identical to the total energy of the original proton and antiproton. Collisions that leave them intact will result in their having less momentum because some of the available energy will have been converted into many other subatomic particles that materialise out of the fireball, leaving less kinematic energy for the protons and antiprotons after their collision.
What is always conserved is not the rest mass energy Mc^2 of colliding particles but their total relativistic energy E.

a reply to: micpsi


No problems just trying to learn and posts are formatted as questions.

Does a photon exert a gravitational pull?


I know a photon has zero rest mass, but it does have plenty of energy. Since energy and mass are equivalent does this mean that a photon (or more practically, a light beam) exerts a gravitational pull on other objects? If so, does it depend on the frequency of the photon?general-relativity gravity light mass photons?

If you stick to Newtonian gravity it's not obvious how a photon acts as a source of gravity, but then photons are inherently relativistic so it's not surprising a non-relativistic approximation doesn't describe them well. If you use General Relativity instead you'll find that photons make a contribution to the stress energy tensor, and therefore to the curvature of space.

physics.stackexchange.com...


You see I have several questions.

originally posted by: Kashai

You see I have several questions.

If that was your question, you received a correct answer.

eta: one which I gave you about four years ago when you asked the same question, I might add.

a reply to: Bedlam



Yes that is true but what about the effect of photons upon space-time curvature and gravitationally?

a reply to: Bedlam


Good to hear

originally posted by: Kashai
a reply to: Bedlam
Yes that is true but what about the effect of photons upon space-time curvature and gravitationally?

Both answers seem complete to me. Each photon contributes to the stress-energy tensor according to its energy. It's sort of a vector thing, though. Two photons running along in parallel won't exhibit any 'gravitational' attraction to each other, but two coming right at each other + delta will exhibit a maximal attraction. Not that it's much, even when you optimize it. Thus my comment years ago to you that not only do you need a lot of photons to form a kugelblitz, you have to line them up just right.

a reply to: Bedlam

Could the entire mass of all photons in the Universe be applicable to curvature?

As well as pretty much else.