Matter-antiMatter annihilation,Mesons?

[ShayanJ]

If matter and antiMatter will annihilate each other after coming into contact,how can a meson come into existence?
thanks

 

[Bill_K]

Mesons are made up of a quark and an antiquark, and have a temporary existence, in the same way that positronium exists temporarily. A neutral pion, for example, self-annihilates into two photons in 10^-16 sec. "Charmonium", a combination of a charmed quark and antiquark, is especially interesting because it can exist in several well-defined states analogous to atomic levels.

 

[blechman]

It is also very misleading to say "matter and antimatter annihilate each other!" Remember that there are MANY types of antimatter. Antielectrons, anti-up quarks, etc.

So if you have a bound state made up of a down quark and an anti-strange quark (the simplest example being a meson called a "Kaon"), then the down and anti-strange quarks will NOT annihilate each other, despite the matter and antimatter nature of the particles! What happens instead is that the strange quark in the Kaon will decay.

Strictly speaking, I should say that the PROBABILITY of Kaon decay through annihilation is vanishingly small. So "annihilation" is not the only (or most important) way for mesons to decay.

 

[ShayanJ]

You mean for example just a pair of up quark and antiquark will annihilate each other?
Or the above annihilation is the most probable?

 

[blechman]

You mean for example just a pair of up quark and antiquark will annihilate each other?
Or the above annihilation is the most probable?

an up - anti-up quark bound state is (for example) the neutral pion - the quarks there will annihilate into 2 photons. This is the dominant channel for the neutral pion to decay.

You can compute the time it will take this annihilation to happen from the time the meson is formed - this is the "lifetime" of the particle. The computed time agrees excellently with experiment.

 

[ShayanJ]

No,I meant,Do you mean that only quark-antiquark pairs which of the same type annihilate?The example being up-antiup quark pair.

 

[blechman]

No,I meant,Do you mean that only quark-antiquark pairs which of the same type annihilate?The example being up-antiup quark pair.

to leading order, yes. it turns out that different quarks can annihilate each other, but it must go through a quantum correction, which makes it a much rarer event, and therefore much less important.

 

[ShayanJ]

Your post was just disappointing iam.You really could explain.

 

[Drakkith]

Your post was just disappointing iam.You really could explain.

It's best to not even respond to trolls. They smell bad and have poor hand-eye coordination.

 

[ShayanJ]

Its my first time encountering one of them and also hearing your second sentence.What does it mean?Is it a proverb or idiom or sth?

 

[Drakkith]

Its my first time encountering one of them and also hearing your second sentence.What does it mean?Is it a proverb or idiom or sth?

Lol. I don't know if you are serious or not, so I apologize if I have confused you or something.

 

[smith345]

Antiparticles look and behave just like their corresponding matter particles, except they have opposite charges. For instance, a proton is electrically positive whereas an antiproton is electrically negative. Gravity affects matter and antimatter the same way because gravity is not a charged property and a matter particle has the same mass as its antiparticle.

 

[Drakkith]

Antiparticles look and behave just like their corresponding matter particles, except they have opposite charges. For instance, a proton is electrically positive whereas an antiproton is electrically negative. Gravity affects matter and antimatter the same way because gravity is not a charged property and a matter particle has the same mass as its antiparticle.

While true, I'm wondering why you posted this here. I don't believe it was that relevant to the discussion.

 

[smith345]

antiparticles are produced in pairs in high-energy proton-antiproton collisions. This computer representation shows the decay products of the short-lived candidate particle produced in a collision. The decay products are used to identify the B_s mesons produced in the collision. (Courtesy of DZero collaboration)

 

[Drakkith]

antiparticles are produced in pairs in high-energy proton-antiproton collisions. This computer representation shows the decay products of the short-lived candidate particle produced in a collision. The decay products are used to identify the B_s mesons produced in the collision. (Courtesy of DZero collaboration)

I think you forgot the link.