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Ryan Reed
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There are exotic atoms such as the protonium (proton+antiproton) and positronium (electron+positron); I was wondering if quark-antiquark particles could appear even if they only exist for a fraction of a second.
Why is it important if the quark and anti-quark have the same flavor?ohwilleke said:Not only are there quark-antiquark particles called mesons. There exist a particular subset of mesons called quarkonium, which are composed of a quark of a particular flavor and an anti-quark of the same flavor. For example, charmonium is a meson made of a charm quark and an anticharm quark.
PineApple2 said:Why is it important if the quark and anti-quark have the same flavor?
ohwilleke said:A meson with a charm quark and an antidown quark shouldn't be able to annihilate
ChrisVer said:This is wrong. A meson with a charm and an antidown quark would be the [itex]D^+[/itex] charmed meson.
The [itex]c,\bar{d}[/itex] can still go through a s-channel (with Ws) into other particles, and you can have [itex]D^+ \rightarrow l^+ \nu_l[/itex]. They have a small Branching fraction, but they are not "forbidden". The BR of [itex]l=e, \tau[/itex] haven't been observed and pdg gives upper bounds, but [itex]l=\mu[/itex] has been measured.
A better example for proving that wrong are the Kaon decays. eg [itex]K^+ \rightarrow \mu^+ \nu_\mu[/itex] (63.55%) and K+ is a [itex]u\bar{s}[/itex].
What you say would be true if there was no possible transition between generations (no CKM matrix). It would be true however to say that J/ψ (cc*) or Y (bb*) do have much shorter lifetime. But it's difficult to make use of it, because they have so many different decay modes (either the mesons or the quarkonia).
That restriction sounds a bit arbitrary.ohwilleke said:When I say that a meson is not able to annihilate, I do not mean that it is not able to decay. What I mean instead when I say that I meson is not able to annihilate is that it cannot decay directly to photons, leaving behind no quarks, directly from its current state without intermediate W boson interactions.
That does not work, that process is forbidden by energy conservation. The W boson in the overall decay is not real.ohwilleke said:I would describe that sequence of events a B0 meson decaying into a D+ meson and a W- boson [...]
Quark-antiquark particles are subatomic particles that are composed of a quark and an antiquark. They are the building blocks of hadrons, which are a type of subatomic particle that includes protons and neutrons.
Quark-antiquark particles have a unique property called color charge, which is a fundamental force that allows them to interact with each other. They also have a fractional electric charge, unlike other subatomic particles which have integer electric charges.
Yes, quark-antiquark particles are found in nature. They are a fundamental part of the standard model of particle physics and are present in the particles that make up the matter around us.
Quark-antiquark particles can be created through high-energy collisions, such as those that occur in particle accelerators. They can also be created through the decay of other particles.
Quark-antiquark particles play a crucial role in understanding the behavior of matter and the forces that govern the universe. They help explain the structure of protons and neutrons and provide insight into the early stages of the universe after the Big Bang.