26 votes
Accepted

Why is the charmed eta meson its own antiparticle, but the neutral kaon is not?

Mesons are not elementary, they are composed of quarks. So take a look at their quark content. The charmed eta meson consists of a charm and an anti-charm quark, denoted $c\overline{c}$. An anti ...
lemon's user avatar
  • 13.2k
22 votes
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Are there any Baryons that have quark-antiquark combinations?

No, a three-quark baryon can not be be made out of two quarks and one anti-quark (and vice versa) as this would necessarily give the particle color. Each quark carries one of three colors (red, blue, ...
edh's user avatar
  • 346
19 votes

Are there any Baryons that have quark-antiquark combinations?

Pentaquarks contain three quarks and a quark-antiquark pair, and they are baryons, since baryons are defined as having an odd number of valence quarks.
interoception's user avatar
12 votes
Accepted

Why does charmonium (and phi mesons) not decay via quark and antiquark annihilation?

That is more or less what we do, except... Annihilation through a photon is electromagnetic rather than strong, so this is a suppression. Annihilation through a single gluon can't happen because the ...
RogerJBarlow's user avatar
  • 10.1k
12 votes
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Meson as hadron and boson

Since a meson is composed of two spin 1/2 particles, its total spin must be an integer, which makes it a boson.
Jon's user avatar
  • 196
12 votes
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Does the Pauli exclusion principle apply to mesons?

So I guess the answer here is both yes and no. The best example of this is probably the existence of bose einstein condensates in laboratories. These are (almost) always made up of atoms that exhibit ...
Thomas Tappeiner's user avatar
9 votes
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What's the difference between a meson and a glueball?

This is a good question, and the basic answer is "there is no rigorous difference" (which is the main problem with experimental efforts to identify glueballs). 1) Electrically charged states, or ...
Thomas's user avatar
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8 votes
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How to understand the makeup of neutral pi and eta mesons?

Note that in the 3-dimensional complex space spanned by basis $\boldsymbol{\lbrace}\boldsymbol{u}\overline{\boldsymbol{u}},\boldsymbol{d}\overline{\boldsymbol{d}},\boldsymbol{s}\overline{\boldsymbol{s}...
Frobenius's user avatar
  • 15.7k
8 votes

Meson as hadron and boson

(Anti)quarks are spin 1/2, so two of them is either spin-0 or spin 1: bosons. But it's more than that. The pions are (one of) the force carrying boson in quantum hadrodynamics, which is an effective ...
JEB's user avatar
  • 33.7k
7 votes

Why are all mesons unstable?

You are almost right about quarks and antiquarks annihilating within the meson, but for example, a π+ contains an up and an anti-down quark, and those are not antiparticles of each other. The picture ...
CR Drost's user avatar
  • 37.7k
7 votes

How can a meson beam be created?

It is an engineering problem. A brief description is here. In this experiment, a beam of ∼ 100 GeV proton from the Super Proton Synchrotron (SPS) are used to produce pions off a conventional solid ...
anna v's user avatar
  • 234k
6 votes
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Derivation of Gell-Mann Okubo relation for mesons

This is a good question that puzzled theorists for a while, until the modern understanding of chiral symmetry breaking in QCD clarified itself. The crucial thing to note is that the quadratic formula ...
Cosmas Zachos's user avatar
6 votes

How Does QCD Explain Nuclear Fission?

Brief and simple question with no brief and simple answer. Pion exchange is not alone in explaining the nuclear effective potential, and especially its repulsive core. How QCD connects to standard ...
Cosmas Zachos's user avatar
6 votes

Does the Pauli exclusion principle apply to mesons?

The subtlety in putting two identical mesons in the "same state" is that not only are the mesons indistinguishable from each other, but they aren't well-defined composites at all: We can't ...
nanoman's user avatar
  • 3,830
6 votes

Does the kaon participate in the weak interaction?

You are correct. All of the quarks and leptons of the Standard Model, and their composites, participate in the strong, electromagnetic, and weak interactions. The leptons, which lack color charge, ...
rob's user avatar
  • 89.9k
6 votes

Does the kaon participate in the weak interaction?

This text book is really a shame. As you had detected correctly, the kaons feel also the weak force, e.g. in the decay mode $K^+ \to \mu^+ \nu_\mu$ being mediated by the exchange of a virtual $W^+$ ...
Hyperon's user avatar
  • 6,073
5 votes

How can we explain that $\Sigma \pm$ have different masses whereas K$\pm$ have the same mass?

K$^+$ and K$^-$ are antiparticles - they contain the same quarks, but in a different configuration. K$^+$ is $u \overline{s}$, while K$^-$ is $\overline{u} s$. $\Sigma^+$ and $\Sigma^-$ are not ...
Gremlin's user avatar
  • 2,323
5 votes
Accepted

Definition of a meson?

According to the Particle Data Group [1], Mesons are [strongly interacting particles that] have baryon number $\mathcal{B}=0$. In the quark model, they are $q\bar{q}'$ bound states of quark $q$ and ...
Bosoneando's user avatar
  • 5,644
5 votes

How to understand the makeup of neutral pi and eta mesons?

$ \newcommand{\FR}[2]{{\textstyle \frac{#1}{#2}}} \newcommand{\BK}[3]{\left|{#1},{#2}\right\rangle_{#3}} \newcommand{\BoldExp}[2]{{#1}^{\boldsymbol{#2}}} ...
Frobenius's user avatar
  • 15.7k
4 votes
Accepted

What is a sigma meson?

For example: The existence and properties of the sigma meson have been controversial for almost six decades, despite playing a central role in the spontaneous chiral symmetry of QCD or in the ...
anna v's user avatar
  • 234k
4 votes

Does an Anti $\eta^0$ meson exist?

The antiparticle of eta meson is the eta meson itself. $$ \eta = \dfrac{1}{\sqrt{6}}(u\bar{u} + d\bar{d} -2s\bar{s})$$ As you can see, since the eta is composed of the terms $q\bar{q}$, therefore ...
Bruce Lee's user avatar
  • 5,237
4 votes

Why can omega meson not decay into two charged pions?

Here are the quantum numbers for omega and rho. They differ in G parity, and G parity is conserved in strong interactions ( am using this paper ), it is a generalization of C parity. The strong ...
anna v's user avatar
  • 234k
4 votes

Applying ladder operators to Isospin states for quarks

The antiquarks are in the "antifundamental representation." If a quark in the fundamental representation transforms as $q_i\rightarrow U_{ij}q_j$, an antiquark transforms as $\bar{q}_i\rightarrow \bar{...
octonion's user avatar
  • 8,700
4 votes

Scalar pseudo-Goldstones from hypothetical $SU(3)_V$ symmetry breaking in QCD

I think you may be asking a few related questions, so here's my attempt to answer some of them: Are there examples of scalar Goldstone bosons? Yes, at least at a hypothetical level. One simple ...
Henry Deith's user avatar
  • 1,116
4 votes

What is the matter anti-matter asymmetry in the decay of the neutral K meson?

I'm not an expert in HEP, but I guess what you mean by asymmetry in the decay of K meson is the $\textbf{CP violation}$ process and Cronin together with Fitch demonstrated this in their experiment ...
Robert Poenaru's user avatar
4 votes
Accepted

Rho and Omega meson mixing

For two particles to interfere, you need them to have similar quantum numbers. For example, a $\rho^+$ could not interfere with the neutral $\phi$ or $\omega$, since the respective transition would ...
Cosmas Zachos's user avatar
4 votes

Are there any Baryons that have quark-antiquark combinations?

Yes, there are some oddball baryons that contain four quarks and one anti-quark. They're called pentaquarks. These could be thought of as a baryon with three quarks plus a meson with a quark anti-...
DarenW's user avatar
  • 5,869
4 votes
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Positive Kaon decay into $\pi^+$ and $\pi^0$ suppressed

Cabibbo suppressed, but not FCNC (Apologies for poor drawing quality)
RogerJBarlow's user avatar
  • 10.1k
4 votes
Accepted

What is a/the $K^*$ meson, and why is it important?

$K^*$ on its own is taken as being the $K^*(892)$. Sloppy notation maybe, but it is met with a lot, and has a clean signature whereas the higher excitations are harder to pull out from the data. The ...
RogerJBarlow's user avatar
  • 10.1k

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