Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [mesons]

Μesons are unstable hadronic subatomic particles of integral spin, and hence bosons. They are composed of one quark and one antiquark, and bound together by the strong interaction to a physical size of roughly one fermi.

2
votes
1answer
47 views

What's the mass of $D_1(2430)^{\pm}$?

What's the mass of $D_1(2430)^{\pm}$? The standard reference http://pdglive.lbl.gov/ParticleGroup.action?init=0&node=MXXX035 only shows the data for $D_1(2430)^0$ but not for $D_1(2430)^{\pm}$. ...
1
vote
1answer
51 views

How does the nuclear interaction keep protons and neutrons together?

The strong force holds atoms hadrons together by using gluons to change the color charge of quarks and making the hadrons color nutral. But how does the nuclear force keep protons together, I heard ...
1
vote
2answers
52 views

Orbital parity of simple bound states in atomic and particle physics

The parity operator commutes with the Hydrogen atom Hamiltonian. The energy eigenfunctions are parity eigenstates with orbital parity $(-1)^\ell$ which follows from the fact that $Y_{\ell m}(\theta,\...
0
votes
1answer
34 views

Conversion of gluons into hadrons

Why and how does a gluon become a hadron when it leaves a hadron? Is this an analogous process to the way a quark becomes a meson, when it is "forced" out of (let's say) a proton?
1
vote
2answers
52 views

Confusion regarding the orbital angular momentum of mesons in an excited state

I came across the statement that Mesons can have a spin of a whole number (e.g. 1 or 2) instead of the regular 0, as a result of the orbital angular momentum they have in their excited states, with ...
1
vote
1answer
95 views

Rho and Omega meson mixing

I am new to particle physics. So this might seem to be a trivial question. I read about $\omega$ and $\phi$ meson states being written in terms of octet and singlet state. In the same way, can $\...
1
vote
0answers
49 views

Mixing Parameters of the $D^{0}$ Meson

Consider mixing in the $D^{0}$ charm meson system as discussed, for example here. Such mixing is characterised by the mixing parameters $x=\frac{\Delta m}{\Gamma}$, and $y=\frac{\Delta\Gamma}{2\Gamma}$...
1
vote
0answers
27 views

What is the time period in which an interaction with a π-meson takes place?

The longer-range inter-nucleon force is not a direct result of the gluon field, but is indirectly affected by a quark-antiquark pair (meson). If this ‘residual’ strong interaction between nucleons ...
0
votes
1answer
48 views

What meson influences the nucleon-nucleon interaction at a far range and why?

What meson influences the nucleon-nucleon interaction at a far range and why? Nucleon-Nucleon (NN) interaction is divided up into three parts a) long range (>2fm) b) medium range (1 to 2fm) c) ...
0
votes
0answers
28 views

Description of strong force as exchange of meson or as exchange of quark and antiquark

The (residual) strong force between nucleons can be desribed as The exchange of a meson (from a nucleon to the other), as in picture b) The exchange of a quark and an antiquark: in picture a) one ...
0
votes
1answer
36 views

Use of energy–momentum relation for virtual particle deriving Klein Gordon equation

Here it is claimed that A virtual particle does not precisely obey the energy–momentum relation $m^2c^4 = E^2 − p^2c^2$ But then why is Klein Gordon relation (in the context of Yukawa theory) ...
0
votes
1answer
66 views

Mass of mesons and baryons

In my introduction to nucleons and particles (basic) course, we were given the following formula to compute the mass of mesons and baryons : \begin{eqnarray} M(\text{meson}) & = & m_1 + m_2 ...
1
vote
1answer
57 views

Does the decay of $\rho^0$ meson imply that charged pions have non-integer orbital angular momentum?

In the decay $\rho_0\rightarrow \pi^+ + \pi^-$ the $\rho_0$ has total angular momentum 1 and the $\pi^\pm$ both have spin zero. In order to conserve total angular momentum, the pions must therefore ...
1
vote
1answer
114 views

Width of the J/$\psi$ resonance

The J/$\psi$ resonance has a mass of ~3 GeV but its width is only of 100 keV, why is it so narrow compared to the total mass? How can the width of these resonances be calculated?
0
votes
1answer
55 views

What is the process transforming $K_L$ mesons into $K_S$ mesons?

First of all, I could not find any good book/webpage where I can read about K mesons, can somebody point me to a good reading? The second point is about $K_L$ and $K_S$ mesons. As I can read, they are ...
0
votes
1answer
49 views

Can somebody explain the relation of Young diagrams and particle physics?

I have the mesons octet and there are Young diagrams below them. how are they drawn? what do they represent?
0
votes
0answers
86 views

If colour charge is like electric charge how do baryons hold together when all the colour charges have the same sign?

So a quark and an antiquark in a meson have colour charges of the same colour but opposite sign eg $r \bar{r}$, so I think this is like an electric charge with a positive and negative particle so ...
0
votes
1answer
55 views

Can a kaon decay into 4 pions?

Since a Kaon's wavefunction is composed of $K_S$ and $K_L$ which are CP-even and CP-odd respectively. The Kaon can decay into $\pi \pi \pi \pi$ through $K_S$ since the 4 pions have CP-parity $= (-1)^4 ...
0
votes
1answer
124 views

How can i predict the decay modes and branching ratios of the phi-meson (mass 1020 MeV)?

I have looked up the pdg and found different decay modes in which three of them are the most occurring in nature. They are $\rm\phi\rightarrow K^+K^-$, $\rm\phi\rightarrow K_0\bar K_0$, and $\rm\phi\...
5
votes
1answer
132 views

How are the 'physical' isospin zero states determined?

Consider the light mesons. Since $3 \times \bar{3} = 8 + 1$, the states should be grouped into $\mathfrak{su}(3)$ octets and singlets. In the case of the spin zero states (the pseudoscalars), the ...
0
votes
1answer
77 views

Calculating matrix elements for quarkonium decay amplitudes

In this paper (Appendix A) several decay amplitudes are calculated. How does this work? Note that $$ |n \bar n \rangle = \frac{1}{\sqrt{2}} (| u \bar u \rangle + |d \bar d\rangle ) \\ \eta = \cos \...
1
vote
0answers
23 views

vector mesons identified with positive parity

I have seen in some sources (like in https://arxiv.org/abs/1610.06090, page 11, footnote 11 but also in some few more) that vector mesons are assigned with positive parity $(J^P)=1^+$. In Particle ...
2
votes
1answer
381 views

Why can't omega meson decay into two neutral pions?

Here it says this decay mode is a violation of C-parity. I don't understand how that works. So $\omega$ has $C=-1$ and $J=1$ and $\pi^0$ has $C=1$ and $J=0$, that means the orbital angular momentum ...
2
votes
1answer
45 views

Which mesons are possible?

That's probably a plain question but I wonder: Which mesons can exist? The only limitation I'm aware of is the charge (antiparticle+particle). Ok, finally also the color (anticolor+color) but I assume ...
0
votes
1answer
160 views

Neutral kaon semileptonic decays, why is $\overline{K^0}\rightarrow l^+\nu\pi^-$ not allowed?

On several texts it is stated that the semileptonic decays are different for the $K^0$ and $\overline{K^0}$, and each only gives leptons of particular charges (see www.hep.ph.ic.ac.uk/~dauncey/will/...
0
votes
0answers
70 views

Conservation laws in the context of a particle decay

The question I'm looking at involves a K meson of mass 494MeV/c^2 travelling across a lab and decaying into two pi mesons of mass 137MeV/c^2, one of which is left at rest. I have used the idea that ...
1
vote
2answers
316 views

Wavefunctions of (Pseudo)-scalar/vector meson and Tensor meson

Two quarks can bound to form a meson, and the wavefunction consists of several quantum degrees of freedom: $$ \psi=\psi(\text{flavor})\psi(\text{color})\psi(\text{orbital})\psi(\text{spin}) $$ ...
2
votes
1answer
120 views

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

In 1964 Cronin and Fitch discovered that there is asymmetry in the weak decay of the neutral K meson. What is this asymmetry and what causes it?
0
votes
1answer
112 views

Are bottomonium and charmonium the only quarkonium systems?

I had a question: Are bottomonium and charmonium the only quarkonium systems? I was searching the internet and found that these two systems have been experimetally observed but the toponium has ...
1
vote
2answers
163 views

What is a $D^{0 \ast}$ meson?

What are the quark contents of $D^{0 \ast}$ meson? How to distinguish between $D^{0 \ast}$ meson and $D^{0}$ meson as I guess both have same quark content.
3
votes
1answer
152 views

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

The eight light pseudoscalar mesons of QCD are the pseudo-Goldstone bosons of the spontaneously broken chiral (axial) $SU(3)_A$ quark flavor symmetry. If we consider the hypothetical case of also ...
0
votes
1answer
185 views

Applying ladder operators to Isospin states for quarks

I'm having trouble finding the isospin representation of the meson isospin triplet $|\rho\rangle$. Starting from the $|\rho^+\rangle$ meson $|u^\uparrow\bar d^\uparrow\rangle$ (where the arrows ...
1
vote
1answer
202 views

The right quark combination for a meson

If I have a meson nonet, it contains the octet and the singlet ($\eta'$). For example in the $J^P=0^-$-case, I have 'simple' mesons like $K^0$ with $d\bar{s}$, but I also have mesons, which are mixed ...
0
votes
1answer
42 views

Why do $I,J,P$ still need confirmation for the B mesons?

If I open the PDG (say here), and look at the quantum numbers of the $B$ mesons it says, for every $B$ meson, "I, J, P need confirmation". However, this disclaimer doesn't appear for any other type of ...
1
vote
1answer
73 views

Which particle decays are quickest?

The $ρ^0$ and $\pi^0$ mesons have the same quark content, (uu*-dd*)/sqrt(2) and have masses of 775 MeV/c^2 and 135 MeV/c^2 respectively. The ρ0 has a lifetime ~ 10^-24s while pi0 has a lifetiem of ~10^...
0
votes
0answers
593 views

Meson wave function

I have a basic question about pseudoscalar mesons wavefunction. As I understand it, mesons are bosons so they have a total symmetric wavefunction under exchange of particles. For pseudoscalar mesons,...
8
votes
2answers
259 views

What's the difference between a meson and a glueball?

There is a blog post by Matt Strassler about the structure of hadrons. He contrasts the "conventional" picture of hadrons shown below: with one that he considers to be more accurate: From the ...
1
vote
2answers
948 views

Why can omega meson not decay into two charged pions?

Why is the decay of the $\omega$ meson similiar to the neutral $\rho^{0}$ meson into two charged $\pi$ prohibited? My first thought was that it has something to do with isospin conservation in the ...
1
vote
1answer
347 views

Why is a Kaon strange?

I've read that because Kaons are produced by the strong interaction and decay by the weak interaction that this makes them strange. However protons and neutrons decay by the weak interaction as well i....
3
votes
1answer
111 views

Why are there both scalar and vector mesons?

I understand that the term "vector meson" denotes a meson particle (composite particle with a quark and an antiquark) which transforms as a vector under the Lorentz group. Since both the quark and the ...
2
votes
0answers
726 views

Overall symmetry of pion wave function

Mesons are bosons, therefore their wavefunction must be symmetric under particle exchange. Overall, the meson wave function ($\text{WF}$) has the following contributions: $$\text{WF} = \lvert \text{...
5
votes
2answers
497 views

Why are all mesons unstable

My question is: why are all mesons unstable? Shouldn't the lightest mesons like the pion be stable because they are made from the lightest quarks (and anti-quarks)? Or could the they annihilate (the ...
0
votes
2answers
114 views

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

I guess it is because of the forces between the quarks inside them but I am not quite sure how to explain it.
0
votes
1answer
122 views

Physical significance of the decomposition $3\times \bar{3}=8+1$: Does the singlet state differs from the states in the octet?

Under $SU(3)$, $3\times \bar{3}=8+1$ i.e., the tensor product of the fundamental and the conjugate (to the fundamental) representation is reducible: 1 represents the singlet under $SU(3)$, and 8 ...
0
votes
1answer
108 views

Explicit construction of states from $3\times \bar{3}=8+1$

Under $SU(3)$, $3\times \bar{3}=8+1$ i.e., the tensor product of the fundamental and the conjugate (to the fundamental) representation is reducible: 1 represents the singlet under $SU(3)$, and 8 ...
1
vote
2answers
70 views

What is this notation using $\psi$ and $J$ to represent particles in a quark-based interaction?

The $c\bar{c}$ meson decays to a lighter meson in the following reactions: $$\psi(3686)\rightarrow J/\psi(3097)+\eta^0$$ $$\psi(3686)\rightarrow J/\psi(3097)+\pi^0.$$ My aim is to find out which ...
0
votes
1answer
826 views

Gluons and mesons

I just read somewhere that both gluons and mesons transmit the strong force, gluons between quarks inside hadrons, but mesons between nucleons. I thought that the strong force would have one field, ...
3
votes
2answers
740 views

What is a sigma meson? [duplicate]

I have seen some articles talking about the role of sigma meson in nuclear force, but more articles omit it and only mention pion, rho and omega (e.g., Wikipedia). What is this sigma meson?
-2
votes
2answers
290 views

mu-meson experiment [closed]

for the experiment that moving mu-mesons live longer, we used as an example their straight-line motion in the atmosphere. But if make mu-mesons in a laboratory and cause them to go in a curve with a ...
-1
votes
1answer
81 views

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

An $\eta^0$ meson has a very short lifetime that it hardly ever exists independently. My question is ’With such a short lifetime, is it possible to observe the existence of an Anti $\eta^0$ meson? ( ...