Baryons are hadrons (particles composed of quarks) with an odd number, at least 3, of valence quarks. The term is also often used in astrophysics, e.g. "baryonic matter", with a much looser definition understood to mean any matter composed mostly of baryons, but which may also include leptons and other particles, often in opposition to "dark matter".
Questions tagged [baryons]
182 questions
36
votes
5 answers
How do we know neutrons have no charge?
We observe that protons are positively charged, and that neutrons are strongly attracted to them, much as we would expect of oppositely charged particles. We then describe that attraction as non-electromagnetic "strong force" attraction. Why posit…
MacThule
- 421
26
votes
5 answers
Why isn't there a second baryon octet?
Let's temporarily ignore spin. If 3 denotes the standard representation of $SU(3)_F$, 1 the trivial rep, 8 the adjoint rep and 10 the symmetric cube, then it's well-known that
$$ 3 \otimes 3 \otimes 3 = 1 \oplus 8 \oplus 8 \oplus 10.$$
Interpreting…
Evans
- 834
21
votes
5 answers
How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content?
Title says it all: How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content? Doesn't this make them the same baryon?
spraff
- 5,256
16
votes
1 answer
Is it a coincidence that quarks have exactly -1/3 or 2/3 the electron's charge?
I have read these questions:
Why do quarks have a fractional charge?
Is there an explanation for the 3:2:1 ratio between the electron, up and down quark electric charges?
Hypercharge for $U(1)$ in $SU(2)\times U(1)$ model
Is there any idea why…
Árpád Szendrei
- 30,008
15
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3 answers
Are there any Baryons that have quark-antiquark combinations?
I'll be honest, I only have a Highschool education, so there might be something obvious I'm overlooking. However particle physics is of massive Interest to me.
My question is, I know there are unstable quark-antiquark pairs that form Mesons, but…
RudyJD
- 481
13
votes
1 answer
Probability of forming mesons vs baryons
When a heavy quark hadronizes it has some probability of forming a meson vs forming a baryon. I suspect there is a well known branching ratio for each type of hadron. Does anyone know what the probability is or, even better, a reference that…
JeffDror
- 9,093
13
votes
2 answers
Why there are no $uuu$ and $ddd$ baryons with spin 1/2?
What is preventing $Δ^{++}$ and $Δ^-$ spin 3/2 baryons from going to a lower-energy state with spin 1/2 similar to that of protons and neutrons? I don't think the Pauli exclusion principle can prevent it because the quarks have different colors. …
proski
- 241
12
votes
2 answers
Why is there no baryon isospin singlet with spin 3/2?
All of the baryons in the spin-1/2 octet except the $\Lambda$ isospin singlet have spin-3/2 excited states in the baryon decuplet. What is it that prevents the existence of a $\Lambda^{*}$ baryon with $I=0$, $s=-1$, and $S=3/2$?
JackR
- 223
11
votes
1 answer
Why do we antisymmetrize the baryon's wavefunction but not the meson's?
A many-body wavefunction of identical fermions must be antisymmetrized because of fermionic statistics. We don’t antisymmetrize the meson wavefunction because it contains a quark and an antiquark, and they are not identical fermions. But in particle…
wonderich
- 8,086
10
votes
1 answer
$SU(3)_F$ flavour symmetry and $SU(2)$ isospin symmetry
There is an approximate $SU(3)_F$ flavour symmetry that exists at the quark level between $u$, $d$ and $s$ quarks. But we often talk about an approximate isospin $SU(2)$ between up and down quark only? Why?
Solidification
- 12,736
10
votes
3 answers
Can superpositions of baryons with different electric charge and strangeness exist?
I am trying to find out whether the following baryons can exist:
$$ |X\rangle = \frac{|u u u\rangle + |d d d\rangle + |s s s\rangle}{\sqrt{3}} $$
$$ |Y\rangle = \frac{|u u u\rangle + |d d d\rangle - 2|s s s\rangle}{\sqrt{6}} $$
I haven't found in…
Mario Krenn
- 800
10
votes
4 answers
Baryon asymmetry
Baryon asymmetry refers to the observation that apparently there is matter in the Universe but not much antimatter. We don't see galaxies made of antimatter or observe gamma rays that would be produced if large chunks of antimatter would annihilate…
Marton Trencseni
- 3,105
9
votes
1 answer
How do topological excitations of the pion field carry a baryon number?
I have heard (numerous times) that topologically nontrivial pion field configurations carry baryon number. It's clear the the field configurations can carry a topological quantum number (the winding number or homotopy class). However, what I do…
Buzz
- 17,816
8
votes
1 answer
Has non-conservation of baryon number been observed?
CP violation (as I understand it) allows for non-conservation of baryon number, and thus can contribute (at least a little) to the baryon asymmetry in the universe today (far more matter than antimatter).
But have we ever seen baryon number change…
Kevin Kostlan
- 6,875
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8
votes
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What fraction of the mass of all baryonic matter are black holes?
Is there a calculation of how much of the mass of baryonic matter is black holes, including supermassive black holes in the center of galaxies?
Arman Armenpress
- 956