Questions tagged [isospin-symmetry]
Isospin is a symmetry in nuclear physics under the interchange of neutrons and protons. The strong nuclear force conserves isospin, but the symmetry is broken by the electromagnetic force, which only operates between protons.
189
questions
0
votes
1
answer
60
views
Why is isospin utilized in determining the branching fraction of $K_1(1270)\to K\pi\pi$ final states?
The branching fraction of $\mathcal{B}_{K_1 \rightarrow K^{+} \pi^{+}\pi^{-}}$ is determined by $$\mathcal{B}_{K_1 \rightarrow K^{+} \pi^{+}\pi^{-}}=\frac{1}{3} \times \mathcal{B}_{K_1 \rightarrow K \...
- 17
2
votes
2
answers
158
views
Relation between parity and symmetry for deuteron
I am currently reading the book Física Nuclear y de Partículas by Antonio Ferrer Soria. In this book the following claim is made (this is at translationn from the Spanish):
The wave function of ...
- 23
0
votes
0
answers
41
views
Isospin and quark composition of neutral pion
We have that the neutral pion has quark composition given by:
$$\pi^0=\frac{u\bar{u}-d\bar{d}}{\sqrt{2}}$$
I want to justify this. This can be deduced by reasoning with isospin. We know that:
$$|\pi^0\...
- 119
3
votes
1
answer
70
views
Isospin doublet and quark content from contraction of quarks
Let's introduce a quark $SU(2)$ doublet. We are in the $m_u \approx m_d$ limit. So we have
$$
q = \begin{pmatrix}
u\\
d
\end{pmatrix}.
$$
Then we can construct the Nucleonic field
$$
N := q q q = \...
- 1,611
1
vote
1
answer
96
views
Allowed Isospin states of two nucleons
I have a question on my Quantum Mechanics homework where we consider protons and neutrons to be manifestations of the same particle -- a nucleon. We think of the proton as the "isospin up state&...
0
votes
1
answer
53
views
Two nucleons system with total isospin quantum number $T = 1$
I am confused with the resolution of this question:
A system of two nucleons is in a state with a total isospin quantum number $T = 1$. What are the possible values for the total spin quantum number $...
- 1
2
votes
1
answer
172
views
Question about the wavefunctions of a system of non-identical fermions
If one interchanges two identical fermions in the wavefunction of a $N$-particle system, the total wavefunction changes by a sign i.e., the total wavefunction should be antisymmetric under the ...
- 11.8k
1
vote
1
answer
60
views
Mass of different isospin baryons
Why are the masses of baryons (of same quark content) with different isospin, different? - Is there a physical intuition/explanation to this? Does higher isospin baryons always higher mass than lower ...
- 69
1
vote
1
answer
124
views
$\Sigma^0$ baryon decay
I’ve seen it stated that the sigma baryon $\Sigma^0$ only decays to $\Lambda^0 \gamma$, and then $\Lambda^0$ decays to $p\pi^{-}$ or $n\pi^0$.
I understand that the weak interaction conserves weak ...
- 69
2
votes
1
answer
58
views
Nonconservation of hypercharge in Higgs decay
From Wikipedia, Higgs boson has hypercharge of +1 and isospin of -1/2.
W bosons have hypercharge 0 and isospin +-1.
Now Higgs boson can decay into 2 W bosons of opposite electric charge. No matter how ...
- 203
1
vote
1
answer
150
views
Why not put the anti-quarks in the conjugate representation?
The isospin doublet consisting of $u$ and $d$-quark is defined as
$$
\begin{pmatrix}
u\\
d
\end{pmatrix}.
\tag{1}
$$
But the isospin doublet consisting of the antiquarks, $\bar{u}$ and $\bar{d}$, is ...
- 11.8k
0
votes
1
answer
180
views
Why does isospin symmetry survive chiral symmetry breaking?
In QCD there is a breaking of chiral symmetry such that, for the lightest quarks only, we have
$$\langle \overline{u} u \rangle = \langle \overline{d} d \rangle = \mathrm{const.}$$
where the constant ...
- 841
0
votes
1
answer
118
views
Why can't $uus$ and $uds$ quark content have $I = 1$ Isospin?
Well, I know the isospin singlet with $I=0$ and isospin triplet with $I = 1$. But for $I = 0$, why it must be $uds$ quark content rather than other assembly like $uus$ or $dds$? $ud$ can have $I = 0$ ...
1
vote
0
answers
43
views
If isospin is only approximately conserved by strong interaction, why do we never see isospin violation?
Due to the mass difference between the $u$-quark and the $d$-quark, SU(2) isospin symmetry is only an approximate symmetry (even in a universe devoid of weak and EM interactions). This suggests to me ...
- 11.8k
1
vote
1
answer
39
views
Non-leptonic weak decay with $|\Delta T=3/2|$ suppression (from "Inward bound" Pais' book)
In Abraham Pais' "Inward Bound" book at page 564 it is mentioned that if we describe the weak interactions with the usual current-current interaction (including Cabibbo angle) we still do ...
- 1,082