All Questions
Tagged with standard-model homework-and-exercises
54
questions
2
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1
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How to use the quark model to explain that the $D^+$ won't be a strange particle?
For the system of $K^-,\pi^+,\pi^+$, with the invariant mass spectrum peaking about 1.87 GeV, call this resonant peak $D^+$; we find its spin to be zero by experiment.
Using the quark model, how ...
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2
votes
0
answers
53
views
Is this an allowed interaction?
I am looking to understand whether this reaction is allowed:
$$e^+ + e^- \rightarrow K^0 + \pi^0.$$
Baryon number is conserved
Charge is conserved
Total intrinsic spin of underlying particles is ...
- 31
0
votes
1
answer
404
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Doubts about conservation laws/numbers
I'm new to the forum ( sorry for my bad English, I'm Italian).
I'm new to the study of particle physics and I have some doubts about conservation laws and numbers.
For example, I found this exercise ...
1
vote
1
answer
622
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Symmetry factor of a Feynman Diagram
I saw there are already many questions here about the symmetry factor of Feynman diagrams but most of them are about theories that contain only scalars.
My question is: What is the symmetry factor of ...
- 313
0
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1
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259
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Possible reactions / decays in the standard model
If we are in the Standard Model and we have the following processes:
$$e^+ + e^- \to \mu + \mu^-\\
p + p \to K^+ + \Sigma^+ \\
p + n \to \Lambda^0 + \Sigma^+ \\
e^+ + e^- \to u + \tilde{t}
$$
And ...
- 1,398
0
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1
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343
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How to calculate the branching fraction for a decay with a given Cabibbo angle
Lets suppose I know the branching fraction of a decay. How can I calculate the branching fraction in a different final state with the Cabibbo angle?
For example:
$$D^+ \rightarrow \bar K^0 + e^+ + \...
- 437
0
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1
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94
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The $3×3$ representation of weak $SU(2)$
I'm reading chapter 11.2 of the Cheng and Li textbook 'Gauge theory of elementary particle physics'. It says that $T_+$, $T_-$ and $Q$ do not form a closed algebra. In order to fix this problem the ...
1
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0
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Is there a $t$-channel process for $q\bar{q} \rightarrow gg$? [duplicate]
Let's consider the process $q\bar{q}\rightarrow gg$. Is the following Feynman diagram allowed:
I ask because of the following reason: At the upper vertex, the $q$ emits a gluon $g$ and the propagator ...
user248824
1
vote
2
answers
2k
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How Would a Feynman Diagram Look Like for a Proton-Proton Collision?
The LHC is a proton-proton collider. If I wanted to draw a leading order Feynman diagram for a two-quark production in proton-proton collisions, would it be correct to draw sth like this, or would ...
user248824
-1
votes
1
answer
170
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Pion decay $\pi^{+} \rightarrow e^{+}\nu_{e}$ and $\pi^{+} \rightarrow \mu^{+}\nu_{\mu}$
I have a quick question:
I want to calculate how much more likely we expect the process $\pi^{+} \rightarrow e^{+}\nu_{e}$ to be in comparison to $\pi^{+} \rightarrow \mu^{+}\nu_{\mu}$.
I know that in ...
user248824
2
votes
1
answer
443
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Feynman Diagrams - Specific Questions
I have a very naive question concerning Feynman diagrams: If we consider the process $\pi^{+}\rightarrow \mu^{+}\nu_{\mu}$ via the weak interaction, then we get this Feynman Diagram according to ...
user248824
0
votes
1
answer
87
views
Is the $p + p \to K^+ + K^+ + n + n$ process allowed in the SM?
In an exercise it asks to prove why certain processes cannot happen in the Standard Model. One such process is the following:
$$ p + p \to K^+ + K^+ + n + n $$
This process conserves baryonic number ...
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3
votes
1
answer
169
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Why are the lifetimes of the neutral and charged $\Xi$ hyperons so different?
According to the Particle Data Group, the lifetimes of the neutral and charged $\Xi$ baryons differ significantly: $\tau(\Xi^-) = (1.639 \pm 0.015) \times 10^{-10}$ s, while $\tau(\Xi^0) = (2.90 \pm 0....
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1
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2
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Is kaon decay to muons possible?
$$K^0 \rightarrow \mu^+ + \mu^-$$
Just like a neutral kaon decays into a pair of pions, can it also decay into a pair of muons? If not, why?
- 97
-2
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1
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86
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Anomalous magnetic moment [closed]
I have the two values of the anomalous magnetic moments:
$$ a_{\mu}^{SM}=(1 165 917 760 \pm 662)\cdot 10^{-12} \\
a_{\mu}^{exp}=(1 165 920 910 \pm 630) \cdot 10^{-12} $$
Where the first is the ...
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