A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong ...

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2
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0answers
42 views

Lepton and strangeness conservation [closed]

Do I have a misunderstanding here at all? The question states: One of the following equations represents a possible decay of the K$^+$ kaon. \begin{align}\mathrm K^+&\to\pi^++\pi^0\\\mathrm ...
-1
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1answer
43 views

Can a massless quark exist?

Is there any possible way to extract all the mass of a quark? Probably under extreme Gs or heat or pressure?
2
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0answers
37 views

Identical Particle Wavefunctions

Consider the process $$\rho^0\rightarrow\pi^0+\pi^0$$ The $\rho^0$ has $J=1$ whilst the two pions have $S_{tot}=0$ and thus require $L_{tot}=1$ by conservation of angular momentum. Consequently this ...
7
votes
2answers
102 views

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?
0
votes
1answer
33 views

Gluon to quark scattering

I am trying to calculate the $g g\to q \bar q$ amplitude but am finding it intractably complex. I have determined that there are only two independent polarizations that contribute non-zero ...
3
votes
2answers
237 views

Do Standard Model Yukawa couplings depend on the gauge choice?

In the standard model and the Unitary gauge, we write the Higgs field as $ \phi = \frac{1}{\sqrt{2}} \begin{pmatrix} 0 \\ v + H \end{pmatrix}$ and the Yukawa couplings (leaving out the neutrino ...
2
votes
0answers
95 views

Shouldn't there be 6 fundamental forces? [closed]

I'm listening to Leonard Susskind's The Black Hole War. In it he states (paraphrased) that a string wrapped around a compact dimension once imparts one unit of charge. Wrapped one way, it's a ...
2
votes
0answers
45 views

Are the pions really all that light?

I'm studying the sigma model where the pions are identified as the (pseudo) Nambu-Goldstone bosons of chiral symmetry breaking ("pseudo" from mild isospin symmetry violation). This argument usually ...
2
votes
1answer
260 views

$G$-parity in an electromagnetic decay

I am looking at the decay $\eta\rightarrow\pi^+\pi^-\gamma$ and I would assume that the decay itself (ignoring the $\pi\pi$ final state interaction that is obviously strong) is electromagnetic since ...
1
vote
1answer
53 views

Why don't all the gluon's get converted into energy in an uranium atom undergoing fission?

I have following questions and arguments. why do only gluons get converted into energy in an uranium atom undergoing fission? why don't all the gluons get converted into energy? which conditions ...
4
votes
1answer
160 views

Pion decay: V-A vs. V coupling

For the Decay $$ \pi^- \to \mu^- \bar{\nu}_\mu $$ the Feynman rules for this tell us that the vertex couples with $\gamma^\mu (1-\gamma^5) / \sqrt{2} $. This gives me the reduced amplitude of $$ M = ...
6
votes
1answer
154 views

Why did it take so long to find the Higgs?

The $W$ and $Z$ boson took a long time to be discovered because they were so heavy; we couldn't produce them in a particle collider until the 80's. But the Higgs boson isn't that much heavier than the ...
3
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0answers
65 views

Few questions regarding String-Net theory and the Standard Model

A friend today showed me this post and after reading Prof. Wen's answer, few questions came to my mind. Prof. Wen says: all fermions (elementary or composite) must carry gauge charges (see ...
5
votes
1answer
228 views

Why is there no fundamental force following from the $SU(4)$ symmetry?

I've understood that the three fundamental interactions described by the Standard Model (the electromagnetic, the weak and the strong force) are thought to correspond (roughly) to gauge invariances ...
12
votes
2answers
680 views

What's the deepest reason why QCD bound states have integer charge?

What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, ...
3
votes
2answers
68 views

Are the properties assigned to quarks meaningful?

Suspect this may have been asked before, but can't find it. My question is: If you can never have a free quark, what sense does it make to attribute properties to them, since you can never ...
1
vote
0answers
29 views

How do I go about understanding particle physics? [closed]

My science project has tasked me in creating a research paper on the standard model of particle physics, but I'm not in highschool yet. I don't know how to go about learning the math and the concepts ...
1
vote
1answer
47 views

The charges of the forces

I am trying to establish a simplified understanding of the fundamental forces to explain them to a young audience. If we say that gravity has one charge (attractive), electromagnetism has two charges ...
0
votes
1answer
116 views

Why are quarks fundamental particles? [closed]

A neutron decays into a proton by changing one of its down quark into an up quark and releasing energy, positron and neutrino particle. So, a down quark can decay into an up quark. If a quark ...
7
votes
1answer
135 views

The process $\mu^+\mu^-\rightarrow hh$

I am doing some calculations in the Standard Model. I have a question that seems rather simple but makes me think a lot. I want to compute the cross section of the following process at the leading ...
4
votes
1answer
260 views

Computing box diagrams with non-vanishing external momenta

I'm trying to explicitly compute the following box diagram in the Feynman-t'Hooft gauge: If I neglect the impulsion of the $s$ quark, then the final amplitude is given by $$\mathcal{A} \propto ...
1
vote
1answer
71 views

Is there a standard resource that lists all understood particle-particle relationships?

I am just starting to dig a little deeper into particle interactions, and just have an introductory college physics background (no quantum mechanics). But I am interested in the conditions of the ...
4
votes
2answers
133 views

Top quark mass $m_t$ at energy scales $\mu < m_t$?

Edit - Maybe formulated differently: Does it make sense to talk about the top mass at energies below $m_t$, although in all processes the corresponding energy scale is above $m_t$, because of the rest ...
1
vote
1answer
88 views

How do Higgs field provide mass to other particles? [closed]

I know this question has been posted so many times here but still I have some confusions about Higgs mechanism. I watched some videos relating to Higgs mechanism and they says the Higgs field provide ...
1
vote
0answers
32 views

Where does the square root of two in the conversion between the Fermi constant and the weak coupling constant come from?

As in the title, where does the square root of two in the conversion $$ G_{F}=\frac{\sqrt{2}g^{2}}{8m_{W}^{2}} $$ between the Fermi constant and the weak coupling constant come from? I was able to ...
5
votes
2answers
236 views

What is the exact relation between $\mathrm{SU(3)}$ flavour symmetry and the Gell-Mann–Nishijima relation

I'm trying to understand how the Gell-Mann–Nishijima relation has been derived: \begin{equation} Q = I_3 + \frac{Y}{2} \end{equation} where $Q$ is the electric charge of the quarks, $I_3$ is the ...
2
votes
2answers
269 views

Is $SU(2)$ really broken by the Higgs VEV or just hidden?

It's generally stated in the textbooks that whent the Higgs field acquires a certain vev the corresponding symmetry is spontaneously broken. For example in A. Zee - QFT in a Nutshell: But none of ...
3
votes
2answers
121 views

Origin of Mexican hat potential in Higgs mechanism

I have recently read a layman's version of the Higgs mechanism with a Mexican hat potential. The only thing I don't get is what actually causes the Higgs potential to have a Mexican hat shape?
2
votes
3answers
64 views

How is each neutrino associated with a specific charged lepton?

For instance, why is an electron neutrino called that and what is its relationship with an electron?
1
vote
3answers
124 views

What is the difference between toy models and normal models? [closed]

Here is the short description of scientific model: an imperfect or idealized representation of a physical system And the definition of toy model: a simplified set of objects and equations ...
0
votes
1answer
59 views

Computing the pole mass from a given $\overline{MS}$ mass?

Given a Yukawa coupling as a function of scale $\mu$ and a vev, therefore $m_R(μ)=Y(μ)⟨ϕ⟩$, how can I compute the corresponding pole mass $m_p$? Relations I was able to find are (page 39) ...
1
vote
1answer
119 views

Mirror/Parity symmetry in spin

We just saw parity symmetry and we were told about the experiments to see the non parity symmetry of disintegration, in particular one involving the reaction: $$^{60}Co\longrightarrow^{60}Ni+ e + ...
1
vote
1answer
66 views

Why only left-handed neutrinos have been observed yet?

This is what I understood (it may be wrong, so please correct me): since every particle is "divided" into a lefthand and a righthand partner, which is what guarantees the particles to have mass, and ...
-1
votes
1answer
303 views

Is the neutral pi meson a relativistic electron positron pair?

Is the neutral pi meson a relativistic electron positron pair? An electron position pair orbiting at relativistic speeds is proposed as a model of a neutral pi meson by Ernest Sternglass. However, ...
16
votes
1answer
3k views

Origin of electric charge

Baryons have charges that are the result of a polynomial calculation of their building blocks (quarks)'s fractional charges. But what gives these quarks electric charges? What interactions do they ...
1
vote
1answer
71 views

Why do we say that gluons carry color charge?

We know that gluons are Lie algebra $su(3)$-valued one-form fiels $A_{\mu}$. And because of $[A_\mu,A_\nu]$ does not vanish generally for the non-Abelian case, gluons have self-interactions. Now how ...
2
votes
1answer
206 views

Group theoretical reason that Gluons carry color-charge and anti-colorcharge

I was wondering how it is possible to see from the $SU(3)$ Gauge Theory alone that Gluons carry two charges colors: $g\overline{b}$ etc. Some background: The W-Bosons (pre-symmetry breaking) ...
18
votes
2answers
1k views

What is (meant by) a non-compact $U(1)$ Lie group?

In John Preskill's review of monopoles he states on p. 471 Nowadays, we have another way of understanding why electric charge is quantized. Charge is quantized if the electromagnetic $U(l)_{\rm ...
1
vote
2answers
99 views

How is an electron “recycled” in a neutron?

A proton is made up, they say, by 2 up and 1 down quark, drowned in a sea of virual paricles: when an electron is captured this process thereby changes a nuclear proton to a neutron and ...
3
votes
1answer
48 views

Does the Peccei-Quinn (PQ) mechanism require fine-tuning?

The strong CP problem: the QCD theta parameter can not be arbitrarily small due to 't Hooft's doctrine of naturalness (a parameter can be arbitrarily small only when putting it to zero provides an ...
0
votes
0answers
50 views

Mass of an imaginative stable top quark at low energies? [duplicate]

Masses are not fixed quantities, but change with energy because of the renormalization group running. These can be calculated in a given renormalization scheme, for example, the MS scheme: Imagine ...
17
votes
5answers
9k views

Why don’t photons interact with the Higgs field?

Why don’t photons interact with the Higgs field and hence remain massless?
1
vote
3answers
81 views

What are the six quark mass values when extrapolated to Planck energy?

Let us assume that the standard model is correct up to Planck mass. (Yes, I know, this is a big assumption.) If we continue the running of quark masses with energy (due to renormalization), what are ...
0
votes
1answer
73 views

What maximum energy can be stored in a gluon field flux tube

Question is as clear as stated in title. What is the maximum energy that can be stored in a gluon field flux tube without production of an quark anti-quark pair? And how much it usually store in a ...
-1
votes
4answers
108 views

What is mass constituted by quarks in a proton?

In a question I read Quarks in a hadron- where does the mass come from "The sum of the masses of the quarks in a proton is approximately $30~\text{MeV}/c^2$, whereas the mass of a proton is ...
5
votes
2answers
833 views

Quarks in a hadron- where does the mass come from

We know that the sum of the masses of the quarks in a proton is approximately $9.4^{+1.9}_{-1.3}~\text{MeV}/c^2$, whereas the mass of a proton is $\approx931~\text{MeV}/c^2$. This extra mass is ...
2
votes
1answer
74 views

Baryon number violation in the Standard Model

Anomaly cancellation in the Standard model requires $B-L$ to be constant, which is done using perturbative diagrammatic expansion. Secondly, baryon number is conserved as an $U(1)$ global field ...
0
votes
1answer
53 views

Couplings of fields in the Standard Model

Could someone please explain what this task implies: Calculate coupling of fields: $\bar{e}_{R}e_{R}Z, HW^{+}W^{-}, W^{+}\bar{c}_{L}d_{L}$? (Exercise refers to the Standard Model Lagrangian). What do ...
0
votes
0answers
29 views

Can you recommend me a book on the discoveries and properties of these particles? [duplicate]

Possible Duplicate: Good book about elementary particles for high school students? Some days ago, I've found this: When I was in high-school, They taught me about electrons, protons and ...
3
votes
1answer
65 views

Can the effective vertex for $\gamma\to3\pi$ be derived directly from the anomaly?

My question is whether the effective vertex for $\gamma\to3\pi$ can be derived directly from the anomaly (given in the first equation below), in analogy with the $\pi^0\to2\gamma$ vertex? As far as I ...