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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16 views

Unitarity Gauge : how to undo the gauge transformation

I will simplify the argument. Let's consider a Gauge Boson (like the gauged one of U(1), $A_\mu$). Then, consider the Higgs boson with exponential representation, then $$H = ...
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0answers
32 views

A Question about a $U(1)_{B-L}$

I know I can write the QCD lagrangian like this: $$ \mathcal{L} = (i\bar{q}_{R} \gamma_{\mu}\partial_{\mu} {q}_{R} + i\bar{q}_{L}\gamma_{\mu}\partial_{\mu} {q}_{L}) + \text{other terms} $$ When ...
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1answer
32 views

Is there a reason why every meson and baryon has an integer electric charge? [duplicate]

Is there a reason why every meson and baryon has an integer electric charge? For example, why is there no meson existing of two up quarks, giving a charge of $\frac43$?
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0answers
24 views

Electroweak phase transition

Is it true that when the temperature of the universe was greater than ~200GeV the Higgs did not have any nonzero vacuum expectation value, hence all the particles were massless? So if one calculates ...
0
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1answer
43 views

Gauge Bosons at Finite Temperature

I was reading a paper¹, and it states: " Therefore, the gauge fields themselves cannot be entities of the physical reality, as any observations should be independent of the chosen gauge" I'm trying ...
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18 views

Non-zero spin meson have ever seen experimentally? [on hold]

Have been ever shown ( in experiment) none-zero spin meson? We should have it?
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1answer
44 views

Which elementary particles have been seen up to now?

Which elementary particles have been shown up to now? which one except Graviton, haven't seen? I need an update one, I am searching but I couldn't find. If anyone could answer me, I am so thankful.
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1answer
49 views

Understanding standard model and symmetry

I just want to know whether my understanding regarding standard model and symmetry is correct or utter nonsense. The standard model is the (yet incomplete) Lagrangian of the universe. The ...
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2answers
54 views

Where does $W$ boson mass come from in neutron decay?

Here's a diagram of neutron decay. Up and down quarks have rest masses of 2-4 MeV. The $W$ boson has a rest mass of 80 GeV. Where has this extra mass come from?
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1answer
58 views

With the descent of Newtonian mechanics is Newton's third law still valid?

Or more specifically, with the standard model, quantum theory and other advances in physics, all those experiments in CERN and other accelerators, was there any occurrence where this law was violated? ...
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1answer
44 views

What is the equation for a freely propogating glueball? [closed]

What is the equation for a freely propogating glueball? Can glueball dissipate into heat? What is the lifetime of glueball? Does glueball obtain a mass somehow?
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3answers
76 views

How do particles get their charge?

How does an electron get its charge? And how can it maintain that charge for very long (infinite) periods of time? And how come a neutron has no charge since and a proton does? They are both made of ...
0
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3answers
128 views

Why is this particle interaction forbidden?

Why is this interaction forbidden? $$\nu_e+\bar{\nu}_e\rightarrow K^+ + K^-$$ Lepton number is conserved, charge is conserved, baryon number is irrelevant since these are mesons. Energy is conserved ...
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0answers
38 views

Up/Down Quark Color and Isospin

I'm reading some notes that say the reason that the strong interaction conserve isospin is because the up and down quarks have the same color... but I'm not very convinced. Is this a universal truth? ...
2
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2answers
73 views

Why do particle physicists use the $h\rightarrow{\gamma\gamma}$ decay mode rather than $h\rightarrow{b\bar{b}}$?

Just wondering, the $h\rightarrow{\gamma\gamma}$ decay mode is often quoted as being most sensitive to measuring the mass of the Higgs particle, why isn't the $h\rightarrow{b\bar{b}}$ decay channel ...
2
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1answer
35 views

How come two protons create top-antitop quark pair? (A question regarding CERN courier May 2016)

I am not very well versed in particle physics lingo but as much as I know $p$ stands for proton and $t$ stands for top-quark. Then, how could this be possible? I hope I am wrong about what is ...
0
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0answers
24 views

Can glueballs, consisting of massles gluons, get a mass without reference to a Higgs field? [duplicate]

Glueballs, the by the standard model predicted combinations of short-lived combinations of massless gluons, have a mass between 1.4 and 5 (MeV). But where is this mass coming from? From interaction ...
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0answers
35 views

standard model classical limit [duplicate]

"The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, as well as classifying all the subatomic particles known". Since it includes ...
0
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0answers
28 views

Symmetry breaking with adjoint matter, departing from vacuum in different way

$$L=-\frac{1}{4}TrF_{\mu\nu}F^{\mu\nu}+\frac{1}{2}D_\mu\phi D^\mu \phi -\lambda V(\phi)$$ Say we have a potential $V(\phi)=(|\phi|^2-v^2)^2$, and 3-component real scalar field $\phi=(\phi_1, \phi_2, ...
0
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2answers
78 views

What particles do these Feynman diagram lines represent?

What particles could be represented by A and B (labels I have added myself - this is not a homework question)? For A, it looks like it's supposed to be a photon, but I was under the impression that ...
5
votes
3answers
121 views

Do quark charges repel one another?

Positive electrical charges repel other positive charges, and negatives repel negatives. But does that happen for quarks, too? I never saw mention of it, but if so, that would mean the up quarks in a ...
0
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0answers
31 views

Why can an electric chargeless Z-particle decay in three photons?

The Z-particle that is supposed to convey the weak force has no electrical charge. So how is it possible the particle can decay in three photons. Because the weak and e.m. force are more or less ...
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1answer
11 views

Conservation of $C$-Parity and $P$-parity

Under what situations are $C$-Parity $C=(-1)^{L+S}$ and/or $P$-parity $P=-(-1)^L$ conserved? ( $L$ here is the relative angular momentum and S is the total intrinsic spin). It would make sense that ...
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2answers
133 views

Can superpositions of baryons with different 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 - ...
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0answers
43 views

Are quadrilinear weak boson couplings possible?

$ZZ\rightarrow ZZ$, $ZZ\rightarrow W^+ W^-$, etc. Are these interactions possible?
3
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2answers
27 views

Standard-model flavor symmetry

If we consider the chiral Lagrangian after the spontaneous symmetry breaking, we have got fermion masses and Yukawa couplings to the physical Higgs boson. So it follows global symmetries in flavor ...
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1answer
69 views

What gives a particle its identity?

A lot of very smart people have stitched together the standard model, and I accept it. I don't understand it, but I assume there should be a mechanism of sorts that gives a particle some fundamental ...
1
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1answer
69 views

Is the standard model a quantized gauge theory?

I have studied some quantum field theory and gauge theory but I am definitely not an expert. I am aware that in quantizing electrodynamics one has to fix a gauge. I have read that for general gauge ...
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1answer
67 views

Raising and lowering operators for a composite isospin $SU(2)$ system

Consider pion states composed of $q \bar q$ pairs where $q \in \left\{u,d \right\}$ transforms under an $SU(2)$ isospin flavour symmetry. These bound states transform in the tensor product $R_1 ...
3
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0answers
77 views

What is the meaning of SU(2) triplet scalar field? [closed]

The following is an about a Left-Right Symmetric model. $SU(2)\otimes SU(2)$ $(2\otimes 2=3\oplus 1)$ will generate a triplet, which in Left-Right Symmetric model is ...
0
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1answer
40 views

What are all charge-like quantum numbers?

What are all charge-like quantum numbers? In particle physics there are often things (like charge conjugation) that apply to all charge like quantum numbers. Everytime I read something about ...
11
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1answer
552 views

Why is the charmed eta meson its own antiparticle, but the neutral kaon is not?

I have a limited understanding of antiparticles, so this may be why I am unable to explain why certain mesons are their own antiparticles, while others are not. My understanding is that antiparticles ...
0
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1answer
37 views

Why do the different lepton generations have different masses?

I've been reading Mark Srednicki's book on Quantum Field Theory, and toward the end (Chapter 88), he describes how the different generations of leptons acquire mass via Yukawa interactions. However, ...
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0answers
24 views

What is the difference between the generation of mass for Fermions compared with Bosons in the standard model?

I've seen a few questions asking how the Higgs mechanism generates mass for particles of the standard model. However, I haven't seen any which specify the differences between Bosons and Fermions in ...
2
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0answers
41 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 ...
3
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1answer
69 views

Interpreting the Cross Section Ratio R

Below is experimental data for the ratio $$R=\frac{\sigma(e^+e^-\rightarrow hadrons)}{\sigma(e^+e^-\rightarrow\mu^+\mu^-)}$$ as a function of the centre of mass energy $\sqrt s$. I am interested in ...
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1answer
33 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
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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?
2
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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
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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 ...
7
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4answers
238 views

Why don't we call the fermions in the standard model force carriers?

Maybe this is a chicken-and-egg problem, but couldn't we call all the bosons fundamental and treat the fermions as force carriers between them? EDIT: After all we never see the asymptotic states of ...
1
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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 ...
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 ...
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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 ...
3
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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
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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 ...
5
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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 ...
1
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1answer
87 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 ...