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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31 views

Flavour basis to mass basis

I am not really understood why we need to change the basis from flavour basis to mass basis after Spontaneous symmetry breaking applying to Yukawa Lagragian? why we can't take (or not making ...
3
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2answers
103 views

Sufficient conditions for a interaction to be classified as weak, strong, …?

Let us say I have been given the equation of a interaction/decay/etc. between particles: $$X+Y\rightarrow A+B$$ Are their any sufficient conditions that we can use to determine the type of interaction ...
-1
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0answers
22 views

Problems with the strong interaction and the rest of the standard model [duplicate]

This question has been heavily revised from what I asked earlier: Michio Kaku, in his QFT a Modern Introduction says (in paraphrase) that the $SU(3)$ gauge symmetry of the strong interaction must be "...
-4
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0answers
50 views

What does Michio Kaku mean when he says that the Strong Interaction must be “penciled in” to the Standard Model [on hold]

This is a very heavily revised question asked earlier: Michio Kaku, in his QFT a Modern Introduction says (in paraphrase) that the $SU(3)$ gauge symmetry of the strong interaction must be "penciled ...
1
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1answer
71 views

How does one write the standard model Lagrangian in other smaller Lagrangian counterparts?

How does one write the standard model Lagrangian in other smaller Lagrangian counterparts? Before electroweak symmetry breaking by the Higgs Mechanism: $L_{EW} = L_{g} + L_{f} + L_{h} + L_{y}$ Where ...
6
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1answer
85 views

Why neutrino is always left handed

Why all neutrinos are always left handed while all anti-neutrinos are right handed.
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1answer
37 views

How do the right-handed fermions acquire mass?

I am constructing a presentation on how elementary particles acquire mass via interaction with Higgs field. I asked this question previously in a different form and received the usual clap trap, so I ...
0
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0answers
30 views

Influence of matter of a star on masses of neutrinos

It is well known that if neutrinos has masses then from Dirac equation it follows that they propagate (in vacuum) as a eigenstates of mass (not as eigenstates of interaction). It's wave function is of ...
3
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0answers
36 views

How do force carrying particles “give” force? [duplicate]

So, I am not taking physics in school, but I do have an interest in it, and I was wondering, in the standard model, all of the force carrying particles (photons, Z Bosons, W Bosons, gluons, and (...
1
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1answer
46 views

Lagrangian of Yukawa Interaction and Quark Mixing

I'm trying to understand the original of quark and lepton mass. Here's a paragraph from the book: "Massive neutrinos in physics and astrophysics" by R. N. Mohapatra and P. B. Pal : The gauge ...
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0answers
12 views

Selection Rules in FCNC mediated diagrams

I am studying the flavour changing processes mediated by flavor changing neutral current (FCNC). Are there any selection rules involved in assigning the flavor to the outgoing quark? Can the ...
0
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1answer
43 views

Representation in $SU(2)_{L}\times U(1)_{Y}$

I'm reading the book "Massive neutrinos in physics and astrophysics" by R. N. Mohapatra and P. B. Pal, and have a question about its notation. The Equation 2.10, it says: $$ q_{L}=\binom{u_{L}}{d_{L}}...
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1answer
31 views

Constructing singlet from doublets

Can we construct a gauge invariant term using the SU(2) doublet $l_L=(\nu_e e)^T$ and $(l_L)^c=C\bar{l}^T_L$? Since, both are doublets under SU(2), and $2\times 2=3+1$, I wonder what will be the ...
5
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3answers
134 views

Does string theory explain the existence of 3 generations of quarks/leptons?

I am wondering whether string theory explains the existence of 3 families of quarks/leptons or not. I have a very limited understanding of string theory, as of now, and I have a mathematical ...
0
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0answers
45 views

Examples of other hierarchy problems

The commonly quoted version of the hierarchy problem (at least, the one that I have heard), is concerned with the surprisingly low mass of the Higgs. We would expect the Higgs mass squared to have ...
1
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2answers
80 views

De Broglie- Bohm Quantum Theory

From what I have read the Standard Model of Particle Physics uses quantum mechanics,special relativity, along with other assorted mathematics to make predictions and provide a framework for QED, QCD, ...
1
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1answer
71 views

Generators of $SU(2)\times U(1)$

I'm currently reading about spontanous symmetry breaking. In particular about a Lagrangian that is invariant under $SU(2)\times U(1)$, in other words pretty standard QFT stuff. I know that the ...
0
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0answers
16 views

How to know the cross section in this Fig

I wonder how to calculate the cross section of ( p p > gamma gamma b b~) (blue region) in the opposite plot, the y-axis is the number of events divided by 100 GeV with luminosity = 100 $\mbox{fb}^{-1}...
0
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1answer
26 views

Can CP-violation arise due to interference between two tree-level diagrams in a QFT?

In Leptogenesis, CP-asymetry arises due to the interference of the tree-level amplitude $N\rightarrow l_\alpha\phi$ (where $N$ is heavy sterile neutrino, $l_\alpha$ is a lepton flavour, and $\phi$ is ...
3
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1answer
267 views

Understanding CP-violation from a toy model of two fermions and a scalar boson

Consider a field theory given by the following Lagrangian $$\mathcal{L}_{int}=y\overline{\psi_1}\psi_2\phi+y^*\overline{\psi}_2\psi_1\phi^\dagger$$ where $\phi$ is a complex scalar field, and $\psi_1,\...
5
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0answers
75 views

What is the cause of the minor mass difference between the proton and the neutron?

As known, the proton is from two up and a single down quark, while the neutron is from a single up and two down quarks. The down quark is a little bit more massive and the up, and so the neutron is ...
4
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2answers
283 views

How it is possible to mediate a weak interactions by very heavy particle such as Boson?

When considering a weak decay interaction such as leptons , the weak force is mediate by huge particle such as bosons (W+ or W- ). How it is possible to have a such heavy particle within less massive ...
1
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1answer
73 views

Understanding type of force interaction in particle decays

Are there any fundamental rules of thumbs that can be used to identify the type of force interaction (weak, electromagnetic, strong) in a particle decay without drawing the Feynman diagrams at the ...
8
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1answer
185 views

How does the Higgs field provide mass to the known elementary particles and does even thinking about amplitude and frequency have any bearing on it?

One of the first things I was looking for when I found this site was a clarification on what an increase of mass/energy is when Matt Strassler was using the analogy of tightening a spring and applying ...
0
votes
1answer
67 views

If we were able to manipulate enough energy, could we use the higgs field for any practical application? [closed]

My question is, the fields in the standard model interact with each other, and when we are able to manipulate some of them through different engineered devices, we can transform the energy field into ...
3
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2answers
78 views

Does the Flavor symmetry forbid $uu\rightarrow cc,ss$?

This question comes from the reading of this paper. They suppose a flavor symmetry group $G_F = U(3)_q\times U(3)_{d} \times U(2)_{d}$ which acts on the three LH quarks $q_L$, three RH quarks $u_R$ ...
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1answer
58 views

Is it possible the weak force isn´t fundamental? [closed]

Once the strong force was thought to be a fundamental force mediated by the massive pion. Later colour and gluons were introduced. The old strong force was a residue force of the new fundamental force....
8
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3answers
1k views

How many kinds of “weak charges” exist?

For electricity, we have one charge, for the strong force three. How many are there connected to the weak force? Three, because of the W- and Z-particles?
2
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0answers
27 views

Where do the intrinsic parities of particles come from?

It is known that some particles have negative intrinsic parity - for example pion $\pi$. I was wondering if this parity can be understood. I read somewhere that parity of quarks is defined to be ...
0
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3answers
50 views

How does quark color affect the identity of a hadron?

I've read about colors relating to quarks and hadrons and I know that they can change colors because of the exchange with gluons, but does changing color change the type of hadron? Does a proton ...
4
votes
2answers
68 views

Why does confinement apply only to quarks, and not to nucleons?

When energy is input in an attempt to break quark bonds one simply generates more quarks through hadronisation. The explanation my physics book gives for this is that "the strength of the strong ...
2
votes
1answer
56 views

Is there scale invariance in the region of QCD aymptotic freedom?

It is said that in the deep inelastic scattering, scale invariance emerges. In the scattering of electrons off protons, this reflects the asymptotic freedom. Now I got a question. Normally, a system ...
0
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1answer
57 views

How are the standard model and the Higgs boson actually confirmed experimentally in practice?

This is my mental picture on how we can make predictions from a theory (I'm not a physicist so this might be quite wrong) : Typically, we solve a partial differential equation (analytically if we can,...
3
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3answers
68 views

Why do we need $SU(2)\times U(1)$ invariant mass terms if the symmetry will be broken anyway?

In the SM we can not add fermionic mass terms like $m \overline{e}_R e_L$ to the Lagrangian since these terms are not invariant under $SU(2)\times U(1)_Y$. After introducing the Higgs in the unitary ...
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2answers
51 views

Clarification of the concept of Boson Mediator and 'Mediation' in Physics? [closed]

I would like to have a clear concept of Higgs 'mediator' and that 'mediation' speak in physics, what you 'swap' a particle with ...
0
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0answers
14 views

What's the minimum practical energy for top production at a hadron collider?

I'm curious about what the minimum energy needed to (practically) detect the top quark would be, in a hadron collider. Obviously it has to be greater than the strict minimum energy of 350 GeV due to ...
0
votes
1answer
86 views

Number of degrees of freedom in the Standard Model Lagrangian

Consider a Lagrangian $L$ which depends on a number of fields $F_1$, $\cdots$, $F_N$ and their (spacetime) derivatives. Each of those fields $F_n$ is valued in $\mathbb{R}^{k_n}$. Is the Standard ...
1
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1answer
63 views

Difference between the CKM and the PMNS matrix

My question is very simple: is there a fundametal difference between the CKM (responsible for quark mixing) and the PMNS matrix (responsible for lepton mixing)? The CKM matrix allows (in charged ...
4
votes
1answer
97 views

Photons are self-conjugate but neutrinos may or may not: why is that?

Caution: This may be a very naive question but I find it confusing. Moreover, I believe this question is based on potential misconception. I would like it to be clarified. Although the neutrinos are ...
1
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2answers
61 views

Why $U(1)_Y$ hypercharge rather than $U(1)_\text{em}$ electromagnetism?

In the Standard Model we have $SU(2)_I\times U(1)_Y$, where $U(1)_Y$ is weak hypercharge and $SU(2)_I$ is the symmetry group of weak isospin. Why do we introduce $U(1)_Y$ of weak hypercharge rather ...
1
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0answers
21 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 = e^{i\pi(x)/v}\left(\begin{...
0
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0answers
36 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 ...
0
votes
1answer
43 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 $\frac43$?
0
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0answers
30 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
47 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 ...
0
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1answer
48 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
57 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 ...
1
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2answers
70 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? ...
0
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1answer
49 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?