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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4answers
115 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 $931~\...
5
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2answers
859 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
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1answer
97 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
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1answer
55 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
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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
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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 ...
3
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2answers
2k views

Book for particles physics [duplicate]

Possible Duplicate: Particle physics getting started I'm looking for a book that introduces the building blocks refer to the standard model for a course in nuclear physics. There are good ...
26
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2answers
743 views

Finding the vacuum which breaks a symmetry

I will start with an example. Consider a symmetry breaking pattern like $SU(4)\rightarrow Sp(4)$. We know that in $SU(4)$ there is the Standard Model (SM) symmetry $SU(2)_L\times U(1)_Y$ but depending ...
30
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1answer
1k views

How close does a particle-antiparticle pair need to be for annihilation to happen?

I've most often seen the statement that the annihilation of a particle and its antiparticle occurs when they 'collide' with one another. So in other words when they get very close to one another right?...
33
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4answers
13k views

Why do electron and proton have the same but opposite electric charge?

What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of ...
3
votes
2answers
124 views

Feynman diagram, which virtual particle?

Hi I have been asked to produce the lowest order Feynman diagram for the following scattering process: $$a.~~~ \mu^-+\mu^-\rightarrow \mu^-+\mu^-$$ $$b.~~~ \mu^-+\mu^+\rightarrow \mu^-+\mu^+$$ The ...
2
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0answers
25 views

Why do mesons like the J/Psi or Y exist? Shouldn't the quark/anti-quark pair annihilate? [duplicate]

q/qbar->photon is part of Drell Yan, so it's kinematically allowed. Is this somehow related to the difference in speed phenomenologically between a strong and a weak decay? As in is this annihilation ...
5
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1answer
89 views

How do symmetries break in cosmology?

The way I understand spontaneous symmetry breaking in thermodynamic systems is that the symmetry is actually explicitly broken by an infinitesimally small field. The system chooses one of the non-...
17
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7answers
2k views

What Do We Get From Having Higher Generations of Particles?

Background: I have written a pop-science book explaining quantum mechanics through imaginary conversations with my dog-- the dog serves as a sort of reader surrogate, popping in occasionally to ask ...
1
vote
1answer
93 views

Help me understand Lepton universality

I understand that we have three pairs of Leptons (generations). $(\nu_e , e^-), (\nu_{\mu}, \mu), (\nu_{\tau}, \tau^-)$ But what is this principle of Lepton universality? I have obviously tried ...
6
votes
3answers
197 views

Can all laws of physics derived by a single or lists of more general laws?

(This is actually my first question - please understand my lack of knowledge and bad English..) I have always been curious about deriving thousands of laws from more general ones.. Can general laws ...
5
votes
1answer
1k views

Fermion mass Higgs mechanism

How does a fermion, like an electron, get its mass through the Higgs-mechanism? Can someone explain me this with formulas (Lagrangian)? I know that the Yukawa interaction has something to do with ...
5
votes
1answer
148 views

SU(2) confinement picture

Preamble: In section 2 of these lecture notes (Gerard 't Hooft, 1998) an alternative interpretation of the weak interaction is presented, in which the weak force is confined, much like the strong ...
7
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2answers
687 views

How quark electric charge directly have been measured?

How quarks electric charge directly have been measured when quarks never directly observed in isolation? (Due to a phenomenon known as color confinement.)
0
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1answer
85 views

why does the higgs mechanism need to exist?

I feel like this is kind of a pleb question but I'm gonna ask it anyway. As far as I know, mass is fundamentally the property that a field has when it can have energy without having momentum. But why ...
6
votes
0answers
364 views

750 GeV diphoton resonance: KK graviton?

As everybody of you may know at LHC they found this probable resonance (https://cds.cern.ch/record/2114808, https://cds.cern.ch/record/2114853?ln=en). It may be a scalar or a KK graviton mode. Now, ...
4
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3answers
2k views

Equation of everything

Is this equation in the image true? Can you give some topics that I can cover the equation? Similar equation from http://www.preposterousuniverse.com:
0
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1answer
147 views

Is it true that the standard model does not predict the mass of the electron?

I read that the standard model has parameters that have to be put in such as the mass of the electron, because nobody has been able to calculate the mass of the electron. Is this true?
8
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3answers
3k views

How do I know the proton isn't made of 3 anti-down quarks?

I have a proton, how do I know that it is made of 2 up quarks and 1 down quark or if it is made of 3 anti-down quarks, each with different color charges? This question is also applicable to the ...
3
votes
2answers
124 views

Quark composition of the neutral pion

I wonder why the neutral pi meson is $$ | \pi^0\rangle = \frac{1}{\sqrt{2}}\left(\vert u\overline {u}\rangle - \vert d \overline{d} \rangle \right) $$ and not $$ | \pi^0\rangle = \frac{1}{\sqrt{2}}...
12
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3answers
1k views

How can neutrinos oscillate though the lepton flavors have differing masses?

Since the total mass-energy for the neutrino presumably does not change when a neutrino changes lepton flavor, though the mass is different, what compensates for the gain or loss of mass? Does the ...
0
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2answers
100 views

Is there any stable hadron?

Neutron can decay into proton and I think some hypothesis claim that proton can also undergoes decay into subatomic particles... Is there any hadron that never decays?
2
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3answers
430 views

Is there a connection between gluons and photons?

I was wondering if there is any sort of connection between a gluon and a photon since they are both considered massless.
2
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1answer
66 views

What exchange particles can change lepton flavor?

So I know that in the standard model $W^+$ and $W^-$ can change lepton flavors but $Z^0$ cannot. I don't think photons can (is this correct?) and gluons can't because they would not interact with ...
2
votes
0answers
147 views

Feynman amplitude for electron-positron annihilation and $W^{\pm}$ production

I'm working with this interaction Hamiltonian density $$ H_{int}(x) = ig\bar{\Psi}_{\nu_e}(x)\gamma^\rho P_L \Psi_e(x)V_\rho(x) + igV^\dagger_\rho(x)\bar{\Psi}_e(x)\gamma^\rho P_L \Psi_{\nu_e} $$ ...
0
votes
2answers
78 views

Negative Mass Square

I'm reading a book about neutrino physics (from 1997). In the chapter about neutrino mass they list results of certain experiments. All of them get a negative value for $m(\nu_e)^2$ but a positive one ...
0
votes
1answer
45 views

Is there a name for leptons that are not neutrinos?

Is there a name for leptons that are not neutrinos? Not sure if its exists, its not particularly easy to search for. Is there a name for the set of charged leptons (or leptons that are not neutrinos)? ...
3
votes
1answer
62 views

Interpretation of 4-vector quantum field operator

Peskin and Schroeder, on page 24, quotes the following expression for a generic (scalar) field operator: $$ \phi(\mathbf{x})|0\rangle = \int \frac{d^3\,p}{(2\pi)^2}\frac{1}{2E_{\mathbf{p}}}e^{-i\...
0
votes
0answers
36 views

What is the form of Higgs potential, when written using higgs mass and quartic coupling.

Usually we write Higgs potential as $V=-\frac{1}{2}m^2 \phi^2 + \frac{1}{4}\lambda \phi^4$ What are the present reliable values of parameters '$\lambda$' and '$m$'? Is '$m$' used here Higgs mass? If ...
1
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0answers
49 views

Measuring expectation value in quantum field theory and in quantum mechanics

There is a way of calculating the vacuum expectation value $\langle 0|\hat\phi|0\rangle$ theoretically in a quantum field theory like there is a rule to compute expectation value of any operator A (...
8
votes
2answers
1k views

Was the Higgs mass correctly predicted by asymptotic safety of gravity?

This paper was published in Phys Lett B in 2009, and predicted the Higgs mass to be 126 GeV based on the asymptotic safety of gravity. Is this prediction taken seriously by the theory community, or is ...
0
votes
1answer
1k views

What is the relationship between the Higgs field and quarks?

I have some difficulty considering the relative size of each and the meaning behind the shape of Higgs boson. I ask relating to the structures of both the Higgs field and quarks. How is it that the ...
0
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0answers
28 views

Subnuclear reactions: combining quarks

When you try and pull two quarks apart, you don't get two separate quarks, but instead: the energy stored in the field between them gets high enough to create more quarks, and instead of two ...
4
votes
2answers
221 views

Are antimatter particles made of ---?

Consider some particle P, and the antiparticle aP. Is it the case that: aP is made of the "usual" elementary particles, and indeed the same elementary particles as P, but arranged (or something) in ...
3
votes
2answers
178 views

Feynman diagram for attractive forces

I’m looking at Feynman diagrams for attractive forces and I'm thoroughly confused. Below are three diagrams from HyperPhysics: These all illustrate instances where the forces are attractive. ...
2
votes
1answer
53 views

Why aren't all possible VEVs of the Higgs field in (quantum) superposition?

It is is usually said the the Higgs field chooses a Vacuum Expectation Value (VEV), around which we now expand our field operators. From this a mass term emerges, and one or more gauge fields acquire ...
0
votes
1answer
59 views

What is the gauge field in Bose-Einstein condensation?

The Hamiltonian for bosons has $\phi^{\dagger}\phi$ terms in it which makes it U(1) invariant. Bose-Einstein Condensation apparently breaks such symmetry by choosing a definite phase, even though I ...
0
votes
4answers
83 views

Change in the half-life of a neutron

What would happen if the half-life of a neutron was much more less than it is now? How could this affect the nuclei?
4
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1answer
232 views

What does the discovery of a pentaquark signify?

at a particle collider a pentaquark was discovered. My question in short is what does the discovery of a pentaquark signify? Is there a theory that it supports or something like that?
0
votes
2answers
39 views

Pair annihilation - can annihilation be moderated?

I recently asked this question: How close does a particle-antiparticle pair need to be for annihilation to happen? And that received a good answer. But there was a second part to my question that ...
10
votes
2answers
1k views

Neutrino oscillations versus CMK quark mixing

I wish to describe in simple but correct terms the analogy between the Cabibbo–Kobayashi–Maskawa (CMK) and Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrices. The CMK matrix describes the rotation ...
1
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0answers
24 views

QCD condensate and lepton mass

I read that the QCD U(1) anomaly is caused by the QCD condensate giving rise to quark masses. Does the QCD condensate also give masses to leptons (electron, mu, tau, neutrinos), or are these masses ...
0
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0answers
36 views

Anomalies, neutrino condensate and neutrino masses

Is neutrino number conservation not affected by the U(1) QCD and QED anomalies due its zero U(1) charge? Is this the reason why the neutrino should be massless and there should be no lepton family ...
1
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0answers
44 views

Chiral anomaly and fermion number conservation

Chiral anomalies in QED and QCD violate fermion number conservation, since a U(1) vector symmetry corresponds to fermion number conservation. However, only the LH and RH fermion numbers are not ...
2
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1answer
146 views

Feynman diagrams and gluon collisions/interactions?

We have been given this question which essentially asks us to draw the lowest order Feynman diagrams for various processes. One of them is: $$ g + g \rightarrow \bar{t}+t $$ Now, I am not an expert ...