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snp.gupta
2018-Nov-26, 12:00 PM
What is the nature of "Charge" of Electron, It is defined as negative charge, but what is its basic structure? How it differs from charge of positron or proton ? And how these two are different from the charge of Neutron or neutrino....?
=snp

profloater
2018-Nov-26, 01:01 PM
I think that is a fundamental question. Charge is a name we give to a property. A while back there was just the negative charge of the electron in integers (Millikan oil drop experiment) but now with quantum theory there is fractional charge on quarks which make up protons etc. By convention we call an accumulation of electrons a negative charge and a deficit of electrons a positive charge so this is not two things, it's about electron exchange which is the basis of chemistry. Quarks have other properties named as spin, charm and colour, words to explain the behaviours we observe in particle experiments. When electricity was first experimented a convention of current flow was from plus to minus but now we know the flow (itself a simplification) is of electrons from an accumulated negative charge towards a positive plate or zone which has been stripped of electrons. So to go beneath the name is to ask for another name for a property we observe and model mathematically.

snp.gupta
2018-Nov-26, 07:59 PM
Thank you profloater for the nice reply….

……..but now with quantum theory there is fractional charge on quarks which make upprotons etc…….
So you mean quarks are fundamental?

Byconvention we call an accumulation of electrons a negative charge and a deficitof electrons a positive charge so this is not two things, it's about electronexchange which is the basis of chemistry.
Then what will be positrons,Neutrons etc…?

Quarks haveother properties named as spin, charm and colour, words to explain thebehaviours we observe in particle experiments.
Will these spin charm andcolour be sufficient to explain its charge?

……. So to gobeneath the name is to ask for another name for a property we observe and modelmathematically.
No another name ,fundamental differences and structures of these please….

Shaula
2018-Nov-26, 08:09 PM
Perhaps you can define what you mean by 'structure'?

Charge is a measure of the strength of interaction of a particle or quasiparticle with an EM field. Are you asking which theories describe the interactions of charged particles? Are you asking where charge comes from?

profloater
2018-Nov-26, 08:09 PM
Once you are describing what we think are fundamental such as the electron, to ask how they work is just looking for a different name for a property we observe. That’s what i’m trying to explain. charge is a name for a property that is consistent in experiments. If we call charge a fundamental property it is at the root of all subsequent description. Of course physics keeps trying to improve the model because there are inconsistencies.

snp.gupta
2018-Nov-26, 10:54 PM
Hi Shaula,

Perhaps you can define what you mean by 'structure'?

Arrangement and Shape of mass may be, I just used that word structure


Charge is a measure of the strength of interaction of a particle or quasiparticle with an EM field. Are you asking which theories describe the interactions of charged particles? Are you asking where charge comes from?
Yes I am asking where charge comes from? Thank you for clarification and answering …

snp.gupta
2018-Nov-27, 01:25 AM
Onceyou are describing what we think are fundamental such as the electron, to askhow they work is just looking for a different name for a property we observe.That’s what i’m trying to explain. charge is a name for a property that isconsistent in experiments. If we call charge a fundamental property it is atthe root of all subsequent description. Of course physics keeps trying toimprove the model because there are inconsistencies.
You are correct profloater.
What I want to understand is…. what are the differences in properties between different charged particles like Electron, Positron and Nuetrino etc. These differences may be in physical structure, behave like vortex, different directions of spin, different colours, different charms, or how many quarks these particles are made-up off etc….

You are correct, once again saying that Physicists keep onimprove the models for over coming the inconsistencies ….

Shaula
2018-Nov-27, 05:43 AM
Hi Shaula,

Arrangement and Shape of mass may be, I just used that word structure
Leptons, quarks and bosons are currently modelled as point particles, not having any structure. Hadrons and other composite particles are modelled in a number of ways, their internal structure is quite complex. It is also dominated by colour interactions so more the domain of QCD than QED. In general, though, you have two or three charged particles bound by colour forces and, as with any bound system, their distribution function is quite dynamic. This article (https://www.aps.org/units/dnp/research/proton.cfm) gives some references you can follow to read more on this.



Yes I am asking where charge comes from? Thank you for clarification and answering …
Noether's theorem (or the Ward–Takahashi identity, the quantum version) link global symmetries to conserved quantities. The conserved quantity for the EM field (the underlying symmetry is the invariance of the field under a phase shift of the wavefunction) is charge. So in a sense charge is linked to the symmetry of the EM field under a transformation.

In the current models that is about as far down as we have gone. Despite a lot of people looking. Charge is basically a fundamental property in the current model. Conservation of charge can be linked back to a field symmetry but the actual value of charge and which fundamental particles have it is not part of the model - it is something we measure and then describe the behaviours of.

Shaula
2018-Nov-27, 05:50 AM
You are correct profloater.
What I want to understand is…. what are the differences in properties between different charged particles like Electron, Positron and Nuetrino etc. These differences may be in physical structure, behave like vortex, different directions of spin, different colours, different charms, or how many quarks these particles are made-up off etc….
The Standard Model gives an overview of the fundamental particles:
https://en.wikipedia.org/wiki/Standard_Model

Composite particles are known as hadrons:
https://en.wikipedia.org/wiki/Hadron
And broken down into mesons (quark+antiquark):
https://en.wikipedia.org/wiki/Meson
And baryons (3 quarks):
https://en.wikipedia.org/wiki/Baryon

There are some more exotic ones out there but these are the basics. There are a lot of composite particles out there, more than I can easily talk about in a short post! I'd say have a read of the references and see if specific questions drop out of this.

snp.gupta
2018-Nov-28, 01:42 AM
Thank you Shaula

For your Nice clarifications... both of them.
Let me go through the reading materials and come back to you ASAP

snp.gupta
2018-Dec-09, 04:48 PM
What gives stability to Baryons over quarks?
I read some of the wiki pages, still this was not clear.... Can you please help me Shaula..?


Thank you Shaula

For your Nice clarifications... both of them.
Let me go through the reading materials and come back to you ASAP

Shaula
2018-Dec-09, 05:14 PM
What gives stability to Baryons over quarks?
I read some of the wiki pages, still this was not clear.... Can you please help me Shaula..?
Colour charge, fundamentally. It seems to be a rule that only colourless particles can freely exist. There are two ways to create something colourless - r+g+b (or their antiparticles) or s colour + its anticolour. Hence Hadrons (three components) and Mesons (two components). Hadrons are some kind of r+g+b and mesons are a colour + anti-colour.

The reason for only colourless free particles is probably understood qualitatively but not proven analytically yet. However whenever we try to isolate anything possessing colour charge (anything strongly interacting, which is basically quarks and gluons) we fail.

See:
https://en.wikipedia.org/wiki/Color_confinement

snp.gupta
2018-Dec-13, 11:03 AM
Colour charge, fundamentally. It seems to be a rule that only colourless particles can freely exist. There are two ways to create something colourless - r+g+b (or their antiparticles) or s colour + its anticolour. Hence Hadrons (three components) and Mesons (two components). Hadrons are some kind of r+g+b and mesons are a colour + anti-colour.

The reason for only colourless free particles is probably understood qualitatively but not proven analytically yet. However whenever we try to isolate anything possessing colour charge (anything strongly interacting, which is basically quarks and gluons) we fail.

See:
https://en.wikipedia.org/wiki/Color_confinement
Thank you Shaula,
1. What is exactly colour Change in some simple words please....

2. So you mean to say..." Quarks and gluons" are the MOST fundamental particles???

Shaula
2018-Dec-14, 06:07 AM
1. What is exactly colour Change in some simple words please....
Well, similarly to electric charge it is a fundamental property of particles. But instead of characterising the particle's interaction via the electromagnetic force it characterises the interaction via the strong force. Every strongly interacting particle has a colour charge (so far quarks are the only strongly interacting fermions and gluons are the vector bosons associated with the strong force, so play a similar role to photons in the electromagnetic domain but are more complex because they carry colour charge). The colour charge of a quark can be red, anti-red, green, anti-green, blue or anti-blue (gluons are more complicated). To make a particle colourless you follow the convention that r+g+b (or the anti version) = colourless and colour + anti-colour = colourless.

See:
https://en.wikipedia.org/wiki/Color_charge


2. So you mean to say..."Quarks and gluons" are the MOST fundamental particles???
Well, not just quarks and gluons. And only 'as far as we currently know'. The Standard Model of particle physics has 16 fundamental fermions. There are 6 quarks (up, down, charm, strange, top, bottom), and 6 leptons (electron, muon, tau, electron-neutrino, muon-neutrino, tau-neutrino). The Standard Model also has 4 vector bosons which are associated with the forces (photon for the EM force, gluon for the strong force, W and Z bosons for the weak force) and a scalar boson (the Higgs, linked to what mass is and why some particles have mass). All of these particles and their anti-particles are equally fundamental and the most fundamental particles we know of.

The EM force and the weak force are actually aspects of the same underlying force, known as the electroweak force. When we do that unification the SM gets a little simpler in the the fermions break down into two groups. The quarks interact strongly and via the electroweak force. The leptons only interact via the electroweak force.

See:
https://en.wikipedia.org/wiki/Standard_Model

snp.gupta
2018-Dec-25, 05:08 AM
Well,similarly to electric charge ……

……
……… the electroweak force.
So mean to say, an Electron or Positroncan’t be sub-divided into quarks and gluons is it not? How the mass will cometo them by? By Higgs? Higgs will be giving mass, so it will be part of Electronor Positron…? Sill somewhat confused, In simple words please…..

snp.gupta
2018-Dec-25, 05:58 AM
I was reading about Zwiigg's proposal which was eventually replaced by Gell-Mann's quarks and mathematical model. That report says, ofcourse quarks have never been observed. We are not able to see them directly because the Strong Force between them increases as we try to separate them fromeach other. If we could separate them, they said, the Strong Force would accordingly destroy them. Gluons are the supposed carriers of the Strong Force,another hypothetical particle that has never been observed for the same reasonswe can't observe quarks.
Is this correct?

Shaula
2018-Dec-25, 06:58 AM
So mean to say, an Electron or Positroncan’t be sub-divided into quarks and gluons is it not? How the mass will cometo them by? By Higgs? Higgs will be giving mass, so it will be part of Electronor Positron…? Sill somewhat confused, In simple words please…..
You are right that electrons and positrons cannot, as far as we currently know, be subdivided.

The Higgs mechanism doesn't definitely account for the mass of most particles as things stand. The Higgs mechanism is currently only well formulated for vector bosons, specifically the W and Z bosons. It gives them mass and explains why they are the only ones with mass (the photon and gluon are both massless). It is proposed but not proven that fermions also couple to this field to gain mass but that is not proven. In neither case does this make the Higgs a part of the particle - the Higgs is the scalar boson associated with a field that the particles interact with (analogously a photon is associated with the EM field but that doesn't mean charged particles 'contain' photons in a meaningful sense).

Shaula
2018-Dec-25, 07:08 AM
I was reading about Zwiigg's proposal which was eventually replaced by Gell-Mann's quarks and mathematical model. That report says, ofcourse quarks have never been observed. We are not able to see them directly because the Strong Force between them increases as we try to separate them fromeach other. If we could separate them, they said, the Strong Force would accordingly destroy them. Gluons are the supposed carriers of the Strong Force,another hypothetical particle that has never been observed for the same reasonswe can't observe quarks.
Is this correct?
Quarks have never been isolated. That is very different to being observed. Quarks and gluons have been observed many times in scattering experiments. One of the strongest pieces of evidence for quarks are the deep inelastic scattering experiments that show protons are made up of 3 tightly bound particles. We've also indirectly scattered things off gluons inside composite particles. So both of these particles have been observed, just not isolated.

See:
https://en.wikipedia.org/wiki/Deep_inelastic_scattering
https://en.wikipedia.org/wiki/Gluon#Experimental_observations
https://en.wikipedia.org/wiki/Three-jet_event

And the separation of a quark does not lead to its destruction by the strong force. On the contrary trying to pull a quark away from a bound system required so much energy that more quarks are created and immediately bind to the existing quarks. Take a proton (uud - up, up, down quark bound together). Start trying to remove an up quark. It requires so much energy that what happens is something like: uud -> uuduu' -> uud + uu' (where u' is an anti-up quark). So you get a proton and a meson (pion in this case)

See:
https://en.wikipedia.org/wiki/Color_confinement

snp.gupta
2018-Dec-25, 01:58 PM
Thank you Shaula
For such fast repply, I will post again after seeing the references you gave...
Best

Strange
2018-Dec-25, 06:47 PM
2. So you mean to say..." Quarks and gluons" are the MOST fundamental particles???


This page has a nice graphic summarising the known particles that make up the standard model: https://en.wikipedia.org/wiki/Elementary_particle