# Energy of a particle

#### touqra

For a test particle which is all by itself and is at rest, the total energy of the particle is the rest mass.

But what if let say, this test particle is a proton. This proton is at rest and is not in the vicinity of any other particles. It is all by itself. Considering that proton has charge, from QED, we know that this proton will emit virtual photons with certain probability. Would this change the energy of the proton, and hence the rest mass of the proton?

From gravitational force, and that the proton has a mass, the proton will exert a gravitational field that spreads to the whole space. If there is another massive particle nearby, then, there will be an attraction potential energy, and hence, it will change the energy of the proton.
But what if there are no particles nearby? The proton still exerts a field. Will the proton's energy (rest mass) be changed due to its own field?

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#### Meir Achuz

Homework Helper
Gold Member
The physical mass of a particle does include all these self-field effects, and more from strong interactions. Actually, most of the physical mass of the proton results from its three constituent quarks.

#### mathman

most of the physical mass of the proton results from its three constituent quarks.
This is not quite true. Most of the mass is from the internal motion of the quarks and gluons that make up the proton, not from the quark mass irself.

#### touqra

mathman said:
This is not quite true. Most of the mass is from the internal motion of the quarks and gluons that make up the proton, not from the quark mass irself.
Thanks. But my question is still unanswered. Perhaps I should not use proton. Maybe I should use electron. There is no known smaller constituents that make an electron, so let's take electron as the smallest entity.
Electrons can produce a gravitational field or produce virtual photons even without the presence of any other particles. So, do these production of fields and photons change the energy of the electron? Like adding a potential energy or the likes.

#### marlon

Meir Achuz said:
Actually, most of the physical mass of the proton results from its three constituent quarks.
This is not correct since most of the proton mass comes from the "motion" of virtual quark anti-quark pairs and virtual gluons inside the proton.

Dynamical quarks
marlon

Last edited:

#### Meir Achuz

Homework Helper
Gold Member
mathman said:
This is not quite true. Most of the mass is from the internal motion of the quarks and gluons that make up the proton, not from the quark mass irself.
I did not say "from the quark mass itself".

#### Meir Achuz

Homework Helper
Gold Member
marlon said:
This is not correct since most of the proton mass comes from the "motion" of virtual quark anti-quark pairs and virtual gluons inside the proton.
Dynamical quarks
marlon
Now look on your web for "constituent quark".

#### Meir Achuz

Homework Helper
Gold Member
touqra said:
Thanks. But my question is still unanswered. Perhaps I should not use proton. Maybe I should use electron. There is no known smaller constituents that make an electron, so let's take electron as the smallest entity.
Electrons can produce a gravitational field or produce virtual photons even without the presence of any other particles. So, do these production of fields and photons change the energy of the electron? Like adding a potential energy or the likes.
The first sentence of my first post "The physical mass of a particle does include all these self-field effects," answered for the electron. There is a big shift in the rest energy due to the photons and pairs in a physical electron..

#### marlon

touqra said:
Thanks. But my question is still unanswered.
Maybe you wanna look at paragraph S3a of this site

regards
marlon

I think if there are no fields in the vicinity of the electron it these corrections are unimportant. I think the electron self-energy is only relevant when it's interacting with something else

#### marlon

I think if there are no fields in the vicinity of the electron it these corrections are unimportant. I think the electron self-energy is only relevant when it's interacting with something else
I completely agree with this

marlon

"Energy of a particle"

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