Quark and particle mass

[Chaotic42]

Hey folks.

I'm looking at this chart from Duke University called "Standard Model of Fundamental particles and Interactions" and it lists the mass of up quarks at .003 GeV/c^2 and down quarks at .006 GeV/c^2.

It says that protons are made out of "up+up+down" quarks, and says the proton mass is .938 GeV/c^2. Adding up the mass of 2xup + down only yields .012 GeV/c^2.

Where does the other .926 GeV/c^2 come from?

 

[MichaelD]

My Quark is Massive.

 

[amish]

i think that it came from here.

 

[Random Variable]

I think a proton has two "up" quarks or something.

EDIT: Nevermind. That's what you said. 😱

 

[TuxDave]

http://www2.slac.stanford.edu/vvc/theory/quarks.html


Quark Masses

Quarks only exist inside hadrons because they are confined by the strong (or color charge) force fields. Therefore, we cannot measure their mass by isolating them. Furthermore, the mass of a hadron gets contributions from quark kinetic energy and from potential energy due to strong interactions. For hadrons made of the light quark types, the quark mass is a small contribution to the total hadron mass. For example, compare the mass of a proton (0.938 GeV/c2) to the sum of the masses of two up quarks and one down quark (total of 0.02 GeV/c2).

 

[EyeMWing]

WTF is a quark?

/me thank god that MIS doesn't require theoretical subatomic physics

 

[Heisenberg]

Originally posted by: EyeMWing
WTF is a quark?

/me thank god that MIS doesn't require theoretical subatomic physics

A fundamental particle that mesons and baryons are made up of.

 

[EyeMWing]

Originally posted by: Heisenberg

Originally posted by: EyeMWing
WTF is a quark?

/me thank god that MIS doesn't require theoretical subatomic physics

A fundamental particle that mesons and baryons are made up of.

Hey, I know what a meson bomb is, they were quite explosive in Freespace 2. :nerd;

 

[ed21x]

Originally posted by: Chaotic42
Hey folks.

I'm looking at this chart from Duke University called "Standard Model of Fundamental particles and Interactions" and it lists the mass of up quarks at .003 GeV/c^2 and down quarks at .006 GeV/c^2.

It says that protons are made out of "up+up+down" quarks, and says the proton mass is .938 GeV/c^2. Adding up the mass of 2xup + down only yields .012 GeV/c^2.

Where does the other .926 GeV/c^2 come from?

supposedly on that level, mass doesn't exist anymore, so adding two together has some kind of synergy resulting in more energy.

speaking of which, i have a physics final in 15 hours 🙁

 

[Trygve]

Binding energy, kinetic energy, all that good stuff. The .003 GeV and .006 GeV figures are the current or invariant masses. Within a particle, you can also talk about the "constituent masses" of the quarks--let's say they're around .311 GeV and .315 GeV within a proton.

One easy way to see why there has to be the distinction is to look at other particles like, say, pi mesons, which have a quark/antiquark pair of some combination of up or down quarks. If the current masses of the quarks were the main factor in the mass of the hadrons they make up, you'd expect that a pi meson would have about two-thirds of the mass of the proton: about .623 GeV. They don't; they're more like .140 GeV (unless my recollection is way off here). So, when they're in a pi meson, up and down quarks have a different "constituent mass" (though they would still have the same "current mass").