# Heavier proton, lighter deuteron?

Hi,

The mass of a bound system of quarks (e.g. proton) is larger than the mass of its constituents. You could say this is because the mass of the system corresponds to the energy in the color field, which is larger when the quarks are closer (even if the force is weaker then).

For a bound system of electric charges (e.g. H atom), it is the opposite: mass of bound system is smaller than mass of its constituents. I understand this is because the electric force decreases with distance, while the color force increases with distance.

Now, we would expect a bound system of nucleons (e.g. deuteron) to have a behaviour similar to that of a system of quarks, since the strong force (force between nucleons) is just a residual color force. But this is not the case: the deuteron's mass is less than the mass of its constituents.

Does that mean that the strong force decreases with distance? If this is so, how can you get that from a force (color) that increases with distance?

Thank you

## Answers and Replies

the color force between the quarks of proton in deutron and a free proton is equal. now add to deuteron the quarks and color of neutron which is greater than the proton itself.
did u say that the electric force decreases so mass decreases?
now electric forces are carried by massless photons not mass containing gluons.

however i think that gluons do not necessarily have some mass unlike w and z bosons

ZapperZ
Staff Emeritus
nabodit said:
however i think that gluons do not necessarily have some mass unlike w and z bosons

Hum... did you cut-and-paste this from somewhere but forgot to either include the links, or delete the references to those links?

:)

Zz.

Here is some other copy/paste 'work' :)

Lattice QCD (very introductory)

http://www.cerncourier.com/main/article/44/5/13

What are dynamical quarks and why is the hadronmass bigger then the sum of the constituent quarkmasses (which is the opposite to the mass of nucleus being smaller then the sum of the constituent nucleon masses, because of the negative binding energy):

http://www.cerncourier.com/main/article/44/5/13/1/cernlatt2_6-04

Those dynamical quarks generate less mass at larger distances because the vaccuum energy fluctuations are smaller due to the Heisenberg uncertainty principle (larger distances <--> smaller energies), thus their contributions in nucleons are much smaller as in hadrons. Besides, in this case these quarkpairs are the pions ofcourse, that mediate the residual strong force. Also, the aspects included in the semi-empirical nucleon mass formula are not valid for quarks.

marlon