What is the binding energy of a protium nucleus?

[Pranav Jha]

what is the binding energy of protium (hydrogen-1) nucleus? As i understand binding energy, it is the energy required to bring two nucleons from infinity to a stable state in a nuclues but if there is only one nuclide in a nucleus how do we determine the binding energy for that nucleus?

 

[Pranav Jha]

is the mass of a proton in a protium nucleus (if there is any difference between free proton and a protium nucleus) the same as that of a "free proton"?

 

[quantum123]

That would be the infamous "self-energy". Interesting.
What is the binding energy of a quark?

 

[Pranav Jha]

That would be the infamous "self-energy". Interesting.
What is the binding energy of a quark?

sir/madam, i have just started nuclear physics. Your reply only confused me further

 

[K^2]

It's zero.

 

[quantum123]

Something must be binding the quarks to form the proton (3 quarks inside). So shouldn't there be binding energy?

 

[K^2]

Of course, but that's not what the question is about. The question is about nuclear binding energy. Since there is only one particle, it's zero.

For quarks, it's far more complicated. If you ask how much energy it takes to disassemble a nucleon, the answer is infinite. Quarks do not exist in isolation, and trying to pull them apart will only result in more quarks being created. If you want to compare the mass of the proton to masses of individual quarks, you run into more problems. What is the mass of the quark? Well, a reasonable answer would be whatever goes into quark's Lagrangian to make all the numbers work. That's called a current mass. But again, mass of the proton is significantly higher than sum of the current masses of constituent quarks. So that doesn't give you anything useful either.

 

[quantum123]

According to http://www.sciencedaily.com/releases/2006/12/061213174346.htm, single quarks are detected. So why do you say that quarks do not exist in isolation?

 

[K^2]

A "single quark" in this case means that it exists without it's anti-particle pair. Normally, top quarks are produced via strong interaction. That means that you always find them in t-t-bar pairs. What these researchers have found are top quarks produced by weak interaction. Or alternatively, top quarks destroyed by weak interaction. At any rate, they end up with a top quark without a t-bar pair. However, that quark does not exist in isolation. It exists bound to some other, lighter quark. A lone quark is not a physical particle, as it always exists off the shell, and therefore, cannot be detected. If someone was to detect a lone quark, it'd mean we have to scrap the QCD.

 

[quantum123]

I see. Thanks for the clarification. :)

 

[quantum123]

But how do you put all the electrostatic charges into such a tiny quark against all the electrostatic repulsion in the first place . So there should be some kind of binding energy in the first place, to pack all the charges into this tiny quark ?