Nuclear magneton

The nuclear magneton (symbol or N for nucleon ) is commonly used in nuclear and particle physics as a unit of magnetic moments. It is defined as the amount of the magnetic moment of a Dirac particle with charge and mass of the proton:

With

According to current measurement accuracy, it has the value:

Where the bracketed numbers indicate the estimated standard deviation of the mean corresponding to the last two digits in front of the bracket;

There are

However, since the proton is a composite ( made ​​up of quarks ), particles, the magnetic moment associated with its spin has would be expected to take a much larger value than for a Dirac particle: