In the quark model for hadrons, the neutron is composed of one up quark (charge ⁠+ + 2 / 3 ⁠ e) and two down quarks (charge ⁠− + 1 / 3 ⁠ e) while the proton is composed of one down quark (charge ⁠− + 1 / 3 ⁠ e) and two up quarks (charge ⁠+ + 2 / 3 ⁠ e). The magnetic moment of the nucleons can be modeled as a sum of the magnetic moments of the constituent quarks, although this simple model belies the complexities of the Standard Model of Particle Physics. The calculation assumes that the quarks behave like pointlike Dirac particles, each having their own magnetic moment, as computed using an expression similar to the one above for the nuclear magneton: μ μ q = e q ℏ ℏ 2 m q , where the q-subscripted variables refer to quark magnetic moment, charge, or mass. Simplistically, the magnetic moment of a nucleon can be viewed as resulting from the vector sum of the three quark magnetic moments, plus the orbital magnetic moments caused by the movement of the three charged quarks within it.