The definition of the skin thickness

Last modification: 1996/3/25
We define the nucleon skin by two conditions: A point r is in the proton or neutron skin when

rhoq(r) > 0.75 x rhotot (r),
rhoq(r) > 0.16 x 10-2 fm-3,

where "rho" means density, "q" specifies proton or neutron, and "tot" stands for proton+neutron. A similar definition was given in Ref. [FOT93].

The value of 0.16 fm-3 is chosen as a standard density of the nuclear matter. Since the factors 0.75 and 10-2 in the above definitions could have been differently chosen in rather arbitrary fashions, the absolute sizes of the skin thickness do not have a very precise meaning. Nevertheless, these values are useful to judge how the nucleon skins develop as the nucleus approaches to the drip line in the nuclear chart.

When the nucleus is deformed, the thickness of the skin depends on the direction. We take the arithmetic average of the thicknesses in the x-, y- and z-axes.

For the numerical procedures to determine the skin thickness more accurately than the mesh spacing, click here (html file of 1KB).