For comparison with other dataset, I'm calculating the LS factor using the following formula in ArcGIS:
(1) LS = Power(“flow accumulation”*[cell resolution]/22.1,0.4)*Power(Sin(“slope of degree”*0.01745))/0.09, 1.4)*1.4
but I was not able to find the theoretical formulation of LS it corresponds, I've got the feeling that (1) is the ArcGIS correspective of
(2) LS = (m+1) [ (U/22.13)]^m [sin(slope)/sin(5°)]^n
where U is the unitary upslope contributing area and (2) should be LS factor according to Mitasova et al. (1996) paper.
The following document
http://www.caee.utexas.edu/prof/maidment/giswr2014/ProjectReport/Kim.pdf
seems to support my feelings but in absence of references for (1) in literature I'm not completely sure that (1) and (2) are the "same" formula.
Mitasova H., Hofierka, J., Zlocha, M. & Iverson, L.R. (1996) Modeling topographic potential for erosion and deposition using GIS. International Journal of Geographical Information Science. 10 (5), 629-641.