The class is libLSS/physics/bias/broken_power_law.hpp, class is LibLSS::bias::BrokenPowerLaw.
This class implements the linear bias model. Its corresponding mathematical model is {$$ N_g = \bar{n} (1 + \delta_m)^\alpha \exp\left[-\left(\frac{1+\delta_m}{\rho_g}\right)^{-\epsilon} \right], $$} with {$\bar{n}$} a normalization constant, {$\alpha$} the power law scaling, {$\rho_g$} a truncation scale for the matter, {$\epsilon$} the intensity of the truncation.