h ⁡ ( ϵ , ℓ ; r ) = ( 2 π ⁢ τ ⁢ A ⁡ ( ϵ , ℓ ) 1 − e − 2 ⁢ π / τ ) 1 2 ⁢ G ℓ ⁡ ( − 1 / τ , τ ⁢ r ) h\left(\epsilon ,\ell ;r\right)=\left({\frac {2}{\pi \tau }}{\frac {A(\epsilon ,\ell )}{1-e^{-2\pi /\tau }}}\right)^{\frac {1}{2}}G_{\ell }\left(-1/\tau ,\tau r\right)