# Fitting Beta Emission spectrum data according to fermi function

I was trying to fit beta emission spectrum data to the equation

$$\tau(E_e) \propto (E_e^2 - m_e^2 c^4)(Q-E_e)^2\frac{E/c}{\sqrt{E_e^2 - m_e^2 c^4}}.$$

However, on making a custom equation in Origin, I failed. Is there some information missing in the equation? Or I have to write my own script to fit the data in origin?