The Perfect Cauchy or Lorentzian Curve fitting in MS Excel

Curve fitting is the process of constructing a curve or mathematical function, that has the best fit to a series of data points. Fitted curves can be used as an aid for data visualization, to conclude values of a function where no data are available, and to summarize the relationships among two or more variables.
Equation for Cauchy Curve is, $$Y=\frac{I}{[1+{\left(\frac{x-a}{\gamma }\right)}^2]}$$ Where $I$ is intensity,
$a$ is Position,
$\gamma$ is Scale parameter