I was reading a paper on nuclear physics when I came across the following definite integral:
$$\int_{-\infty}^{\infty}\frac{\zeta}{2\sqrt\pi} \frac{e^{-\frac{\zeta^2}{4} y^2}}{1 + y^2}\mathrm dy$$
The paper gives the expression of the above integral as:
$$\int_{-\infty}^{\infty}\frac{\zeta}{2\sqrt\pi} \frac{e^{-\frac{\zeta^2}{4} y^2}}{1 + y^2}\mathrm dy = \frac{\zeta \sqrt\pi}{2} e^{\frac{\zeta^2}{4}}\left(1-\operatorname{erf}\left (\frac{\zeta}{2}\right )\right)$$
Basically, I have no clue where this result comes from. I have tried the substitution $u = \tan^{-1}y$ so that $\mathrm du = \frac{1}{1 + y^2}\mathrm dy$, but I get the following expression:
$$\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}}\frac{\zeta}{2\sqrt\pi} e^{-\frac{\zeta^2}{4} \tan^2(u)}\mathrm du$$
Which I do not know how to evaluate. Any help on the above integral would be greatly appreciated. Even a hint as to how to proceed further is welcomed. Thank you so much in advance!
PS: This is my first question so I hope the formatting/question wording is not too confusing.
Best,
Nathan