Thank you for your help. It was a part of my homework including determining expectation values. Looking integrals up is allowed. Ususally I use Wolfram Alpha, too, for looking up indefinite integrals. Another page for definite ones, hadn't know that Wolfram has the same function. The other page proposed something with an error function.
I have no big idea about these, my feeling just was I can't solve it this way analytically, but maybe I just don't know enough about. Do you know an easy introductory for that, by the way?
So, I'm glad that this (last) gap in my homework problem was filled - I am not very patient - and I will remember the definite integral function of Wolfram.