Simulation of pp-collision and Z boson production

[Vanadium 50]

This isn't going to work. That procedure forces x2 to have a particular distribution, and that distribution may or may not (in fact, doesn't) match the correct x2 distribution.

What you need to do instead, if you want to go down this path, is once you have the x2, you calculate the probability of getting this x2, and then toss a random number. If the random number matches this probability, you keep the event, otherwise, you start over. This is called reweighting.

 

[mfb]

What do you mean by symmetry? When I compare the u-PDF generating x1 values with the antiu-PDFs, I notice a slightly difference (not a statistical one because the difference is "reproducible").

"quark from proton 1 + antiquark from proton 2" should give the same result as "antiquark from proton 1 + quark from proton 2". If it does not, there is something wrong.

From this, it is not correct to sample only from the u-PDFs I guess.

Sure, you have to account for all quarks. Just add their contributions afterwards?

I don't see how sampling the u-PDF covers processes like anti-s + s -> Z.


I agree with Vanadium in terms of reweighting.

 

[Jan Eysermans]

Indeed, including the distributions for x2 are needed.. I have implemented the method of Vanadium 50 and the results are more or less ok! Thanks everyone.