W scattering cross section blows up

Hi,

Did you put a pt cut on the W in the final state?
Otherwise the cross-section is indeed singular (like e+ e- > e+ e-)

I've generated the three processes:
w+ w- > w+ w- : 3737
w+ w- > h > w+ w-: 1.909e+04 ± 31
w+ w- > w+ w- /h :4.593e+04 ± 38
and this give the expected behavior (very strong destructive interference). So everything seems under-control.

Now I don't really understand why the w+ w- > w+ w- /h didn't blow up.
I run it on my side and the cross-section is huge, with a huge error (5.652e+09 ± 5.395e+13 (pb))
is very slow and the code produce only a couple of events. Didn't you have something similar?

Cheers,

Olivier

On Nov 24, 2013, at 8:51 PM, Luke Bodmer <email address hidden> wrote:

> New question #239752 on MadGraph5:
> https://answers.launchpad.net/madgraph5/+question/239752
>
> I generated three processes. w+ w- > w+ w- /h w+ w- > h > w+ w- and w+ w- > w+ w-. The first two, without the Higgs and only the Higgs, worked perfectly. However the last one, w scattering with no alterations, gave me a cross section that blew up. I don't understand how the interference could cause such a problem. I ran this at 14 TeV center of mass energy with pdf set to zero. Those are the only changes I made. I am using MadGraph 5. What is the issue here? Did I over look something in the process. Thank you.
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.

Thank you for the very quick reply. Actually what you are describing happened when I ran the w+ w- > w+ w- process.

w+ w- > w+ w- : 5.364e+45 ± 2.2e+04 (51 events generated)
w+ w- > w+ w- : 45881 ± 43.1
w+ w- > w+ w- /h : 3.2809e+05 ± 1.25e+03

To cut the Ws in the final state do I cut ptheavy? Also how do you change the higgs mass? I tried using the param card but I am not sure what it means by "following the analytical expressions". And finally, is the 2007 manual the newest edition? Sorry for the simple questions but I have just begun using madgraph. Thank you very much.

Hi,

> To cut the Ws in the final state do I cut ptheavy?

yes that's it.

> Also how do you
> change the higgs mass? I tried using the param card but I am not sure
> what it means by "following the analytical expressions".

The problem is to have the Higss width correct.
For this the best is to use our online calculator:
http://madgraph.hep.uiuc.edu/
(then click on tools -> calculators -> SM (MG5))

> And finally, is
> the 2007 manual the newest edition?

We don't have a real manual.
Since we have the help command to indicate all possible option.

Otherwise, the code is describe here:
http://arxiv.org/abs/arXiv:1106.0522

And we have some tutorial:
https://cp3.irmp.ucl.ac.be/projects/madgraph/attachment/wiki/TASISchool13/13_06_10_tutomg_tasi.pdf

> Sorry for the simple questions but I
> have just begun using madgraph.

No problem this ticket system is foreseen for this kind of question

Cheers,

Olivier

On Nov 25, 2013, at 5:51 AM, Luke Bodmer <email address hidden> wrote:

> Question #239752 on MadGraph5 changed:
> https://answers.launchpad.net/madgraph5/+question/239752
>
> Status: Answered => Open
>
> Luke Bodmer is still having a problem:
> Thank you for the very quick reply. Actually what you are describing
> happened when I ran the w+ w- > w+ w- process.
>
> w+ w- > w+ w- : 5.364e+45 ± 2.2e+04 (51 events generated)
> w+ w- > w+ w- : 45881 ± 43.1
> w+ w- > w+ w- /h : 3.2809e+05 ± 1.25e+03
>
> To cut the Ws in the final state do I cut ptheavy? Also how do you
> change the higgs mass? I tried using the param card but I am not sure
> what it means by "following the analytical expressions". And finally, is
> the 2007 manual the newest edition? Sorry for the simple questions but I
> have just begun using madgraph. Thank you very much.
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.