# deviation between madgraph outcome and own calculations

Hello everyone,

I have a very strange problem when calculating the cross section of the u b > d t process. I calculated it with madgraph simply via

>> generate u b > d t

>> output ubdt

>> launch

I varied the beam energy to get multiple values to check and changed the pdf´s to 0 since I dont want to inclued them right now.

I also calculated the cross section by hand and with another MonteCarlo vegas algorithm. Here are some results:

sqrts [GeV] / madgraph [pb] / own calculations (MonteCarlo and analytic computation agree)[pb]

2000 / 50.85 / 53.85

5000 / 46.37 / 54.23

13000 / 24.94 / 54.33

I checked my own calculations by cross-checking the matrix element squared with madgraph which worked. So then I integrated the phase space by hand and via the MC integration so I would say there are no points where I could have messed up the same thing in both calculations since I basically just input the matrix element in my vegas algorithm. On the other hand it is quite odd that my cross section changes only slightly when varying sqrts pretty much,

In the end my question is wether there is any possibility that I maybe just calculated the wrong thing in madgraph for example I had to change another thing in one of the cards that I just forgot other than the beam energy and the value of the lpp´s?

## Question information

- Language:
- English Edit question

- Status:
- Solved

- Assignee:
- No assignee Edit question

- Solved by:
- Olivier Mattelaer

- Solved:

- Last query:

- Last reply: