Crashing while produce ttH (H to tt) process

Asked by Zhi Zheng on 2020-06-03

Dear MG5 Team,
I am trying to generate event for ttH off shell to tt process, I am running with MG5_aMC_v2_7_2 and using sm model.
Here is lines how I generate this process:
generate p p > h > t t~ t t~
I also set the bwcut to be 300 GeV in both madspin and run parameter card
When decaying the events:
And I get the following error message:
ERROR: Found a weight MUCH larger than the computed max_weight (ratio: 1659.96832792).
    This usually means that the Narrow width approximation reaches it's limit on part of the Phase-Space.
    Do not trust too much the tale of the distribution and/or relaunch the code with smaller BW_cut.
    This is for channel ('t_wpb_wp_csx', 'tx_bxwm_wm_scx', 't_wpb_wp_csx', 'tx_bxwm_wm_scx') with current BW_value at : 297.901'
Command "generate_events run_02" interrupted with error:
IndexError : list index out of range
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/lustre/umt3/user/zhengzhi/MG/MG5_aMC_v2_7_2/ttHtt_offshell/run_02_tag_1_debug.log'.
Please attach this file to your report.

I am just wonder how I can fix such a problem here.

Thanks in advance!
Best,
Zhi

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2020-06-03
Last query:
2020-06-03
Last reply:
2020-06-03

Dear Zhi,

bwcut is not a number in "GeV".
this is a cut proportional to the width so here you have a top mass window of
170 - 300 * 1.5
up
to
170 + 300 * 1.5
The minimun is obviously be set to zero.

MadSpin is using Narrow-width approximation and this is REQUIRED to make it work.
In your case this forbids such window to include 125 GeV (which will lead to onshell higgs and break the approximation. So the absolute maximum for that cut should be around 30.

But even 30 might be too large for narrow-width approximation to hold.

Cheers,

Olivier

> On 3 Jun 2020, at 04:05, Zhi Zheng <email address hidden> wrote:
>
> New question #691103 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/691103
>
> Dear MG5 Team,
> I am trying to generate event for ttH off shell to tt process, I am running with MG5_aMC_v2_7_2 and using sm model.
> Here is lines how I generate this process:
> generate p p > h > t t~ t t~
> I also set the bwcut to be 300 GeV in both madspin and run parameter card
> When decaying the events:
> And I get the following error message:
> ERROR: Found a weight MUCH larger than the computed max_weight (ratio: 1659.96832792).
> This usually means that the Narrow width approximation reaches it's limit on part of the Phase-Space.
> Do not trust too much the tale of the distribution and/or relaunch the code with smaller BW_cut.
> This is for channel ('t_wpb_wp_csx', 'tx_bxwm_wm_scx', 't_wpb_wp_csx', 'tx_bxwm_wm_scx') with current BW_value at : 297.901'
> Command "generate_events run_02" interrupted with error:
> IndexError : list index out of range
> Please report this bug on https://bugs.launchpad.net/mg5amcnlo
> More information is found in '/lustre/umt3/user/zhengzhi/MG/MG5_aMC_v2_7_2/ttHtt_offshell/run_02_tag_1_debug.log'.
> Please attach this file to your report.
>
> I am just wonder how I can fix such a problem here.
>
> Thanks in advance!
> Best,
> Zhi
>
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Zhi Zheng (zhengzhisunny) said : #2

Thanks Olivier Mattelaer, that solved my question.