MadGraph5_aMC@NLO

Settings For High Pt Cuts for Tops and Background

Asked by Herbie Smith

I am confused on the correct run_card settings for performing high pt cuts on quarks. I am using a CM energy of 100 TeV (50 TeV each p-p beams) and making pt cuts at 1 TeV for top quark pairs. The command I'm using to do this is "generate p p > t t~". After the "launch" command, I'm interested in setting cuts in the run_card. I've tried separately to set two options for jet pt cuts ("ptj" and "xptj") to 1 TeV, and they give the same cross-section as when no cuts are applied (~2.7e4 pb), but when setting the pt cut for heavy final states, "ptheavy", to the same value, the cross-section is ~11 pb. Similarly, when setting "ptj1min" to the same value, the cross-section is 0.

A similar behavior occurs for b-bbar quark production ("generate p p > b b~") with the following cross-sections. Note that maxjetflavor = 5 for these calculations:
    no cuts (maxjetflavor = 4): 2.934e9 pb
    ptheavy = 1000 (maxjetflavor = 4): 2.93e9 pb
    ptheavy = 1000 (maxjetflavor = 5): 2.3e9 pb (small cut, since some b's hadronize?)
    ptj1min = 1000 (maxjetflavor = 5): 12.36 pb

My goal is to produce high pt cuts for all of the light quarks as well as tops and bottoms. Is it possible to make the same cuts for each of these processes, or is it necessary to consider the top and bottom quarks as special cases? In general, when should I prefer changing one setting over another?

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

All particle heavier than 20GeV are only sensitive to the ptheavy cut.
( you can change the threshold in the file setcuts.f (line 194)

if you change that threshold, higher then you, you can set maxjetflavor on 6 and the ptj will be applied for all the quark.
(Note that the shower will be confuse if that parameter is on 6 but the mass of the bottom / top are not zero, and the result might not be physical.)

Cheers,

Olivier

On Jul 3, 2014, at 2:41 PM, Herbie Smith <email address hidden> wrote:

> New question #251157 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/251157
>
> I am confused on the correct run_card settings for performing high pt cuts on quarks. I am using a CM energy of 100 TeV (50 TeV each p-p beams) and making pt cuts at 1 TeV for top quarks. I've tried separately to set two options for jet pt cuts ("ptj" and "xptj") to 1 TeV, and they give the same cross-section as when no cuts are applied (~2.7e4 pb), but when setting the pt cut for heavy final states, "ptheavy", to the same value, the cross-section is ~11 pb. Similarly, when setting "ptj1min" to the same value, the cross-section is 0.
>
> My goal is to produce high pt cuts for all of the light quarks as well as tops and bottoms. Is it possible to make the same cuts for each of these processes, or is it necessary to consider the top and bottom quarks as special cases? In general, when should I prefer changing one setting over another?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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