Compute weights for Run2 with EFT sample

Dear expert,

MG version: MG5_aMC_v3_3_1

I have generated 1M events of p p > t t~ at NLO and LO using SMEFT_NLO model and shower the event using Pythia8. I used restrict card with ctg=1.5 and all other WC coefficients are equal to 0. Then, I used the re-weighting card with ctg=[-1.5, 1.2], as shown below.

Using the HepMC tool, I was able to convert my output file to a root file, for instance:

root [8] hepmc3_tree->Scan ("weight_names:weights", "", "colsize=20")

*********************************************************************
* Row * Instance * weight_names * weights *
*********************************************************************
* 0 * 0 * 0 * 0.011425636666666667 *
* 0 * 64 * AUX_ctg_0_09_nlo * 71.3100450000000023 *
* 0 * 65 * AUX_ctg_0_2_nlo * 73.245915999999994 *
* 0 * 66 * AUX_ctg_0_5_nlo * 78.9755789999999962 *
* 0 * 67 * AUX_ctg_1_2_nlo * 94.9058670000000006 *
* 0 * 68 * AUX_ctg_1_nlo * 89.9884909999999962 *
* 0 * 69 * AUX_ctg_neg_0_09_nlo * 68.333241000000001 *
* 0 * 70 * AUX_ctg_neg_0_2_nlo * 66.6307970000000012 *
* 0 * 71 * AUX_ctg_neg_0_5_nlo * 62.437775000000002 *
* 0 * 72 * AUX_ctg_neg_0_nlo * 69.7920110000000022 *
* 0 * 73 * AUX_ctg_neg_1_2_nlo * 55.2151299999999949 *
* 0 * 74 * AUX_ctg_neg_1_5_nlo * 53.2173130000000043 *
* 0 * 75 * AUX_ctg_neg_1_nlo * 56.9128729999999976 *
* 0 * 76 * Weight * 102.830730000000003 *

My understanding is that the variable "Weight" corresponds to ctg=1.5. At this point, I'm curious about the variable "0". Do I need to consider it or can I ignore it?

I have the following questions (please accept my ignorance):

First Question 1:

I want to compute the folowing weight: W = σ * L * Wgen / ΣWgen. [1]

where Wgen is the weight assigned to the event by the MC generator and ΣWgen is the sum of these weights for all the generated events.

In the ATLAS analysis, I compute "ΣWgen" from a separate tree usually called "SumOfWeights " and Wgen= weight_mc . I could not find such a tree when I covert my ".hepmc" file to "root" file.

If I focus on "AUX_ctg_neg_1_nlo", the equation [1] becomes,

W = σ * L * AUX_ctg_neg_1_nlo / ΣAUX_ctg_neg_1_nlo [2]

"ΣAUX_ctg_neg_1_nlo" is the sum of AUX_ctg_neg_1_nlo weight for all the generated events. Does this sound right?

Second question 2:

What is the input value for the cross-section (σ) and L in Equation [2] ? For Run2, for example, should I re-weight the number of events (1M in my case) using, this value was obtained from ATLAS XsecSummaryTTbar web page :

L = 139 fb-1
σ = 76.95
k-factor = 1.1398

Do I need to use other values?

Thank you in advance for your patience as I try to explain the question clearly. Any feedback you provide will be greatly appreciated.

Best,
A.TNOURJI

Reweight_card.dat card:
=======================================
change mode NLO # Define type of Reweighting. For LO sample this command
                   # has no effect since only "LO" mode is allowed.
change helicity False
# SPECIFY A PATH OR USE THE SET COMMAND LIKE THIS:
# set sminputs 1 130 # modify 1/alpha_EW
launch --rwgt_name=ctg_neg_1_5
  set DIM62F 24 -1.5
launch --rwgt_name=ctg_neg_1_2
  set DIM62F 24 -1.2
launch --rwgt_name=ctg_neg_1
  set DIM62F 24 -1
launch --rwgt_name=ctg_neg_0_5
  set DIM62F 24 -0.5
launch --rwgt_name=ctg_neg_0_2
  set DIM62F 24 -0.2
launch --rwgt_name=ctg_neg_0_09
  set DIM62F 24 -0.09
launch --rwgt_name=ctg_neg_0
  set DIM62F 24 0
launch --rwgt_name=ctg_0_09
  set DIM62F 24 0.09
launch --rwgt_name=ctg_0_2
  set DIM62F 24 0.2
launch --rwgt_name=ctg_0_5
  set DIM62F 24 0.5
launch --rwgt_name=ctg_1
  set DIM62F 24 1
launch --rwgt_name=ctg_1_2
  set DIM62F 24 1.2
=======================================