Inconsistent results for the cross-section
Hello,
I am trying to calculate the cross-section for the process e- e+ > mu- mu+ a (see proc_card below), but when trying to compute the cross-section (using generate_events) I obtain inconsistent results, running 10 times the generate_events command I get the following cross-sections:
0.041357 +- 8.6e-05
0.040444 +- 0.000124
0.041067 +- 8.73e-05
0.040212 +- 0.000101
0.040901 +- 0.000107
0.039324 +- 0.00013
0.041297 +- 9.45e-05
0.041584 +- 0.000123
0.04053 +- 0.000153
0.041712 +- 0.000124
here the dispersion is much larger than the supposed error of each value. The run card is almost the default one, I have modified the photon pt cut, see run card below.
If someone can tell me how to obtain consistent results, I would really appreciate that.
Thank you
proc_card_mg5.dat:
#******
#* MadGraph5_aMC@NLO *
#* *
#* * * *
#* * * * * *
#* * * * * 5 * * * * *
#* * * * * *
#* * * *
#* *
#* *
#* VERSION 3.1.1 2021-05-28 *
#* *
#* The MadGraph5_aMC@NLO Development Team - Find us at *
#* https:/
#* *
#******
#* *
#* Command File for MadGraph5_aMC@NLO *
#* *
#* run as ./bin/mg5_aMC filename *
#* *
#******
set group_subprocesses Auto
set ignore_
set low_mem_
set complex_mass_scheme False
set include_
set gauge unitary
set loop_optimized_
set loop_color_flows False
set max_npoint_
set default_
set max_t_for_channel 99
set zerowidth_tchannel True
set nlo_mixed_expansion True
generate e- e+ > mu- mu+ a
define p = g u c d s u~ c~ d~ s~
define j = g u c d s u~ c~ d~ s~
define l+ = e+ mu+
define l- = e- mu-
define vl = ve vm vt
define vl~ = ve~ vm~ vt~
output prova3
run_card.dat:
#******
# MadGraph5_aMC@NLO *
# *
# run_card.dat MadEvent *
# *
# This file is used to set the parameters of the run. *
# *
# Some notation/
# *
# Lines starting with a '# ' are info or comments *
# *
# mind the format: value = variable ! comment *
# *
# To display more options, you can type the command: *
# update full_run_card *
#******
#
#******
# Tag name for the run (one word) *
#******
tag_1 = run_tag ! name of the run
#******
# Number of events and rnd seed *
# Warning: Do not generate more than 1M events in a single run *
#******
10000 = nevents ! Number of unweighted events requested
0 = iseed ! rnd seed (0=assigned automatically=
#******
# Collider type and energy *
# lpp: 0=No PDF, 1=proton, -1=antiproton, 2=photon from proton, *
# 3=photon from electron, 4=photon from muon *
#******
0 = lpp1 ! beam 1 type
0 = lpp2 ! beam 2 type
500.0 = ebeam1 ! beam 1 total energy in GeV
500.0 = ebeam2 ! beam 2 total energy in GeV
#******
# Beam polarization from -100 (left-handed) to 100 (right-handed) *
#******
0.0 = polbeam1 ! beam polarization for beam 1
0.0 = polbeam2 ! beam polarization for beam 2
#******
# PDF CHOICE: this automatically fixes also alpha_s and its evol. *
#******
nn23lo1 = pdlabel ! PDF set
230000 = lhaid ! if pdlabel=lhapdf, this is the lhapdf number
# To see heavy ion options: type "update ion_pdf"
#******
# Renormalization and factorization scales *
#******
True = fixed_ren_scale ! if .true. use fixed ren scale
True = fixed_fac_scale ! if .true. use fixed fac scale
91.188 = scale ! fixed ren scale
91.188 = dsqrt_q2fact1 ! fixed fact scale for pdf1
91.188 = dsqrt_q2fact2 ! fixed fact scale for pdf2
-1 = dynamical_
1.0 = scalefact ! scale factor for event-by-event scales
#******
# Type and output format
#******
False = gridpack !True = setting up the grid pack
-1.0 = time_of_flight ! threshold (in mm) below which the invariant livetime is not written (-1 means not written)
average = event_norm ! average/sum. Normalization of the weight in the LHEF
# To see MLM/CKKW merging options: type "update MLM" or "update CKKW"
#******
#
#******
# Phase-Space Optimization strategy (basic options)
#******
0 = nhel ! using helicities importance sampling or not.
2 = sde_strategy ! default integration strategy (hep-ph/2021.xxxxx)
! 2 is new strategy (using only the denominator)
# To see advanced option for Phase-Space optimization: type "update psoptim"
#******
# Generation bias, check the wiki page below for more information: *
# 'cp3.irmp.
#******
None = bias_module ! Bias type of bias, [None, ptj_bias, -custom_folder-]
{} = bias_parameters ! Specifies the parameters of the module.
#
#******
# Parton level cuts definition *
#******
#
#
#******
# BW cutoff (M+/-bwcutoff*
#******
15.0 = bwcutoff ! (M+/-bwcutoff*
#******
# Standard Cuts *
#******
# Minimum and maximum pt's (for max, -1 means no cut) *
#******
0.1 = pta ! minimum pt for the photons
10.0 = ptl ! minimum pt for the charged leptons
500 = ptamax ! maximum pt for the photons
-1.0 = ptlmax ! maximum pt for the charged leptons
{} = pt_min_pdg ! pt cut for other particles (use pdg code). Applied on particle and anti-particle
{} = pt_max_pdg ! pt cut for other particles (syntax e.g. {6: 100, 25: 50})
#******
# Minimum and maximum E's (in the center of mass frame) *
#******
0.0 = ej ! minimum E for the jets
0.0 = eb ! minimum E for the b
0.0 = ea ! minimum E for the photons
0.0 = el ! minimum E for the charged leptons
-1.0 = ejmax ! maximum E for the jets
-1.0 = ebmax ! maximum E for the b
-1.0 = eamax ! maximum E for the photons
-1.0 = elmax ! maximum E for the charged leptons
{} = e_min_pdg ! E cut for other particles (use pdg code). Applied on particle and anti-particle
{} = e_max_pdg ! E cut for other particles (syntax e.g. {6: 100, 25: 50})
#******
# Maximum and minimum absolute rapidity (for max, -1 means no cut) *
#******
2.5 = etaa ! max rap for the photons
2.5 = etal ! max rap for the charged leptons
0.0 = etajmin ! min rap for the jets
0.0 = etaamin ! min rap for the photons
0.0 = etalmin ! main rap for the charged leptons
{} = eta_min_pdg ! rap cut for other particles (use pdg code). Applied on particle and anti-particle
{} = eta_max_pdg ! rap cut for other particles (syntax e.g. {6: 2.5, 23: 5})
#******
# Minimum and maximum DeltaR distance *
#******
0.4 = drll ! min distance between leptons
0.4 = dral ! min distance between gamma and lepton
-1.0 = drllmax ! max distance between leptons
-1.0 = dralmax ! maxdistance between gamma and lepton
#******
# Minimum and maximum invariant mass for pairs *
#******
0.0 = mmll ! min invariant mass of l+l- (same flavour) lepton pair
-1.0 = mmllmax ! max invariant mass of l+l- (same flavour) lepton pair
{} = mxx_min_pdg ! min invariant mass of a pair of particles X/X~ (e.g. {6:250})
{'default': False} = mxx_only_
#*****
# Minimum and maximum invariant mass for all letpons *
#*****
0.0 = mmnl ! min invariant mass for all letpons (l+- and vl)
-1.0 = mmnlmax ! max invariant mass for all letpons (l+- and vl)
#*****
# Minimum and maximum pt for 4-momenta sum of leptons / neutrino *
# for pair of lepton includes only same flavor, opposite charge
#*****
0.0 = ptllmin ! Minimum pt for 4-momenta sum of leptons(l and vl)
-1.0 = ptllmax ! Maximum pt for 4-momenta sum of leptons(l and vl)
#******
# Inclusive cuts *
#******
0.0 = xptl ! minimum pt for at least one charged lepton
#*****
# Control the pt's of leptons sorted by pt *
#*****
0.0 = ptl1min ! minimum pt for the leading lepton in pt
0.0 = ptl2min ! minimum pt for the second lepton in pt
-1.0 = ptl1max ! maximum pt for the leading lepton in pt
-1.0 = ptl2max ! maximum pt for the second lepton in pt
#******
# maximal pdg code for quark to be considered as a light jet *
# (otherwise b cuts are applied) *
#******
4 = maxjetflavor ! Maximum jet pdg code
#******
#
#******
# Store info for systematics studies *
# WARNING: Do not use for interference type of computation *
#******
False = use_syst ! Enable systematics studies
#
systematics = systematics_program ! none, systematics [python], SysCalc [depreceted, C++]
['--mur=0.5,1,2', '--muf=0.5,1,2', '--pdf=errorset'] = systematics_
# Syscalc is deprecated but to see the associate options type'update syscalc'
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