Difference between LO cross section and NLO cross section
I tried to generate process (p p > o w , W+ > mu+ vm , W- > mu- vm~ where o = c c~and w = W+ W-)to calculate the LO cross section.
which agreement with the cross section given in the paper i.e 1039-+3.206pb
But when i tried to calculate NLO cross section for the same process there is a huge difference in there cross section. (for NLO the cross section =3.06e+04 ± 5.4e+02 ) .I do not know why there such a huge difference.
The relevant paper is https:/
I have NNPDF30lo(262000) for LO and NNPDF30 nlo(260000) for NLO
The events.lhe file for NLO is
<LesHouchesEvents version="3.0">
<header>
<MG5ProcCard>
#******
#* MadGraph5_aMC@NLO *
#* *
#* * * *
#* * * * * *
#* * * * * 5 * * * * *
#* * * * * *
#* * * *
#* *
#* *
#* VERSION 3.2.0 2021-08-22 *
#* *
#* 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
define o = c c~
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~
define o = c c~
define w = W+ W-
import model loop_sm
generate p p > o w [QCD]
output lhapdf4
</MG5ProcCard>
<slha>
#######
## PARAM_CARD AUTOMATICALY GENERATED BY MG5 FOLLOWING UFO MODEL ####
#######
## ##
## Width set on Auto will be computed following the information ##
## present in the decay.py files of the model. ##
## See arXiv:1402.1178 for more details. ##
## ##
#######
#######
## INFORMATION FOR MASS
#######
Block mass
5 4.700000e+00 # MB
6 1.730000e+02 # MT
15 1.777000e+00 # MTA
23 9.118800e+01 # MZ
25 1.250000e+02 # MH
## Dependent parameters, given by model restrictions.
## Those values should be edited following the
## analytical expression. MG5 ignores those values
## but they are important for interfacing the output of MG5
## to external program such as Pythia.
1 0.000000e+00 # d : 0.0
2 0.000000e+00 # u : 0.0
3 0.000000e+00 # s : 0.0
4 0.000000e+00 # c : 0.0
11 0.000000e+00 # e- : 0.0
12 0.000000e+00 # ve : 0.0
13 0.000000e+00 # mu- : 0.0
14 0.000000e+00 # vm : 0.0
16 0.000000e+00 # vt : 0.0
21 0.000000e+00 # g : 0.0
22 0.000000e+00 # a : 0.0
24 8.041900e+01 # w+ : cmath.sqrt(
#######
## INFORMATION FOR SMINPUTS
#######
Block sminputs
1 1.325070e+02 # aEWM1
2 1.166390e-05 # Gf
3 1.180000e-01 # aS (Note that Parameter not used if you use a PDF set)
#######
## INFORMATION FOR YUKAWA
#######
Block yukawa
5 4.700000e+00 # ymb
6 1.730000e+02 # ymt
15 1.777000e+00 # ymtau
#######
## INFORMATION FOR DECAY
#######
DECAY 6 1.491500e+00 # WT
DECAY 23 2.441404e+00 # WZ
DECAY 24 2.047600e+00 # WW
DECAY 25 6.382339e-03 # WH
## Dependent parameters, given by model restrictions.
## Those values should be edited following the
## analytical expression. MG5 ignores those values
## but they are important for interfacing the output of MG5
## to external program such as Pythia.
DECAY 1 0.000000e+00 # d : 0.0
DECAY 2 0.000000e+00 # u : 0.0
DECAY 3 0.000000e+00 # s : 0.0
DECAY 4 0.000000e+00 # c : 0.0
DECAY 5 0.000000e+00 # b : 0.0
DECAY 11 0.000000e+00 # e- : 0.0
DECAY 12 0.000000e+00 # ve : 0.0
DECAY 13 0.000000e+00 # mu- : 0.0
DECAY 14 0.000000e+00 # vm : 0.0
DECAY 15 0.000000e+00 # ta- : 0.0
DECAY 16 0.000000e+00 # vt : 0.0
DECAY 21 0.000000e+00 # g : 0.0
DECAY 22 0.000000e+00 # a : 0.0
#======
# QUANTUM NUMBERS OF NEW STATE(S) (NON SM PDG CODE)
#======
Block QNUMBERS 82 # gh
1 0 # 3 times electric charge
2 1 # number of spin states (2S+1)
3 8 # colour rep (1: singlet, 3: triplet, 8: octet)
4 1 # Particle/
</slha>
<MGRunCard>
#******
# MadGraph5_aMC@NLO *
# *
# run_card.dat aMC@NLO *
# *
# This file is used to set the parameters of the run. *
# *
# Some notation/
# *
# Lines starting with a hash (#) are info or comments *
# *
# mind the format: value = variable ! comment *
# *
# Some of the values of variables can be list. These can either be *
# comma or space separated. *
# *
# To display additional parameter, you can use the command: *
# update to_full *
#******
#
#******
# Running parameters
#******
#
#******
# Tag name for the run (one word) *
#******
tag_1 = run_tag ! name of the run
#******
# Number of LHE events (and their normalization) and the required *
# (relative) accuracy on the Xsec. *
# These values are ignored for fixed order runs *
#******
10000 = nevents
-1.0 = req_acc ! Required accuracy (-1=auto determined from nevents)
-1 = nevt_job ! Max number of events per job in event generation.
! (-1= no split).
#******
# Output format
#******
-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/bias. Normalization of the weight in the LHEF
#******
# Number of points per itegration channel (ignored for aMC@NLO runs) *
#******
0.01 = req_acc_fo ! Required accuracy (-1=ignored, and use the
# These numbers are ignored except if req_acc_FO is equal to -1
5000 = npoints_fo_grid ! number of points to setup grids
4 = niters_fo_grid ! number of iter. to setup grids
10000 = npoints_fo ! number of points to compute Xsec
6 = niters_fo ! number of iter. to compute Xsec
#******
# Random number seed *
#******
33 = iseed
#******
# Collider type and energy *
#******
1 = lpp1 ! beam 1 type (0 = no PDF)
1 = lpp2 ! beam 2 type (0 = no PDF)
6500.0 = ebeam1 ! beam 1 energy in GeV
6500.0 = ebeam2 ! beam 2 energy in GeV
#******
# PDF choice: this automatically fixes also alpha_s(MZ) and its evol. *
#******
lhapdf = pdlabel ! PDF set
260000 = lhaid ! If pdlabel=lhapdf, this is the lhapdf number. Only
! numbers for central PDF sets are allowed. Can be a list;
! PDF sets beyond the first are included via reweighting.
#******
# Include the NLO Monte Carlo subtr. terms for the following parton *
# shower (HERWIG6 | HERWIGPP | PYTHIA6Q | PYTHIA6PT | PYTHIA8) *
# WARNING: PYTHIA6PT works only for processes without FSR!!!! *
#******
PYTHIA6Q = parton_shower
1.0 = shower_scale_factor ! multiply default shower starting
#******
# Renormalization and factorization scales *
# (Default functional form for the non-fixed scales is the sum of *
# the transverse masses divided by two of all final state particles *
# and partons. This can be changed in SubProcesses/
# dynamical_
#******
False = fixed_ren_scale ! if .true. use fixed ren scale
False = fixed_fac_scale ! if .true. use fixed fac scale
91.118 = mur_ref_fixed ! fixed ren reference scale
91.118 = muf_ref_fixed ! fixed fact reference scale
-1 = dynamical_
! dynamical choices. Can be a list; scale choices beyond the
! first are included via reweighting
1.0 = mur_over_ref ! ratio of current muR over reference muR
1.0 = muf_over_ref ! ratio of current muF over reference muF
#******
# Reweight variables for scale dependence and PDF uncertainty *
#******
1.0, 2.0, 0.5 = rw_rscale ! muR factors to be included by reweighting
1.0, 2.0, 0.5 = rw_fscale ! muF factors to be included by reweighting
True = reweight_scale ! Reweight to get scale variation using the
! rw_rscale and rw_fscale factors. Should be a list of
! booleans of equal length to dynamical_
! specify for which choice to include scale dependence.
False = reweight_pdf ! Reweight to get PDF uncertainty. Should be a
! list booleans of equal length to lhaid to specify for
! which PDF set to include the uncertainties.
#******
# Store reweight information in the LHE file for off-line model- *
# parameter reweighting at NLO+PS accuracy *
#******
False = store_rwgt_info ! Store info for reweighting in LHE file
#******
# ickkw parameter: *
# 0: No merging *
# 3: FxFx Merging - WARNING! Applies merging only at the hard-event *
# level. After showering an MLM-type merging should be applied as *
# well. See http://
# 4: UNLOPS merging (with pythia8 only). No interface from within *
# MG5_aMC available, but available in Pythia8. *
# -1: NNLL+NLO jet-veto computation. See arxiv:1412.8408 [hep-ph]. *
#******
0 = ickkw
#******
#
#******
# BW cutoff (M+/-bwcutoff*
# written in the LHE event file *
#******
15.0 = bwcutoff
#******
# Cuts on the jets. Jet clustering is performed by FastJet. *
# - If gamma_is_j, photons are also clustered *
# - When matching to a parton shower, these generation cuts should be *
# considerably softer than the analysis cuts. *
# - More specific cuts can be specified in SubProcesses/cuts.f *
#******
1.0 = jetalgo ! FastJet jet algorithm (1=kT, 0=C/A, -1=anti-kT)
0.7 = jetradius ! The radius parameter for the jet algorithm
5.0 = ptj ! Min jet transverse momentum
-1.0 = etaj ! Max jet abs(pseudo-rap) (a value .lt.0 means no cut)
True = gamma_is_j ! Wether to cluster photons as jets or not
#******
# Cuts on the charged leptons (e+, e-, mu+, mu-, tau+ and tau-) *
# More specific cuts can be specified in SubProcesses/cuts.f *
#******
26.0 = ptl ! Min lepton transverse momentum
2.4 = etal ! Max lepton abs(pseudo-rap) (a value .lt.0 means no cut)
0.0 = drll ! Min distance between opposite sign lepton pairs
0.0 = drll_sf ! Min distance between opp. sign same-flavor lepton pairs
0.0 = mll ! Min inv. mass of all opposite sign lepton pairs
30.0 = mll_sf ! Min inv. mass of all opp. sign same-flavor lepton pairs
#******
# Fermion-photon recombination parameters *
# If Rphreco=0, no recombination is performed *
#******
0.1 = rphreco ! Minimum fermion-photon distance for recombination
-1.0 = etaphreco ! Maximum abs(pseudo-rap) for photons to be recombined (a value .lt.0 means no cut)
True = lepphreco ! Recombine photons and leptons together
True = quarkphreco ! Recombine photons and quarks together
#******
# Photon-isolation cuts, according to hep-ph/9801442 *
# Not applied if gamma_is_j *
# When ptgmin=0, all the other parameters are ignored *
# More specific cuts can be specified in SubProcesses/cuts.f *
#******
20.0 = ptgmin ! Min photon transverse momentum
-1.0 = etagamma ! Max photon abs(pseudo-rap)
0.4 = r0gamma ! Radius of isolation code
1.0 = xn ! n parameter of eq.(3.4) in hep-ph/9801442
1.0 = epsgamma ! epsilon_gamma parameter of eq.(3.4) in hep-ph/9801442
True = isoem ! isolate photons from EM energy (photons and leptons)
#******
# Cuts associated to MASSIVE particles identified by their PDG codes. *
# All cuts are applied to both particles and anti-particles, so use *
# POSITIVE PDG CODES only. Example of the syntax is {6 : 100} or *
# {6:100, 25:200} for multiple particles *
#******
{} = pt_min_pdg ! Min pT for a massive particle
{} = pt_max_pdg ! Max pT for a massive particle
{} = mxx_min_pdg ! inv. mass for any pair of (anti)particles
#******
# Use PineAPPL to generate PDF-independent fast-interpolation grid *
# (https:/
#******
False = pineappl ! PineAPPL switch
regard
Muhammad Irfan
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