Zero cross sect. with no cuts
Hello,
I am relatively new with MadGraph. I am generating the process
ve e- > ve e- a /z
through a new model created with FeynRules. Since I want to look at low energy neutrinos scattering on electrons at rest, I set the electron energy = 0.511 MeV and I put no cuts on the final energy (run_card below). For neutrino energies below 0.8 MeV, MadGraph always returns me with the zero cross section error message, while it works fine for higher energies. As an example, I tried also the neutral current process ve e- > ve e- (a Z exchange) with electron at rest, same cuts and neutrino with .5 MeV energy, and gives me the same error message.
Am I missing some cuts or something else in the run_card?
Thanks,
Michele
#******
# 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
#******
0 = lpp1 ! beam 1 type
0 = lpp2 ! beam 2 type
5e-4 = ebeam1 ! beam 1 total energy in GeV
5.11e-4 = 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 *
#******
False = fixed_ren_scale ! if .true. use fixed ren scale
False = 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"
#******
#
#******
# handling of the helicities:
# 0: sum over all helicities
# 1: importance sampling over helicities
#******
0 = nhel ! using helicities importance sampling or not.
#******
# 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*
#******
-1.0 = bwcutoff ! (M+/-bwcutoff*
#******
# Standard Cuts *
#******
# Minimum and maximum pt's (for max, -1 means no cut) *
#******
0.0 = pta ! minimum pt for the photons
0.0 = ptl ! minimum pt for the charged leptons
0.0 = misset ! minimum missing Et (sum of neutrino's momenta)
-1.0 = ptamax ! maximum pt for the photons
-1.0 = ptlmax ! maximum pt for the charged leptons
-1.0 = missetmax ! maximum missing Et (sum of neutrino's momenta)
{} = 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) *
#******
-1.0 = etaa ! max rap for the photons
-1.0 = 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 *
#******
0.0 = dral ! min distance between gamma and lepton
-1.0 = dralmax ! maxdistance between gamma and lepton
#******
# Minimum and maximum invariant mass for pairs *
#******
{} = 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 *
#*****
#******
# Inclusive cuts *
#******
#******
# 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'
Question information
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- Solved by:
- Michele Tammaro
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