I am trying to generate p p > j j at fixed order NLO on the parton level. Whenever I do this I produce a negative cross-section; -------------------------------------------------------------- Final results and run summary: Process p p > j j [QCD] Run at p-p collider (7000.0 + 7000.0 GeV) Total cross section: -5.229e+08 +- 3.9e+06 pb -------------------------------------------------------------- Scale variation (computed from histogram information): Dynamical_scale_choice -1 (envelope of 9 values): -5.255e+08 pb +-155.7% --443.3% -------------------------------------------------------------- My Banner text is as follows:

3.5.0.alpha MSbar; 1->DIS ! 2->eta (leptonic); 3->beta (leptonic) ! 4->mixed (leptonic); 6->delta (leptonic) ! if pdlabel==emela, this is set automatically #*********************************************************************** # The following block is specific to lepton collisions (lpp=+-3) * #*********************************************************************** True = photons_from_lepton ! whether to include or not photons from ! lepton ISR #*********************************************************************** # 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!!!! * #*********************************************************************** HERWIG6 = parton_shower 1.0 = shower_scale_factor ! multiply default shower starting ! scale by this factor #*********************************************************************** # 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/set_scales.f or via * # dynamical_scale_choice option) * #*********************************************************************** 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_scale_choice ! Choose one (or more) of the predefined ! 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_scale_choice to ! 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 #*********************************************************************** # Customization of the code. List of files containing user hook function #*********************************************************************** = custom_fcts ! List of files containing user hook function #*********************************************************************** # 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://amcatnlo.cern.ch/FxFx_merging.htm for details. * # 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*Gamma). Determines which resonances are * # 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 with jets. * # Otherwise, they will be treated as tagged particles and photon * # isolation will be applied. Note that photons in the real emission * # will always be clustered with QCD partons. * # - 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 15.0 = ptj ! Min jet transverse momentum -1.0 = etaj ! Max jet abs(pseudo-rap) (a value .lt.0 means no cut) False = 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 * #*********************************************************************** 0.0 = ptl ! Min lepton transverse momentum -1.0 = 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) False = lepphreco ! Recombine photons and leptons together False = 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://zenodo.org/record/3992765#.X2EWy5MzbVo) * #*********************************************************************** False = pineappl ! PineAPPL switch #*********************************************************************** ]]> ###################################################################### ## PARAM_CARD AUTOMATICALY GENERATED BY MG5 #### ###################################################################### ################################### ## 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 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(mz__exp__2/2. + cmath.sqrt(mz__exp__4/4. - (aew*cmath.pi*mz__exp__2)/(gf*sqrt__2))) ################################### ## INFORMATION FOR SMINPUTS ################################### BLOCK SMINPUTS # 1 1.325070e+02 # aewm1 2 1.166390e-05 # gf 3 1.190000e-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 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 ################################### ## INFORMATION FOR QNUMBERS 82 ################################### 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/antiparticle distinction (0=own anti) /FixedOrderAnalysis/ ( is the name of the exported # process directory). See the # /FixedOrderAnalysis/analysis_*_template.f file for details # on how to write your own analysis. # ####################################################################### # # Analysis format. # Can either be 'topdrawer', 'root', 'HwU', 'LHE' or 'none'. # When choosing HwU, it comes with a GnuPlot wrapper. When choosing # topdrawer, the histogramming package 'dbook.f' is included in the # code, while when choosing root the 'rbook_fe8.f' and 'rbook_be8.cc' # are included. If 'none' is chosen, all the other entries below have # to be set empty. FO_ANALYSIS_FORMAT = HwU # # # Needed extra-libraries (FastJet is already linked): FO_EXTRALIBS = # # (Absolute) path to the extra libraries. Directory names should be # separated by white spaces. FO_EXTRAPATHS = # # (Absolute) path to the dirs containing header files needed by the # libraries (e.g. C++ header files): FO_INCLUDEPATHS = # # User's analysis (to be put in the /FixedOrderAnalysis/ # directory). Please use .o as extension and white spaces to separate # files. FO_ANALYSE = analysis_HwU_template.o # # ## When linking with root, the following settings are a working ## example on lxplus (CERN) as of July 2014. When using this, comment ## out the lines above and replace with the physical ## path to root, ## e.g. /afs/cern.ch/sw/lcg/app/releases/ROOT/5.34.11/x86_64-slc6-gcc46-dbg/root/ #FO_ANALYSIS_FORMAT = root #FO_EXTRALIBS = Core Cint Hist Matrix MathCore RIO dl Thread #FO_EXTRAPATHS = /lib #FO_INCLUDEPATHS = /include #FO_ANALYSE = analysis_root_template.o # ADDED MYSELF: FO_LHE_postprocessing = noidentification ]]> order = NLO fixed_order = ON shower = OFF madspin = OFF reweight = OFF madanalysis = OFF runshower = False

Does anyone know why this error occurs?

MadGraph5_aMC@NLO

History of question #705112