Omega production at TAPS
The job card explained below is suited to analyze photon production in photon-proton or photon-nucleus reactions. Each fortran namelist given below represents input for one specific module in the code. Note: everything after an exclamation mark (!) is a comment in fortran namelists.
This jobcard can be found in the GiBUU repository as 003_metagExperiment.job
The namelist target controls the target. Do not modify the fermimotion and densitySwitch_Static switches besides for testing.
$target ! Proton: target_Z=1, target_A=1, ! Nb_93 !target_Z=41, !target_A=93, ! Calcium_40 !target_Z=20, !target_A=40, fermimotion=.true. densitySwitch_Static=1 !1=wood-saxon, 2=according NPA 554,554 (Oset) $end
Initialization and final Analysis
The next two namelists control the initialization step and the final analysis step:
$low_photo_induced energy_gamma=1.3 delta_energy=0.01 ! Switch for specific initial channels vecmes =.true. resonances=.true. singlePi =.true. pi0eta =.true. twopi =.true. $end $lowPhotonAnalysis ! Analysis flags outputEvents = .true. ! Print events to file outputEvents_onlyFree = .true. ! Prints only "free" nucleons to file (.false.=print all nucleons) photonAnalyse = .true. ! Generate analysis for final state photons ! Switch off unnessary analysis KruscheOutput = .false. fissumOutput = .false. twoPiOutput = .false. $end
These namelists control the general input for each run:
- The variable numEnsembles defines how many ensembles of test-particles are used to model a physical one, so it defines the granularity of our numerical realization. Use numEnsembles=1000...10000 for a real calculation.
- The variables num_runs_SameEnergy and num_Energies define how many subsequent runs are performed.
- Number of time steps:
- For proton targets we use numTimeSteps=0 since there is no transport step necessary
- For nuclear targets, numTimeSteps should be chosen such that delta_T*numTimeSteps>40.
- Please adjust path_to_input to your directory structure.
- The length of the perturbative vector should be adjusted to your needs to save memory.
$input numEnsembles= 1 ! number of ensembles eventtype = 3 ! 3=photon A numTimeSteps= 0 ! number of time steps delta_T = 0.2 ! time step size num_runs_SameEnergy = 1 ! Number of runs with the same energy num_Energies = 1 ! Number of different energies set_length_perturbative=.true. ! Length of particle vector. Must be adjusted to final state particle yield ! Proton length_perturbative =50 ! Calcium !length_perturbative =1000 ! Niob !length_perturbative =3000 path_to_input='/home/hadron/oliver/buuinput_metag' ! Path to input directory fullensemble =.false. FinalCoulombCorrection =.false. PrintParticleVectors=.false. $end
$initDensity densitySwitch=2 !1=dynamic density according to testparticle density, 2=analytic density prescription splineExtraPolation=.true. !Switch for linear spline extrapolation for dynamically calculated density: Extrapolates density between $end $initPauli pauliSwitch=2 !1=dynamic, 2=analytic $end $propagation delta_P =0.01 ! Delta Momentum for derivatives coulomb =.true. ! Whether to use coulomb in propagation hadronic =.true. ! Whether to use hadronic potentials in propagation DerivativeType =1 ! 1=first order Range-Kutta, 2=second order Range-Kutta predictorCorrector=.true. ! Whether to use a predictor/corrector algorithm to do the propagation $end
Input for potentials
Influences the hadronic potentials. In the scenario below we use no potential for the mesons and our standard Skyrme-type potential for the baryons.
$Coulomb CoulombFlag=.false. $end $mesonPotential pionPot_Switch=0 ! Switch for pionPotential ! 1=Oset potential (NPA 554), which is valid up to 50Mev kinetic energy ! 2=Kapusta suggestion for pion potential (rather unusual) ! 3=Delta Hole potential, which is valid up to 130 MeV kinetic energy ! 4=Smooth spline transition between switch 1 and 3. ! else=no pion potential $end $baryonPotential EQS_Type=5, ! Switch for equation of state for nucleon resonances spin=1/2 ! Parameters for nucleon potentials: ! 1=soft mom-dep lambda = 2.130 ! 2=hard mom-dep lambda = 2.126 ! 3=soft non-mom-dep ! 4=hard non-mom-dep ! 5=medium mom-dep DeltaPot=1, ! Switch for potential of spin=3/2 resonances ! 1=nucleon (spin=1/2) potential times 3/5 [according to ericson/Weise book] ! 2= 100 MeV *rho/rhoNull $end
The collision term
Here one can modify the collision term, e.g. by switching off three-body interactions. The scenario below is standard, so don't modify besides for testing. Note that the parameter minimumEnergy =0.005 in the namelist insertion removes all final state nucleons which have kinetic energies less than 5 MeV.
$hadronFormation tauForma=0.8 ! formation proper time in restframe of hadron $end $collisionTerm energyCheck =0.01 ! accuracy of energy check in GeV oneBodyProcesses =.true. oneBodyAdditional =.true. twoBodyProcesses =.true. threeBodyProcesses =.true. $end $insertion minimumEnergy =0.005 ! Minimal kinetic energy for a proton propagateNoPhoton =.false. ! Photons are propagated $end $master_2Body baryonBaryonScattering = .true. baryonMesonScattering = .true. mesonMesonScattering = .false. $end $modifyParticles stabilityFlag(101) = 4 ! Let Pi^0 Decay $end $pythia MDCY(102,1)=1 ! KC code of pi0, not KF! !Pi^0 unstable in Pythia $end
The widths of the particles
The scenario below corresponds to a broadening of the Delta, but to no broadening of any other particle. Such a broadening can be included by setting mediumSwitch_coll=.true. in the namelist width_Baryon and/or mediumSwitch=.true. in the namelist width_Meson.
$width_Baryon mediumSwitch =.true. ! Switch on/off in-medium width of all baryons at once -> The vacuum width are used. mediumSwitch_coll =.false. ! Use consistent collisional broadening mediumSwitch_Delta =.true. ! Switch on/off in-medium width of the delta. .false.=vacuum width $end $width_Meson mediumSwitch=.false. ! Switch on/off in-medium width of all mesons at once -> The vacuum width are used. $end
Temperature and thermodynamics
Don't touch this! Otherwise computation time blows up
$initThermoDynamics temperatureSwitch=1 ! 1=groundstate calculations (T=0,mu=E_F) ! 2=the full procedure according to testparticle density (real particles only!) $end