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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

Target definition

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

General Input

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

Numerical details

Don't touch!

$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
Last modified 17 months ago Last modified on Jun 24, 2018, 11:14:00 AM