HOWTO Use genr8
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genr8 uses a simple t-channel model for generating meson-baryon qausi-two-body production where the meson and baryon can decay via sequential two-body processes. The t-slope parameter and all the particles involved in the production and decay are specified in an input text file. Here is a sample input file for a fixed photon beam energy of 9 GeV and a t-slope parameter of 5 GeV-2:
%%%%%%%%%%%%%%%%% Start Input Values %%%%%%%%%%%%%%%%%%%% % beamp.x beamp.y beamp.z beamMass 0 0 9 0 % targetp.x targetp.y targetp.z targetMass 0 0 0 0.938 % t-channelSlope 5.0 % number of particles needed to describe the isobar decay of X 4 % % particle# 0&1 are always the X&Y %part# chld1# chld2# parent# Id nchild mass width charge flag % baryon (Y) decay 0 * * * 14 0 0.938 0.0 +1 11 % meson (X) decay 1 2 3 * 0 2 0.77 0.150 0 00 2 * * 1 9 0 0.140 0 -1 11 3 * * 1 8 0 0.140 0 +1 11 !EOI %%%%%%%%%%%%%%%%%%%%% End Input Values %%%%%%%%%%%%%%%%%%%%%%% % for narrow widths particles(stable to strong interactions) % set width to zero (i.e. eta, pi's). % %flag 00 =isobar or resonance %flag 01 = production particle that decays i.e. eta, pizero .. %flag 11 = production particle that does not decay i.e. piplus,... %flag 10 = final state particle not in production i.e. gamma %
genr8 creates a text file containing the four-vectors for each particle in each event.
genr8 usage: [-A<name>] < infile -d debug flag -n Use a particle name and not its ID number (ascii only) -M<max> Process first max events -l<lfevents> Determine the lorentz factor with this many number of events (default is 10000) -r<runNo> default runNo is 9000. -P save flag= 11 & 01 events(default saves 11 & 10 events) -A<filename> Save in ascii format. -s<seed> Set random number seed to <seed>. (default is to set using current time + pid) -h Print this help message
To convert the text file to hddm format, run genr8_2_hddm.
Usage: genr8_2_hddm [options] file.ascii Convert an ascii file of events generated by genr8 into HDDM for use as input to hdgeant. options: -r# Set the run number (overiding what's in input file) -V"x y z_min z_max" set the vertex for the interaction. (default: x=0 y=0 z_min=65 z_max=65) -b"beam_particle_name" set the beam particle type [gamma]. -t"target_particle_name" set the target particle type [proton]. -P# Set the incident particle momentum in GeV. (default: calculate from momentum of final state particles.) -s# Set the momentum resolution of the beam in MeV. [5MeV]. (Only used if -P option is present.) -h print this usage statement.