NeXus for BRAHMS
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General Information
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The input file
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The output file
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More information
General Information
NEXUS is based upon the hypothesis that the behaviour of high energy interactions
is universal. For example, the parton dynamics in deep inelastic scattering
is based on the same equations as the one in proton-proton interactions,
the fragmentation in electron-positron is treated the same way as in lead-lead
collisions etc. Such a universal approach has the great advantage that
theoretical uncertainties on the level of proton-proton or nucleus-nucleus
scattering can be fixed by studying more elementary systems as electron-positron
annihilation or deep inelastic scattering. It runs of various UNIX-based
computing platforms. Current implementations include GNU G77 (Linux,
AIX). This version has been adapted for BRAHMS_CVS.
This document is an introduction to use of NEXUS in the frame of BRAHMS
Collaborations.
Its purpose is to serve as a short guide to the experienced heavy ion
physicist on how to run the program.
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The input file
The figure shows a typical input-file for Nexus .
Input file is located in $(NEXUS_HOME)/lib and is named "inputfile"
fname histo nexus_auau_03.histo
fname check nexus_auau_03.check
fname data nexus_auau_03.data
fname initl nexus.initl ! DO NOT delete or modify
fname inidi nexus.inidi ! DO NOT delete or modify
fname iniev nexus.iniev ! DO NOT delete or modify
fname inirj nexus.inirj ! DO NOT delete or modify
application hadron
set nevent 100 !number of events
set ecms 200. !energy in CMS
set laproj 79 !charge of projectile
set maproj 197 !mass of projectile
set latarg 79 !charge of target
set matarg 197 !mass of target
set bminim 0.0 !the minum value of impact parameter
set bmaxim 3.0 !impact parameter equal to 3.0 fm
run
stop
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The output file
The output file of NeXus adapted for BRAHMS is the OSC1997A format. It
is named "oscar.dat" .
The file-header look like:
OSC1997A
final_id_p_x
neXus 1.0 (197, 79)+(197, 79) eqsp 2.00E+02 1
The event line lists:
nrevt nptevt b phievt
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nrevt.......... event number
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nptevt ........ number of (stored)
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particles per event
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bimevt ........ absolute value of impact parameter
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phievt ........ angle of impact parameter
The particle line lists:
i idptl pptl(1,i) pptl(2,i) pptl(3,i) pptl(4,i) pptl(5,i) xorptl(1,i) xorptl(2,i) xorptl(3,i) xorptl(4,i)
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i ...................particle number
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idptl(i) ...... .particle id
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pptl(1,i) ..... x-component of particle momentum
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pptl(2,i) ..... y-component of particle momentum
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pptl(3,i) ..... z-component of particle momentum
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pptl(4,i) ..... particle energy
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pptl(5,i) ..... particle mass
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xorptl(1,i) ... x-component of formation point
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xorptl(2,i) ... y-component of formation point
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xorptl(3,i) ... z-component of formation point
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xorptl(4,i) ... formation time
You can select from the next id particle specificatins.
Example:
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particle
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ID
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pi-
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-120
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pi+
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120
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k+
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130
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k-
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-130
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p
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1120
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pbar
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-1120
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n
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1220
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Last updated at: February 4, 2000
Any comments, suggestions please contact
Sorin ZGURA,
e-mail: zis@rcf.rhic.bnl.gov