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g4sbs

Seamus Riordan
riordan@jlab.org
July 31, 2013

Build using the standard cmake facilities. CTEQ tables built in automatically for DIS
If you would like to get on a mail notification list, contact Seamus (riordan@jlab.org)

*IF YOU ARE DOING DEVELOPMENT, PLEASE DO NOT WORK IN THE master BRANCH*

You need the BigBite field map for this as well, which can be found

http://hallaweb.jlab.org/12GeV/SuperBigBite/downloads/map_696A.dat

To build:

mkdir build
cd build
cmake ../g4sbs  
#  see below if you get an error about old versions
make

To run:

./g4sbs run_example.mac

run_example.mac demonstrates most of the features by example


# NOTE:  On the JLab farm, a newer version of cmake is available
# So, if it complains about being too old, try:
/apps/cmake/bin/cmake ../g4sbs

#########################################################

Coordinate systems in hall:

+z is down the nominal beam axis
+y is "up" (away from gravity)
+x makes a right handed coordinate system

Coordinate systems for detectors:

+z is nominally down the "central axis" in the particle direction

+x is "down" (into the floor)

+y makes a right handed coordinate system

#########################################################

Hits in the GEM chambers have tracking performed on them doing
straight line fits with resolutions.

At the moment tracking is done in a very dumb way for simplicity!  
It will end up averaging all the hits together if there is more 
than one track.  It would be wise to ensure that tr.nhit <= 4

ROOT file output structure:

-----------------------------------------------
ev.*
count	Counts given the beam time/luminosity
rate	Counts per second given luminosity
solang	Integrating over this variable will give solid angle 
sigma	Cross section [cm^-2]
W2	Invariant mass squared [GeV^2]
xbj	Bjorken-x
Q2	Q2 [GeV^2]
th	Polar angle of electron with zaxis [rad]
ph	Azimuthal angle of electron with zaxis [rad]
Aperp	perp component of asymmetry
Apar 	parallel component of asymmetry
vx,y,z	Vertex position [cm]
ep	Scattered electron momentum [GeV]
np	Scattered nucleon momentum [GeV]
epx,y,z Lab components of electron momentum  [GeV]
npx,y,z Lab components of nucleon momentum  [GeV]
nth 	Polar angle of nucleon wrt z-axis [rad]
nph     Azimuthal angle of nucleon wrt z-axis [rad]
pmperp	Missing momentum perp-component [GeV]
pmpar 	Missing momentum par-component [GeV]
nucl	Nucleon when scattering type, 0 for neutron, 1 for proton
fnucl	Final nucleon type (pion prod may change flavor), 0 for neutron, 1 for proton

-----------------------------------------------
tr.*
x	Track x coordinate intercept with z= 0 plane [m]
y	Track y coordinate intercept with z= 0 plane [m]
xp	Track dx/dz
yp	Track dy/dz
tx,ty,typ,txp
	"True" track variables defined by track projection at first chamber
hcal	0 if no hit in HCAL,  1 if hit
bb	0 if no hit in BB cal, 1 if hit
gemtr	0 if no track found in GEMs, 1 if track found
hcx	HCAL x hit position [cm]
hcy	HCAL y hit position [cm]
bcx	BB cal x hit position [cm]
bcy	BB cal y hit position [cm]
hct	HCAL time-of-flight [ns]
hctex	HCAL expected time-of-flight from momentum-transfer [ns]
hclx,y,z
	HCAL hit position in lab coordinates [cm]
hcdang	HCAL angular difference between q and nucleon p [rad]

-----------------------------------------------
gen.*
thbb	BigBite angle [rad]
thhcal	HCAL angle [rad]
dbb	BigBite distance from target [m]
dhc	HCAL distance from target [m]
Ebeam	Beam energy [GeV]

-----------------------------------------------
ht.*
ndata	Number of hits in ht.* array
gid	GEM ID (counting starts at 1)
x,y,z	GEM hit position (incl. resolution effects) [m]
dx,dy	dx/dz and dy/dz of track at hit
tx,ty	"True" GEM hit position (perfect resolution) [m]



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