8/17/99  J. Seger


The STARlight Monte Carlo models 2-photon interactions in peripheral heavy
ion collisions.  The physics approach is described in STAR Note 243.  The
Monte Carlo has several input parameters which may be specified by the
user; these parameters are read from a file named "starlight.in",
described below. The output of the Monte Carlo is written to an ascii file
named "starlight.out". The format of the output can be chosen so that it
can be read by GSTAR.
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STARlight is linked with one other routine, hencken.f, that calculates the
luminosity function as per K. Hencken.  The data file jet.dat is read by
starlight.f and contains modified branching ratios for jetset.
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The contents of a sample starlight.in file are listed below, with 
explanation.

79	// atomic number of the colliding ions (symmetric 
	collisions are assumed)
179	// atomic mass of the colliding ions
100	// gamma for the colliding ions
4.0	// maximum value for w (w is the gamma-gamma center of mass
	energy, w = 4(E1)(E2)
50	// number of bins for w-integration (used in cross-section
	calculation)
3.0	// maximum value for y (y is the rapidity, y = 0.5 ln(E1/E2) )
30	// number of bins for y-integration (used in cross-section 
	calculation)
10000	// number of events to produce
331	// channel of interest (in jetset notation); currently supported
	options listed below
345738	// random number seed
2	// This line specifies the form of the output.  A 1 here 
	will lead to a text file in an obsolete format.  A 2 here 
	leads to a text file which is readable by gstar.  At this 
	point in time, a 2 will almost always be preferable.  
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Currently supported channel options:
      jetset id		particle
   ---------------------------------
	221		eta			
	331		eta-prime
	441		eta-c
	10221		f0(975)
	225		f2(1270)
	115		a2(1320)
	335		f2(1525)
	33		rho0 pair
	11		e+/e- pair
	13 		mu+/mu- pair
	15		tau+/tau- pair