Sergio J. Sciutto
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c
c Routine directly callable from C/C++ (it could be necessary to
c append an underscore, "_", to its name depending on the C/C++
c compiler used).
c
c
subroutine fitghf(bodata0, eodata0, depths, nallch, weights, ws,
+ minnmax, nminratio, bodataeff, eodataeff,
+ nmax, xmax, x0, lambda, sqsum, irc)
c
c Evaluating the shower maximum parameters (Nmax, Xmax, X0, lambda)
C via a four parameter fit of the available shower data to the
c Gaisser-Hillas function for the profile of charged particles
c (T. K. Gaisser and A. M. Hillas, in Proc. 15th ICRC (Plovdiv),
c vol. 8, p. 353 (1977)):
c
c (Xmax - X0)
c -----------
c / X - X0 \ lambda / Xmax - X \
c Nch(X) = Nmax | ----------| exp | -------- |
c \ Xmax - X0 / \ lambda /
c
c Where:
c
c Nch(X) is the number of charged particles at depth X (in g/cm2).
c Nmax is the maximum number of particles, Xmax is the depth of the
c maximum, X0 and lambda are additional varying parameters.
c
c Nch(X) is zero for X <= X0.
c
c Written by: S. J. Sciutto, La Plata 1997, 1998; Fermilab 1999;
c La Plata 1999, 2000; Fermilab 2003;
c La Plata 2004, 2006.
c
c
c Arguments:
c =========
c
c bodata0, eodata0 (input, integer) Positive integer parameters
c defining the number of data points to use
c in the fit.
c depths.......... (input, double precision, array(eodata0)) Depths
c of the observing levels used in the fit. Only
c the range (bodata0:eodata0) is used.
c nallch.......... (input, double precision, array(eodata0)) Number
c of charged particles crossing the different
c levels. Only the range (bodata0:eodata0) is
c used.
c weights......... (input, double precision, array(eodata0))
c Positive weights to be assigned to each one of
c the data points. Only the range
c (bodata0:eodata0) is used.
c ws.............. (input, integer) If ws = 2, the weights are
c evaluated internally (proportionally to the
c square root of the number of particles).
c If ws = 1 they must be provided as input data.
c If ws = 2 the array "weights" is not used.
c minnmax......... (input, double precision) Threshold value for
c the maximum number of particles in the input
c data set. The fit is not performed if the
c maximum number of particles is below this
c parameter. If minnmax is negative, it is
c taken as zero.
c nminratio....... (input, double precision) Positive parameter
c used to determine the end of the data set.
c Must be equal or greater than 5. Once the
c maximum of the data set is found. the points
c located after this maximum up to the point
c where the number of charged particles is less
c than the maximum divided nminratio. The
c remaining part of the data is not taken into
c account in the fit. A similar analysis is
c performed with the points located before the
c maximum. The recommended value is 100. A very
c large value will enforce inclusion of all the
c data set.
c bodataeff,
c eodataeff....... (output, integer) The actual range of data
c points used in the fit.
c nmax............ (output, double precision) Estimated number of
c charged particles at the shower maximum. If no
c fit was possible, then the value coming from a
c direct estimation from the MC data is returned.
c xmax............ (output, double precision) Fitted position of
c the shower maximum (g/cm2). If no fit was
c possible, then the value coming from a direct
c estimation from the MC data is returned.
c x0.............. (output, double precision) Fitted position of
c the point where the GH function is zero.
c lambda.......... (output, double precision) Fitted parameter
c lambda.
c sqsum........... (output, double precision) The resulting
c normalized sum of squares:
c
c 2
c 1 N [Nch(i) - GH(i)]
c sqsum = ---------- SUM -------------------
c N * Nmax i=1 GH(i)
c
c (N is the number of points used in the fit).
c irc............. (output, integer) Return code. Zero means that
c the fit was successfully completed.
c
c
c<--->
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