Least Squares fits to K+ ->  mu+ nu
-----------------------------------

These are least squares fits subject to the constraint
that the DCA is zero.
The fits were made using Blobel's APLCON for 4 parameters
subject to 1 constraint.
The fit parameters were px and py for the K+ and mu+.

The object was to check if the fit improved the 
missing mass distribution.

Fig. 1  6 plots  

Plot 1 shows the fitted (red)  and unfitted (black) missing mass distributions.
Evidently the fit does not improve the missing mass distribution.

Plot2 shows the pull distribution together with a fitted gaussian distribution 
plus the chi**2 p-value  distribution.  The pull distribution is approximately gaussian with sd 
close to unity, but the distribution is slightly  leptokurtic.  The p-value distribution
is close to flat.

Plot 3 shows the chi**2 distribution with mean ~ 1.0 as would be expected
for a one-constraint fit. The distribution has  the long tail expected
for non-gaussian errors.

Plots 4,5  explore the effect of cuts on probability, cda and chisq 
on the missing mass distribution.  None are effective in removing the tails
of the distribution. 

For completeness, Plot 6 shows the unfitted  cda distribution.