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I have been investigating the problem of neutral candidates that originate
from tracks to whom they should be matched but are not.
Two variables are used to quantify the distance between a neutral cluster
and a tracks: dph and dth, the difference between the phi(theta) of the
track extrapolated to the EMC and the cluster centroid one.

The scatter plot of the two (zoomed around (0,0)) is shown in
http://www.slac.stanford.edu/~rfaccini/phys/vub/aug02/dthdph.eps

You can see that random track-photon associations would show a depletion
around (0,0) , but close to the origin there is a bump.
This can be better seen in
http://www.slac.stanford.edu/~rfaccini/phys/vub/aug02/dph-dth32-dtmc.eps
where dph is shown for -0.03<dth<0.02 rad (top: cocktail, bott: data)
and in
http://www.slac.stanford.edu/~rfaccini/phys/vub/aug02/dth-dph44-dtmc.eps
where dth is shown for |dph|<0.04 rad

There is clear evidence of unmatched neutral candidates. The data seem to
be reasonably reproduced by MC, but it is probably adviceable to remove
them.

In conclusion,I would suggest we throw away neutral candidates if
there exists a track in the event with
	|dph|<0.04  -0.03<dth<0.02  rad

	ciao
	ric