H2 pion fractions
		EJB	March 23, 2000

For the sake of completeness, I took a quick look again at
the pion fractions in the tail of the CTIME spectra for the
H2 pulsecounting data (I don't recall whether anyone did this),
so that we'd have some more up-to-date numbers to compare
to Richard's result for the D2 data.

I used the Sep 98 pulse counting data, and performed a fit like
Richard's 
		P(t) = A + B*exp(-(t-34)/2.2)

to the tail after the main portion of the CTIME spectrum. I did this
for the 5 coincidence runs that were available. I also fit the region
before the beam window just to see if it's the same as the constant
term after the beam window. I define the pion fraction to be the 
fitted value of B divided by the mean # counts per bin in the beam
window region.

The results of the fit are below: for
anyone who wants to look at pictures they can be found at

	www2.physics.umd.edu/~beise/sample/ctime/

run #	 tube #	    pi frac        bkgnd after	    bkgnd before
		     (%)              (%)              (%)
--------------------------------------------------------------
5002      3        3.12 +- 0.28    0.12+-0.03       0.13+-0.45
5028      3        5.6  +- 1.3     1.13+-0.26       1.63+-3.50
5006      5        2.28 +- 0.18    0.24+-0.03       0.12+-0.49
5010      7        4.73 +- 0.89    1.84+-0.20       4.08+-4.80
5004      8        4.18 +- 0.32    0.12+-0.03       0.22+-0.58
5008      9        3.00 +- 0.19    0.17+-0.02       0.25+-0.67

With the exception of tube 7, the backgrounds before and
after are pretty consistent. The values are all in pretty good
agreement, and  consistently higher than the estimate by Bryon (more
consistent with the old Monte Carlo result). His fit was 2.4+-0.4%.

It's interesting to note the increase with decreasing scattering angle.
	 mir#	theta	pifrac
	-----------------------
	  5      161    2.3
	  9      154    3.0
	 3,8     146    (3.1,4.2)
	  7      138    4.7    

Betsy


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 Elizabeth J. Beise               phone: (301)-405-6109
 Dept. of Physics                 FAX:   (301)-405-8558
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