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Nitrogen contamination
If there was a contamination of heavier elements in the emission layer, the
yield of
would be reduced due to muon transfer from the proton to
the heavy element. In some of the runs, we observed muonic X rays from
muonic nitrogen atomic transitions, indicating contamination of the
target. From the analysis of the Lyman series X rays, the contamination
level was estimated to be a few ppm level by Francoise
Mulhauser [83,231]. In the constant rate, infinite medium
approximation, the probability of
production
can be expressed as:
where c_{N2} is the concentration of N_{2} molecules, and
the muon transfer rate from a proton to a
nitrogen atom. Using the proton to triton transfer rate
s^{1}, and
formation rate
s^{1}, both obtained from our earlier
measurements in solids [83], together with the transfer rate to
nitrogen
s from
Ref. [232] (measured in a gas), we can estimate the reduction
factor for the
production
,
which is normalized to the pure target yield
.
Table 8.12 presents the correction factor for two
series of target sets which are of relevance in our analysis.
Table 8.9:
The
production probability
with possible nitrogen contamination, and the
reduction factor
,
normalized to a pure emission target
.
Target 
ID 
c_{N2} (Ref. [231]) 


SETc_{t}=0.1% (a) 
II1 to II4 
3.3^{+6.8}_{3.3} ppm 
0.621^{+0.14}_{0.28} 

SETc_{t}=0.1% (b) 
II6 to II11 
2.3^{+4.6}_{2.3} ppm 
0.611^{+0.11}_{0.23} 


We note that the estimate of nitrogen contamination by Mulhauser gives
asymmetric errors as quoted in the table, but we take the average of two
extreme values of 1
error bars for convenience in the data
treatment. In our analysis, we assume that reduction in
emission is
proportional to the factor
given here, neglecting the effects
of the
transfer, which is presumably much
smaller.
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