Data from NOMAD
July 16, 1999
NOMAD was run - first filled with LST - then with H2O. As the data
will show, there is a difference. To understand this, we considered
the effect of the transmission of LST, water and plexiglass as a
function of wavelenth, the Q. E. of the RCA 8575 and the Cerenkov
spectrum for a beta =1 non-showering straight-through muon. We assume
n = 1.6 for LST. The PMT's are coupled to plexiglass cookies which
then couple to the liquid. The transmission curves, Q. E. and
Cerenkov spectra for LST and water are shown below. The Cerenkov
yield is in arbitrary units. The resulting yield, integrated to give
a ratio of light yield of H2O relative to LST of 1.7. Note - this
calculation ignores any geometry effects of light collection in the
liquid - plexiglass - PMT system. Note that if we assume for LST, n =
1.6, the ratio of yields becomes 1.9.
Next we looked at the ADC spectra for Phototube #6 for the LST and
H2O runs. The spectra were fitted with a Gaussian to find the mean
and sigma. The relative p.e. yield was estimated by comparing:
for H2O and LST. The result is:
So we are underestimating the ratio of H2O/LST by a factor of 2.4
if we assume that n = 1.6 and by 2.1 if n = 1.5. That would suggest
that geometrical effects at the liquid/plexiglass/PMT interfaces are
important - and that is what Dave Blair is now working on.
Plots:
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