From the 3 data sample,
events are selected by requiring
that there is no
in the event and that
candidates from 2
pairs are constrained to
of the
mass (0.5
0.6
).
We do not require just the presence of the
because
production
is 50 times larger than
. Without cutting on the
,
the
signal competes with the
combinatoric background.
The invariant mass distribution of 3
is then formed for different
minimum total energy in the LGD. These distributions
for 4 different energy thresholds are shown in Fig. 1,
where one can see how the
peak becomes more prominent when
the total energy threshold is increased.
The number of is found from the fit of these distributions to
3 Gaussians: one corresponding to the residual
peak,
one broad corresponding to the background (BG)
and the third one for the
. To keep the number of parameters small,
the position of the background Gaussian is set to be equal to the position of
the
peak, while the width of the BG is fixed to the
width by
. In addition,
the width of
is kept constant during fitting,
.
Constants a and b are adjusted until good fits with reasonable
looking background is found. Obtained
mass, width and yield for
different energy cuts are given in the Table 1.
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3.5 | 0.931 | 0.065 | 555513.0 | ||||
4.0 | 0.943 | 0.065 | 460076.0 | ||||
4.5 | 0.954 | 0.070 | 228128.0 | ||||
5.0 | 0.967 | 0.075 | 87140.4 |
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