Search for tau decays to the eta meson Page: 4 of 19
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Figure 1: Inclusive distribution of two-photon invariant masses in 1-prong r decays.
Sixes of the expected ij signals for S9b branching ratio of various t decay inodes
are shown by the Bolid curves.
The distribution of the invariant mass or 'n-pairs, AfT11 from the selected
events is plotted in Fig. 1. There is no peak observed at the tj mass. A shape of
the expected rj signal is obtained from the Monte Carlo simulation of various r
decays to rj. It ia represented by a Gaussian, with a width of 26 MeV, modified by
a power-law tail an the low-mass aide. A fit of the rj peak on a smooth polynomial
background gives (-10±23) rj counts. A detection efficiency strongly depends
upon a photon multiplicity in the r decay, decreasing rapidly due to the increased
overlap probability. This is demonstrated in Fig 1 by plotting sizes of the expected
signals for the different r —•») channels, assuming a branching ratio of 5%. Thus,
we present an upper limit for each channel independently,
BR(i--i/7r 77) <0.391 (95^ CL),
BR(f -*vs-'a-'u) <0.991 (959* CL).
BR(t- ir'rr*rj)<3.l9f. (D5l* CL),
BR{r- -t/X fjr?) <2.S9f (9SC{ CL).
In the efficiency calculation, the above decays have been simulated by phase space
models. A systematic uncertainty of 209c in the branching ratio calculations is
folded into the upper limits. The systematic error includes uncertainties in the
number of r leptons produced and in the efficiency calculation. It is dominated
by fluctuations of the Monte Carlo data
Our event sample in the inclusive analysis contains unknown contamination of
the non-r background. A subtraction of the background would only improve the
upper limits, therefore, it is not necessary
The first report on the status of our inr lusive analysis was communicated to the
Berkeley Conference, 1966 10 . A significant •> peak was observed in the inclusive
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Skwarnicki, T. Search for tau decays to the eta meson, article, December 1, 1987; United States. (https://digital.library.unt.edu/ark:/67531/metadc1069638/m1/4/?rotate=90: accessed May 7, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.