Measurement of $\beta \beta$ Decay-Simulating Events in Nuclear Emulsion with Molybdenum Filling

Abstract

The measurement of positron--nucleus collisions was used to estimate the possibility of suppressing background events that simulate $\beta \beta$ decay in the emulsion region adjacent to molybdenum conglomerates. The range of the escape of two relativistic particles from the interaction was found to be $<d>=(0.60\pm 0.03)\mu$m, which approximately corresponds to the grain size of developed nuclear emulsion. No correlation of the values of d with the angle between two relativistic particles was observed. It was shown that it was possible to exclude $\beta \beta$ decay background from electrons emerging in the decay of elements of naturally occurring radioactive chains. The background from $\beta$ decays of ${}^{90}$Sr and ${}^{40}$K available in emulsion around Mo conglomerates was determined by the ratio of the volume $(\sim d^3)$ to the total volume of emulsion and was found to be $1.5\cdot 10^{-2}$. It was shown that the backgrounds from ${}^{40}$K, ${}^{90}$Sr and natural radioactivity could be significantly suppressed and would not limit the sensitivity of the experiment with 1 kg ${}^{100}$Mo.

6 pages, 4 figures