The fine print: can data from different channels be compared?

Coincidence rates between two tubes, one in each bin - or all in a row - that we interpret as due to the passage of a secondary cosmic ray particle (1) cannot be directly compared because of the geometrical configuration of the detector, with adjacent tubes separated both horizontally and vertically by 15.6 mm.

Indeed, when considering 0° ("vertical") and "slant" matches, it must be taken into account that the distances between the tubes are not the same in both cases: tubes that are vertical are separated by a smaller distance, and will therefore accept cosmic rays from a wider cone than those defining slant directions (the difference being greater the larger the angle). The "geometric acceptances" of the different pairs of tubes are then said to be different, as shown in the figure below.

_{Fig. C2-1 The cones in which different pairs of tubes accept coincidences have different apertures, with those of the tubes that are closest to each other always being greater.}

The difference is not very large for close tube pairs, but strictly speaking, the different acceptances should be taken into account and a geometrical correction factor should be included, which we are planning to calculate via a simulation.

_{(1) Although it is certain that events due to other causes such as electronic noise or coincidental coincidences produced by one or even two particles (which could also be due to environmental terrestrial radioactivity) will "slip through".}