Top, angular power spectrum as a function of the multipole moment l of observed β events (black points) compared with 104 uniformly distributed events from Monte Carlo simulations at 1σ (dark pink) and 2σ (pink) confidence levels (C.L.). Data are compatible with a uniform distribution within the uncertainty of 0.59 cpd per 100 t. Inset, angular distribution of the β events. Bottom, normalized radial distribution of β events r/r0 (black points), where r0 = 2.5 m is the radius of the sphere surrounding the analysis fiducial volume. The linear fit of the data (red solid line) is shown along with the 1σ (yellow) and 2σ (green) confidence level bands. The data are compatible with a uniform distribution within 0.52 cpd per 100 t.