CERN Accelerating science

\small A \bbonu\ event (left) and a single electron background event from a 2.44~MeV \BI\ gamma (right) in Monte Carlo simulation (both events simulated at 15~bar gas pressure).

\small A \bbonu\ event (left) and a single electron background event from a 2.44~MeV \BI\ gamma (right) in Monte Carlo simulation (both events simulated at 15~bar gas pressure).

\small Distribution of the energy deposition in the two blob candidates of a track, for Monte Carlo \bbonu\ (left) and \TL\ (right) events, simulated in the NEXT final detector \cite{bckgrmodel}. Blob candidates are defined as the sum of all charge within a 2~cm radius of each end-point of the tracks.

\small Distribution of the energy deposition in the two blob candidates of a track, for Monte Carlo \bbonu\ (left) and \TL\ (right) events, simulated in the NEXT final detector \cite{bckgrmodel}. Blob candidates are defined as the sum of all charge within a 2~cm radius of each end-point of the tracks.

\small Tracking plane signals for two arbitrary pulse slices, as an illustration of the hit-finder algorithm. (Left) A slice with clear signal, (right) a slice that does not pass the minimum energy cut (see text for more details).

\small Tracking plane signals for two arbitrary pulse slices, as an illustration of the hit-finder algorithm. (Left) A slice with clear signal, (right) a slice that does not pass the minimum energy cut (see text for more details).

\small Energy spectra for the \NA\ source (left) and the \THO\ source (right), for those events passing the selection criteria described in the text.

\small Energy spectra for the \NA\ source (left) and the \THO\ source (right), for those events passing the selection criteria described in the text.

\small Energy distribution at the end-points of the tracks coming from \NA\ decay (left) and those coming from the $^{228}$Th decay (right) for 2~cm radius blob candidates.

\small Energy distribution at the end-points of the tracks coming from \NA\ decay (left) and those coming from the $^{228}$Th decay (right) for 2~cm radius blob candidates.

\small Example of a \NA\ gamma track. The $zx$ and $zy$ projections (on top) and the $yx$ projection in the lower frame are drawn. The energy scale is in keV (color coded) and the longitudes are in mm. The single electron candidate exhibits one blob at one end of the track.

\small Example of a double escape peak candidate from the \THO\ data sample. The $zx$ and $zy$ projections (on top) and the $yx$ projection in the lower frame are drawn. The energy scale is in keV (color coded) and the longitudes are in mm. The double electron candidate exhibits two blobs, one at each end of the track.

\small Left: proportion of events with blob candidate overlapping, as a function of the blob candidate radius. Right: the figure of merit, $\epsilon/\sqrt{b}$ as a function of the blob candidate radius and the minimum blob candidate energy.

\small Left: proportion of events with blob candidate overlapping, as a function of the blob candidate radius. Right: the figure of merit, $\epsilon/\sqrt{b}$ as a function of the blob candidate radius and the minimum blob candidate energy.

\small Two-blob cut efficiency for the Monte Carlo \NA\ (left) and \THO\ (right) samples.

\small Two-blob cut efficiency for the Monte Carlo \NA\ (left) and \THO\ (right) samples.

\small Two-blob cut efficiency for the Monte Carlo \THO\ sample, selecting events with pair production only (left) and events without pair production (right).

\small Two-blob cut efficiency for the Monte Carlo \THO\ sample, selecting events with pair production only (left) and events without pair production (right).

\small Comparison between data and Monte Carlo simulations, for the reconstructed length of the tracks (left) and the reconstructed energy inside the blob candidate with higher energy (right). \NA\ samples are used.

\small Comparison between data and Monte Carlo simulations, for the reconstructed length of the tracks (left) and the reconstructed energy inside the blob candidate with higher energy (right). \NA\ samples are used.