Pulse Shape Analysis with scintillating bolometers

TL;DR

This paper explores pulse shape analysis in scintillating bolometers to identify interacting particles, potentially simplifying detector design for rare event searches like neutrinoless double beta decay.

Contribution

It demonstrates the feasibility of particle identification through pulse shape analysis in macro-bolometers using scintillating crystals, reducing the need for double read-out systems.

Findings

Pulse shape analysis can distinguish between electrons, gamma rays, and alpha particles.

Results obtained with CaMoO4 crystal bolometers show promising particle identification.

The behavior is explained by energy partitioning between heat and scintillation channels.

Abstract

Among the detectors used for rare event searches, such as neutrinoless Double Beta Decay (0$\nu$DBD) and Dark Matter experiments, bolometers are very promising because of their favorable properties (excellent energy resolution, high detector efficiency, a wide choice of different materials used as absorber, ...). However, up to now, the actual interesting possibility to identify the interacting particle, and thus to greatly reduce the background, can be fulfilled only with a double read-out (i.e. the simultaneous and independent read out of heat and scintillation light or heat and ionization). This double read-out could greatly complicate the assembly of a huge, multi-detector array, such as CUORE and EURECA. The possibility to recognize the interacting particle through the shape of the thermal pulse is then clearly a very interesting opportunity. While detailed analyses of the signal time development in purely thermal detectors have not produced so far interesting results, similar analyses on macro-bolometers ($\sim$10-500 g) built with scintillating crystals showed that it is possible to distinguish between an electron or $\gamma$-ray and an $\alpha$ particle interaction (i.e. the main source of background for 0$\nu$DBD experiments based on the bolometric technique). Results on pulse shape analysis of a CaMoO$_4$ crystal operated as bolometer is reported as an example. An explanation of this behavior, based on the energy partition in the heat and scintillation channels, is also presented.