Optimisation of amplification and gas mixture for directional Dark Matter searches with the CYGNO/INITIUM project

Astrophysical and cosmological observations suggest the existence of beyond standard model ingredient known as dark matter (DM). One of the most supported class of theories suggests that DM is composed of weakly interactive massive particles (WIMPs), possibly detectable via weak interaction with standard matter resulting in the recoil of the latter. The motion of the Sun and Earth with respect to the Galactic Centre is expected to induce a strong directional dependence in the recoil spectrum. Direct detection experiments capable of measuring the angular features of the recoils gain access to a wide range of advantages such as the possibility to positively claim a discovery of DM. The CYGNO project sets into this context, with the aim of deploying a large directional detector for rare event searches as DM. It exploits a gaseous time projection chamber filled with a He:CF4 gas mixture with a segmented amplification stage and granular optical readout. In this thesis, it is presented the work carried out with small CYGNO prototypes to maximise the light yield without degrading spatial and energy resolution, the addition of highly electronegative gases to induce a reduction of the electron cloud diffusion while drifting towards the amplification stage, very relevant to precisely measure the topological information of the recoil tracks. Moreover, the potential performances of directional detectors in the context of a direct DM search are analysed with the use of rigorous statistical tools both in the improvement in setting limits in the WIMP to nucleon sensitivity and in the capability of discerning two different DM models exploiting a directional detector.