Direct detection of dark matter through electronic recoil: theory and simulations

In this master thesis project, we focus on developing the phenomenology of electronic recoils induced by dark matter (DM) scattering in direct detection experiments within the MadDM package, which is so far capable of computing nuclear recoils for generic DM models. We consider a specific class of electronic recoils, namely ionization signals, that arise in dual-phase liquid/gas detectors like XENON1T. We implement the dominant interaction term of electronic recoil rate for spin 0 and spin 1/2 DM particles. There are several building blocks needed to achieve the automatic computation of the scattering rate. The first step is the computation of the scattering matrix element square: it requires the building of simplified DM electron models as well as models with four-fermion interactions in FeynRules and the generation of UFO files for all models, as MadDM takes those as input files. At the MadDM level, these files are then read to generate the elastic scattering amplitudes for the simplified and effective models and take the interference term in such a way to single out the dominant DM-electron scattering term. The second step is to embed the electron, which is supposed to be free in the previous calculation, into the atom: this is achieved by encoding the ionization form factor for the xenon atom. Finally, the expected rate in the XENON10 and XENON1T detectors can be computed by encoding their likelihood. The user is able to compute the expected DM electron rate for his/her favourite model and set automatically bounds on light DM from direct detection searches. We proceed further on this thesis by categorizing and implementing all possible dominant terms describing the scattering of a DM particle of spin 0 or 1/2 and an electron. We conclude by describing a scalar dark QED model, and we make constraints on its parameters computing the relic density using the new MadDM extension