Search for line-like and box-like features in Galactic gamma-ray spectra as signatures of dark matter using 15+ years of Fermi-LAT data

Dark Matter particles may either self-annihilate or decay, producing detectable Standard Model particles, including gamma rays. These processes could lead to excesses in the gamma-ray energy spectra observed on Earth. In this work we search for these excesses in the MilkyWay in an energy range from 1 GeV to 1 TeV. We developed a maximum likelihood fit procedure in sliding energy windows to search for line-like features (smoking gun signals) as indirect signature of dark matter self-annihilation and decay processes that directly produce gamma rays. We analyzed a dataset collected by the Fermi Large Area Telescope in 185 months using a combined maximum likelihood technique. We selected five regions of interests in the sky to optimize sensitivity for different theoretically motivated dark matter scenarios. We also accounted for systematic uncertainties using the Galactic Plane as a control region. Furthermore, a study is currently ongoing involving the search for possible box-shaped spectral features in the gamma-ray spectra, which could imply a scenario in which DM particles annihilate or decay into long-lived mediators, that in turn decay into final states with gamma rays detectable on Earth. We do not find any significant detections, so we set more stringent upper limits for the DM velocity-averaged annihilation cross section compared to those quoted in literature.