Neutrinoless double beta decay experiment

The search for neutrinoless double beta decay ($0νββ$) is one of the key experiments for determining unresolved properties of neutrinos. Experimental observation of $0νββ$ would provide a clear demonstration of the Majorana nature of neutrinos and a lepton number violating process in particle physics. This report is a brief review describing the $0νββ$ process and its significance. The detector technologies used in the present and proposed $0νββ$ experiments are compared among their recent experimental results. Moreover, the sensitivities for $0νββ$ discovery in a number of present and proposed $0νββ$ experiments are introduced.