Experimental Tests of Baryon and Lepton Number Conservation

Baryon number ($B$) conservation underlies the apparent stability of ordinary matter by forbidding the decay of nucleons, while lepton number ($L$) conservation plays a central role in the structure of lepton interactions and the possible origin of neutrino mass. In the Standard Model, $B$ and $L$ are accidental global symmetries rather than imposed fundamental principles. However, they are expected to be violated in many extensions of the theory, including frameworks of unification and processes in the early Universe. This review summarizes the status of experimental tests of $B$ and $L$ conservation and discusses them within a unified framework for interpreting current and future searches across different processes and experimental approaches, outlining historical and theoretical motivation, key physical processes, as well as their broader connections and complementarity to other searches.