baryonlepton

Baryonlepton is not a standard, independently defined particle or quantum number in the core of the Standard Model. In physics literature, the term is sometimes used informally to refer to a unified description of baryon number B and lepton number L, or more specifically to the symmetry associated with the combination B−L. In this usage, baryonlepton serves as a framework to track how baryons and leptons behave together in interactions, rather than indicating a new particle.

In the Standard Model, B and L are approximately conserved at the perturbative level, but nonperturbative processes known as sphalerons violate B+L while preserving B−L. This makes B−L a more robust quantity within the Standard Model’s electroweak sector. The idea of a fundamental B−L symmetry is common in many beyond-Standard-Model theories, where it may be gauged and accompanied by a new gauge boson (often called Z′) and additional fermions such as right-handed neutrinos.

Breaking of B−L can have important phenomenological consequences. In seesaw mechanisms, for example, the generation of small neutrino masses can be tied to the breaking of B−L. B−L-violating processes are also a focus of cosmological models of baryogenesis and leptogenesis, which seek to explain the observed matter–antimatter asymmetry of the universe.

Overall, baryonlepton is best understood as a descriptive term for the interplay between baryon and lepton numbers, and for the role of B−L in theories beyond the Standard Model. There is no widely recognized separate particle or conserved quantity by that exact name in established physics.