Protontien

Protontien is a hypothetical elementary particle proposed in certain extensions to the Standard Model as a mediator of a new short-range force among baryons. The name suggests its baryonic origin, combining proton with a suffix used for speculative particles. In typical theoretical setups, protontien is a neutral spin-1 gauge boson that couples to baryon number with a coupling strength g_B and has a mass m_PT that can span a range from well below 1 MeV to a few hundred MeV depending on the model. Its interactions are assumed to be short-range, distinguishing it from the longer-range pion-mediated force, and it may couple to protons and neutrons with similar strength. If m_PT exceeds twice the electron mass, the protontien can decay to electron-positron pairs; lighter versions may be effectively stable on experimental timescales or decay invisibly into dark-sector particles.

Theoretical motivations include addressing tensions in nuclear force modeling, providing a portal to dark matter, or illustrating how baryon-number related gauge symmetries could manifest at low energies. Protontien can arise in models with an extra U(1) gauge symmetry linked to baryon number or in composite theories featuring a protobaryonic bound state.

Experimental status remains unsettled, with no confirmed detection. Bounds are derived from precision nucleon-nucleon scattering data, nuclear binding energies, meson decays, stellar cooling limits, and collider searches, all of which constrain the allowed mass and coupling ranges. Ongoing and planned experiments in fixed-target facilities and low-energy colliders continue to search for signals of protontien or constrain its parameter space.

See also: Z' boson, dark photon, baryon-number gauge boson.