In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are
W⁺
,
W⁻
, and
Z⁰
. The
W^±
 bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles. The
Z⁰
 boson is electrically neutral and is its own antiparticle. The three particles each have a spin of 1. The
W^±
 bosons have a magnetic moment, but the
Z⁰
has none. All three of these particles are very short-lived, with a half-life of about 3×10⁻²⁵ s. Their experimental discovery was pivotal in establishing what is now called the Standard Model of particle physics.

The
W
 bosons are named after the weak force. The physicist Steven Weinberg named the additional particle the "
Z
 particle", and later gave the explanation that it was the last additional particle needed by the model. The
W
 bosons had already been named, and the
Z
 bosons were named for having zero electric charge.

The two
W
 bosons are verified mediators of neutrino absorption and emission. During these processes, the
W^±
 boson charge induces electron or positron emission or absorption, thus causing nuclear transmutation.

The
Z
 boson mediates the transfer of momentum, spin and energy when neutrinos scatter elastically from matter (a process which conserves charge). Such behavior is almost as common as inelastic neutrino interactions and may be observed in bubble chambers upon irradiation with neutrino beams. The
Z
 boson is not involved in the absorption or emission of electrons or positrons. Whenever an electron is observed as a new free particle, suddenly moving with kinetic energy, it is inferred to be a result of a neutrino interacting with the electron (with the momentum transfer via the Z boson) since this behavior happens more often when the neutrino beam is present. In this process, the neutrino simply strikes the electron (via exchange of a boson) and then scatters away from it, transferring some of the neutrino's momentum to the electron.