Scalar boson

A scalar boson is a boson whose spin equals zero.^[1] A boson is a particle whose wave function is symmetric under particle exchange and therefore follows Bose–Einstein statistics. The spin–statistics theorem implies that all bosons have an integer-valued spin.^[2] Scalar bosons are the subset of bosons with zero-valued spin.

The name scalar boson arises from quantum field theory, which demands that fields of spin-zero particles transform like a scalar under Lorentz transformation (i.e. are Lorentz invariant).

A pseudoscalar boson is a scalar boson that has odd parity, whereas "regular" scalar bosons have even parity.^[3]

Examples

The only fundamental scalar boson in the Standard Model of particle physics is the Higgs boson,^[1] the existence of which was confirmed on 14 March 2013 at the Large Hadron Collider by CMS and ATLAS.^[4] As a result of this confirmation, the 2013 Nobel Prize in physics was awarded to Peter Higgs and François Englert.^[5]
Various known composite particles are scalar bosons, e.g. the alpha particle and scalar mesons.^[6]
The φ⁴-theory or quartic interaction is a popular "toy model" quantum field theory that uses scalar bosonic fields, used in many introductory quantum textbooks^[7]^{[page needed]} to introduce basic concepts in field theory.

There are no fundamental pseudoscalars in the Standard Model, but there are pseudoscalar mesons, like the pion.^[8]