Higgs boson

The Higgs boson is the last particle in the Standard Model of particle physics which has not yet been observed. Its existence was first proposed by Prof. Peter Higgs of Edinburgh University in 1964 as a means to explain the origin of the masses of the elementary particles by the introduction of an fundamental scalar field. This gives all the fundamental particles mass via a process of spontaneous symmetry breaking called the Higgs Mechanism.

The Higgs Mechanism

The Higgs Mechanism is vital in explaining the masses of the electroweak W and Z bosons. To understand the problem in giving mass to the vector bosons let us first consider the QED sector of the Standard Model Lagrangian.

${\mathcal {L}}_{QED}={\overline {\psi }}(i\gamma ^{\mu }\partial _{\mu }-m)\psi -j_{em}^{\mu }A_{\mu }-{\frac {1}{4}}F_{\mu \nu }F^{\mu \nu }$

Now consider how things will change if we perform a local phase rotation such that:

$\psi (x)\rightarrow \psi '(x)=e^{i\alpha (x)}\psi (x)$

We would expect the Langrangian to remain invariant under such a rotation since to do otherwise would mean that if I chose a different phase than someone else where we could get different physics results.