Higgs boson

The Higgs boson is a massive spin-0 elementary particle in the Standard Model of particle physics that plays a key role in explaining the mass of other elementary particles. Its experimental discovery was announced in a seminar July 4, 2012. This particle was first proposed by Professor 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 boson was popularised as the "God particle" by the Nobel Prize-winning physicist Leon M. Lederman in his 1993 popular science book The God Particle: If the Universe Is the Answer, What is the Question? co-written with science writer Dick Teresi.

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.

Search for the Higgs boson

Studies using the Fermilab's Tevatron collider suggest a range for the mass of the Higgs boson between 115-150 GeV (gigaelectronvolts), assuming the correctness of the Standard Model of particle physics. See review of the experiments:

The Higg’s particle was not made in the Tevatron collider, but by using the high energies of the Large Hadron Collider in Geneva. This discovery was an early goal of this major international project.

The discovery is a bit anticlimactic, as theory has incorporated the Higgs boson for decades. As said by Stephen Hawking:

“This is an important result and should guaranty Higgs the Nobel Prize” the physicist predicted. “But it is a pity in a way, because the great advances in physics have come from experiments that gave results we didn’t expect.”