Higgs boson: discovery and definition

Higgs boson is a fundamental particles of the Standard Model of particle physics, was discovered in 2012 at LHC.

To know what is the Standard Model and about the particles mentioned on this post, click on the button below.

How it was discovered?

In 1964, three scientific articles published independently, described how elementary particles could adquire mass through interaction with a type of field, at that time it was called the “Brout-Englert-Guralnik-Hagen-Higgs-Kibble” field.

These are the three articles from Physical Review Letters, which predicted the existence of Higgs boson, they are on a permanent exhibition called Universe of Particles, in CERN.

The Higgs boson has a lifespan with only $1\cdot 10^{-22}$ seconds. Therefore, it’s only possible to observe traces left after decay. ATLAS and CMS of LHC experiments detected these traces.

ATLAS and CMS

Atlas is a particle detector, whose center is where collisions occur.

ATLAS discovered Higgs boson. — This is the layout of the ATLAS detector. It features detectors made of millions of silicon pixels to track the trajectories of particles produced after collisions. The calorimeters measure the particles’ energy, while the toroidal and solenoid magnets bend the paths of charged particles to determine their electric charge. Finally, the muon spectrometer detects muons. Source: ATLAS Open Data.

The CMS (Compact Muon Solenoid) works similar to ATLAS. The main difference is the CMS has a solenoid made of superconductor cable, which can generate a magnetic field of 4 Tesla, approximately 100,000 times more intense than Earth’s magnetic field. The solenoid’s function is to curve trajectories of particles with electric charge.

The CMS layout. Silicon detectors track trajectories, while calorimeters measure particles’ energy. And in the outermost part, there are muon detectors with iron yoke. Source: TensorFlow Blog.

Generation and decay of Higgs boson

Production and decay of Higgs boson — These are Feynman diagrams, graphic representations of interaction between subatomic particles. Source: Nature.

Generation of Higgs boson (H) by fusion of two gluons (g).
H production, by fusion of two bosons (W/Z).
Another possible production by boson fusion.
Generation through top or bottom quarks (t/b).
H emission due to a quark top.
H decays in a pair of W or Z bosons.
H can decay in a pair of photons (γ) or in a photon and a boson (Z).
Decay in a pair of bottom or charm quarks.
H decays in a pair of leptons (τ/μ).

Detecting Higgs boson

Before the LHC, the LEP and Tevatron colliders searched for the Higgs boson. The LEP (Large Electron-Positron Collider) was CERN’s particle accelerator from 1989 to 2000, colliding electrons and positrons (the antimatter counterpart of electrons). Although it did not find the Higgs boson, it determined that its mass could not be less than 114 GeV (giga-electron volts).

LEP collider, on franco-swiss border. Source: ICEPP.

Tevatron was a Fermilab’s collider, it was in Batavia, Illions, USA, it was the biggest of its time before the LHC. It carried out collisions betwenn protons and antiprotons until September 30, 2011. Tevatron discarded the possibility of Higgs boson mass be around 160 GeV.

The LHC collides pairs of protons and operates at higher energies and collision rates than previous accelerators. Consequently, it had a greater probability of producing rare events, such as the creation and decay of the Higgs boson. The ATLAS and CMS experiments sought to detect Higgs boson decays into photon pairs or W/Z bosons, recording trillions of collisions between 2011 and 2012.

This is the graphic of collisions that decay in pairs of photons, here shows a number bigger of collisions than predicted, with energy approximately 125 GeV, confirming the theory’s predictions. The red curve is for calibration, which follows collisions’ pattern. Source: Atlas experiment.

This is the graphic of collisions that decay in bosons. The blue part indicates Higgs boson production. Source: Atlas experiment.

Collision graphics on CMS show the same results.

Higgs boson’s function

It confirms the existence of the Higgs field and explains why particles have mass, except for the photon and gluon. The Higgs field permeates the entire universe, and particles moving through this field experience a resistance to their motion, which is mass. The stronger the interaction with the field, the greater the mass.

2 thoughts on “Higgs boson: discovery and definition”

Pedro Ney Stroski says:

24/05/2025 at 16:24

For more information about LHC (Large Hadron Collider), access this post.
https://www.electricalelibrary.com/en/2020/03/31/electrical-e-library-at-cern-part-2/

Prof. Prem raj Pushpakaran says:

02/06/2025 at 12:34

Prof. Prem raj Pushpakaran writes — 2025 marks the birth centenary year of Simon van der Meer, and let us celebrate the occasion!!!