top quark

References

top quark

physics

Also known as: truth quark

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 14, 2026

Quick Summary

The top quark is one of the six fundamental subatomic particles known as quarks, which are believed to be constituents of matter. Quarks combine to form protons and neutrons. The six quark flavors are grouped into three pairs: up and down, charm and strange, and top and bottom. The top quark is the heaviest of these, with a mass approximately 173.8 GeV/c², comparable to a lead nucleus.12

Discovered in 1995 at Fermi National Accelerator Laboratory, the top quark's existence was crucial for completing the Standard Model of particle physics. Its significant mass and role in the Standard Model continue to be areas of research, potentially offering insights into the asymmetry between matter and antimatter in the universe.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

2 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

Carlo Rubbia
…for the sixth quark, called top, had been found. The discovery of this quark confirmed an earlier prediction that three pairs of these particles should exist.
Read More
…for the sixth quark, called top, had been found. The discovery of this quark confirmed an earlier prediction that three pairs of these particles should exist.
Read More

Fermi National Accelerator Laboratory
…of this pair is the top quark, which is the sixth and most-massive quark; in 1995 it was also discovered at Fermilab. Scientists inferred the existence of the top quark, produced in the Tevatron as a result of 1.8-TeV proton-antiproton collisions, on the basis of its decay characteristics. In 2010,…
Read More
…of this pair is the top quark, which is the sixth and most-massive quark; in 1995 it was also discovered at Fermilab. Scientists inferred the existence of the top quark, produced in the Tevatron as a result of 1.8-TeV proton-antiproton collisions, on the basis of its decay characteristics. In 2010,…
Read More

meson
…of a companion particle, the top quark. This sixth quark type, or “flavour,” was discovered in 1995. Conclusive proof of its existence culminated the search for one of the last missing pieces in the Standard Model of particle physics, which describes the fundamental particles and their interactions.
Read More
…of a companion particle, the top quark. This sixth quark type, or “flavour,” was discovered in 1995. Conclusive proof of its existence culminated the search for one of the last missing pieces in the Standard Model of particle physics, which describes the fundamental particles and their interactions.
Read More

quark
Binding forces and massive quarks
…type of quark called “top” (t), after its proposed flavour. According to theory, the top quark carries a charge of 2/3e; its partner, the bottom quark, has a charge of −1/3e. In 1995 two independent groups of scientists at the Fermi National Accelerator Laboratory reported that they had found…
Read More
…type of quark called “top” (t), after its proposed flavour. According to theory, the top quark carries a charge of 2/3e; its partner, the bottom quark, has a charge of −1/3e. In 1995 two independent groups of scientists at the Fermi National Accelerator Laboratory reported that they had found…
Read More