particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and ...

, a B-factory, or sometimes a

beauty Beauty is commonly described as a feature of objects that makes these objects pleasurable to perceive. Such objects include landscapes, sunsets, humans and works of art. Beauty, together with art and taste, is the main subject of aesthetics, o ...

factory, is a particle collider experiment designed to produce and detect a large number of B mesons so that their properties and behavior can be measured with small statistical

uncertainty Uncertainty refers to Epistemology, epistemic situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown. Uncertainty arises in partially ...

. Tau leptons and D mesons are also copiously produced at B-factories.

History and development

A sort of "prototype" or "precursor" B-factory was the

HERA-B The HERA-B detector was a particle physics experiment at the HERA accelerator at the German national laboratory DESY that collected data from 1993 to 2003. It measured 8 m x 20 m x 9 m and weighed 1000 tons. The HERA-B collaboration consisted of s ...

experiment at

DESY The Deutsches Elektronen-Synchrotron (English ''German Electron Synchrotron''), commonly referred to by the abbreviation DESY, is a national research center in Germany. It operates particle accelerators used to investigate the structure of matt ...

that was planned to study B-meson physics in the 1990–2000s, before the actual B-factories were constructed/operational. However, usually HERA-B is not considered a B-factory. Two B-factories were designed and built in the 1990s, and they operated from late 1999 onward: the

Belle experiment The Belle experiment was a particle physics experiment conducted by the Belle Collaboration, an international collaboration of more than 400 physicists and engineers, at the High Energy Accelerator Research Organisation ( KEK) in Tsukuba, Ibar ...

at the KEKB collider in

Tsukuba is a city located in Ibaraki Prefecture, Japan. , the city had an estimated population of 244,528 in 108,669 households and a population density of 862 persons per km². The percentage of the popu