Bottom quark

The existence of a third generation of quarks to explain observed CP violation in kaon decay was predicted in 1973 by Makoto Kobayashi and Toshihide Maskawa. They did not propose names for their two theorised particles, and many physicists started to call them truth and beauty quarks. The names top and bottom, which became the accepted terms, were introduced by Haim Harari in 1975 to match the names of the first generation of quarks (up and down), reflecting the fact that the two were the "up" and "down" component of a weak isospin doublet. Evidence for the bottom quark was first obtained in 1977 by the Fermilab E288 experiment team led by Leon M. Lederman, when proton-nucleon collisions produced bottomonium decaying to pairs of muons. The discovery was confirmed about a year later by the PLUTO and DASP2 Collaborations at the electron-positron collider DORIS at DESY. It was reported at the time that DESY scientists were in favor of the name "beauty", while the American scientists tended towards "bottom". == Distinct character ==

The bottom quark's "bare" mass is around The combination of high mass and low transition rate gives experimental collision byproducts containing a bottom quark a distinctive signature that makes them relatively easy to identify using a technique called "B-tagging". For that reason, mesons containing the bottom quark are exceptionally long-lived for their mass, and are the easiest particles to use to investigate CP violation. Such experiments are being performed at the BaBar, Belle and LHCb experiments. == Hadrons containing bottom quarks ==

Some of the hadrons containing bottom quarks include: • B mesons contain a bottom quark (or its antiparticle) and an up or down quark. • and mesons contain a bottom quark along with a charm quark or strange quark respectively. • There are many bottomonium states, for example the meson and χb(3P), the first particle discovered in LHC. These consist of a bottom quark and its antiparticle. • Bottom baryons have been observed, and are named in analogy with strange baryons (e.g. ). == See also ==