Bottom quark

The bottom quark is a fundamental building block of our universe. It is also known as the beauty quark or the b quark. As an elementary particle, it belongs to the third generation of quarks. This particle carries a negative electric charge, written as − e. Scientists study it to understand the complex rules of physics. It plays a vital role in how other particles behave and change.

This quark operates through the electroweak interaction and quantum chromodynamics. These are the physical laws that describe how all quarks function. One unique feature is its exceptionally low rate of transition. This means it does not change into lighter quarks very quickly. It is often produced when a top quark decays. The Higgs boson also frequently decays into bottom quarks.

Bottom quarks can exist in several different types of particles called hadrons. Some are known as B mesons, which contain a bottom quark and an up or down quark. Others are called B_cs mesons, which pair a bottom quark with a charm or strange quark. There are also bottomonium states, such as the upsilon meson. These special states consist of a bottom quark and its own antiparticle. Scientists have even observed bottom baryons.

Physicists first predicted the bottom quark in 1973. Makoto Kobayashi and Toshihide Maskawa described it theoretically. They used this particle to explain a concept called CP violation. In 1975, Haim Harari introduced the name "bottom." Evidence for the particle appeared in 1977 through the Fermilab E288 experiment. This team was led by Leon M. Lederman. They observed proton-nucleon collisions that produced bottomonium decaying into muon pairs.

The discovery was confirmed a year later at the DORIS collider. This facility is located at DESY. During this time, scientists had different ideas about the name. DESY scientists preferred the name "beauty." American scientists tended to use the name "bottom." Eventually, "bottom" became the most common name. This was done to match the names of other quarks, like "top," "up," and "down."

The physical properties of the bottom quark are quite extreme. Its bare mass is approximately four times the mass of a proton. This is many orders of magnitude larger than common light quarks. Most bottom particles have a lifetime of about 10⁻¹² seconds. This is longer than the lifetime of charmed particles, which is about 10⁻¹³ seconds. However, it is still shorter than the lifetime of strange particles.

Because the bottom quark is heavy and stable, it is easy to find. Scientists use a special technique called B-tagging to identify it. This method looks for the distinctive signature left by bottom quarks in collisions. This makes mesons containing bottom quarks very useful for research. They are the easiest particles to use when investigating CP violation. Current experiments like BaBar, Belle, and LHCb continue this work.