Physicists at the LHCb studied how a subatomic particle called Lambda-b decayed into three other particles. It is crucial to distinguish real signals from merely data fluctuations that can lead to erroneous conclusions of finding something. In the past many scientists from many different research groups have all claimed to discover pentaquarks, but all were cast into doubt by subsequent alternative work. The pentaquark has a long history of doubtful discovery.
Whilst usually thought of existing in threes and twos, the theories on quarks allowed for the existence of the pentaquark - a particle composed of five quarks, specifically made up of four quarks and an antiquark.
Baryons are made of three quarks (thus have a baryon number of 1) for example the proton (uud charge=+1 ) and neutron (udd, charge=0), whereas mesons are made of a quark-antiquark pair (thus have a baryon number of 0). Up, charm and top quarks have an electric charge of +⅔, while the down, strange, and bottom quarks have an electric charge of -⅓. Quarks are all assigned a baryon number of ⅓. Experiments at the Stanford LAC in the late 1960s provided evidence of quarks, and subsequent experiments at particle colliders have gathered evidence for all six flavours, with the top quark the last to be discovered in 1995. Up and down quarks are the most common in the universe, whereas the other four can only be produced in high energy collisions such as cosmic rays or within a particle accelerator. There a six types of quarks, called flavours - up (u) and down (d), strange (s) and charm (c), top (t) and bottom (b). Every type of quark has a corresponding antiquark, that differ in that some properties have equal magnitiude but an opposite sign. Also, they are the only fundamental particles to experience all four fundamental forces - electromagnetism, gravity, strong interaction and weak interaction. They have various basic properties including electric charge, mass, and spin. Quarks are only found together within hadrons, and never on their own - a phenomenon called colour confinement.
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