Pentaquarks

In 2003, researchers at the SPring-8 synchrotron in Harima, Japan, claimed to have discovered a pentaquark. Unlike baryons (like the familiar proton and neutron) that consist of three quarks, and mesons (like the pion and kaon) that consist of a quark and an antiquark, the pentaquark would consist of four quarks and an antiquark. The many experiments carried out in 2003 that claimed to have created the particle consisted of an interaction between a gamma ray and a neutron. The resulting pentaquark had a lifetime of 10^-20 seconds, before decaying into a meson and a neutron. However, new extensive experiments carried out at the Thomas Jefferson National Accelerator Facility in Virginia have failed to find these elusive particles, although more than 50 times more precise than any previous study.