A new study has identified a remarkable exotic type of particle that does not fit into traditional models. The new research was undertaken as part of the Large Hadron Collider beauty (LHCb) Collaboration, a multinational endeavor to recognize new forces and particles, at CERN in Geneva, Switzerland; it led by physicists at Syracuse University. According to a press release, the particle in question is an exotic hadron consisting of two quarks and two anti-quarks.
Quarks are found in the nuclei of atoms; when they merge in sets of three, they form larger particles known as baryons, of which protons are the most widely known. When one quark interacts with one anti-quark, which has the same mass but opposite charge, they create a meson. Mesons often are found in cosmic rays, as well as in the decay products of man-made reactions, such as those in particle accelerators and nuclear reactors. Baryons, mesons, and several other classes of particle are categorized as hadrons.
Such was the way of particle physics until 2007, when the Belle Collaboration, a team of 400 scientists, announced an exotic hadron known as Z(4430), which they postulated to be composed of two quarks and two anti-quarks, rather than the three quarks of a baryon or one quark and one anti-quark of a meson. The Belle findings were met with skepticism. A few years later, BaBar, another international collaboration, tested Belle’s hypothesis and, though they did not disprove Belle’s findings, BaBar saw no merit in proposing a new type of exotic hadron. Belle replied with another study of their own and found statistical support for the existence of Z(4430).
LHCb employed the analytical techniques used by both Belle and BaBar and verified that Z(4430) does exist. The team analyzed its own data set, examining tens of thousands of meson decays among trillions of collisions at the LHC. Thanks to the immense data set, particle properties could be measured with great accuracy.