Analysis of data from the Large Hadron Collider has confirmed the existence of a weird new subatomic particle called a pentaquark. Pentaquarks are configurations of 5 other quarks, and it’s discovery has been a prize long-sought by physicists. The new particles may be found in collapsing stars, but in order to understand this discovery, let’s back up. First of all, what is a quark?

Quarks arose in the 1964 as a way to explain the behavior of particles discovered through high-energy atomic collisions (this is what the Large Hadron Collider, like all particle accelerators, actually does: it smashes atoms and subatomic particles together allowing us to see what happens). Any high school chemistry student is familiar with the basic building blocks of atoms— electrons, protons, and neutrons. A physicist named Murray Gell-Mann conceived of the quark— super-tiny, point-like subatomic particles that combine to form protons and neutrons— in order to explain the particle collision results. Quarks are the building blocks of the building blocks, like the grains of clay in a brick.

Quark theory explained everything that physicists were observing, leading to the Standard Model that by some arcane means explains the entire structure of the universe. The Standard Model predicted 6 types of quarks: up, down, top, bottom, charm, and strange. They are differentiated based on properties such as mass and charge. The last to be experimentally confirmed was the heaviest, the top quark.

Having confirmed the existence of each type of quark, attention turned to combinations of quarks. Arrangements of three quarks or two quarks were common, and the Standard Model predicted that these could combine into 5 quark configurations—pentaquarks. However, until now, no known particle was made of more than three quarks. As such, there was a massive attempt to find the pentaquark, with competing research groups rushing to be the first to experimentally prove its existence. Its discovery was announced with great fanfare repeatedly, until a 2005 meta-analysis dumped a bucket of nope on all the reports. Negative results, it seems, vastly outpaced actual evidence of the pentaquark.

Until, possibly, now. The new data is seen as more reliable than previous announcements, but given the history some caution is in order. This is a field where particles last for fractions of seconds, and proof must be provided based on such fleeting encounters. Evidence can be slow to follow theory, but when it does, minds are blown.



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American Scientist, Vol. 80, No. 5 (September-October 1992), pp. 430-443
Sigma Xi, The Scientific Research Society
Science News, Vol. 167, No. 20 (May 14, 2005), p. 318
Society for Science & the Public