Meet the pentaquark, CERN’s latest particle discovery

14 Jul 2015

Cut out image of the LHC via Daniel Dominguez

The confirmed existence of a new particle – the pentaquark – made by CERN’s Large Hadron Collider (LHC) could offer answers into how the matter that makes up everything is constituted.

It’s been 51 years since the pentaquark was first theorised by American physicist Murray Gell-Mann who, along with George Zweig (who were working independently from one another), theorised the existence of the quark, an incomprehensibly-small subatomic particle.

Interestingly, the quark was given this name by Gell-Man from James Joyce’s Finnegan’s Wake from the line: “Three quarks for a muster mark.”

During his original proposal, Gell-Mann had suggested the existence of a category of particles known as baryons, which includes protons and neutrons, being comprised of three fractionally-charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs.

Working off this basis, Gell-Man’s model also allowed for the existence of other quark composite states, which in this case was the pentaquark, composed of four quarks and an antiquark.

Pentaquark diagram

Possible layout of the quarks in a pentaquark particle. The five quarks might be tightly bonded (left). Image via Daniel Dominguez

The only problem had been, until now, no conclusive evidence for pentaquarks had been seen but now, with the power of the LHC, a research team has been able to publish its conclusive findings showcasing the discovery of the pentaquark.

“The pentaquark is not just any new particle,” said LHC spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over 50 years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.”

The research team will now develop the next step in its analysis, which will be to study how the quarks are bound together within the pentaquarks.

Colm Gorey was a senior journalist with Silicon Republic