LHC discovers pentaquarks - strengthening standard model

CERN’S Large Hadron Collider particle accelerator finds evidence of elusive particle made of five quarks after 50 year long hunt

Photo by: CERN
Photo by: CERN

Updated Jul 28, 2015

Scientists operating the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) confirmed the existence of a class of particles known as pentaquarks on Tuesday. The discovery came as part of an experiment called LHCb, the scientists at CERN said in a statement.

Although the existence of pentaquarks was first independently predicted in 1964 by physicists Murray Gell-Mann and George Zweig, scientists had searched for these particles no avail for 51 years.

“The pentaquark is not just any new particle,” LHCb spokesperson Guy Wilkinson said. “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 fifty years of experimental searches.”

Gell-Mann and Zweig were the first scientists to lay the foundations of the standard model of particles physics which classifies all subatomic particles along with electromagnetic fields and weak and strong nuclear interactions.

Quarks are the building blocks of hadrons, subatomic particles such as protons and neutrons. Each quark has a property called flavour – up, down, strange, charm, top or bottom - which describes it.

In the 1970s physicists proved the existence of hadrons consisting of two or three quarks. Only in recent years have scientists found compelling evidence of tetraquarks - particles which are made up of four quarks.

A pentaquark consists of four quarks and one antiquark, with an antiquark having equal magnitude but an opposite electric charge to a quark.

“More precisely [the pentaquark consists of] … two up quarks, one down quark, one charm quark and one anti-charm quark,” physicist Tomasz Skwarnicki from Syracuse University said.

Scientists at CERN think that the quarks in pentaquarks are either “tightly bound or loosely bound in a sort of meson [two quarks] baryon [three quarks] molecule.”

To further investigate this possibility, scientists will collect new data in second LHC run.

“What we want to do now is to look for other five-quark particles and try and understand more about their nature, and this may tell us something about how even the matter inside our bodies is bound together,” Wilkinson told Reuters.

“It may also have cosmic consequences for ... understanding what happens to stars at the end of their life.”

TRTWorld and agencies