LHC Spots Elusive Pentaquark In High Energy Collisions
While the world waited with bated breath the arrival of New Horizons at Pluto on Tuesday, the Large Hadron Collider quietly made yet another phenomenal discovery; a type of quark particle that has been earlier theorized but never found.
The Large Hadron Collider (LHC) is in its second run this year, three years after it discovered the Higgs Boson. The LHC is colliding high energy proton beams to study the remnants of such collisions to answer several questions in particle physics, including those pertaining to dark matter. On Tuesday, LHC researchers were certain their peaks in data corresponded to a pentaquark particle, composed of four quarks and anti-quark. These particles were theorized when quarks were first discovered but remained elusive in experiments.
When researchers looked at the data the detectors at LHC had gathered after collisions, they found that a baryon [class of particles including neutron and protons] had decayed into other particles including a proton and a J-psi. Detailed analysis of the data revealed that two intermediate states, Pc(4450)+ and Pc(4380)+, are involved in the production of decay particles.
"More precisely the states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark," LHC's operator CERN said in a press release.
"The pentaquark is not just any new particle. 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. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we're all made, is constituted," said LHCb spokesperson Guy Wilkinson.
Researchers now plan to the study the forces holding the quark-antiquark together in pentaquark states.
"The quarks could be tightly bound or they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei." said LHCb physicist Liming Zhang.
