New particle discovered at the LHC
15 Jul 2015 by qmcqmmjcbp.d qmcqmmjcbp.d
Physicists at CERN have discovered a new class of particles known as pentaquarks.
A research team at the LHCb experiment at CERN’s Large Hadron Collider examined the decay of a baryon – a composite subatomic particle – and found the new particle which consists of four quarks and one antiquark bound together.
“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 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,” said LHCb spokesperson Guy Wilkinson.
In 1964, Professor Murray Gell-Mann suggested the first quark model that allows the existence of other quark composite states such as pentaquarks. Until now, however, their existence has not been confirmed.
In the study, published in the journal Physical Review Letters, the team studied the decay of a baryon known as ?b into three other particles - a J/?, a proton and a charged kaon. The team then investigated the spectrum of masses of the J/? and the proton and discovered that intermediate states – named Pc (4450) + and Pc (4380) + – were sometimes involved in their production.
“Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states. More precisely the states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark,” said LHCb physicist Tomasz Skwarnicki of Syracuse University.
Next, the scientists will study how the quarks are bound together within the pentaquarks.
