By Joshua Ostrer
On April 7, researchers at the Large Hadron Collider, the world’s largest particle collider, discovered a new particle, Z4430.
The Large Hadron Collider (LHC), which took over 10 years to construct and which cost over $4 billion, made international headlines in 2013 with the discovery of the Higgs boson, known as the “god particle.” The Higgs boson particle is created from the collison of protons.
The discovery went a long way in explaining fundamental principles of mass, theorized as early as 1964.
However, this past week, the LHC made another illuminating discovery in identifying a new particle known as Z4430.
The particle is so named because it has a mass of 4430 MeV (Mega electron volts) and a strange particle state that doesn’t exactly fit the quark model, referred to as the XYZ state.
The Belle experiment was performed by the Belle Collaboration, a group of over 400 physicists and engineers.
“We are very happy to have confirmed this resonance, this particle, which in fact is a very strange object,” said LHC spokesperson Pierluigi Campana in a CERN informational video.
The group published the finding in a report released on April 7 called, “Observation of the resonant character of the Z(4430) — state.”
While more research still needs to be done, experts are optimistic that Z4430 exists.
Z4430 is possibly the first discovered tetraquark.
A quark is an elementary particle, believed to be the smallest possible form of matter. A tetraquark is a group of four of these quarks.
In pairs, quarks form a short-lived particle known as a meson. In triplets, quarks form protons and neutrons, the crucial components of the atom.
What is odd about the Z4430 particle is that it has a mass that is roughly four times larger than a proton, causing confusion over why a set of four quarks would weigh so much more than a group of three.
“The strange thing is that it does not fit very well into the quark model,” said Pierluigi Campana.
“We now have undisputable proof that nature is able to form more complex, more sophisticated objects than proposed by Gel-Mann in 1964,” said LHC physicist Richard Jacobsson.
Researchers have found over 4,000 of these supposed tetraquarks.
While tetraquarks’ existences have been hypothesized before, their actual existences could not be verified to this extent before the LHC.
A Belle experiment conducted in 2003 claimed to have found a state that looked like a state of four quarks bound together, but that study did not come close to the certainty produced by the 2014 experiment.
The LHC functions by firing particle beams at 99.9 percent of the speed of light through two adjacent pipes.
The two pipes, each measuring over 17 miles in distance, intersect at four different points, leading to collisions between the particle beams allowing scientists to witness the results of these high-speed collisions.
While there isn’t a hundred percent certainty of the tetraquark’s existence, there seems to be a hefty confidence in the finding.
“The significance of the Z(4430) signal is overwhelming — at least 13.9 sigma — confirming the existence of this state … The LHCb analysis establishes the resonant nature of the observed structure, proving that this is really a particle and not some special feature of the data,” said Pierluigui Campana to CERN, the European Organization for Nuclear Research.
The reason that there is still doubt about the existence of the tetraquark is that it is very hard to prove that a particular tetraquark is anything more than a pair of loosely bound mesons.
However, the data seems to suggest such a theory is unlikely due to the observed mass difference between the tetraquark and what would be expected of a pair of mesons.
While the potential discovery of the tetraquark has attracted international attention, the precise significance of the finding will not be apparent for a long time.
The tetraquark has the potential to illuminate science’s understanding of matter at its most fundamental level, but exactly what practical or theoretical significance that will amount to is unknown at this point.
For more information on the Large Hadron Collider or progress on the discovery and significance of tetraquarks, visit home.web.cern.ch.