Exotic Hadron Particle Confirmed by LHCBy: Brian Powell - April 15, 2014
Quarks, or subatomic, elementary particles of other subatomic particles, have only been known to exist since the 1960’s. Since that time, though, scientists have made great progress with identifying key characteristics of quarks and their utility. Quarks come in six different flavors – up, down, strange, charm, bottom, and top. These quarks combine in different ways to form either baryons or mesons, both of which fall under the hadron category. The most common forms of baryon particles are protons and neutrons, while mesons are usually observed as products of nuclear decay. Quarks are also the other subatomic particle to experience all four fundamental forces of nature – strong, weak, electromagnetic, and gravity. Because of this, all quarks had been explainable by the Standard Model of particle physics. Until now, that is.
On April 9, scientists at the CERN Laboratory in Switzerland made an amazing new discovery. While the scientists were waiting for the repairs and improvements of the Large Hadron Collider to be complete and for the particle accelerator to come back online, they decided to look at some of the data the LHC had collected during its previous online operations.
What the scientists discovered may change the face of particle physics forever.
The scientists studied the decay of more than 25,000 mesons from 180 trillion proton-to-proton collisions and were faced with stunning news. The tetraquark, which had first been postulated in 2003, was confirmed as true by the data the scientists studied.
This tetraquark, composed of four quarks, defies the laws of all known particle physics. Until this point, scientists knew only of the two previously mentioned types of hadrons – baryons and mesons. Baryons are composed of three quarks, while mesons are composed of two – both a quark and an antiquark.
The Standard Model of particle physics predicts the existence of both categories of hadrons; it does not, however, predict any semblance of a tetraquark.
“We’ve confirmed the unambiguous observation of a very exotic state—something that looks like a particle composed of two quarks and two anti-quarks. The discovery certainly doesn’t fit the traditional quark model. It may give us a new way of looking at strong-interaction physics,” stated study co-leader Tomasz Skwarnicki, a high-energy physicist at Syracuse University.
When the particle was first proposed in 2003, it was called Z(4430) and derived from observations of a previous particle collider which implied that a particle heavier than any other known subatomic particle existed. Unfortunately for those scientists, they were not able to prove to the scientific community that such a particle did, indeed, exist.
“Some experts argued that [the] initial analysis [of Z(4430)] was naïve and prone to arrive at an unjustified conclusion. As a result, many physicists concluded that there was no good evidence to prove this particle was real,” recalled Skwarnicki.
The scientists are CERN, though, are quite positive of their results. The report of the tetraquark came with a certainty of 13.9 sigma. In layman’s math, this means that the margin of error with the result is 1*10^-44, or about the same as winning the lottery multiple times in a row.
“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,” reported LHCb spokesperson Pierluigi Campana.
While the scientists would love to postulate about the impact of this discovery, essentially nothing is known about this exotic hadron particle. And, in even worse news, no new research will be conducted until the LHC is back online in 2015. However, the wait will be rewarded as the new LHC will be twice as powerful as it previously was and six times as powerful as any other particle collider in the world.
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