New particles discovered with Hadron Collider

The Hadron Collider is still immensely useful years on (Photographer: Luigi Selmi).

by Joshua Green

The Large Hadron Collider (LHC) has yielded yet another new experimental discovery. Scientists based at one of the LHC’s detectors simply named LHCb have discovered entirely new states of a particle called the Omega-c-zero.

The Omega-c-zero particle is a type of baryon. Baryons are particles that are made up from three other particles called quarks which are fundamental and are not composed of any other particle. Protons and neutrons, for example, are made up from a combination of “up” and “down” quarks which give the proton and neutron their positive and neutral electronic charges. Protons and neutrons are two of the three ‘obvious’ constituents of an atom.

The Omega-c-zero baryon is a type of baryon that a person would rarely come across in nature. Why is this you might be asking? Well, the Omega-c-zero particle for starters does not have ‘up’ and ‘down’ quarks but different types of quarks do exist that take their place. Three ‘strange’ quarks make up an Omega baryon in general. In contrast, the Omega-c-zero particle is the form of Omega baryon that is made from two ‘strange’ quarks and a ‘charm’ quark (hence the c in the name). The baryon in question was first discovered in 1994 as part of the E-687 experiment at Fermilab. The observation made at CERN were observations made of different forms of the Omega-c-baryon and were previously theoretically predicted. When a Omega-c-baryon decays, the product of this was experimentally seen as five states that were all more energetic than the last. They have been called Oc(3000)0, Oc(3050)0, Oc(3066)0, Oc(3090)0 and Oc(3119)0 which is how the naming procedure works. The numbers after the Oc represent their energies in ‘megaelectronvolts’. For comparison, the energy of the ‘ground state’ (least energetic) Omega-c-baryon is quoted as 2697.5 ± 2.6 megaelectronvolts.

What fuels the excitement behind the discovery, which is what fuels most particle physics experiments and theory, is that of understanding more and more about the fundamental physics that governs what we observe. A first physical phenomenon that gives light into the importance of experimental discoveries like this is the strong force. Now, the strong force is one of the four fundamental interactions that govern how particles interact and any force seen in nature can be broken down or traced back to these four forces. The strong force is responsible for binding the quarks discussed above to form the proton, neutron and the Omega-c-baryon.

Is it hoped that the discovery of the five excited states of the Omega-c-baryon will shed light on the strong interaction; how the quarks bind together. It is also hoped that this discovery will help understand very ‘exotic’ particles such as pentaquarks which are particles comprised of five quarks. This could lead to many greater discoveries further down the line.

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