- Scientists using the world’s largest and most powerful particle accelerator have discovered a new system of five particles all in a single analysis.
- The uniqueness of this discovery is that observing five new states all at once is very rare, researchers said.
- The LHCb experiment is one of seven particle physics detector experiments collecting data at the Large Hadron Collider accelerator at CERN (European Organisation for Nuclear Research).
- The collaboration has announced the measurement of a very rare particle decay and evidence of a new manifestation of matter —antimatter asymmetry, to name just two examples.
- The new particles were found to be in excited states — a particle state that has a higher energy than the absolute minimum configuration (or ground state) — of a particle called Omega-c-zero.
About Omega-c-zero & Xi-c-plus:
- Omega-c-zero is a baryon, a particle with three quarks, containing two “strange” and one “charm” quark.
- Omega-c-zero decays via the strong force into another baryon, called Xi-c-plus, (containing a “charm”, a “strange” and an “up” quark) and a kaon K-.
- Then the Xi-c-plusparticle decays in turn into a proton p, a kaon K- and a pion p+.
- From the analysis of the trajectories and the energy left in the detector by all the particles in this final configuration, the LHCb collaboration could trace back the initial event — the decay of the Omega-c-zero — and its excited states.
- These particle states are named, according to the standard convention, Oc(3000)0, Oc(3050)0, Oc(3066)0, Oc(3090)0 and Oc(3119)0. The numbers indicate their masses in megaelectronvolts (MeV), as measured by LHCb.
- The next step will be the determination of the quantum numbers of these new particles — characteristic numbers used to identify the properties of a specific particle — and the determination of their theoretical significance.
Importance of the Discovery:
- This discovery will contribute to understanding how the three constituent quarks are bound inside a baryon and also to probing the correlation between quarks, which plays a key role in describing multi-quark states, such as tetraquarks and pentaquarks.
- A baryon is a composite subatomic particle made up of three quarks (a triquark, as distinct from mesons, which are composed of one quark and one antiquark).
- Baryons and mesons belong to the hadron family of particles, which are the quark-based particles.
- The name “baryon” comes from the Greek word for “heavy” , because, at the time of their naming, most known elementary particles had lower masses than the baryons.
- As quark-based particles, baryons participate in the strong interaction, whereas leptons, which are not quark-based, do not.
- The most familiar baryons are the protons and neutrons that make up most of the mass of the visible matter in the universe.
- Electrons (the other major component of the atom) are leptons.
- Each baryon has a corresponding antiparticle (antibaryon) where quarks are replaced by their corresponding antiquarks.
- For example, a proton is made of two up quarks and one down quark; and its corresponding antiparticle, the antiproton, is made of two up antiquarks and one down antiquark.