Chi_b (3P) – A New Member to The Particle Zoo!

Image of Large Hadron Collider

Since restarting operations in 2009, the Large Hadron Collider (LHC) situated in the Franco-Swiss border has made its first confirmed observation of a new particle. Titled Chi_b (3P) by physicists from UK, who worked on the ATLAS experiment, this particle could help scientists understand the fundamental forces better.

The result is however still unpublished but is available in Arxiv pre-print server for reference. As explained before, the LHC is exploring some of the greatest questions in theoretical physics by creating the conditions of our early universe through proton-proton collisions.

Prof. Roger Jones who works at the ATLAS detector explained that the Chi_b (3P) is an excited state or rather a heavier variant of the Chi particle, which was discovered about 25 years ago. Physicists James Walder said that though scientists had predicted Chi-b (3P)’s existence then, it was never seen until now.

Image of LHC Tunnel

Just like the Higgs and photon, Chi_b (3P) is a boson, which means that it will carry some force and obey Bose-Einstein statistics. However, it is unlike Higgs in that it has an internal structure composed of relatively heavy particles viz. beauty quark (also known as bottom quark) and its antiquark, explains Prof. Jones. The quarks that build protons, neutrons and other hadrons come in six flavors viz. up, down, strange, charm, top and bottom. An interesting aspect of this finding is what it tells us about the strong nuclear force (carried by gluons) that binds both the quarks together.

The measurements made in this machine tests theoretical calculations of the forces and discoveries of new particles such as Chi_b (3P), takes us closer to achieving a fuller understanding of the structure of our universe and cementing our views about how it is held together.

This particle’s discovery is particularly important since once we better understand the strong force, we could explain the thing happening in the background of the collisions where we are currently looking for the Higgs. According to Prof. Paul Newman of the University of Birmingham, this marks the first time a new particle has been discovered in the LHC and that it is proof that the machine ran successfully in 2011. Andy Chisholm, a PhD student at Birmingham, who worked on the analysis team, added that the analysis of billions of these particle collisions is fascinating because of the potentially interesting things buried in the data. They were lucky this time since they looked at the right place in the mess at the right time.

Image of CERN Scientist

The LHC is expected to fill the gaps that exist in the Standard Model of Particle physics thereby opening horizons in new physics. The main aim for which the machine was built is to find the elusive Higgs boson; which, if exists could give satisfactory explanation of why matter has mass. That discovery could also throw more light on the workings of gravity, especially in the realm of unified field theories.

The machine, which resides inside a 27 km ring-shaped tunnel, 175 meters below the ground fires streams of protons on opposite directions every day and produce billions of collisions. The beams are controlled by magnets and the carnage of the collisions that happen are recorded using detectors. It was only 10 days ago when scientists at CERN announced that they are pretty close to finding the Higgs boson and Chi_b (3P) could be a step closer to this goal.


  1. Amos, J. “LHC reports discovery of its first new particle.” BBC News – Science & Environment. Dec 22, 2011. (accessed Dec 23, 2011).
  2. Brown, M. “Large Hadron Collider discovers a new particle: the Chi-b(3P).” Dec 22, 2011. (accessed Dec 23, 2011).
  3. Collaboration, The ATLAS. “Observation of a New Chi_b State in Radiative Transitions to Gamma (1S) and Gamma(2S) at ATLAS.” Dec 21, 2011. (accessed Dec 23, 2011).
  4. “Large Hadron Collider finds new variant of particle.” Dec 23, 2011. (accessed Dec 23, 2011).

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