LHCb discovers two excited states for the Λb beauty particle

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May 16, 2012

Graphic above: The new excited states show clear signals at masses of 5912 MeV/c2 and 5920 MeV/c2 (Image: LHCb collaboration).

The Large Hadron Collider beauty (LHCb) experiment at CERN today announced that it has observed two new excited states of the Λ_b beauty baryon. Though the Standard Model of particle physics predicts the existence of these new states, this is the first time they have been confirmed in an experiment.

Baryons are subatomic particles whose mass is equal to or greater than that of a proton. Like protons and neutrons, the Λ_b beauty baryon is composed of three quarks. In Λ_b these are up, down and beauty quarks.

LHCb physicists found the signals for the Λ_b particlesin a sample of about 60 trillion proton—proton collisions which were delivered by the LHC operating at a centre-of-mass energy of 7 TeV in 2011. They measured the masses of the new excited states as 5912 MeV/c2 and 5920 MeV/c2 respectively - over five times greater than the mass of a proton or neutron.

 CERN, the research of the secrets of the Universe

The result adds to a growing list of discoveries at CERN in recent months. Last month the Compact Muon Solenoid (CMS) experiment observed a new excited state for the Ξb beauty baryon, and back in December 2011 ATLAS detected a new "quarkonium state" containing a beauty quark bound with its antiquark.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 Member States.

Find out more:

LHCb result:

    LHCb experiment: http://lhcb-public.web.cern.ch/lhcb-public/

    CERN Bulletin: Two beautiful new particles: http://cdsweb.cern.ch/journal/CERNBulletin/2012/20/News%20Articles/1449100

Other recent discoveries:

    CMS: Observation of a new Ξb beauty particle: http://cms.web.cern.ch/news/observation-new-xib0-beauty-particle

    ATLAS discovers its first new particle: http://www.atlas.ch/news/2011/ATLAS-discovers-its-first-new-particle.html

Images, Text, Credit: CERN.

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