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13 November 2012
Image above: A beam of protons enters the LHCb detector on the left, creating a B0s particle, which decays into two muons (purple tracks crossing the whole detector). (Image: LHCb/CERN).
Today at the Hadron Collider Physics Symposium in Kyoto, Japan, the Large Hadron Collider beauty (LHCb) collaboration presented evidence for one of the rarest particle decays ever observed.
The Standard Model of particle physics predicts that the B0S particle, which is made of a bottom antiquark bound to a strange quark, should decay into a pair of muons (μμ) about 3 times in every billion (109) decays. LHCb's measurement, from an analysis of data from 2011 and part of that from 2012, gives a value of (3.2+1.5-1.2) × 10-9. LHCb spokesperson Pierluigi Campana told the CERN Bulletin that the value is "in very good agreement with the prediction."
Particle physicists describe the certainty of a result on a scale that goes up to 5 sigma. One sigma could be a random statistical fluctuation in the data, 3 sigma counts as evidence, but only a full 5-sigma result is a discovery. The significance of the LHCb measurement is 3.5 sigma and therefore is classified as the first evidence for the B0s →μμ decay.
CERN LHC - To discover the secrets of the Universe
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:
Conference website: http://www.icepp.s.u-tokyo.ac.jp/hcp2012/
LHCb: http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html
CERN Bulletin: A rare sight: http://cdsweb.cern.ch/journal/CERNBulletin/2012/46/News%20Articles/1493237?ln=en
Images, Text, Credit: CERN / LHCb.
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