LHCb adds a new piece to developing puzzle in particle physics.

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The LHCb experiment at CERN , in which UZH physicists play a prominent role, has performed a new measurement showing an unexpected deviation from the Standard Model of particle physics.

LHCb
LHCb
LHCb
The LHCb experiment at CERN in Geneva, in which UZH physicists play a prominent role, has performed a new measurement showing an unexpected deviation from what predicted by the so-called Standard Model of particle physics. This theory describes the nature and the interactions of the elementary constituents of matter. So far, the Standard Model has been very successful in describing the measurements performed at the at Large Hadron Collider (LHC)

In the Standard Model, each elementary particle appears in three “replica” (also referred to as “flavours”) which differ only by their mass. Why we have three copies of elementary particles, and why they differ only by their mass, is one of the big open question in particle physics. One of the heavier partner of the electron is the muon (μ). The theory predicts that processes where electron or muons are produced have identical properties, once their different masses are taken into account. This is known as Lepton Universality and is a fundamental property of the Standard Model. 

The analysis just presented by the LHCb collaboration measures the ratio (RK) between the probabilities that a Bomeson decays into a K meson accompanied by a muon-anitmuon pair (μ+μ-) or an electron-antielectron pair (e+e-). This measurement deviates from Standard Model predictions, as shown in the Figure.

 

Contact:

Prof. Nicola Serra
Physik-Institut
Winterthurerstrasse 190
CH-8057 Zürich