Until recently, all particle physics measurements fit the predictions of the Standard Model, a widely-accepted framework describing subatomic particles and how they interact. Scientists at CERN’s Large Hadron Collider (LHC), the world’s largest and strongest particle collider, study subatomic particles by smashing them together at speeds close to the speed of light and observing the results.
Over the past few months, researchers at the LHC have taken a step toward proving that at least one process may not follow the rules of the Standard Model. Because the Standard Model is a scientific cornerstone of how we view our world, describing the building blocks of matter and how they fit together, any proven digression from its predictions would be monumental.
One of the most important facets of the Standard Model is its classification of subatomic particles. One such particle, slightly smaller than a proton but several levels larger than the smallest known particles, is called a “b-meson.” In 2011 and 2012, scientists at the LHC observed b-meson decay, in which a b-meson is broken into several smaller particles, including tau leptons and muons. A component of the Standard Model called “lepton universality” dictates that these two elementary particles should be produced at the same rate. Lepton universality is important: according to UMD team lead Hassan Jawahery, “Lepton universality is truly enshrined in the Standard Model. If this universality is broken, we can say that we’ve found evidence for non-standard physics.”
The 2011-2012 observations showed slight but potentially important deviations from the predicted rate of production of tau leptons and muons through b-meson decay when analyzed in 2015. At the time, there was insufficient evidence to declare a violation of the Standard Model. New methods of analysis this year, however, have allowed scientists to move one
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