RWTH Aachen University: The symmetry between electrons and muons is shaky

The standard model of particle physics describes the behavior of all forces and particles in the universe. However, there is growing evidence that the Standard Model may have problems explaining all of the measurements. An international team of particle physicists from the Large Hadron Collider beauty collaboration, LHCb for short, will present two central measurements for the first time on Tuesday, March 23, 2021, as part of the Moriond EW conference and in a seminar at the CERN research center in Geneva. The data was collected at the LHCb detector at CERN, RWTH Aachen University, TU Dortmund University and the University of Heidelberg are significantly involved in these measurements.

The Standard Model of Particle Physics predicts that the electron’s heavy partners, the muon and tau particles, behave just like the electron. This identical behavior of the particles, which all belong to the group of leptons, is called lepton universality. In the LHCb experiment, some measurements are used to determine whether the behavior is actually identical or whether there are slight deviations. The focus is on very rare particle decays of B + mesons. According to the theory, they should split up into the final states “K + e + e-” and “K + mu + mu” equally often. However, it was found that B + mesons decay somewhat more frequently into the final state K + e + e-. The result could indicate a violation of lepton universality. The test value is still at a significance of 3.1 standard deviations,

“The symmetry between electrons and muons is shaky! If we confirm the measurement with further data, that would be a strong indication of new physics phenomena beyond the standard model, ”said Dr. Eluned Smith from the I. Physikalisches Institut B at RWTH Aachen. Together with Dr. Martino Borsato from the University of Heidelberg and Professor Johannes Albrecht from the TU Dortmund carried out the analysis.

“This result is part of a series of measurements that together give a consistent picture. The data currently require clear explanations and models that go beyond the standard model, such as the existence of so-called leptoquarks, ”adds Albrecht.

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