• John
  • Felde
  • University of Maryland
  • USA

Latest Posts

  • James
  • Doherty
  • Open University
  • United Kingdom

Latest Posts

  • CERN
  • Geneva
  • Switzerland

Latest Posts

  • Aidan
  • Randle-Conde
  • Université Libre de Bruxelles
  • Belgium

Latest Posts

  • Vancouver, BC
  • Canada

Latest Posts

  • Laura
  • Gladstone
  • MIT
  • USA

Latest Posts

  • Steven
  • Goldfarb
  • University of Michigan

Latest Posts

  • Fermilab
  • Batavia, IL
  • USA

Latest Posts

  • Seth
  • Zenz
  • Imperial College London
  • UK

Latest Posts

  • Nhan
  • Tran
  • Fermilab
  • USA

Latest Posts

  • Alex
  • Millar
  • University of Melbourne
  • Australia

Latest Posts

  • Ken
  • Bloom
  • USA

Latest Posts

Aidan Randle-Conde | Université Libre de Bruxelles | Belgium

View Blog | Read Bio

Advent Calendar 2012 December 20th

When it comes to the Standard Model the g-2 measurements give us both the best agreement between theory and experiment, and one of the biggest discrepancies that just won’t seem to go away! Lepton universality is one of the most stringently tested symmetries we have, and yet it does not stand up to the most precise measurements. This is a very big hint that there should be new physics out there!



  • http://tinyurl.com/d9eh7kd Iliana Bonalumi

    Discrepancies to the standard model. A threat? No! A chance for new exciting physics! Thanks for sharing :)

  • EDBM

    This story reminds me a little about the story of the Bohr model of the hydrogen atom, which (if I remember correctly) predicted the energy levels of the electron pretty well, but failed to scale up to two or more electrons.

    When you say that there might be other particles involved in the mu-photon interaction, I don’t quite get what would enable it for the muon and not the electron. I suppose theorists have speculated about this, are there any strong hypotheses about it and if so is anyone going to try and find out about it?

    And is there anything known about the corresponding situation with the tau, or is that too hard to measure?

  • http://aidanatcern.wordpress.com Aidan Randle-Conde

    Hi, good questions! The reason why the muon might be more sensitive to new particles than the electron is simply because it is heavier, so the amount of “extra” energy required to create new particles is smaller. When the muon (or electron) emits a virtual photon its mass must change to account for the emission of energy. This is allowed under the uncertainty principle as long as the muon (or electron) reabsorbs the photon quickly enough. This virtual photon can then create pairs of virtual particles as a second order correction. Since the muon can change its virtual mass more than the electron can, it’s more likely to create pairs of virtual particles and that’s why the muon is more sensitive to the new physics than the electron is.

    As you point out, we would expect the tau to be even more sensitive to these new particles, but unfortunately its lifetime is so short (7 orders of magnitude smaller than that of the muon) that making measurements with the tau is extremely difficult, and probably impossible.

  • KevinTran

    Nice post!