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Advances in High Energy Physics
Volume 2013, Article ID 769240, 9 pages
Research Article

Towards Reviving Electroweak Baryogenesis with a Fourth Generation

Department of Physics, National Taiwan University, Taipei 10617, Taiwan

Received 22 June 2012; Accepted 27 December 2012

Academic Editor: Tao Han

Copyright © 2013 Wei-Shu Hou and Masaya Kohda. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Electroweak baryogenesis is an attractive scenario for explaining the baryon asymmetry of the universe. However, it does not work within the standard model due to two reasons: (1) the strength of CP violation from the Kobayashi-Maskawa mechanism with three generations is too small; (2) the electroweak phase transition is not first order for the experimentally allowed Higgs boson mass. We discuss possibilities to solve these problems by introducing a fourth generation of fermions and how electroweak baryogenesis might be revived. We also discuss briefly the recent observation of a Higgs-like boson with mass around 125 GeV, which puts the fourth generation in a difficult situation, and the possible way out.