Ece Aşılar, Esin Çavlan, Oktay Doğangün, Sinan Kefeli, Erkcan Özcan, Mehmet Şahin, Gökhan Ünel
Recent improvements to OPUCEM, the tool for calculation of the contributions of various models to oblique parameters, are presented. OPUCEM is used to calculate the available parameter space for the four family Standard Model given the current electroweak precision data. It is shown that even with the restrictions on Higgs boson and new quark masses presented in the 2011 autumn conferences, there is still enough space to allow a fourth generation with Dirac type neutrinos. For Majorana type neutrinos, the allowed region is even larger. The electroweak precision data also favors non-zero mixing between light and fourth generations, thus effectively reducing current experimental limits. Additionally, calculations with OPUCEM show that even 5th and 6th generations are compatible with the existing electroweak precision data, with a probability comparable to or higher than the Standard Model with 3 generations.
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http://arxiv.org/abs/1112.0507
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