Impact of a Higgs boson at a mass of 126 GeV on the standard model with three and four fermion generations

Eberhardt, Otto; Herbert, Geoffrey; Lacker, Heiko; Lenz, Alexander; Menzel, Andreas; Nierste, Ulrich; Wiebusch, Martin

Abstract

We perform a comprehensive statistical analysis of the standard model (SM) with three and four generations using the latest Higgs search results from LHC and Tevatron, the electroweak precision observables measured at LEP and SLD, and the latest determinations of MW, mt, and αs. For the three-generation case we analyze the tensions in the electroweak fit by removing individual observables from the fit and comparing their predicted values with the measured ones. In particular, we discuss the impact of the Higgs search results on the deviations of the electroweak precision observables from their best-fit values. Our indirect prediction of the top mass is mt=175.7+3.0−2.2  GeV at 68.3% C.L., which is in good agreement with the direct measurement. We also plot the preferred area in the MW-mt plane. The best-fit Higgs boson mass is 126.0 GeV. For the case of the SM with a perturbative sequential fourth fermion generation (SM4) we discuss the deviations of the Higgs signal strengths from their best-fit values. The H→γγ signal strength now disagrees with its best-fit SM4 value at more than 4σ. We perform a likelihood-ratio test to compare the SM and SM4 and show that the SM4 is excluded at 5.3σ. Without the Tevatron data on H→bb¯ the significance drops to 4.8σ.

Citation

Eberhardt, O., Herbert, G., Lacker, H., Lenz, A., Menzel, A., Nierste, U., & Wiebusch, M. (2012). Impact of a Higgs boson at a mass of 126 GeV on the standard model with three and four fermion generations. Physical Review Letters, 109(24), Article 241802. https://doi.org/10.1103/physrevlett.109.241802

• Journal Article Type: Article
• Publication Date: Dec 11, 2012
• Deposit Date: Mar 15, 2013
• Publicly Available Date: Jul 18, 2014
• Journal: Physical Review Letters
• Print ISSN: 0031-9007
• Electronic ISSN: 1079-7114
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 109
• Issue: 24
• Article Number: 241802
• DOI: https://doi.org/10.1103/physrevlett.109.241802