Vector-like bottom quarks in composite Higgs models

• Published in: The journal of high energy physics 2014-03, Vol.2014 (3), p.1-46, Article 37
• Main Authors: Gillioz, M., Gröber, R., Kapuvari, A., Mühlleitner, M.
• Format: Article
• Language: English
• Subjects: Classical and Quantum Gravitation; Compatibility; Deviation; Elementary Particles; High energy physics; Joining; Particulate composites; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quarks; Relativity Theory; Searching; Standard model (particle physics); String Theory
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP03(2014)037

A bstract Like many other models, Composite Higgs Models feature the existence of heavy vector-like quarks. Mixing effects between the Standard Model fields and the heavy states, which can be quite large in case of the top quark, imply deviations from the SM. In this work we investigate the possibility of heavy bottom partners. We show that they can have a significant impact on electroweak precision observables and the current Higgs results if there is a sizeable mixing with the bottom quark. We explicitly check that the constraints from the measurement of the CKM matrix element V tb are fulfilled, and we test the compatibility with the electroweak precision observables. In particular we evaluate the constraint from the Z coupling to left-handed bottom quarks. General formulae have been derived which include the effects of new bottom partners in the loop corrections to this coupling and which can be applied to other models with similar particle content. Furthermore, the constraints from direct searches for heavy states at the LHC and from the Higgs search results have been included in our analysis. The best agreement with all the considered constraints is achieved for medium to large compositeness of the left-handed top and bottom quarks.