A rationale for long-lived quarks and leptons at the LHC: low energy flavour theory

• Published in: The journal of high energy physics 2012-02, Vol.2012 (2), Article 123
• Main Authors: Éboli, O. J. P., Savoy, C. A., Funchal, R. Zukanovich
• Format: Article
• Language: English
• Subjects: Anomalies; Broken symmetry; Classical and Quantum Gravitation; CP violation; Elementary Particles; Fermions; Flavor (particle physics); Hadrons; High energy physics; Large Hadron Collider; Leptons; Neutral currents; Physics; Physics and Astronomy; Protons; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quarks; Relativity Theory; Representations; Standard model (particle physics); String Theory; Symmetry
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP02(2012)123

A bstract In the framework of gauged flavour symmetries, new fermions in parity symmetric representations of the standard model are generically needed for the compensation of mixed anomalies. The key point is that their masses are also protected by flavour symmetries and some of them are expected to lie way below the flavour symmetry breaking scale(s), which has to occur many orders of magnitude above the electroweak scale to be compatible with the available data from flavour changing neutral currents and CP violation experiments. We argue that, actually, some of these fermions would plausibly get masses within the LHC range. If they are taken to be heavy quarks and leptons, in (bi)-fundamental representations of the standard model symmetries, their mixings with the light ones are strongly constrained to be very small by electroweak precision data. The alternative chosen here is to exactly forbid such mixings by breaking of flavour symmetries into an exact discrete symmetry, the so-called proton-hexality, primarily suggested to avoid proton decay. As a consequence of the large value needed for the flavour breaking scale, those heavy particles are long-lived and rather appropriate for the current and future searches at the LHC for quasi-stable hadrons and leptons. In fact, the LHC experiments have already started to look for them.