2010/01/01 by Martin Spinrath, Spinrath, Martin
Engineering · Physics and Astronomy · #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Neutrino Physics Research #Particle accelerators and beam dynamics #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.1009.2511
openalex publication_date 2010/09/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We derive predictions for Yukawa coupling ratios within GUTs generated from\noperators with mass dimension four and five. These relations are a\ncharacteristic property of unified flavour models and can reduce the large\nnumber of free parameters related to the flavour sector of the SM. The Yukawa\ncouplings of the down-type quarks and charged leptons are affected within SUSY\nmodels by tan beta-enhanced threshold corrections. We analyse these corrections\nand give simple analytic expressions and numerical estimates for them. The\nthreshold corrections sensitively depend on the soft SUSY breaking parameters.\nEspecially, they determine if the affected Yukawa couplings are enhanced or\nsuppressed. In a first approach, we make some plausible assumptions about the\nsoft SUSY parameters. In a second, more sophisticated approach we use three\ncommon breaking schemes in which all the soft breaking parameters at the\nelectroweak scale can be calculated from only a handful of parameters. Within\nthis approach, we apply various phenomenological constraints on the\nsupersymmetric parameters and find in this way new viable Yukawa coupling\nrelations, for example ymu/ys = 9/2 or 6 or ytau/yb = 3/2 in SU(5).\nFurthermore, we study a special class of quark mass matrix textures for small\ntan beta where theta13u = theta13d = 0. We derive sum rules for the quark\nmixing parameters and find a simple relation between the two phases delta12u\nand delta12d and the right unitarity triangle angle alpha which suggests a\nsimple phase structure for the quark mass matrices. To complement the\naforementioned considerations, we give two explicit examples in an SU(5)\ncontext, one for large and one for small tan beta which implement the Yukawa\ncoupling relations mentioned before. The models have interesting\nphenomenological consequences like, for example, quasi-degenerate neutrino\nmasses in the case of small tan beta.\n