BT2: Implications of unified models with extra dimensions
Recent progress in merging field-theoretic models of grand unification (the so-called orbifold GUTs) with string theory has facilitated the construction of potentially realistic and nevertheless predictive models. These models exhibit certain interesting features (which are not put in by hand but are a consequence of stringy consistency relations) such as a relation between the top Yukawa coupling and the (unified) gauge coupling, non-Abelian discrete flavour symmetries and a novel solution to the MSSM μ problem. It is desirable to obtain a better understanding of these models and their phenomenological implications. The program here is quite challenging. To study these models one has to derive the spectra, calculate the couplings, identify phenomenologically viable minima of the effective potential, and compute their properties (including quantum corrections). The embedding of orbifold GUTs in string theory has been initiated in [1, 2, 3, 4]. The first example of a potentially realistic model has been presented in [5, 6]. Meanwhile, a large sample of similar models has been constructed [7] and discussed [8, 9]. Clearly, once one has obtained a deeper understanding of the models one can discuss many phenomenological implications, including flavour-related topics. More importantly, the models (e.g. the way the μ problem is solved in these constructions) is expected to lead to an inequivocal prediction for LHC.
References:
Recent progress in merging field-theoretic models of grand unification (the so-called orbifold GUTs) with string theory has facilitated the construction of potentially realistic and nevertheless predictive models. These models exhibit certain interesting features (which are not put in by hand but are a consequence of stringy consistency relations) such as a relation between the top Yukawa coupling and the (unified) gauge coupling, non-Abelian discrete flavour symmetries and a novel solution to the MSSM μ problem. It is desirable to obtain a better understanding of these models and their phenomenological implications. The program here is quite challenging. To study these models one has to derive the spectra, calculate the couplings, identify phenomenologically viable minima of the effective potential, and compute their properties (including quantum corrections). The embedding of orbifold GUTs in string theory has been initiated in [1, 2, 3, 4]. The first example of a potentially realistic model has been presented in [5, 6]. Meanwhile, a large sample of similar models has been constructed [7] and discussed [8, 9]. Clearly, once one has obtained a deeper understanding of the models one can discuss many phenomenological implications, including flavour-related topics. More importantly, the models (e.g. the way the μ problem is solved in these constructions) is expected to lead to an inequivocal prediction for LHC.
References:
- T. Kobayashi, S. Raby, and R.-J. Zhang,
Constructing 5d orbifold grand unified theories from heterotic strings,
Phys. Lett. B593 (2004) 262-270, hep-ph/0403065. - S. Förste, H.P. Nilles, P.K.S. Vaudrevange, and A. Wingerter,
Heterotic brane world,
Phys. Rev. D70 (2004) 106008, hep-th/0406208. - T. Kobayashi, S. Raby, and R.-J. Zhang,
Searching for realistic 4d string models with a Pati-Salam symmetry: Orbifold grand unified theories from heterotic string compactification on a Z(6) orbifold,
Nucl. Phys. B704 (2005) 3-55, hep-ph/0409098. - W. Buchmuller, K. Hamaguchi, O. Lebedev and M. Ratz,
Dual models of gauge unification in various dimensions,
Nucl. Phys. 712 (2005) 139, hep-ph/0412318. - W. Buchmuller, K. Hamaguchi, O. Lebedev and M. Ratz,
Supersymmetric standard model from the heterotic string,
Phys. Rev. Lett.96 (2006) 121602, hep-ph/0511035. - W. Buchmuller, K. Hamaguchi, O. Lebedev and M. Ratz,
Supersymmetric standard model from the heterotic string. II,
Nucl. Phys. 785 (2007) 149, hep-th/0606187. - O. Lebedev, H.P. Nilles, S. Raby, S. Ramos-Sanchez, M. Ratz, P.K.S. Vaudrevange and A. Wingerter,
A mini-landscape of exact MSSM spectra in heterotic orbifolds,
Phys. Lett. 645 (2007) 88, hep-th/0611095. - O. Lebedev, H.P. Nilles, S. Raby, S. Ramos-Sanchez, M. Ratz, P.K.S. Vaudrevange and A. Wingerter,
Low Energy Supersymmetry from the Heterotic Landscape,
Phys. Rev. Lett. 98 (2007) 181602, hep-th/0611203. - O. Lebedev, H.P. Nilles, S. Raby, S. Ramos-Sanchez, M. Ratz, P.K.S. Vaudrevange and A. Wingerter,
The Heterotic Road to the MSSM with R parity,
0708.2691 [hep-th].
