Phenomenology of Twisted Moduli in Type I String Inspired Models

Abstract

We make a first study of the phenomenological implications of twisted moduli in type I intersecting D5-brane models, focussing on the resulting predictions at the LHC using SOFTSUSY to estimate the Higgs and sparticle spectra. Twisted moduli can play an important role in giving a viable string realisation of sequestering in the limit where supersymmetry breaking comes entirely from the twisted moduli. We focus on a particular string inspired version of gaugino mediation in which the first two families are localised at the intersection between D5-branes, whereas the third family and Higgs doublets are allowed to move within the world-volume of one of the branes. The soft supersymmetry breaking third family sfermion mass terms are then in general non-degenerate with the first two families. We place constraints upon parameter space and predictions of flavour changing neutral current effects. Twisted moduli domination is studied and, as well as solving the most serious part of the SUSY flavour problem, is shown to be highly constrained. The constraints are weakened by switching on gravity-mediated contributions from the dilaton and untwisted T-moduli sectors. In the twisted moduli domination limit we predict a stopheavy MSSM spectrum and quasi-degenerate lightest neutralino and chargino states with wino-dominated mass eigenstates. A. Derivation of the SUSY breaking F-terms 28B. Phenomenological problems with "pure"gMSB 30 imental signatures at future colliders, and also non-standard gauge coupling unification at scales well below M X ∼ 2 × 10 16 GeV [5]. The Dirichlet branes are required for consistency, but provide a mechanism for localising matter and gauge fields (open string states) on a lower-dimensional slice of the full 10d spacetime in which gravity (closed strings) lives. These exciting new features have lead to a renaissance in string phenomenology, and renewed attempts to derive the (supersymmetric) Standard Model directly from a string theory compactification.Recent developments have also motivated the study of higher-dimensional field theories that may describe the low-energy limit of string theory. Many string-inspired ideas and techniques including branes, orbifolding and Kaluza-Klein towers are now commonly used in model-building [6]. These models are studied with effective field theory (EFT) techniques valid up to some ultraviolet (UV) cutoff scale Λ U V < M * , where the string-like features cannot be resolved. In particular, branes can be associated with orbifold fixed points rather than the string-theoretic picture of hypersurfaces where open strings end, and strings are treated as point-particles. Also Standard Model states can be allocated arbitrarily to different points/branes in the higher-dimensional space, and often orbifold symmetry assignments dictate whether a particular coupling is allowed or not [7].Many new models have been constructed to investigate quasi-realistic extensions of the (supersymmetric) Standard Model, where the extra-dimensional framework offers novel solutions to proble...

Collider signals and neutralino dark matter detection in relic-density-consistent models without universality

“…The normal scalar mass hierarchy model (NMH) examines the effect of generational non-universality in the SSB sfermion mass parameters [41,20,42]. While constraints from K −K mass difference restrict first and second generation scalar masses to be nearly universal, the constraints arising from B −B mixing are much less strict, and some nonuniversality of third generation matter scalars compared to first/second generation matter scalars can be allowed.…”

Natural dark matter from type I string theory

“…In this paper we extend our previous analysis of the non-universal MSSM to a semi-realistic type I string theory model of the form originally proposed in [4] and phenomenologically analysed in [5] (see also [6], [7], [8], [9]). Using such a string model we can address two questions.…”

“…Within this paper we follow [5] in taking T 2 + T 2 = 50 and Y 2 + Y 2 = 0. This maintains the validity of the series expansion in δ GS /(T 2 + T 2 ) used to determine the F-terms.…”

“…The ratio of GUT scale gaugino masses is determined by φ, as shown in Table 1. To analyse the low energy gaugino mass ratio, and so study the composition of theχ Table 2: Benchmark points from [5]. B and C overclose the universe and so are ruled out by dark matter.…”

“…The model we use to address these points is the type I string inspired model in [4] in which we can obtain SUSY breaking from any of twisted (Y) moduli, untwisted (T) moduli or the dilaton (S). The phenomenology of SUSY breaking in this model has been studied in [5]. Neutralino dark matter has not so far been studied in this string model, or any string model involving twisted moduli, although it has been studied in other string models [10]- [13].…”