We discuss the possibility of introducing an SU(2) global flavour symmetry in the context of flat extra dimensions. In particular we concentrate on the 5-dimensional case and we study how to obtain the flavour structure of the Standard Model quark sector compactifying the fifth dimension on the orbifold S1/Z2 a la Scherk-Schwarz (SS). We show that in this case it is possible to justify the five orders of magnitude among the values of the quark masses with only one parameter: the SS flavour parameter. The non-local nature of the SS symmetry breaking mechanism allows to realize this without introducing new instabilities in the theory.
We analyze superfield representations of BPS-conditions for the self-dual static solutions of D = 4, N = 2 supersymmetric Yang-Mills theory.
The restrictions on the lightest Higgs boson mass in the minimal supersymmetric models are briefly reviewed. The particle spectrum is considered in the framework of the simplest modification of NMSSM that allows to avoid the domain wall problem and to get the self--consistent solution in the strong Yukawa coupling limit. The lightest Higgs boson mass in the investigated model can reach $125 GeV$ at values of $\tan\beta\ge 1.9$ and does not exceed $130.5\pm 3.5 GeV$.
We discuss the embedding of R-Parity preserving Minimal Left Right Supersymmetric models into Pati-Salam and SO(10) GUTs.
The Coset Space Dimensional Reduction scheme is briefly reviewed. Then a ten-dimensional supersymmetric $E_8$ gauge theory is reduced over symmetric and non-symmetric six-dimensional coset spaces. In general a four-dimensional non-supersymmetric gauge theory is obtained in case the used coset space is symmetric, while a softly broken supersymmetric gauge theory is obtained if the used coset space is non-symmetric. In the process of exhibiting the above properties we also present two attractive models, worth exploiting further, which lead to interesting GUTs with three families in four dimensions.
We consider the problem of supersymmetry breaking in 5 dimensional N=1 supersymmetric models with S^1/Z_2 compactification.
The SUSY contribution to the muon magnetic moment anomaly, a_mu^SUGRA, and the electron electric dipole moment, d_e, is discussed within the framework of a modified mSUGRA model where the magnitudes of the soft breaking masses are universal, but arbitrary phases are allowed. It is shown analytically how the cancellation mechanism can allow for large phases (i.e. theta_B <~ 0.4) and still suppress the value of d_e below its current experimental bound. The dependence of a_mu^SUGRA on the CP violating phases are analytically examined, and seen to decrease it but by at most a factor of about two. This reduction would then decrease the upper bound on m_1/2 due to the lower bound of Brookhaven data, and hence lower the SUSY mass spectrum, making it more accessible to accelerators. At the electroweak scale, the phases have to be specified to within a few percent to satisfy the experimental bound on d_e, but at the GUT scale, fine tuning below 1% is required for lower values of m_1/2. This fine tuning problem will become more serious if the bound on d_e is decreased.
We construct SU(5) SUSY GUT in 5D compactified on S^1/Z_2 orbifold where the matter fields are living in the five dimensional bulk. SU(5) symmetry is broken down to the Standard Model gauge group by the orbifold projection which automatically ensures stability of proton in all orders of perturbation theory. The model predicts extra mirror quark-lepton families which along with the GUT particles and the excitations of extra dimensions could be observable at high energy colliders providing the unification scale is in the TeV range.
It is shown that a realistic SUSY SU(6) GUT can dynamically generate the GUT scale and solve at the same time the doublet-triplet splitting problem. The cosmological implications of such a model are briefly reviewed.
The origin of quark and lepton masses is one of the outstanding problems of physics. As the experimental data becomes more and more accurate, testing theories of fermion masses requires greater care. In this talk we discuss a theoretical framework for testing those theories with a high energy desert. It is only with precision tests that we can hope to narrow the set of viable, beyond the standard model theories.
Single production at hadron and photon colliders of gluinos and sneutrinos of supersymmetric models, as well as radions of the Randall-Sundrum model, is discussed. In the case of supersymmetry, R-parity breaking is needed in order to produce single susy particles. Resonant production of radions is considered at gamma-gamma collider.
We consider interaction of two lumps corresponding to 0-branes in noncommutative gauge theory
The large freedom in the SM fermionic mass matrices allows for large LH and LH quark rotations. This is a natural possibility in view of the observed large leptonic mixing. Proton decay and especially its gauge mediated decay is sensitive also to those mixing angles which are non-relevant in the SM. A model with realistic mass matrices and large rotations is presented.. It is shown that the large leptonic mixing leads to enhancement of the proton decay branching ratios involving muons.
A brief overview is given of recent developments in the analyses of large phases and CP violation in supersymmetric unified models. The problem of experimental electric dipole moment constraints and large phases is discussed. Implications of large phases on supersymmetric phenomena are reviewed. The possibility of generating a muon electric dipole moment much larger than implied by the scaling relation d_μ/d_e≃ m_μ/m_e from lepton flavor nonuniversality and within reach of the recently proposed Brookhaven experiment for a sensitive probe of d_μ is also discussed.
We summarize some recent progress in constructing four-dimensional supersymmetric chiral models from Type II orientifolds. We present the construction a supersymmetric Standard-like Model and a supersymmetric GUT model to illustrate the new features of this approach and its connection to M theory on compact, singular G_2 holonomy spaces. The Standard-like model presented is the first example of a three-family supersymmetic orientifold model with the Standard Model as part of the gauge structure. We also discuss the connection of how chiral fermions arise in this class of models with recent results of M theory compactified on G_2 holonomy spaces.
It is shown that two definitions for the exterior differential in superspace, giving the same exterior calculus, when applied to the Poisson bracket lead to the different results. Examples of the even and odd linear brackets, corresponding to semi-simple Lie groups, are given and their natural connection with BRST and anti-BRST charges is indicated.
We report on the result of a search for charginos and neutralinos in ee collisions at centre-of-mass energies between 203 GeV and 208 GeV at LEP. No evidence for such particles is found in a data sample of 220 pb 1 per experiment. Improved upper limits for these particles are set on the production cross sections. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived, as well as new lower limits on the masses of these supersymmetric particles. Chargino masses below 103 GeV are excluded over large regions of the parameter space of the Minimal Supersymmetric Standard Model.
We discuss physical implications of the four-dimensional effective supergravity, that describes low-energy physics of the Randall--Sundrum model with moduli fields in the bulk and charged chiral matter living on the branes. Cosmological constant can be cancelled through the introduction of a brane Polonyi field and a brane superpotential for the 4d dilaton. We deduce a generalization of the effective 4d action to the case of a general, not necessarily exponential, warp factor. We note, that breakdown of supersymmetry in generic warped models may lead to the stabilization of the interbrane distance.
