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Solving the mu problem in gauge mediated supersymmetry breaking models with flavor symmetry  [PDF]
K. S. Babu,Yukihiro Mimura
Physics , 2001,
Abstract: We suggest a solution to the \mu problem of gauge mediated supersymmtery breaking models based on flavor symmetries. In this scenario the \mu term arises through the vacuum expectation value of a singlet scalar field which is suppressed by a flavor symmetry factor relative to the scale of dynamical SUSY breaking. The same flavor symmetry also ensures that the soft SUSY breaking parameter B\mu is not much larger than \mu^2, a necessary condition for the stability of electroweak symmetry breaking. Explicit examples where B\mu ~ \mu^2 and B\mu << \mu^2 are presented. The latter case provides a natural solution to the supersymmetric CP problem. We show that the same flavor symmetry that suppresses the \mu and the B\mu parameters can also play a role in explaining the fermion mass and mixing hierarchy puzzle.
A Solution to the Strong CP Problem with Gauge-Mediated Supersymmetry Breaking  [PDF]
Otto C. W. Kong,Brian D. Wright
Physics , 1998, DOI: 10.1103/PhysRevD.58.015002
Abstract: We demonstrate that a certain class of low scale supersymmetric ``Nelson-Barr'' type models can solve the strong and supersymmetric CP problems while at the same time generating sufficient weak CP violation in the $K^{0}-\bar{K}^{0}$ system. In order to prevent one-loop corrections to $\bar{\theta}$ which violate bounds coming from the neutron electric dipole moment (EDM), one needs a scheme for the soft supersymmetry breaking parameters which can naturally give sufficient squark degeneracies and proportionality of trilinear soft supersymmetry-breaking parameters to Yukawa couplings. We show that a gauge-mediated supersymmetry breaking sector can provide the needed degeneracy and proportionality, though that proves to be a problem for generic Nelson-Barr models. The workable model we consider here has the Nelson-Barr mass texture enforced by a gauge symmetry; one also expects a new U(1) gauge superfield with mass in the TeV range. The resulting model is predictive. We predict a measureable neutron EDM and the existence of extra vector-like quark superfields which can be discovered at the LHC. Because the $3\times 3$ Cabbibo-Kobayashi-Maskawa matrix is approximately real, the model also predicts a flat unitarity triangle and the absence of substantial CP violation in the $B$ system at future $B$ factories. We discuss the general issues pertaining to the construction of such a workable model and how they lead to the successful strategy. A detailed renormalization group study is then used to establish the feasibility of the model considered.
Gaugino Mediated Supersymmetry Breaking  [PDF]
Z. Chacko,Markus A. Luty,Ann E. Nelson,Eduardo Ponton
Physics , 1999, DOI: 10.1088/1126-6708/2000/01/003
Abstract: We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a "3-brane" in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane, supersymmetry breaking is communicated to gauge and Higgs fields by direct higher-dimension interactions, and to quark and lepton fields via standard-model loops. We show that this gives rise to a realistic and predictive model for supersymmetry breaking. The size of the extra dimensions is required to be of order 10-100 times larger than fundamental scale (e.g. the string scale). The spectrum is similar to (but distinguishable from) the predictions of "no-scale" models. Flavor-changing neutral currents are naturally suppressed. The \mu term can be generated by the Giudice-Masiero mechanism. The supersymmetric CP problem is naturally solved if CP violation occurs only on the observable sector 3-brane. These are the simplest models in the literature that solve all supersymmetric naturalness problems.
Gauge Mediated Supersymmetry Breaking and Spontaneous CP Violation as a Solution to the Strong CP Problem  [PDF]
Otto C. W. Kong
Physics , 1998,
Abstract: The origin of CP violation is a major mystery, especially in relation to the strong CP problem. CP being a spontaneously broken symmetry could provide an elegant solution. However, such models have difficulty making themselves compatible with low-energy supersymmetry, which is popularly accepted as the solution to the hierarchy problem. We demonstrate that a certain class of low scale supersymmetric ``Nelson-Barr'' type models can solve the strong and supersymmetric CP problems while at the same time generating sufficient weak CP violation in the $K^{0}-\bar{K}^{0}$ system. Gauge-mediated supersymmetry breaking is used to provide the needed squark mass degeneracies and $A$-term proportionalities; though that proves to be still insufficient for a generic Nelson-Barr model. The workable model we consider here, essentially a supersymmetric version of the aspon model, has the Nelson-Barr mass texture enforced by a U(1) gauge symmetry, broken at the TeV scale. The resulting model is predictive with rich phenomenology soon to be available. Feasibility of the model considered is established by a detailed renormalization group studies.
Variations on Minimal Gauge Mediated Supersymmetry Breaking  [PDF]
Michael Dine,Yosef Nir,Yuri Shirman
Physics , 1996, DOI: 10.1103/PhysRevD.55.1501
Abstract: We study various modifications to the minimal models of gauge mediated supersymmetry breaking. We argue that, under reasonable assumptions, the structure of the messenger sector is rather restricted. We investigate the effects of possible mixing between messenger and ordinary squark and slepton fields and, in particular, violation of universality. We show that acceptable values for the $\mu$ and $B$ parameters can naturally arise from discrete, possibly horizontal, symmetries. We claim that in models where the supersymmetry breaking parameters $A$ and $B$ vanish at tree level, $\tan\beta$ could be large without fine tuning. We explain how the supersymmetric CP problem is solved in such models.
CP Violation and the Scale of Supersymmetry Breaking  [PDF]
Michael Dine,Erik Kramer,Yosef Nir,Yael Shadmi
Physics , 2001, DOI: 10.1103/PhysRevD.63.116005
Abstract: Supersymmetric models with a high supersymmetry breaking scale give, in general, large contributions to epsilon_K and/or to various electric dipole moments, even when contributions to CP conserving, flavor changing processes are sufficiently suppressed. Some examples are models of dilaton dominance, alignment, non-Abelian flavor symmetries, heavy first two generation sfermions, anomaly mediation and gaugino mediation. There is then strong motivation for `approximate CP', that is a situation where all CP violating phases are small. In contrast, in supersymmetric models with a low breaking scale it is quite plausible that the CKM matrix is the only source of flavor and CP violation. Gauge mediation provides a concrete example. Approximate CP is then unacceptable. Upcoming measurements of the CP asymmetry in B to \psi K_S might exclude or support the idea of approximate CP and consequently probe the scale of supersymmetry breaking.
A New Approach to mu-Bmu
Csaki, Csaba;Falkowski, Adam;Nomura, Yasunori;Volansky, Tomer
High Energy Physics - Phenomenology , 2008, DOI: 10.1103/PhysRevLett.102.111801
Abstract: We present a new approach to the mu-Bmu problem of gauge mediated supersymmetry breaking. Rather than reducing the generically large contribution to Bmu we point out that acceptable electroweak symmetry breaking can be achieved with mu^2 << Bmu if at the same time Bmu << m_Hd^2. This hierarchy can easily appear in models where the Higgs fields are directly coupled to the supersymmetry breaking sector. Such models can yield novel electroweak symmetry breaking vacua, can deal with the supersymmetric flavor and CP problems, allow for gauge coupling unification, and result in distinct phenomenological predictions for the spectrum of superparticles.
Z'-mediated Supersymmetry Breaking
Langacker, Paul;Paz, Gil;Wang, Lian-Tao;Yavin, Itay
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevLett.100.041802
Abstract: We consider a class of models in which supersymmetry breaking is communicated dominantly via a U'(1) gauge interaction, which also helps solve the \mu problem. Such models can emerge naturally in top-down constructions and are a version of split supersymmetry. The spectrum contains heavy sfermions, Higgsinos, exotics, and Z' ~ 10-100 TeV; light gauginos ~ 100-1000 GeV; a light Higgs ~ 140 GeV; and a light singlino. A specific set of U'(1) charges and exotics is analyzed, and we present five benchmark models. Implications for the gluino lifetime, cold dark matter, and the gravitino and neutrino masses are discussed.
Z'-mediated Supersymmetry Breaking  [PDF]
Paul Langacker,Gil Paz,Lian-Tao Wang,Itay Yavin
Physics , 2007, DOI: 10.1103/PhysRevLett.100.041802
Abstract: We consider a class of models in which supersymmetry breaking is communicated dominantly via a U'(1) gauge interaction, which also helps solve the \mu problem. Such models can emerge naturally in top-down constructions and are a version of split supersymmetry. The spectrum contains heavy sfermions, Higgsinos, exotics, and Z' ~ 10-100 TeV; light gauginos ~ 100-1000 GeV; a light Higgs ~ 140 GeV; and a light singlino. A specific set of U'(1) charges and exotics is analyzed, and we present five benchmark models. Implications for the gluino lifetime, cold dark matter, and the gravitino and neutrino masses are discussed.
New Mechanisms of Gauge-Mediated Supersymmetry Breaking  [PDF]
Lisa Randall
Physics , 1996, DOI: 10.1016/S0550-3213(97)00225-3
Abstract: We introduce new mechanisms for the communication of supersymmetry breaking via gauge interactions. These models do not require complicated dynamics to induce a nonvanishing F term for a singlet. The first class of models communicates supersymmetry breaking to the visible sector through a ``mediator" field that transforms under both a messenger gauge group of the dynamical supersymmetry breaking sector and the standard model gauge group. This model has distinctive phenomenology; in particular, the scalar superpartners should be heavier by at least an order of magnitude than the gaugino superpartners. The second class of models has phenomenology more similar to the ``standard" messenger sectors. A singlet is incorporated, but the model does not require complicated mechanisms to generate a singlet F term. The role of the singlet is to couple fields from the dynamical symmetry breaking sector to fields transforming under the standard model gauge group. We also mention a potential solution to the $\mu$ problem.
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