118479322
Dark matter asymmetry in supersymmetric Dirac leptogenesis
Abstract We discuss asymmetric or symmetric dark matter candidate in the supersymmetric Dirac leptogenesis scenario. By introducing a singlet superfield coupling to right-handed neutrinos, the overabundance problem of dark matter can be evaded and various possibilities for dark matter candidate arise. If the singlino is the lightest supersymmetric particle (LSP), it becomes naturally asymmetric dark matter. On the other hand, the right-handed sneutrino is a symmetric dark matter candidate whose relic density can be determined by the usual thermal freeze-out process. The conventional neutralino or gravitino LSP can be also a dark matter candidate as its non-thermal production from the right-handed sneutrino can be controlled appropriately. In our scenario, the late-decay of heavy supersymmetric particles mainly produces the right-handed sneutrino and neutrino which is harmless to the standard prediction of the Big-Bang Nucleosynthesis.
42769057
Conditions for large non-Gaussianity in two-field slow-roll inflation
We study the level of primordial non-Gaussianity in slow-roll two-field inflation. Using an analytic formula for the non-linear parameter fNL in the case of a sum or product separable potential, we find that it is possible to generate significant non-Gaussianity even during slow-roll inflation with Gaussian perturbations at Hubble exit. In this paper we give the general conditions for obtaining large non-Gaussianity and calculate the level of fine-tuning required to obtain this. We present explicit models in which the non-Gaussianity at the end of inflation can exceed the current observational bound of .
7390821
Spectral running and non-Gaussianity from slow-roll inflation in generalized two-field models
Theories beyond the standard model such as string theory motivate low energy effective field theories with several scalar fields which are not only coupled through a potential but also through their kinetic terms. For such theories we derive the general formulae for the running of the spectral indices for the adiabatic, isocurvature and correlation spectra in the case of two-field inflation. We also compute the expected non-Gaussianity in such models for specific forms of the potentials. We find that the coupling has little impact on the level of non-Gaussianity during inflation.
119366917
Double suppression of FCNCs in supersymmetric models
A mechanism for double suppression of flavor-changing neutral currents (FCNCs) and CP violating phases in supersymmetric models is suggested. At M{sub SUSY} they are suppressed due to a nonabelian discrete flavor symmetry, and the infrared attractive force of gauge interactions in extra dimensions are used to suppress them at the compactification scale. We present a concrete model, which is a simple extension of S{sub 3} invariant minimal supersymmetric standard model, where only SU(2){sub L} and SU(3){sub C} gauge multiplets are assumed to propagate in the bulk. We find that a disorder of 2 orders of magnitude in soft supersymmetry breaking parameters above the compactification scale may be allowed to satisfy experimental constraints on FCNC processes and CP violating phenomena.
118604242
Quasar polarization with two axionlike particles
Abstract Recently, it was shown, that the absence of circular polarization of visible light from quasars, severely constrains the interpretation of axion like particles (ALPs) as a solution for the generation of the linear polarization. Furthermore, the new observation of the linear polarization in the radio wavelength from quasars, similar to the earlier observation performed in the optical band, makes the ALPs scenario inconsistent with at least one of the two observations. In this study we extend this scenario, to two axion like particles, one scalar and another pseudoscalar. We find, that the effects from scalar and pseudoscalar cancel out each other, thereby suppressing the circular polarization, while preserving consistent linear polarization, as observed in both visible and radio waves bands.
14862395
Softness of brane-localized supersymmetry breaking on orbifolds
Abstract We consider the brane-localized supersymmetry breaking in 5D compactified on S 1 / Z 2 . In case of a bulk gaugino with arbitrary brane masses for its even and odd modes, we find the mass spectrum and the wave functions of gaugino. We show that the gaugino masses at the distant brane are soft in the usual sense in the effective field theory with zero modes of bulk gauge fields and they are also extremely soft in view of the one-loop finite mass of a brane scalar in the KK regularization.
119256844
Effective interactions of axion supermultiplet and thermal production of axino dark matter
We discuss the effective interactions of axion supermultiplet, which might be important for analyzing the cosmological aspect of supersymmetric axion model. Related to axino cosmology, it is stressed that three seemingly similar but basically different quantities, the Wilsonian axino-gluino-gluon coupling, the 1PI axino-gluino-gluon amplitude, and the PQ anomaly coefficient, should be carefully distinguished from each other for correct analysis of the thermal production of axinos in the early Universe. It is then noticed that the 1PI axino-gluino-gluon amplitude at energy scale p in the range MΦ < p < vPQ is suppressed by MΦ2/p2 in addition to the well-known suppression by p/16π2vPQ, where MΦ is the mass of the heaviest PQ-charged and gauge-charged matter supermultiplet in the model, which can be well below the PQ scale vPQ. As a result, axino production at temperature T > MΦ is dominated by the production by matter supermultiplet, not by the production by gauge supermultiplet. Still the axino production rate is greatly reduced if MΦ ≪ vPQ, which would make the subsequent cosmology significantly altered. This would be most notable in the supersymmetric DFSZ model in which MΦ corresponds to the Higgsino mass which is around the weak scale, however a similar reduction is possible in the KSVZ model also. We evaluate the relic axino density for both the DFSZ and KSVZ models while including the axino production in the processes involving the heaviest PQ-charged and gauge-charged matter supermultiplet.
14057206
Heterotic SO(32) model building in four dimensions
Four dimensional heterotic SO(32) orbifold models are classified systematically with model building applications in mind. We obtain all 3, 7 and 2N models based on vectorial gauge shifts. The resulting gauge groups are reminiscent of those of type-I model building, as they always take the form SO(2n0) ? U(n1) ? ... ? U(nN?1) ? SO(2nN). The complete twisted spectrum is determined simultaneously for all orbifold models in a parametric way depending on n0,...,nN, rather than on a model by model basis. This reveals interesting patterns in the twisted states: They are always built out of vectors and anti-symmetric tensors of the U(n) groups, and either vectors or spinors of the SO(2n) groups. Our results may shed additional light on the S-duality between heterotic and type-I strings in four dimensions. As a spin-off we obtain an SO(10) GUT model with four generations from the 4 orbifold.
120650932
Electromagnetic and Axial Form Factors of Octet and Decuplet Baryons
We report from a study of the elastic electromagnetic and axial form factors of all lowest baryon states with flavors up, down, and strange along relativistic constituent-quark models. We consider the baryons as relativistic bound states of three constituent quarks and solve the eigenvalue problem of the invariant mass operator. The corresponding eigenstates are employed to calculate manifestly covariant form factors within the point form of Poincaré-invariant quantum mechanics. The electromagnetic and axial current operators are constructed along the spectator model in point-form relativistic dynamics. We have thus obtained covariant predictions for the electroweak form factors, for momentum transfers up to Q2 ~ 4 GeV2, as well as the electric radii, magnetic moments, and axial charges. The theoretical results in general agree very well with existing phenomenological data. In cases, where no experimental information is yet available, the results are well compatible with data from lattice quantum chromodynamics.
119238385
THERMAL PRODUCTION OF AXINO DARK MATTER
We discuss certain features of the low energy effective interactions of axion supermultiplet, which are relevant for axino cosmology, and examine the implication to thermal production of axino in the early Universe.
118129565
Axial properties of the nucleon and N* resonances
We report results from a theoretical study of axial charges and axial form factors of the nucleon N and its resonant states N*. By employing relativistic constituent-quark models we could produce for the first time covariant predictions for the axial-current matrix elements. The calculations are performed in the point form of Poincare-invariant quantum mechanics. The axial charge as well as the axial form factor of the nucleon are reproduced close to phenomenology. The axial charges of the N*(1535) and N*(1650) resonances – the only cases where such a comparison is possible – agree well with results from quantum chromodynamics on the lattice that have recently become available. Here, we present the axial charges of all N* excitations below ~2 GeV and two examples of N* axial form factors. These results should be interesting for comparison with other approaches, especially with regard to the issue of chiral-symmetry restoration in higher-lying hadron resonances.