Top 2014: Theory Summary

This write-up is the summary of the theoretical presentations at the Top 2014 Workshop held in Mandelieu France from September 29 to October 3, 2014.Comment: 7 page

A High Quality Composite Axion

The strong CP problem is a compelling motivation for physics beyond the Standard Model. The most popular solutions invoke a global Peccei-Quinn symmetry, but are challenged by quantum gravitational corrections which are thought to be incompatible with global symmetries, arguing that realistic theories contain additional structure. We explore a construction in which the Peccei-Quinn symmetry is protected to arbitrary order by virtue of a supersymmetric, confining $SU(N)_L \times SU(N) \times SU(N)_R \times U(1)_X$ product gauge group, achieving $\bar\theta < 10^{-11}$ for an $SU(5)$ model with $f_a \lesssim 3 \times 10^{11}$ GeV. This construction leads to low energy predictions such as a $U(1)_X$ gauge symmetry, and for $X = B-L$ engineers a naturally order ~TeV value for the $\mu$ parameter of the MSSM.Comment: 17 pages, 2 figures, 3 table

Top Spin and Experimental Tests

We examine pair mass dependence near threshold as a means to measure the spin of the top quark in hadron collisions, and we discuss the possibility that a top squark signal could be hidden among the top events.Comment: 9 pages, RevTeX, 3 figures. Contribution to the Thinkshop on Top-Quark Physics for the Tevatron Run II, Fermilab, October 16 - 18, 199

Supersymmetry Breaking, Fermion Masses and a Small Extra Dimension

We present a supersymmetric model in which the observed fermion masses and mixings are generated by localizing the three generations of matter and the two Higgs fields at different locations in a compact extra dimension. Supersymmetry is broken by the shining method and the breaking is communicated to standard model fields via gaugino mediation. Quark masses, CKM mixing angles and the mu term are generated with all dimensionless couplings of O(1). All dimensionful parameters are of order the five-dimensional Planck scale except for the size of the extra dimension which is of order the GUT scale. The superpartner spectrum is highly predictive and is found to have a neutralino LSP over a wide range of parameter space. The resulting phenomenology and interesting extensions of the model are briefly discussed.Comment: Comments and References added, submitted to JHE

Collider Constraints on Dipole-Interacting Dark Matter

Dark matter which interacts through a magnetic or electric dipole moment is an interesting possibility which may help to resolve the discrepancy between the DAMA annual modulation signal and the null results of other searches. In this article we examine relic density and collider constraints on such dark matter, and find that for couplings needed to explain DAMA, the thermal relic density is generically in the right ballpark to account for cosmological measurements. Collider constraints are relevant for light WIMPs, but less constraining that direct searches for masses above about 10 GeV.Comment: 11 pages, 2 figures, extended discussion, added references, conclusion unchange

Collisions of Jets of Particles from Active Galactic Nuclei with Neutralino Dark Matter

We examine the possibility that energetic Standard Model particles contained in the jets produced by active galactic nuclei (AGN) may scatter off of the dark matter halo which is expected to surround the AGN. In particular, if there are nearby states in the dark sector which can appear resonantly in the scattering, the cross section can be enhanced and a distinctive edge feature in the energy spectrum may appear. We examine bounds on supersymmetric models which may be obtained from the Fermi Gamma-ray Space Telescope observation of the nearby AGN Centaurus A.Comment: 20 pages, 9 figures; v2: version published in JCA