John March-Russell

Abstract:

In string realizations of the Randall-Sundrum scenario, the higher-spin Regge excitations of Standard Model states localized near the IR brane are warped down to close to the TeV scale. We argue that, as a consequence of the localization properties of Randall-Sundrum models of flavour, the lightest such resonance is the spin-3/2 excitation of the right-handed top quark over a significant region of parameter space. A mild accidental cancellation allows this resonance to be as light or lighter than the Kaluza-Klein excitations of the Standard Model states. We consider from a bottom-up effective theory point of view the production and possible observability of such a spin-3/2 excitation at the LHC and Tevatron. Current limits are weaker than might be expected because of the excess of WWjj events at the Tevatron reported by CDF for an invariant mass of 400-500 GeV.

Abstract:

The DAMA collaboration have claimed to detect particle dark matter (DM) via an annual modulation in their observed recoil event rate. This appears to be in strong disagreement with the null results of other experiments if interpreted in terms of elastic DM scattering, while agreement for a small region of parameter space is possible for inelastic DM (iDM) due to the altered kinematics of the collision. To date most analyses assume a simple galactic halo DM velocity distribution, the Standard Halo Model, but direct experimental support for the SHM is severely lacking and theoretical studies indicate possible significant differences. We investigate the dependence of DAMA and the other direct detection experiments on the local DM velocity distribution, utilizing the results of the Via Lactea and Dark Disc numerical simulations. We also investigate effects of varying the solar circular velocity, the DM escape velocity, and the DAMA quenching factor within experimental limits. Our data set includes the latest ZEPLIN-III results, as well as full publicly available data sets. Due to the more sensitive dependence of the inelastic cross section on the velocity distribution, we find that with Via Lactea the DAMA results can be consistent with all other experiments over an enlarged region of iDM parameter space, with higher mass particles being preferred, while Dark Disc does not lead to an improvement. A definitive test of DAMA for iDM requires heavy element detectors.