Cartography with Accelerators Locating Fermions in Extra Dimensions at Future Lepton Collid.pdf

a r X i v : h e p - p h / 0 1 0 1 2 7 8 v 1 2 4 J a n 2 0 0 1 SLAC-PUB-8746 January 2001 Cartography with Accelerators: Locating Fermions in Extra Dimensions at Future Lepton Colliders ? Thomas G. Rizzo Stanford Linear Accelerator Center Stanford University Stanford CA 94309, USA Abstract In the model of Arkani-Hamed and Schmaltz the various chiral fermions of the Standard Model(SM) are localized at different points on a thick wall which forms an extra dimension. Such a scenario provides a way of understanding the absence of proton decay and the fermion mass hierarchy in models with extra dimensions. In this paper we explore the capability of future lepton colliders to determine the location of these fermions in the extra dimension through precision measurements of conventional scattering processes both below and on top of the lowest lying Kaluza-Klein gauge boson resonance. We show that for some classes of models the locations of these fermions can be very precisely determined while in others only their relative positions can be well measured. ?Work supported by the Department of Energy, Contract DE-AC03-76SF00515 1 Introduction The possibility that the gauge bosons of the Standard Model(SM) may be sensitive to the existence of extra dimensions near the TeV scale has been entertained for some time; in the literature the cases with both factorizable[1] and non-factorizable[2] metrics(such as in the Randall-Sundrum(RS) model[3]) have been considered. The phenomenology of these models in either case is particularly sensitive to how the SM fermions are treated. In the simplest scenario, the fermions remain on the wall located at the fixed point yi = 0 and are not free to experience the extra dimensions. (Here, lower-case Roman indices label the co-ordinates of the additional dimensions while Greek indices label our usual 4- d space-time.) However, since 5-d translational invariance is broken by the wall, the SM fermions interact with the Kaluza-Klein(KK) tower exc