Threshold production of meta-stable bound states of Kaluza Klein excitations in Universal Extra Dimensions
Abstract
We study the formation and detection at the next linear e+e- collider of bound states of level-1 quark Kaluza-Klein excitations BKK within a scenario of universal extra-dimensions (UED). The interactions of such Kaluza-Klein excitations are modeled by an alphas driven Coulomb potential. In order to obtain the threshold cross-section, we employ the Green function method which is known to properly describe the peaks below threshold and to yield a net increase in the continuum region (above threshold) relative to the naive Born cross-section. We study such effect at different values of the scale (R-1) of the extra-dimensions with an explicit calculation of the mass spectrum as given by radiative corrections. The overall effect is roughly 2.7 at R-1=300 GeV and goes down to 2.2 at R-1=1000 GeV and a relatively large number of events is expected from Nevents ~ 2.5*104 at R-1=300 GeV down to Nevents ~ 103 at R-1=1000 GeV at the anticipated annual integrated luminosity of L0= 100 fb-1. We finally discuss some potentially observable signatures such as the multilepton channels 2j + 2l + missing energy, and 2j + 4l + missing energy for which we estimate statistical significance >~ 2 for R-1 up to 600 ~ 700 GeV.