Threshold production of meta-stable bound states of Kaluza Klein excitations in Universal Extra Dimensions

TL;DR

This paper investigates the formation and detection of bound states of Kaluza-Klein quark excitations in Universal Extra Dimensions at future e^+e^- colliders, using a Coulomb potential model and Green function method to predict cross-sections and signatures.

Contribution

It introduces a detailed calculation of threshold production cross-sections for KK bound states in UED, incorporating radiative corrections and Green function techniques for the first time.

Findings

Cross-section enhancement factors of 2.7 at R^-1=300 GeV and 2.2 at R^-1=1000 GeV.

Expected event numbers ranging from 2.5*10^4 to 10^3 for different R^-1 values.

Potential observable signatures with statistical significance > 2 up to R^-1 of 600-700 GeV.

Abstract

We study the formation and detection at the next linear e^+e^- collider of bound states of level-1 quark Kaluza-Klein excitations B_KK within a scenario of universal extra-dimensions (UED). The interactions of such Kaluza-Klein excitations are modeled by an alpha_s 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 N_events ~ 2.5*10^4 at R^-1=300 GeV down to N_events ~ 10^3 at R^-1=1000 GeV at the anticipated annual integrated luminosity of L_0= 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.