Probing large extra dimensions using top production in photon-photon collisions

Theories with large extra dimensions predict an infinite tower of Kaluza-Klein states in the 1 TeV range, which can consequently have significant implications for experimental observables. One such observable, which gets affected by the exchange of spin-2 Kaluza-Klein particles, is the tt̄ production cross-section in photon-photon collisions at NLC energies. We study this process and obtain bounds on the effective quantum gravity scale MS between 1600 and 5400 GeV (depending on the centre-of-mass energy). We show that the use of polarisation will further strengthen these bounds.