Double-tag events in two-photon collisions at LEP

Double-tag events in two-photon collisions are studied using the L3 detector at LEP centre-of-mass energies from roots = 189 GeV to 209 GeV The cross sections of the e(+)e(-) --> e(+)e(-) hadrons and gamma*gamma* --> hadrons processes are measured as a function of the product of the photon virtualities, Q(2) = rootQ(1)(2) Q(2)(2), of the two-phonon mass, W(gammagamma), and of the variable Y = ln(W(gammagamma)(2)/Q(2)). The average photon virtuality is [Q(1)(2)] = [Q(2)(2)] = 16 GeV(2). The results are in agreement with next-to-leading order calculations for the process gamma*gamma* --> q (q) over bar in the interval 2 less than or equal to Y less than or equal to 5. An excess is observed in the interval 5 < Y <= 7, corresponding to W(gamma gamma). greater than 40 GeV. This may be interpreted as a contribution of resolved photon QCD processes or the onset of BFKL phenomena. (C) 2002 Elsevier Science B.V. All rights reserved.