Events with no charged particles produced between the two leading jets are studied in proton-proton collisions at root s = 7 TeV. The jets were required to have transverse momentum p(T)(jet) > 40 GeV and pseudorapidity 1.5 0.2GeV in the interval -1 < eta < 1 between the jets are observed in excess of calculations that assume no color-singlet exchange.
The fraction of events with such a rapidity gap, amounting to 0.5-1% of the selected dijet sample, is measured as a function of the pT of the second-leading jet and of the rapidity separation between the jets. The data are compared to previous measurements at the Tevatron, and to perturbative quantum chromodynamics calculations based on the Balitsky-Fadin-Kuraev-Lipatov evolution equations, including different models of the non-perturbative gap survival probability.