  The first measurement of the electroweak production cross section of a Z
boson with two jets (Zjj) in pp collisions at sqrt(s) = 7 TeV is presented,
based on a data sample recorded by the CMS experiment at the LHC with an
integrated luminosity of 5 inverse femtobarns. The cross section is measured
for the lljj (l = e, mu) final state in the kinematic region m[ll] >50 GeV,
m[jj] > 120 GeV, transverse momenta pt[j] > 25 GeV and pseudorapidity
abs(eta[j]) < 4.0. The measurement, combining the muon and electron channels,
yields sigma = 154 +/- 24 (stat.) +/- 46 (exp. syst.) +/- 27 (th. syst.) +/- 3
(lum.) fb, in agreement with the theoretical cross section. The hadronic
activity, in the rapidity interval between the jets, is also measured. These
results establish an important foundation for the more general study of vector
boson fusion processes, of relevance for Higgs boson searches and for
measurements of electroweak gauge couplings and vector boson scattering.
