The elastic electroproduction of phi mesons is studied at HERA with the H1
detector for photon virtualities 1 < Q(2) < 15 GeV2 and hadronic centre of
mass energies 40 < W < 130 GeV. The Q(2) and t dependences of the cross sec
tion are extracted (t being the square of the four-momentum transfer to the
target proton). When plotted as function of (Q(2) + M-v(2)) and scaled by
the appropriate SU(5) quark charge factor, the phi meson cross section agre
es within errors with the cross sections of the vector mesons V = rho, omeg
a and J/psi. A detailed analysis is performed of the phi meson polarisation
state and the ratio of the production cross sections for longitudinally an
d transversely polarised phi mesons is determined. A small but significant
violation of s-channel helicity conservation (SCKC) is observed. (C) 2000 E
lsevier Science B.V. All rights reserved.