Measurement of elastic electroproduction of φ mesons at HERA

The elastic electroproduction of φ mesons is studied at HERA with the H1 detector for photon virtualities 1 <Q2 <15 GeV2 and hadronic centre of mass energies 40 <W <130 GeV. The Q2 and t dependences of the cross section are extracted (t being the square of the four-momentum transfer to the target proton). When plotted as function of (Q2 + M(v)/2) and scaled by the appropriate SU(5) quark charge factor, the φ meson cross section agrees within errors with the cross sections of the vector mesons V = p, ω and J/ψ. A detailed analysis is performed of the φ meson polarisation state and the ratio of the production cross sections for longitudinally and transversely polarised φ mesons is determined. A small but significant violation of s-channel helicity conservation (SCHC) is observed. (C) 2000 Elsevier Science B.V.