Observation of the strange sea in the proton via inclusive phi-meson production in neutral current deep inelastic scattering at HERA

摘要

Inclusive phi (1020)-meson production in neutral current deep inelastic e(+) p scattering has been Measured with tile ZEUS detector at HERA using an integrated luminosity of 45 pb(-1) The phi mesons were studied in the range 10 < Q(2) < 100 GeV2, where Q(2) is the virtuality of the exchanged photon. and in restricted kinematic regions in the transverse momentum, p(T). pseudorapidity, eta. and the scaled momentum in the Breit frame, x(p). Monte Carlo models with tile strangeness-suppression factor as determined by analyses of e(+)e(+) annihilation events overestimate the cross sections. A smaller value of the strangeness-suppression factor reduces the predicted cross sections. but fails to reproduce the shapes of tile Measured differential cross sections. High-momentum phi mesons in the current region of the Breit frame give the first direct evidence for the strange sea in the proton at low x. (C) 2002 Published by Elsevier Science B.V. [References: 50]