Two-particle correlations in invariant mass are studied separately for
like-sign and unlike-sign charged particles produced in deep inelastic
positron-proton scattering in a new kinematical domain. The data were taken
with the H1 detector at the HERA storage ring in 1994, in which 27.5 GeV
positrons collided with 820 GeV protons at a centre of mass energy sqrt{s}=300
GeV. The observed enhancement of the like-sign correlations at low invariant
masses is related to the dimensions of the hadronic source. The data are
compared to different QCD models where the hadronization is performed with the
string-fragmentation model. Results are presented for the first time separately
for diffractive and non-diffractive scattering, in domains of four-momentum
transfer, Bjorken-x, and hadronic center of mass energy, and in intervals of
charged particle multiplicity. The observed source radii do not differ strongly
from those measured in lower energy lepton-nucleon inelastic scattering, and
e^+e^- annihilation.Comment: 36 pages, 10 Figure