  Analysing two-particle azimuthal and pseudorapidity-azimuth correlations of
high-pT hadrons, experiments at the RHIC have obtained results - "the double
hump", "the ridge" etc. - which provide interesting information about
properties of the hot, dense medium produced in central high-energy heavy-ion
collisions as well as of its interaction with products of hard scattering.
However, not all of the observed effects have been fully explained by theory or
models yet; such explanations are hampered in part by the lack of good
reference from lower collision energies. In an attempt to further our
understanding of angular dihadron correlations NA49 has, as one of the first
experiments at the SPS, performed a number of scans of these correlations in
Pb+Pb, Si+Si and p+p collisions at sqrt(sNN) = 17.3 GeV, as well as central
Pb+Pb collisions at sqrt(sNN) = 12.3, 8.8, 7.6 and 6.3 GeV. Results of these
scans have been compared to UrQMD simulations. Our experimental results from
two-particle azimuthal correlations show a flattened away-side peak in central
Pb+Pb (Au+Au) collisions, only weakly depends on collision energy over the
whole investigated energy range - suggesting this effect originates from
sources other than jet-medium interactions. This hypothesis is reinforced by
good agreement with UrQMD regardless of whether jet production was enabled in
the model or not. On the other hand, the amplitude of the near-side peak in
central Pb+Pb (Au+Au) collisions drops visibly with decreasing collision
energy, flattening out around sqrt(sNN) = 8.8 GeV and turning into a depletion
below that energy - possibly an effect related to the onset of deconfinement.
Finally, hints of the ridge structure can be observed in pseudorapidity-azimuth
correlation functions from central Pb+Pb collisions at sqrt(sNN) = 17.3 GeV.
