  The hit combinatorial problem is a main challenge for track reconstruction
and triggering at high rate experiments. At hadron colliders the dominant
fraction of hits is due to low momentum tracks for which multiple scattering
(MS) effects dominate the hit resolution. MS is also the dominating source for
hit confusion and track uncertainties in low energy precision experiments. In
all such environments, where MS dominates, track reconstruction and fitting can
be largely simplified by using three-dimensional (3D) hit-triplets as provided
by pixel detectors. This simplification is possible since track uncertainties
are solely determined by MS if high precision spatial information is provided.
Fitting of hit-triplets is especially simple for tracking detectors in
solenoidal magnetic fields. The over-constrained 3D-triplet method provides a
complete set of track parameters and is robust against fake hit combinations.
The triplet method is ideally suited for pixel detectors where hits can be
treated as 3D-space points. With the advent of relatively cheap and
industrially available CMOS-sensors the construction of highly granular full
scale pixel tracking detectors seems to be possible also for experiments at LHC
or future high energy (hadron) colliders. In this paper tracking performance
studies for full-scale pixel detectors, including their optimisation for
3D-triplet tracking, are presented. The results obtained for different types of
tracker geometries and different reconstruction methods are compared. The
potential of reducing the number of tracking layers and -- along with that --
the material budget using this new tracking concept is discussed. The
possibility of using 3D-triplet tracking for triggering and fast online
reconstruction is highlighted.
