  The Compressed Baryonic Matter (CBM) experiment is being planned at the
international research center FAIR, under realization next to the GSI
laboratory in Darmstadt, Germany. Its physics programme addresses the QCD phase
diagram in the region of highest net baryon densities. Of particular interest
are the expected first order phase transition from partonic to hadronic matter,
ending in a critical point, and modifications of hadron properties in the dense
medium as a signal of chiral symmetry restoration. Laid out as a fixed-target
experiment at the heavy-ion synchrotrons SIS-100/300, the detector will record
both proton-nucleus and nucleus-nucleus collisions at beam energies between 10
and 45$A$ GeV. Hadronic, leptonic and photonic observables have to be measured
with large acceptance. The interaction rates will reach 10 MHz to measure
extremely rare probes like charm near threshold. Two versions of the experiment
are being studied, optimized for either electron-hadron or muon identification,
combined with silicon detector based charged-particle tracking and micro-vertex
detection. The CBM physics requires the development of novel detector sytems,
trigger and data acquisition concepts as well as innovative real-time
reconstruction techniques. Progress with feasibility studies of the CBM
experiment and the development of its detector systems are reported.
