  The Cherenkov Telescope Array (CTA), the new generation very high-energy
gamma-ray observatory, will improve the flux sensitivity of the current
Cherenkov telescopes by an order of magnitude over a continuous range from
about 10 GeV to above 100 TeV. With tens of telescopes distributed in the
Northern and Southern hemispheres, the large effective area and field of view
coupled with the fast pointing capability make CTA a crucial instrument for the
detection and understanding of the physics of transient, short-timescale
variability phenomena (e.g. Gamma-Ray Bursts, Active Galactic Nuclei, gamma-ray
binaries, serendipitous sources). The key CTA system for the fast
identification of flaring events is the Real-Time Analysis (RTA) pipeline, a
science alert system that will automatically detect and generate science alerts
with a maximum latency of 30 seconds with respect to the triggering event
collection and ensure fast communication to/from the astrophysics community.
According to the CTA design requirements, the RTA search for a true transient
event should be performed on multiple time scales (from minutes to hours) with
a sensitivity not worse than three times the nominal CTA sensitivity. Given the
CTA requirement constraints on the RTA efficiency and the fast response ability
demanded by the transient science, we perform a preliminary evaluation of the
RTA sensitivity as a function of the CTA high-level technical performance (e.g.
effective area, point spread function) and the observing time. This preliminary
approach allows the exploration of the complex parameter space defined by the
scientific and technological requirements, with the aim of defining the
feasibility range of the input parameters and the minimum background rejection
capability of the RTA pipeline.
