  Using large number of Rossi X-ray Time Explorer observations of Sco X-1 we
present a detailed investigation of the transition layer (TL) and the
relativistic precession (RP) models. These models predict the existence of the
invariant quantities: an inclination angle delta of the magnetospheric axis
with the normal to the disk for the TLM and a neutron star (NS) mass M_{NS} for
the RPM. Theoretical predictions of both models are tested and their
self-consistency is checked. We establish that: (1) The inferred delta angle is
5.56+/-0.09 degrees. Correlation of the delta-values with the horizontal branch
oscillation (HBO) frequency is rather weak. (2) There is a strong correlation
between an inferred M_{NS} and the HBO frequency in the RPM frameworks. (3) We
infer M_{NS} for different assumptions regarding the relations between the HBO
frequency and the nodal frequency. We find that the inferred M_{NS}=2.7+/-0.1
M_sun cannot be consistent with any EOS of NS matter. We conclude that RPM
fails to describe the data while TLM seems to be compatible.
