  The lateral density distributions (LDD) of inclined cosmic ray air shower are
asymmetric and the corresponding iso-density contours are of increasing
eccentric ellipses with zenith angles of different showers. The polar asymmetry
of the iso-density contours introduces a significant shift of the EAS core,
which is quantitatively expressed as a gap length (GL) parameter between the
EAS core and the center of the modified density pattern consisting of several
equi-density ellipses. The LDD of EAS particles is usually approximated by a
particular type of lateral density function (LDF) which is generally assumed to
be polar symmetric about the EAS axis, and cannot describe the asymmetric LDDs
accurately. A polar angle-dependent modified lateral density function of EASs
has been derived analytically by considering the effect of attenuation of EAS
particles in the atmosphere. From the simulation studies, it has been found
that the GL manifests sensitivity to the cosmic ray mass composition. The
cosmic ray mass sensitivity of the lateral shower age is also re-examined by
applying the modified LDF to the simulated data.
