  We present measurements of the cosmic shear correlation in the shapes of
galaxies in the Suprime-Cam 2.1 deg^2 R_c-band imaging data. As an estimator of
the shear correlation originated from the gravitational lensing, we adopt the
aperture mass variance. We detect a non-zero E mode variance on scales between
2 and 40arcmin. We also detect a small but non-zero B mode variance on scales
larger than 5arcmin. We compare the measured E mode variance to the model
predictions in CDM cosmologies using maximum likelihood analysis. A
four-dimensional space is explored, which examines sigma_8, Omega_m, Gamma and
zs (a mean redshift of galaxies). We include three possible sources of error:
statistical noise, the cosmic variance estimated using numerical experiments,
and a residual systematic effect estimated from the B mode variance. We derive
joint constraints on two parameters by marginalizing over the two remaining
parameters. We obtain an upper limit of Gamma<0.5 for zs>0.9 (68% confidence).
For a prior Gamma\in[0.1,0.4] and zs\in[0.6,1.4], we find
sigma_8=(0.50_{-0.16}^{+0.35})Omega_m^{-0.37} for flat cosmologies and
sigma_8=(0.51_{-0.16}^{+0.29})Omega_m^{-0.34}$ for open cosmologies (95%
confidence). If we take the currently popular LCDM model, we obtain a
one-dimensional confidence interval on sigma_8 for the 95.4% level,
0.62<\sigma_8<1.32 for zs\in[0.6,1.4]. Information on the redshift distribution
of galaxies is key to obtaining a correct cosmological constraint. An
independent constraint on Gamma from other observations is useful to tighten
the constraint.
