We report a measurement of cosmic shear correlations using an effective area of 6.5 ~ { } sq . ~ { } deg . of the VIRMOS deep imaging survey in progress at the Canada-France-Hawaii Telescope .
We measured various shear correlation functions , the aperture mass statistic and the top-hat smoothed variance of the shear with a detection significance exceeding 12 ~ { } \sigma for each of them .
We present results on angular scales from 3 arc-seconds to half a degree .
The consistency of different statistical measures is demonstrated and confirms the lensing origin of the signal through tests that rely on the scalar nature of the gravitational potential .
For Cold Dark Matter models we find \sigma _ { 8 } \Omega _ { 0 } ^ { 0.6 } = 0.43 ^ { +0.04 } _ { -0.05 } at the 95 \% confidence level .
The measurement over almost three decades of scale allows to discuss the effect of the shape of the power spectrum on the cosmological parameter estimation .
The degeneracy on \sigma _ { 8 } - \Omega _ { 0 } can be broken if priors on the shape of the linear power spectrum ( that can be parameterized by \Gamma ) are assumed .
For instance , with \Gamma = 0.21 and at the 95 \% confidence level , we obtain 0.6 < \sigma _ { 8 } < 1.1 and 0.2 < \Omega _ { 0 } < 0.5 for open models , and \sigma _ { 8 } > 0.65 and \Omega _ { 0 } < 0.4 for flat ( \Lambda -CDM ) models .
From the tangential/radial modes decomposition we can set an upper limit on the intrinsic shape alignment , which was recently suggested as a possible contribution to the lensing signal .
Within the error bars , there is no detection of intrinsic shape alignment for scales larger than 1 ^ { \prime } .