We present a statistical analysis of the Chandra 
observation of the source field around the 3C 295 galaxy cluster ( z=0.46 ) aimed at the search for clustering of X-ray sources .
We applied three different methods of analysis , all suggesting a strong clustering in the field on scales of a few arcmin .
In particular 1 ) the logN-logS computed separately for the four ACIS-I chips reveals that there is a significant ( 3.2 \sigma in the 0.5 - 2 keV , 3.3 \sigma in the 2 - 10 keV and 4.0 \sigma in the 0.5 - 10 keV band ) excess of sources to the North-North East and a void to the South of the central cluster .
2 ) the two point , two-dimensional Kolmogorov-Smirnov ( KS ) test , shows the probability that the sources are uniformly distributed is only a few percent .
3 ) a strong spatial correlation emerges from the study of the angular correlation function of the field : the angular correlation function ( ACF ) shows a clear signal on scales of 0.5 \div 5 arcmin , correlation angle in the 0.5 - 7 keV band \theta _ { 0 } = 8.5 ^ { +6.5 } _ { -4.5 } , 90 % confidence limit ( assuming a power law ACF with slope \gamma = 1.8 ) .
This correlation angle is 2 times higher than that of a sample of 8 ACIS-I field at the 2.5 \sigma confidence level .
The above scales translate to 0.2 \div 2 Mpc at the cluster redshift , higher than the typical cluster core radius , and more similar to the size of a “ filament ” of the large scale structure .