Probing the 3-D matter distribution at z∼2 with QSO multiple lines of sight

We investigate the 3-d matter distribution at z∼ 2 with high resolution (r∼ 40,000) spectra of QSO pairs and groups obtained with the UVES spectrograph at ESO VLT. Our sample is unique for the number density of objects and the variety of separations, between ∼ 0.5 and 7 proper mpc. We compute the real space cross-correlation function of the Lyman-α forest transmitted fluxes. There is a significant clustering signal up to ∼ 2 proper mpc, which is still present when absorption lines with high column density (log n ≥ 13.8) are excluded.