The material distribution in a realistic VELO design

The realistic design of the VELO, implemented in SICB, has been used to determine the material distribution traversed by particles before entering the remainder of the LHCb spectrometer. In the range of polar angles, 8 mrad < theta < 270 mrad, the mean X0 traversed, at the exit of the vertex tank, was found to be 18.9 % of an X0. The contributions of the different components of the VELO are given for both the total and different regions of the acceptance phase space. The impact of alternative designs on the material distribution is discussed.