Associated multiplicity to high p_T events and percolation of colour sources

We show that the multiplicity distribution associated to high $p_T$ events is given in terms of the total multiplicity distribution in an universal way due to the fact that these events are self-shadowed. In particular, the mean associated multiplicity is related to the fluctuations on the multiplicity distribution. In the framework of percolation of strings these fluctuations are related to clustering and as a result the associated multiplicity presents a peculiar dependence on centrality which can be experimentally tested.