| Resumen |
We present the observation of doubly produced J/? mesons with the D0 detector at Fermilab in pp¯ collisions at s?=1.96??TeV. The production cross section for both singly and doubly produced J/? mesons is measured using a sample with an integrated luminosity of 8.1??fb?1. For the first time, the double J/? production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section ?eff, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon. |
