Observation and studies of double J/psi production at the Tevatron

V.M. Abazov , G. Bernardi (1) , D. Brown (1) , G. Grenier (2) , T. Kurca (2) , P. Lebrun (2) , J. Lellouch (1) , G. Sajot (3) , J. Stark (3) , J.-F. Grivaz (4) , T. Guillemin (4) , M. Jaffré (4) , P. Pétroff (4) , F. Badaud (5) , Ph. Gris (5) , M.-C. Cousinou (6) , A. Duperrin (6) , W. Geng (6) , E. Kajfasz (6) , S. Kermiche (6) , E. Nagy (6) , N. Osman (6)

1 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
2 IPNL - Institut de Physique Nucléaire de Lyon
3 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
4 LAL - Laboratoire de l'Accélérateur Linéaire
5 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
6 CPPM - Centre de Physique des Particules de Marseille

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

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

V.M. Abazov, G. Bernardi, D. Brown, G. Grenier, T. Kurca, et al.. Observation and studies of double J/psi production at the Tevatron. Physical Review D, 2014, 90 (11), pp.111101. ⟨10.1103/PhysRevD.90.111101⟩. ⟨in2p3-01003951⟩