Evidence for ψψ production in π− interactions at 150 and 280 GeV/c

Diffractive Higgs production from intrinsic heavy flavors in the proton

“…Indeed, the cross section for diffractive gluon radiation (via the triplepomeron term) in pp collisions is known from data, σ |uudcccc > can lead to the production of two J/ψ's [34] or a double-charm baryon state at large x F and small p T . Double-J/ψ events at a high combined x F ≥ 0.5 were in fact observed by NA3 [35]. The observation of the doubly-charmed baryon Ξ + cc (3520) with mean < x F >≃ 0.33 has been reported by the SELEX collaboration at FNAL [36]; the presence of two charm quarks at large x F has, indeed, a natural IC interpretation.…”

Production of associated Y and open charm hadrons in pp collisions at s = 7 $$ \sqrt{s}=7 $$ and 8 TeV via double parton scattering

“…Production of multiple heavy quark pairs in high-energy hadron collisions was first observed in 1982 by the NA3 collaboration in the channels π − (p) nucleon → J/ψ J/ψ + X [1,2]. Soon after, evidence for the associated production of four open charm particles in pion-nucleon reactions was obtained by the WA75 collaboration [3].…”

Observation and studies of doubleJ/ψproduction at the Tevatron

“…directly at the interaction point) of J=ψ, and prompt production of heavier charmonium states, such as the 3 P 1 state χ 1c and the 3 P 2 state χ 2c that decay to J=ψ þ γ, or decay to J=ψ þ X of directly produced ψð2SÞ, and nonprompt B hadron decays. The first observation of J=ψ meson pair production was made in 1982 by the NA3 Collaboration [3,4]. The LHCb Collaboration has measured the double J=ψ (DJ) production cross section in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV [5].…”