Abstract
High-multiplicity pp collisions exhibit features, traditionally associated with nuclear effects. Coherence motivates to treat high-multiplicity pp, pA and AA collisions on an equal footing. We rely on the phenomenological parametrization for mean multiplicities of light hadrons and J/psi, assuming their linear dependence on N_{coll} in pA collisions. The results of this approach underestimate the recently measured production rate of J/psi at very high hadronic multiplicities. The linear dependence of J/psi multiplicity on N_{coll} is subject to predicted nonlinear corrections, related to mutual boosting of the saturation scales in colliding dense parton clouds. A parameter-free calculation of the non-linear corrections allows to explain data for pT-integrated yield of J/psi at high hadronic multiplicities. Calculations are in a good accord with data binned in several pT-intervals as well. As was predicted, Upsilon and J/psi are equally suppressed at forward rapidities in pA collisions. Consequently, their fractional multiplicities at forward rapidities in pp collisions are equal as well, and their magnitude agrees with data.
Highlights
The popular models of multiparticle production in pp and pA collisions are based on the eikonal multi-Pomeron exchange, or Glauber models
It is a model for the elastic scattering amplitude, which is related to the total cross section by the unitarity relation
One can calculate the total inelastic cross section; no relation between the multiple scattering terms in the elastic amplitude and inelastic processes follows from the Glauber model
Summary
The popular models of multiparticle production in pp and pA collisions are based on the eikonal multi-Pomeron exchange, or Glauber models. The unitarity cut of the elastic scattering amplitude can be done simultaneously through several Pomerons, while the other uncut Pomerons play a role in absorptive corrections Those corrections, known as shadowing, lead to a substantial reduction of the total inelastic cross section. Assume the Bethe-Heitler regime of particle production, which, e.g., leads to n-times higher rapidity density of multiplicity dNh=dy for n cut Pomerons compared to a single cut This regime is known to be broken by the Landau-Pomeranchuk effect of coherent radiation from multiple interactions. Charm quarks [12] and charmonia [13,14,15] are shadowed considerably less than light quarks This explains in particular the observed nonuniversality RJ=Ψ > Rh. The effects of coherence possess a strong scale dependence for the relation between fractional multiplicity and number of collisions. It has no relation to the initial state phenomena like shadowing or parton saturation
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