The Collectivity of Heavy Mesons in Proton-Nucleus Collisions

Abstract

Using a model based on the Color Glass Condensate framework and the dilute-dense factorization, we systematically study the azimuthal angular correlations between a heavy flavor meson and a light reference particle in proton-nucleus collisions. The obtained second harmonic coefficients (also known as the elliptic flows) for J/ψ and D 0 agree with recent experimental data from the LHC. We also provide predictions for the elliptic flows of Υ and B meson, which can be measured in the near future at the LHC. This work can shed light on the physics origin of the collectivity phenomenon in the collisions of small systems.

Exploring the Collective Phenomenon at the Electron-Ion Collider

“…Interestingly, as shown in Refs [57][58][59], these two dipoles can also be converted into a quadrupole [62][63][64][65] during the interaction and non-trivial two particle azimuthal correlations can arise as the 1/N 2 c correction to the independent dipole scattering amplitudes. Using the extension of the CGC model from Refs [57,58], not only can one explain the sizable v 2 for J/ψ and open charm [60] measured in pP b collisions, but also make a further prediction [61] for the open bottom meson, which is confirmed by the recent CMS observation [12].…”

“…Based on the above assumptions, we can follow the CGC model developed in Refs [57][58][59][60][61] and compute the corresponding azimuthal angular correlation in γ * A collisions by treating the virtual photon as a hadron with a lifetime longer than the time of interaction. For convenience, our calculation is carried out in the Breit frame.…”

“…Although the integrated v 2 only weakly depends on the cut p max ⊥ [48,49], the differential v 2 is also sensitive to the choice of p max ⊥ when hadron fragmentation functions are used. Besides, it is important to note that the current CGC model employed here is only applicable [60,61] in the low p ⊥ regime.…”

Collectivity in large and small systems formed in ultrarelativistic collisions

“…This approach is able to reproduce many of the features of multiparticle azimuthal correlations observed in small systems [70,71,72]. It has been argued that the large v 2 for J/ψ observed at LHC can be naturally explained as the initial-state effect within the CGC formalism [73,74]. Also, the glasma initial conditions -an ensemble of approximately boost-invariant flux tubes of longitudinal colour electric and magnetic fields stretching between the colour charges in the two receding nuclei (Fig.…”

Asymmetric longitudinal flow decorrelations in proton-nucleus collisions

“…On the other hand, Color Glass condensate (CGC) framework has shown that the correlations between the incoming partons by interacting with the dense gluons in the nucleus can produce significant amount of collectivity [49][50][51][52][53][54][55][56][57][58][59][60]. CGC can also explain heavy meson v 2 in pA collisions [61,62]. It is currently still under debate whether the collectivity in pA collisions is mainly driven by the initial-state gluon saturation dynamics or the final-state hydrodynamic evolution.…”