Testing the nuclear TMD gluon densities with heavy flavor production in proton-lead collisions at LHC

Abstract

We employ a simple model for nuclear modification of ordinary parton densities in a proton to evaluate the Transverse Momentum Dependent gluon and quark distributions in nuclei (nTMDs) within the popular Kimber-Martin-Ryskin/Watt-Martin-Ryskin approach. The model is based on a global analysis of available deep inelastic scattering data for different nuclear targets within the rescaling model, incorporating Fermi motion effects. The derived nTMDs are tested with latest CMS data on inclusive $b$-jet and $B^+$ meson production in proton-lead collisions collected at $\sqrt s = 5.02$ and $8.16$~TeV using the High Energy Factorization framework. We predict the corresponding nuclear medium modification factors to be about of $0.8 - 1.2$ in the probed kinematical region, which is consistent with other estimations. Specially we highlight a possibility to investigate the nuclear modification of parton densities by applying different cuts on the final states in such processes.

Figures (3)

• Figure 1: nTMD gluon densities in $^{197}{\rm Au}$ and $^{208}{\rm Pb}$ calculated as functions of ${\mathbf{k}_T^2}$ for several $x$ and $\mu^2$ using the angular ordering and strong ordering conditions. Different scenarios for their nuclear dependence, namely, Fit A, B and C, described in the text (see alsoRescalingModel-Fermi), are applied.
• Figure 2: Transverse momentum spectra of inclusive $b$-jet production compared to CMS dataCMS-bjets (left panels), normalized double differential cross sections as functions of longitudinal momentum fractions of proton, $x_p$, and nucleus, $x_A$ (center panels), and nuclear modification factors $R_{p\rm Pb}^{{b\textrm{-jet}}}$ (right panels). Different scenarios for their nuclear dependence, namely, Fit A, B and C, described in the text (see alsoRescalingModel-Fermi), with AO condition are applied. The uncertainty band is shown for Fit A results only.
• Figure 3: Transverse momentum and rapidity spectra of inclusive $B^+$-jet production compared to CMS dataCMS-BCMS-B8 (upper panels) and corresponding nuclear modification factors $R_{p\rm Pb}^{B^+}$ (lower panels). Different scenarios for their nuclear dependence, namely, Fit A, B and C, described in the text (see alsoRescalingModel-Fermi), with AO condition are applied. The uncertainty band is shown for Fit A results only.