Light-Cone Models for Intrinsic Charm and Bottom

TL;DR

This work investigates intrinsic heavy quark content in the proton using light-cone Fock-space descriptions, focusing on charm and bottom distributions. It compares multiple five-quark and meson-baryon models, showing that all yield similar heavy-quark x-dependence with heavy quarks concentrating at large x. Quantitatively, intrinsic charm could carry a small but non-negligible fraction of proton momentum (around 0.5%), dominating over perturbative contributions at large x and potentially leading to measurable asymmetries such as $\bar{c}(x) > c(x)$ in certain configurations. The findings imply intrinsic heavy flavors have limited impact on light-quark and gluon PDFs but offer testable signatures in heavy-quark tagged jets and diffractive processes at high-energy colliders.

Abstract

Expectations for the momentum distribution of nonperturbative charm and bottom quarks in the proton are derived from a variety of models for the Fock space wave function on the light cone.

Figures (9)

• Figure 1: Momentum distribution of $c$ or $\bar{c}$ from the 5-quark model with the exponential suppression of Eq. (\ref{['eq:fq6']}) (left), or the power-law suppression of Eq. (\ref{['eq:fq7']}) (right). Solid curves are the BHPS model of Eq. (\ref{['eq:fq4']}). All curves are normalized to $1\%$ integrated probability.
• Figure 2: Momentum distribution of $c$ and $\bar{c}$ from the $(udc)(u \bar{c})$ model (\ref{['eq:fq8']}), and $c = \bar{c}$ from the $(uud)(c \bar{c})$ model (\ref{['eq:fq9']}).
• Figure 3: (a) Momentum distribution of $\Lambda_c^{+}$ from $p \to \overline{D}^0 \Lambda_c^{+}$ with $\Lambda_p = 10$ (dashed), $4$ (solid), $2$ (dotted). (b) Momentum distribution of $c$ from $\Lambda_c \to u d c$ with $\Lambda_{\Lambda} = 4$ (dashed), $2$ (solid), $1$ (dotted). (c) Resulting distribution of $c$ in $p$ with $\Lambda_p = 4$ and $\Lambda_{\Lambda} = 2$ and BHPS model (solid).
• Figure 4: (a) Momentum distribution of $\overline{D}^0$ from $p \to \overline{D}^0 \Lambda_c^+$ with $\Lambda_p = 10$ (dashed), $4$ (solid), $2$ (dotted). (b) Momentum distribution of $\bar{c}$ from $\overline{D}^0 \to \bar{c}\, u$ with $\Lambda_D = 4$ (dashed), $2$ (solid), $1$ (dotted). (c) Resulting distribution of $\bar{c}$ in $p$ with $\Lambda_p = 4$ and $\Lambda_D = 2$.
• Figure 5: (a) Momentum distribution of $J\!/\!\psi$ from $p \to p \, J\!/\!\psi$ with $\Lambda_{p\,J\!/\!\psi}=5$ (dashed), $3$ (solid), $1$ (dotted). (b) Momentum distribution of $c$ or $\bar{c}$ from $J\!/\!\psi \to c \bar{c}$ with $\Lambda_{\bar{c}c}=5$ (dashed), $2$ (solid), $1$ (dotted). (c) Resulting distribution of $c$ or $\bar{c}$ in $p$ with $\Lambda_{p\, J\!/\!\psi}=3$, $\Lambda_{c\bar{c}}=2$.