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Resolved photoproduction of the $B_c$ meson in electron-proton collisions

Na Cai, Xi-Jie Zhan, Tai-Fu Feng

TL;DR

The paper investigates photoproduction of the $B_c$ meson at electron–proton colliders within NRQCD factorization. It includes both direct gamma+g production and resolved contributions from gg and qqbar subprocesses, modeling photons with the Weizsäcker–Williams flux and convolving with proton PDFs and photon densities. Key findings show that the gamma+g channel dominates total cross sections across studied colliders, while the resolved gg channel contributes at the level of about ten percent at low p_T, and the qqbar channel is negligible; feed-down from excited states enhances the prompt yield. The results emphasize the need to include resolved photons for precision predictions at future ep colliders and indicate sizable B_c yields at FCC–ep, enabling tests of heavy-quark dynamics and NRQCD factorization.

Abstract

We present a systematic study of $B_c$ meson photoproduction at electron--proton colliders within the framework of nonrelativistic QCD (NRQCD) factorization. In addition to the dominant direct channel $γ+g\to B_c+X$, we include resolved contributions initiated by $g+g$ and $q+\bar q (q=u,d,s)$ subprocesses. Total cross sections and transverse-momentum distributions are calculated for several collider configurations, including HERA, LHeC, FCC-$ep$, and EIC. The numerical results show that the $γ+g$ channel provides the leading contribution to the total cross section, while the resolved $g+g$ channel yields a non-negligible correction at the level of ${\cal O}(10\%)$ in the low-$p_T$ region where most events are produced. The $q+\bar q$ channel is found to be numerically insignificant.

Resolved photoproduction of the $B_c$ meson in electron-proton collisions

TL;DR

The paper investigates photoproduction of the meson at electron–proton colliders within NRQCD factorization. It includes both direct gamma+g production and resolved contributions from gg and qqbar subprocesses, modeling photons with the Weizsäcker–Williams flux and convolving with proton PDFs and photon densities. Key findings show that the gamma+g channel dominates total cross sections across studied colliders, while the resolved gg channel contributes at the level of about ten percent at low p_T, and the qqbar channel is negligible; feed-down from excited states enhances the prompt yield. The results emphasize the need to include resolved photons for precision predictions at future ep colliders and indicate sizable B_c yields at FCC–ep, enabling tests of heavy-quark dynamics and NRQCD factorization.

Abstract

We present a systematic study of meson photoproduction at electron--proton colliders within the framework of nonrelativistic QCD (NRQCD) factorization. In addition to the dominant direct channel , we include resolved contributions initiated by and subprocesses. Total cross sections and transverse-momentum distributions are calculated for several collider configurations, including HERA, LHeC, FCC-, and EIC. The numerical results show that the channel provides the leading contribution to the total cross section, while the resolved channel yields a non-negligible correction at the level of in the low- region where most events are produced. The channel is found to be numerically insignificant.
Paper Structure (4 sections, 3 equations, 2 figures, 5 tables)

This paper contains 4 sections, 3 equations, 2 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Formulation and calculation
  3. Numerical results and discussions
  4. Summary

Figures (2)

  • Figure 1: Some typical Feynman diagrams for calculating the partonic cross section $\hat{\sigma}$ of $B_c$ photoproduction at $ep$ collider. The diagrams are drawn by JaxoDraw Binosi:2003yf.
  • Figure 2: The $p_t$ distributions for $B_c$ photoproduction. (a,b,c,d): $p_t$ distributions of four $B_c$ states and "prompt $B_c$" means production of the ground $B_c$ after including the feed-down contributions from excited states with $100\%$ decay probability to it. (e,f,g,h): $p_t$ distributions for the channels in Eq. (\ref{['eq:channel-1']},\ref{['eq:channel-2']},\ref{['eq:channel-3']}) of the ground $B_c$ production.