Photoproduction of doubly heavy baryon at the LHeC

Abstract

The photoproduction of doubly heavy baryon, ${\Xi }_{cc}$, ${\Xi }_{bc}$ and ${\Xi }_{bb}$, is predicted within the nonrelativistic QCD at the Large Hadron Electron Collider (LHeC). The ${\Xi }_{Q{Q}^{\prime }}$ production via the photon-gluon fusing channel $\gamma +g\to ⟨Q{Q}^{\prime }⟩[n]+\bar{Q}+\overline{Q^{\prime }}$ and the extrinsic heavy quark channel $\gamma +Q\to ⟨Q{Q}^{\prime }⟩[n]+\overline{Q^{\prime }}$ have been considered, where $Q$ or $Q^{\prime }$ stand for heavy $c$ or $b$ quark and $⟨Q{Q}^{\prime }⟩[n]$ stands for a $Q{Q}^{\prime }$ diquark with given spin- and color- configurations $[n]$. The diquark shall fragmentate into ${\Xi }_{Q{Q}^{\prime }}$ baryon with high probability. For ${\Xi }_{cc}$ and ${\Xi }_{bb}$ production, $[n]$ equals ${[}^1{S}_0{]}_{\text{6}}$ (in configurations spin-singlet ${}^1{S}_0$-wave and color-sextuplet $\text{6}$) or ${[}^3{S}_1{]}_{\bar{\text{3}}}$ (in configurations spin-triplet ${}^3{S}_1$-wave and color-antitriplet $\bar{\text{3}}$) and for ${\Xi }_{bc}$ production, $[n]$ equals ${[}^1{S}_0{]}_{\bar{\text{3}}}$, ${[}^1{S}_0{]}_{\text{6}}$, ${[}^3{S}_1{]}_{\bar{\text{3}}}$ or ${[}^3{S}_1{]}_{\text{6}}$. A detailed comparison of those channels and configurations on total and differential cross sections, together with their uncertainties, is presented. We find the dominate contributions for ${\Xi }_{Q{Q}^{\prime }}$ production are from extrinsic heavy quark channel and for ${[}^3{S}_1{]}_{\bar{\text{3}}}$ configuration; While other diquark states can also provide sizable contributions to the ${\Xi }_{Q{Q}^{\prime }}$ production. As a combination of all the mentioned channels and configurations and by taking $m_c=1.80\pm 0.10$ GeV and $m_b=5.1\pm 0.20$ GeV, we observe that $(6.70_{-1.10}^{+1.40})\times 10^3$ ${\Xi }_{bb}$, $(8.81_{-2.20}^{+3.08})\times 10^6$ ${\Xi }_{cc}$ and $(4.63_{-0.92}^{+1.21})\times 10^5$ ${\Xi }_{bc}$ events can be generated at the LHeC in one operation year.