Further study on excited $\Xi_{QQ^{\prime}}$ via photoproduction at CEPC and FCC-ee

Abstract

Within the framework of NRQCD, the photoproduction of doubly heavy baryons $\Xi_{cc}$, $\Xi_{bc}$, $\Xi_{bb}$ and their $P$-wave excited states has been systematically investigated. The production mechanism is that a color anti-triplet or sextuplet diquark $\langle QQ^{\prime} \rangle$ is first produced, and then evolved into a corresponding doubly heavy baryon $\Xi_{QQ^{\prime}}$ via the subprocess $\gamma+\gamma \rightarrow \langle QQ^{\prime} \rangle[n] +\bar{Q^{\prime}}+\bar{Q} \rightarrow \Xi_{QQ^{\prime}} +\bar{Q^{\prime}}+\bar{Q}$. Here, $Q^{(\prime)}$ denotes the heavy quark $b$ or $c$, [$n$] is the color and spin quantum number of intermediate diquark, which can be $[^3S_1]_{\bar{\textbf{3}}/\textbf{6}}$ and $[^1S_0]_{\bar{\textbf{3}}/\textbf{6}}$ for $S$-wave states, or $[^1P_1]_{\bar{\textbf{3}}/\textbf{6}}$ and $[^3P_J]_{\bar{\textbf{3}}/\textbf{6}}$ with $J=0,~1,~2$ for $P$-wave states. Predictions for the cross sections, differential distributions, and theoretical uncertainty have been analyzed. The results indicate that, at $\sqrt{s}=91$ GeV, the contribution of photoproduction for $P$-wave $\Xi_{cc}$, $\Xi_{bc}$, and $\Xi_{bb}$ is approximately $2.19\%$, $4.23\%$, $1.26\%$ of the contribution for $S$-wave, respectively. As the collision energy increases, the contribution of $P$-wave also increases. Assuming that the highly excited state can decay into ground state with $100\%$ efficiency, the total produced events at CEPC and FCC-ee can be as high as $\mathcal{O}(10^8)$, $\mathcal{O}(10^7),$ and $\mathcal{O}(10^5)$ corresponding to $\Xi_{cc}$, $\Xi_{bc}$, and $\Xi_{bb}$, respectively, which is very promising to be detected in future experiments.