Further study on excited ${\Xi }_{Q{Q}^{\prime }}$ 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 $⟨Q{Q}^{\prime }⟩$ is first produced, and then evolved into a corresponding doubly heavy baryon ${\Xi }_{Q{Q}^{\prime }}$ via the subprocess $\gamma +\gamma \to ⟨Q{Q}^{\prime }⟩[n]+\overline{Q^{\prime }}+\bar{Q}\to {\Xi }_{Q{Q}^{\prime }}+\overline{Q^{\prime }}+\bar{Q}$. Here, $Q^{(\prime )}$ denotes the heavy quark $b$ or $c$, [$n$] is the color and spin quantum number of intermediate diquark, which can be ${[}^3{S}_1{]}_{\bar{\text{3}}/\text{6}}$ and ${[}^1{S}_0{]}_{\bar{\text{3}}/\text{6}}$ for $S$-wave states, or ${[}^1{P}_1{]}_{\bar{\text{3}}/\text{6}}$ and ${[}^3{P}_J{]}_{\bar{\text{3}}/\text{6}}$ 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.

Comments: 22 pages, 5 figures and 11 tables