Evidence of $\pcs$ in $\Upsilon(1,2S)$ inclusive decays at Belle

Abstract The LHCb experiment has reported evidence of $\pcs$, which is a candidate for penta-quark state with the quark content of $[udsc\bar{c}]$. Using the data samples of $102 \times 10^6$ $\yones$ events and $158 \times 10^6$ $\ytwos$ events collected with the Belle detector, we search for the $\pcs$ in the $\lamjpsi$ final state in $\yonetwos$ inclusive decays. The branching fractions of $\lamjpsi$ in the $\yonetwos$ inclusive decays are measured to be $\BR[\yones \to \lamjpsi + anything] = (17.7 \pm 2.2 \pm 1.2) \times 10^{-6}$ and $\BR[\ytwos \to \lamjpsi + anything] = (11.3 \pm 1.4 \pm 1.0) \times 10^{-6}$. In addition, the cross section of inclusive $\lamjpsi$ production in $\EE$ annihilation is measured to be $\sigma(e^+ e^- \to \lamjpsi + anything) = (94 \pm 8 \pm 6)~\fb$ at $\sqrt{s} = 10.52~\gev$. An accumulation is seen near the mass of $\pcs$ in the $\lamjpsi$ mass spectrum, and a fit with mass and width constrained to those of the $\pcs$ yields a significance of $3.3\sigma$, considering statistical fluctuations and systematic uncertainties. An alternative fit without constraints yields a mass of $(4469.5 \pm 4.1 \pm 4.1)~\mevcs$, and a width of $(14.3 \pm 9.2 \pm 6.3)~\mev$. The quoted uncertainties are statistical and systematic, respectively.
Tags
Working group Quarkonium
Principal authors @  Xiaolong Wang, Shiqing Xie, Shiming Zou
Reference Phys.Rev.Lett. 135, 041901 (2025), DOI: 10.1103/pf8m-6j69
Document BELLE2-PUB-DRAFT-2024-017
Links arXiv:2502.09951, Inspire,
Bibtex 
@article{Belle:2025pey,
    author = "Adachi, I. and others",
    collaboration = "Belle, Belle-II",
    title = "{Search for Pcs(4459) and Pcs(4338) in Upsilon(1S,2S) inclusive decays at Belle}",
    eprint = "2502.09951",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2025-002, KEK Preprint 2024-50",
    doi = "10.1103/pf8m-6j69",
    journal = "Phys. Rev. Lett.",
    volume = "135",
    number = "4",
    pages = "041901",
    year = "2025"
}