Measurements of $\ddot{I}ˆ(2S)$ and $\ddot{I}{‡}_{c1}(3872)$ production within fully reconstructed jets

Abstract

This paper presents the first measurement of $\ddot{I}ˆ(2S)$ and $\ddot{I}{‡}_{c1}(3872)$ meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the $J/\ddot{I}ˆ$($\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}$)$\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of $13\text{TeV}$ in 2016, corresponding to an integrated luminosity of $1.64{\text{fb}}^{-1}$. The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum ($p_{\mathrm{T}}(\text{tag})/p_{\mathrm{T}}(\text{jet})$), is measured differentially in $p_{\mathrm{T}}(\text{jet})$ and $p_{\mathrm{T}}(\text{tag})$ bins. The distributions are separated into promptly produced quarkonia from proton-proton collisions and quarkonia produced from displaced $b$-hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD) predictions followed by a QCD parton shower.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1618/ (LHCb public pages)