Speaker
Description
We present a global determination of the charmonium relativistic velocity parameters $\langle v^2_{\psi(2S)} \rangle$ and $\langle v^2_{J/\psi} \rangle$ from decay widths and high-$P_T$ prompt charmonium measurements at the LHC, combined with NLO NRQCD predictions for direct production and feed-down contributions from $\chi_c$ and $\psi(2S)$.
Building on a leading-power fragmentation framework that includes ${O} (v^2)$ relativistic corrections and NLL resummation, we fit prompt $\psi(2S)/J/\psi$ yield ratios measured by the ATLAS and CMS collaborations at $\sqrt{s} = 13$ TeV, together with the $\psi(2S)$ CMS polarisation data.
This ratio and the $\psi(2S)$ polarisation along with one decay widths per charmonium allow us to fix the wave functions at the origin $|R_{\psi(2S)}(0)|^2$, $|R_{J/\psi}(0)|^2$, the derivative of the P-wave radial function at the origin $|R^\prime_P(0)|^2$ and the ${O}(v^2)$ colour-octet $\langle {O}^{^3S_1^{[8]}}_{\chi_c} \rangle$ LDME and while providing excellent predictions of the CMS and ATLAS cross section data up to $P_T=360$ GeV for the $J/\psi$ as well as the $J/\psi$ polarization data from CMS.
The data show no preference for a deviation from the central factorisation scale and thus the excellent agreement we obtain with the CMS and ATLAS data and the decay widths demonstrates that NRQCD up to $v^2$ is sufficient to describe $J/\psi$, $\psi(2S)$ and $\chi_c$ hadroproduction at large $P_T$ without including higher $v^2$ NRQCD contributions.