Speaker
Description
Heavy quarkonium production of high transverse momentum ($p_T$) in hadronic collisions can be pursued in the QCD factorization formalism with heavy quarkonium fragmentation functions (FFs). The scale evolution of quarkonium FFs enables us to resum logarithmically enhanced corrections $\alpha_s\ln(p_T^2/m^2)$ with heavy quark mass $m$, which is an essential piece to explore the nonperturbative process of bound quarkonium formation. Boundary conditions of the evolution equations of the FFs at $p_T\sim 2m$ are given by combining perturbatively calculable coefficients in NRQCD and long-distance-matrix elements (LDMEs) for different intermediate states of a produced heavy quark pair. LDMEs correspond to relative weights of individual terms after expanding the input FFs in quark velocity $v$, and should be determined by data fitting.
We demonstrated in Ref.[1] that the QCD factorization approach at leading-power in $1/p_T$ with single parton FFs at twist-2 describes LHC data on the differential cross-section for $J/\psi$ production in hadronic collisions at $p_T$ much larger than the heavy quark mass scale. Meanwhile, at $p_T= \mathcal{O}(2m)$, the subleading power contribution with double parton FFs at twist-4 is more significant than the leading power contribution. In this talk, we will emphasize the role of the subleading power corrections in hadronic quarkonium production. Our recent analysis of the scale evolution of the twist-4 double parton FFs will be shown [2], and the application of the QCD factorization approach to other quarkonium production processes will be discussed.
[1] K.Lee, J.-W.Qiu, G.Sterman, and K.Watanabe, [arXiv:2108.00305 [hep-ph]].
[2] K.Lee, J.-W.Qiu, G.Sterman, and K.Watanabe, in preparation.
