Séminaire du GDR QCD – 12/10/2021

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October 12, 2021 at 3:30pm in Auditorium Joliot Curie (IJCLab), and online

Eta_c prompt hadroproduction: theoretical and experimental aspects

by Maxim Nefedov, Samara University, Russia

From the theoretical point of view, inclusive hadroproduction of eta_c mesons have emerged as one of the cleanest probes in heavy quarkonium production physics, due to the dominance of the color-singlet state of the c-cbar pair. Because of the simplicity of underlying LO QCD subprocess, this is also a good playground to study the instability problems of the QCD perturbative series, arising in quarkonium production processes. In the talk, the high-energy instability of the short-distance cross section of eta_c hadroporduction will be discussed. The large negative NLO corrections to hard-scattering cross section at high partonic center of mass energy ruin the predictive power of the NLO calculation for total and rapidity-differential cross section at pp-collision energy much larger than quarkonium mass. The resummation of these corrections will be performed, using the High-Energy Factorization formalism in the Leading Logarithmic approximation. Resummation solves the perturbative instability problem, and when matched with the full NLO corrections leads to predictions with scale-uncertainties decreased in comparison with LO. Further applications of the formalism to chi_c hadroproduction and J/psi photoproduction will be briefly discussed as well.

Valeriia Zhovkovska, IJCLab, Orsay

This talk is devoted to understanding charmonium production mechanism using data from the LHCb experiment.

Unlike J/psi and psi(2S) states, eta_c meson can be reconstructed only via channels that involve hadrons. The LHCb detector is well suited for such studies. In addition to precise vertex reconstruction and momentum measurement, the experiment can provide an access to hadronic final states due to its excellent particle identification performance. 

Studying charmonium production in the decays to the proton-antiproton final state allows an important measurement of the absolute eta_c production cross section. Study of charmonia production from b-hadron decays is experimentally easier in comparison to prompt production due to the reconstruction of b-decay vertex. Unlike charmonium from b-hadron decays, prompt invariant mass spectra have challenging background conditions.

Using charmonium decays to other hadronic final states, such as phi phi or Lambda Lambda, will allow implication of other charmonium states and will provide an additional access to the LDMEs. This information will allow performing further crucial tests of the universality and heavy-quark spin-symmetry assumptions. Since the LDMEs have different pT dependence, it is important to perform a measurement in the wide transverse momenta region. It can provide additional sensitivity of theoretical fits to specific LDMEs.

Indico: https://indico.ijclab.in2p3.fr/event/7602/