Production of $η_{c}(1S,2S)$ in $e^+ e^-$ and $pp$ collisions
Izabela Babiarz, Wolfgang Schäfer, Antoni Szczurek
备注：
6 pages, 6 figures, a talk presented by I. Babiarz at 40th International Conference on High Energy physics - ICHEP2020, July 28 - August 6, 2020, Prague, Czech Republic (virtual meeting)
We derive the light-front wave function (LFWF) representation of the $γ^{\star} γ^{\star} \to η_{c} (1S),η_{c}(2S)$ transition form factor $F(Q^2_1,Q^2_2)$ for two virtual photons in the initial state. For the LFWF, we use different models obtained from the solution of the Schrödinger equation for a variety of $c\bar{c}$ potentials. We compare our results to the BaBar experimental data for the $η_{c}(1S)$ transition form factor, for one real and one virtual photon. We observe that the onset of the asymptotic behaviour is strongly delayed and discuss applicability of the collinear and/or massless limit.
In addition, we present a thorough analysis of $η_{c}(1S,2S)$ quarkonia hadroproduction in $k_{\perp}$-factorisation in the framework of the light-front potential approach for the quarkonium wave function. The off-shell matrix elements for the $g^{\star} g^{\star} \to η_{c} (1S,2S)$ vertices are derived. We discuss the importance of taking into account the gluon virtualities. We present the transverse momentum distributions of $η_c$ for several models of the unintegrated gluon distributions. Our calculations are performed for four distinct parametrizations for the $c\bar{c}$ interaction potential consistent with the meson spectra. We compare our results for $η_{c}(1S)$ to measurements by the LHCb collaboration and present predictions for $η_{c}(2S)$ production.
We determine the leading Fock-state light front wave functions (LF-LFWFs) of the $ρ$ and J/$ψ$ mesons, for the first time from the Dyson-Schwinger and Bethe-Salpeter equations (DS-BSEs) approach. A unique advantage of this method is that it renders a direct extraction of LF-LFWFs in presence of a number of higher Fock-states. Modulated by the current quark mass and driven by the dynamical chiral symmetry breaking (DCSB), we find the $ρ$ and $J/ψ$ LF-LFWFs different in profile, i.e., the former are broadly distributed in $x$ (the longitudinal light-cone momentum fraction of meson carried by qua…
We develop a mechanism to build the light-front wavefunctions (LFWFs) of meson bound states on a small-sized basis function representation. Unlike in a standard Hamiltonian formalism, the Hamiltonian in this method is implicit, and the information of the system is carried directly by the functional form and adjustable parameters of the LFWFs. In this work, we model the LFWFs for four charmonium states, $η_c$, $J/ψ$, $ψ'$, and $ψ(3770)$ as superpositions of orthonormal basis functions. We choose the basis functions as eigenfunctions of an effective Hamiltonian, which has a longitudinal confinin…
Exclusive $J/ψ$ photoproduction in photon-proton diffractive scattering: A light-front Hamiltonian approach
Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；School of Nuclear Science and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）；CAS Key Laboratory of High Precision Nuclear Spectroscopy, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院高精度核谱学重点实验室，中国科学院近代物理研究所）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构（KEK））
We estimate the production of $Z^a$ bosons via p-p collisions using previous work on $J/Ψ$, $Ψ(2S)$ production in p-p collisions, with the new aspect being the creation of $Z^a$ bosons via quark interactions, with $a$ the component of a $Z$ vector boson. We then estimate the production of $Z^a$ bosons via Pb-Pb collisions using modification factors from previous publications.
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