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  1. We study and demonstrate the ground-state extrapolation of the unpolarized and polarized nucleon quark quasi-PDF matrix elements in a highly boosted hadron frame on the lattice. The calculation is done using the Wilson clover quark on a MILC’s dynamical Nf = 2+1+1 highly improved staggered quarks (HISQ) ensemble with one step hypercubic smearing, and with the lattice spacing a∼0.09 fm and pion mass 310 MeV. Applying the Gaussian momentum-smeared quark sources and comparing various fits in 1-, 2-, and 3-state fitting models, we show that excited state contributions can be under control in the lattice calculation of the nucleon quark quasi-PDF matrix elements.
  2. Within the large momentum effective theory framework, we report the results of the first direct lattice-QCD calculation of the valence quark distribution in the pion. Our results are comparable quantitatively with the results extracted from experimental data as well as from Dyson-Schwinger equation. Future calculations at physical pion mass and larger momentum will be able to discern discrepancies in various existing analyses.
  3. We present a state-of-the-art calculation of the isovector quark helicity Bjorken-$x$ distribution in the proton using lattice-QCD ensembles at the physical pion mass. We compute quasi-distributions at proton momenta $P_z \in \{2.2, 2.6, 3.0\}$~GeV on the lattice, and match them systematically to the physical parton distribution using large-momentum effective theory (LaMET). We reach an unprecedented precision through high statistics in simulations, large-momentum proton matrix elements, and control of excited-state contamination. The resulting distribution is in agreement within $2\sigma$ with the latest phenomenological analysis of the spin-dependent experimental data; in particular, $\Delta \bar{u}(x)>\Delta \bar{d}(x)$.
  4. Abstract Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of ∼80%) and protons (with a polarization of ∼70%) with variable center of mass energies from 15 to 20 GeV and the luminosity of (2–3) × 10 33 cm −2 · s −1 . Polarized deuterons and Helium-3, as well as unpolarized ion beams from Carbon to Uranium, will be also available at the EicC. The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-thresholdmore »production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with cutting-edge technologies. This document is the result of collective contributions and valuable inputs from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.« less
    Free, publicly-accessible full text available December 1, 2022