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Lattice QCD Calculations in Hadron Physics

Final Report Summary - HPLQCD (Lattice QCD Calculations in Hadron Physics)

The computation of nucleon form factors (FFs) and moments of parton distribution functions (PDFs). Codes to compute these quantities have been developed and tested and simulations for the relevant correlation functions have been performed. In order to perform the continuum limit extrapolation, we have used the configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf = 2 dynamical light quarks at three different values of the lattice spacing, namely a ≈ 0.089 fm, a ≈ 0.070 fm and a ≈ 0.051 fm. The physical volume of the lattices is in the range L ≈ [2.1 − 2.4] fm with an additional larger volume L ≈ 2.8 fm for a ≈ 0.089 fm used to study final size effects. In order to keep fixed the physical volume, the smallest lattice spacing a ≈ 0.051 fm requires a very large number of lattice points (483 × 96) and thus the generation of gauge configurations, the inversion of quark propagators and the calculation of correlation functions become computationally very expensive. This lattice spacing is probably the smallest one available amongst all the present simulations of nucleon FFs and PDFs. In the first place we have obtained accurate results for the axial GA(Q2) and pseudo-scalar Gp(Q2) nucleon form factors as a function of the squared momentum transfer Q2 for pion masses in the range of about 260-470 MeV.
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