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Nuclear Theory·nucl-th

Tuesday·August 28, 2018

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 03

    Proton Mass Decomposition from the QCD Energy Momentum Tensor

    Yi-Bo Yang🇺🇸 · Jian Liang🇺🇸 · Yu-Jiang Bi🇨🇳 · Ying Chen🇨🇳 · Terrence Draper🇺🇸 · Keh-Fei Liu🇺🇸 · Zhaofeng Liu🇨🇳

    We report results on the proton mass decomposition and also on related quark and glue momentum fractions. The results are based on overlap valence fermions on four ensembles of DWF configurations with three lattice spacings and three volumes, and several pion masses including the physical pion mass. With fully non-perturbative renormalization (and universal normalization on both quark and gluon), we find that the quark energy and glue field energy contribute 33(4)(4)\% and 37(5)(4)\% respectively in the scheme at GeV. A quarter of the trace anomaly gives a 23(1)(1)\% contribution to the proton mass based on the sum rule, given 9(2)(1)\% contribution from the and quark scalar condensates. The and glue momentum fractions in the scheme are in good agreement with global analyses at GeV.

    ↳ hep-lathep-phnucl-thPRL(2018)·224 citations
  2. 04

    On coupled-channel dynamics in the presence of anomalous thresholds

    M.F.M. Lutz🇩🇪 · C.L. Korpa🇭🇺

    We explore a general framework how to treat coupled-channel systems in the presence of overlapping left and right-hand cuts as well as anomalous thresholds. Such systems are studied in terms of a generalized potential, where we exploit the known analytic structure of t- and u-channel forces as the exchange masses get smaller approaching their physical values. Given an approximate generalized potential the coupled-channel reaction amplitudes are defined in terms of non-linear systems of integral equations. For large exchange masses, where there are no anomalous thresholds present, conventional methods are applicable to derive numerical solutions to the latter. At a formal level a generalization to the anomalous case is readily formulated by use of suitable contour integrations with amplitudes to be evaluated at complex energies. However, it is a considerable challenge to find numerical solutions to anomalous systems set up on a set of complex contours. By a suitable deformations of left-hand and right-hand cut lines we managed to establish a framework of linear integral equations defined for real energies. Explicit expressions are derived for the driving terms that hold for an arbitrary number of channels. Our approach is illustrated in terms of a schematic 3-channel systems. It is demonstrated that despite the presence of anomalous thresholds the scattering amplitude can be represented in terms of 3 phase shifts and 3 in-elasticity parameters, as one would expect from the coupled-channel unitarity condition.

    ↳ hep-phhep-latnucl-thPRD(2018)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE