Quark orbital angular momentum in the proton evaluated using a direct derivative method

Engelhardt, M.; Krieg, S.; Negele, J.; Hasan, N.; Pochinsky, A.; Green, J.; Meinel, S.; Syritsyn, S.

Report/Contribution to a conference proceedings/Contribution to a book

FZJ-2019-00098

Quark orbital angular momentum in the proton evaluated using a direct derivative method

Engelhardt, M. (Corresponding author) ; Green, J. ; Hasan, N.FZJ* ; Krieg, S.FZJ* ; Meinel, S. ; Negele, J. ; Pochinsky, A. ; Syritsyn, S.

2019
SISSA Trieste

36th Annual International Symposium on Lattice Field Theory, Lattice 2018, East Lansing, Michigan, USA, 22 Jul 2018 - 28 Jul 2018 Trieste : SISSA, Proceedings of Science LATTICE2018, 7 p. (2019)

This record in other databases:

Please use a persistent id in citations: http://hdl.handle.net/2128/21169

Report No.: PoS LATTICE2018 (2019) 115

Abstract: Quark orbital angular momentum (OAM) in the proton can be calculated directly given a Wigner function encoding the simultaneous distribution of quark transverse positions and momenta. This distribution can be accessed via proton matrix elements of a quark bilocal operator (the separation in which is Fourier conjugate to the quark momentum) featuring a momentum transfer (which is Fourier conjugate to the quark position). To generate the weighting by quark transverse position needed to calculate OAM, a derivative with respect to momentum transfer is consequently required. This derivative is evaluated using a direct derivative method, i.e., a method in which the momentum derivative of a correlator is directly sampled in the lattice calculation, as opposed to extracting it a posteriori from the numerical correlator data. The method removes the bias stemming from estimating the derivative a posteriori that was seen to afflict a previous exploratory calculation. Data for Ji OAM generated on a clover ensemble at pion mass $m_{\pi } = 317\, \mbox{MeV} $ are seen to agree with the result obtained via the traditional Ji sum rule method. By varying the gauge connection in the quark bilocal operator, also Jaffe-Manohar OAM is extracted, and seen to be enhanced significantly compared to Ji OAM.

Note: 7 pages, 3 figures, to appear in the proceedings of the 23rd International Spin Physics Symposium (SPIN2018), 10-14 September 2018, Ferrara, Italy, and in the proceedings of the 36th Annual International Symposium on Lattice Field Theory (LATTICE2018), 22-28 July 2018, Michigan State University, East Lansing, Michigan, USA

Contributing Institute(s):