Quark orbital angular momentum in the proton evaluated using a direct derivative method
| Autor: | Engelhardt, M., Green, J., Hasan, N., Krieg, S., Meinel, S., Negele, J., Pochinsky, A., Syritsyn, S. |
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| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | PoS SPIN2018 (2019) 047; PoS LATTICE2018 (2019) 115 |
| Druh dokumentu: | Working Paper |
| Popis: | 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. Comment: 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 |
| Databáze: | arXiv |
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