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22-28 July 2018
Kellogg Hotel and Conference Center
EST timezone

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

Jul 25, 2018, 3:20 PM
20m
106 (Kellogg Hotel and Conference Center)

106

Kellogg Hotel and Conference Center

219 S Harrison Rd, East Lansing, MI 48824
Hadron Structure Hadron Structure

Speaker

Michael Engelhardt (NMSU)

Description

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 317 MeV pion mass 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.

Primary author

Presentation Materials