[Hadstruct] [EXTERNAL] Gluon analysis call summary

[Monahan, Christopher]

Hi everyone,

Thank you to everyone that contributed to a useful and productive meeting today. Raza and Tanjib summarised the status of the unpolarised and polarised gluon PDF data. There are approximately 1900 configurations and contractions are completed for momenta up to Pz = 4 in 2pi/L units (for the unpolarised), with Pz = 5 and 6 to be finished in a matter of weeks. Chris C summarised his progress with the disconnected contributions relevant to isoscalar quark PDFs. Chris is working with Kostas to begin the analysis for that data.

Everyone agreed that future publications of unpolarised gluon PDF data should include mixing with isoscalar quark contributions. In addition to the data analysis on the new configurations, this requires two new ingredients, the isoscalar contributions (underway and being led by Chris C) and the gluon momentum fraction, which normalises the reduced pseudo ITD.

For properly normalised results we need the renormalisation parameter, and we discussed how easy it is to determine the relevant parameters in the RI/MOM scheme for the gluon operators (not, is the short version). The most basic calculation would be relatively straightforward to implement, but a proper analysis with sufficiently improved signal-to-noise ratio requires some trickery, see https://urldefense.proofpoint.com/v2/url?u=https-3A__arxiv.org_abs_1805.00531&d=DwIFAw&c=CJqEzB1piLOyyvZjb8YUQw&r=phC8jtUHUVIl1OXaA25HKnc5L16EvLwhrqx4rXYGPWA&m=70przrazDIAsfg7s3jvlH0zCC3i6b5ayD0Du53UuNL5aELRm_Hb5w_SW78ntBD3C&s=-7zj1_Ang0kWhyC0ncOXyo1IvXP5Fkjeqos4gVVJVDk&e= . The timescale for this is a little unclear, so in the meantime, Wayne has volunteered* to lead the data analysis of the momentum fraction of the gluon, with help from Raza and Tanjib. I will try to push forward our RI/MOM analysis, perhaps starting with a perturbative calculation, which was sufficient for ETMC (https://urldefense.proofpoint.com/v2/url?u=https-3A__arxiv.org_abs_1611.06901&d=DwIFAw&c=CJqEzB1piLOyyvZjb8YUQw&r=phC8jtUHUVIl1OXaA25HKnc5L16EvLwhrqx4rXYGPWA&m=70przrazDIAsfg7s3jvlH0zCC3i6b5ayD0Du53UuNL5aELRm_Hb5w_SW78ntBD3C&s=2MJgjrx6BiszMnOI1q5OJqw3W_-3WnyaWOibF1KI5io&e=  and https://urldefense.proofpoint.com/v2/url?u=https-3A__arxiv.org_abs_1706.02973&d=DwIFAw&c=CJqEzB1piLOyyvZjb8YUQw&r=phC8jtUHUVIl1OXaA25HKnc5L16EvLwhrqx4rXYGPWA&m=70przrazDIAsfg7s3jvlH0zCC3i6b5ayD0Du53UuNL5aELRm_Hb5w_SW78ntBD3C&s=a-8pMAL_gzJpZhRtEiwW96nJUvbBpJ8PT5fvAnl8XuM&e= ). In the meantime, I will try to work with Robert and Joe and anyone else that can help, to figure out how to develop the necessary code for the nonperturbative RI/MOM calculation. Wish us all luck.

With these pieces proceeding in parallel, we hope that combining them all into one glorious PRL at the end will be straightforward.

Owing to the importance of the polarised gluon distribution and getting that done quickly, we plan to complete that project as soon as possible, without including the quark contributions for the first calculation.

Regards,
Chris

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Chris Monahan
Pronouns: he/his
Assistant Professor
Department of Physics
William & Mary
757-221-2081
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