[Theory-seminars] Cake Seminar Wednesday - Christian Weiss

[Zheng-Yang Li]

Dear all,

On Wednesday, October 30th, 2024 at 1pm EDT, we will have a cake seminar given by Christian Weiss of Jlab in CC L102 and on the following Zoom link:

https://jlab-org.zoomgov.com/j/1613057553?pwd=pdNgrofOJc5nPmQo0gE7ZtI9BZ7aiS.1

Attendance in person is highly encouraged. Please see below for the title and abstract.

Cake Seminar: Wednesday, October 30th, 2024 at 1pm EDT

Speaker: Christian Weiss (Jlab)

Title: Trace anomaly and pion gravitational form factors in the QCD instanton vacuum

Abstract: The breaking of conformal and chiral symmetry define the mass decomposition of light hadrons in QCD and determine their mechanical properties. We report about a recent study of the pion mass decomposition and gravitational form factors in the instanton liquid model of the QCD vacuum [1]. The picture is abstracted from "cooled" lattice QCD calculations and describes the gauge fields semiclassically as an ensemble of instantons - tunneling trajectories between topological sectors of the gauge theory. Chiral symmetry breaking is caused by the fermionic zero modes induced by the instantons. Conformal symmetry breaking is encoded in the fluctuations of the number of instantons, dictated by the renormalization properties of QCD [2]. It is found that 1/2 of the pion mass arises from gluonic fields through the trace anomaly, the other 1/2 from quark fields through the chiral condensate. The role of the Goldstone boson nature of the pion in its QCD mass decomposition is explained. The pion gluon and quark gravitiational form factors at finite Q2 ~ 1 GeV2 are predicted in good agreement with recent lattice QCD results. We summarize ongoing work extending the approach to the nucleon gravitational form factors, gluonic structure, and twist-3 GPDs [3].

[1] W.Y. Liu, E. Shuryak, C. Weiss, I. Zahed, Phys. Rev. D 110, 054021 (2024)  https://inspirehep.net/literature/2789192
[2] D. Diakonov, M.V. Polyakov, C. Weiss, Nucl. Phys. B 461, 539 (1996)  https://inspirehep.net/literature/400277
[3] J.Y. Kim, C. Weiss, Phys. Lett. B 848, 138387 (2024)  https://inspirehep.net/literature/2714432

See you on Wednesday.

Best regards,
Joe, Zheng-Yang & Gloria

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