Description: Confirming the existence of the strong CP problem in lattice QCD with the gradient flo

This title appears in the Scientific Report : 2021

Confirming the existence of the strong CP problem in lattice QCD with the gradient flo

We calculate the electric dipole moment of the nucleon induced by the quantum chromodynamics θ term. We use the gradient flow to define the topological charge and use Nf=2+1 flavors of dynamical quarks corresponding to pion masses of 700, 570, and 410MeV, and perform an extrapolation to the physical...

Personal Name(s):	Dragos, Jack (Corresponding author)
	Shindler, Andrea / de Vries, Jordy / Yousif, Ahmed / Luu, Tom
Contributing Institute:	Theorie der Starken Wechselwirkung; IAS-4 JARA - HPC; JARA-HPC
Published in:	Physical review / C, 103 (2021) 1, S. 015202
Imprint:	Woodbury, NY Inst. 2021
DOI:	10.1103/PhysRevC.103.015202
Document Type:	Journal Article
Research Program:	Beyond the Standard Model Matrix Elements from lattice QCD Enabling Computational- & Data-Intensive Science and Engineering
Link:	OpenAccess
	Publikationsportal JuSER

Please use the identifier: http://hdl.handle.net/2128/28157 in citations.
Please use the identifier: http://dx.doi.org/10.1103/PhysRevC.103.015202 in citations.

We calculate the electric dipole moment of the nucleon induced by the quantum chromodynamics θ term. We use the gradient flow to define the topological charge and use Nf=2+1 flavors of dynamical quarks corresponding to pion masses of 700, 570, and 410MeV, and perform an extrapolation to the physical point based on chiral perturbation theory. We perform calculations at three different lattice spacings in the range of 0.07fm<a<0.11fm at a single value of the pion mass, to enable control on discretization effects. We also investigate finite-size effects using two different volumes. A novel technique is applied to improve the signal-to-noise ratio in the form factor calculations. The very mild discretization effects observed suggest a continuumlike behavior of the nucleon electric dipole moment toward the chiral limit. Under this assumption our results read dn=−0.00152(71)¯θefm and dp=0.0011(10)¯θefm. Assuming the θ term is the only source of CP violation, the experimental bound on the neutron electric dipole moment limits ∣∣¯θ∣∣<1.98×10−10 (90% CL). A first attempt at calculating the nucleon Schiff moment in the continuum resulted in Sp=0.50(59)×10−4¯θefm3 and Sn=−0.10(43)×10−4¯θefm3.