This title appears in the Scientific Report :
2019
Please use the identifier:
http://hdl.handle.net/2128/24180 in citations.
Confirming the Existence of the strong CP Problem in Lattice QCD with the Gradient Flow
Confirming the Existence of the strong CP Problem in Lattice QCD with the Gradient Flow
We calculate the electric dipole moment of the nucleon induced by the QCD theta 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 410 MeV, and perform an extrapolation to the physical point based...
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Personal Name(s): | Dragos, Jack |
---|---|
Luu, Tom (Corresponding author) / Shindler, Andrea / de Vries, Jordy / Yousif, Ahmed | |
Contributing Institute: |
Theorie der Starken Wechselwirkung; IAS-4 |
Imprint: |
2019
|
Document Type: |
Preprint |
Research Program: |
Theory, modelling and simulation |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
We calculate the electric dipole moment of the nucleon induced by the QCD theta 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 410 MeV, and perform an extrapolation to the physical point based on chiral perturbation theory. We perform calculations at 3 different lattice spacings in the range of 0.07~fm < a < 0.11 fm at a single value of the pion mass, to enable control on discretization effects. We also investigate finite size effects using 2 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 continuum-like behavior of the nucleon EDM towards the chiral limit. Under this assumption our results read dn=-0.00152(71)\ \barθ\ e~fm and dp=0.0011(10)\ \barθ\ e~fm. Assuming the theta term is the only source of CP violation, the experimental bound on the neutron electric dipole moment limits ≤ft|\barθ\right| < 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\ \barθ\ e~fm3 and Sn = -0.10(43)× 10-4\ \barθ\ e~fm3. |