26–28 Sept 2023
Padova
Europe/Rome timezone

Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model

26 Sept 2023, 15:30
1h 20m
Sala Livio Paladin, Palazzo Moroni (Padova)

Sala Livio Paladin, Palazzo Moroni

Padova

Via del Municipio, 1, 35122 Padova PD
Abstract for a Poster Poster session

Speaker

Naohiro Osamura (Nagoya)

Description

When the QCD axion is absent in full theory, the strong CP problem has to
be explained by an additional mechanism, e.g., the left-right symmetry. Even though tree-
level QCD θ ̄ parameter is restricted by the mechanism, radiative corrections to θ ̄ are mostly
generated, which leads to a dangerous neutron electric dipole moment (EDM). The ordinary
method for calculating the radiative θ ̄ utilizes an equation θ ̄ = −arg det mloop based on the q
chiral rotations of complex quark masses. In this paper, we point out that when full theory includes extra heavy quarks, the ordinary method is unsettled for the extra quark contributions and does not contain its full radiative corrections. We formulate a novel method to calculate the radiative corrections to θ ̄ through a direct loop-diagrammatic approach, which should be more robust than the ordinary one. As an application, we investigate the radiative θ ̄ in the minimal left-right symmetric model. We first confirm a seminal result that two-loop level radiative θ ̄ completely vanishes (corresponding to one- loop corrections to the quark mass matrices). Furthermore, we estimate the size of a non- vanishing radiative θ ̄ at three-loop level. It is found that the resultant induced neutron EDM is comparable to the current experimental bound, and the expected size is restricted by the perturbative unitarity bound in the minimal left-right model.

Abstract for a poster all program topics can be contemplated

Primary authors

Dr Atsuyuki Yamada (Nagoya) Junji Hisano (KMI, Nagoya Univ.) Naohiro Osamura (Nagoya) Teppei Kitahara (Nagoya University)

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