Charged pions tagged with polarized photons probing strong CP violation in a chiral-imbalance medium

Mamiya Kawaguchi, Masayasu Harada, Shinya Matsuzaki, and Ruiwen Ouyang
Phys. Rev. C 95, 065204 – Published 9 June 2017

Abstract

It is expected that in a hot QCD system, a local parity-odd domain can be produced due to nonzero chirality, which is induced from the difference of winding numbers carried by the gluon topological configuration (QCD sphaleron). This local domain is called the chiral-imbalance medium, characterized by nonzero chiral chemical potential, which can be interpreted as the time variation of the strong CP phase. We find that the chiral chemical potential generates the parity breaking term in the electromagnetic form factor of charged pions. Heavy ion collision experiments could observe the phenomenological consequence of this parity-odd form factor through the elastic scattering of a pion and a photon in the medium. Then we quantify the asymmetry rate of the parity violation by measuring the polarization of the photon associated with the pion, and discuss how it could be measured in a definite laboratory frame. We roughly estimate the typical size of the asymmetry, just by picking up the pion resonant process, and find that the signal can be sufficiently larger than possible background events from parity-breaking electroweak process. Our findings might provide a novel possibility to make a manifest detection for the remnant of the strong CP violation.

  • Figure
  • Figure
  • Received 11 January 2017
  • Revised 26 April 2017

DOI:https://doi.org/10.1103/PhysRevC.95.065204

©2017 American Physical Society

Physics Subject Headings (PhySH)

Particles & FieldsNuclear Physics

Authors & Affiliations

Mamiya Kawaguchi1,*, Masayasu Harada1,†, Shinya Matsuzaki1,2,‡, and Ruiwen Ouyang3,§

  • 1Department of Physics, Nagoya University, Nagoya 464-8602, Japan
  • 2Institute for Advanced Research, Nagoya University, Nagoya 464-8602, Japan
  • 3College of Physics, Jilin University, Changchun, 130012, China

  • *mkawaguchi@hken.phys.nagoya-u.ac.jp
  • harada@hken.phys.nagoya-u.ac.jp
  • synya@hken.phys.nagoya-u.ac.jp
  • §ruiwen.ouyang@gmail.com

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Issue

Vol. 95, Iss. 6 — June 2017

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