Test Fundamental Symmetries via Precision Measurements of \(\pi ^{0}\), \(\eta \), and \(\eta '\) Decays

Abstract

Light neutral meson decays provide a unique laboratory to test fundamental symmetries in physics. A comprehensive Primakoff experimental program at Jefferson Laboratory (JLab) is aimed at gathering high precision measurements on the two-photon decay widths and the transition form factors at low four-momentum transfer squares for π 0 , η and η ′ via the Primakoff effect. The results of these measurements will offer stringent tests on the chiral anomaly and provide sensitive probe for the origin and dynamics of chiral symmetry breaking in the confinement QCD. In addition, the JLab Eta Factory (JEF) experiment has been recently developed to measure various η decays with emphasis on rare neutral modes. It will have a factor of two orders of magnitude reduction in backgrounds compared to all other existing or planned experiments in the world. Such low background data will serve as important hadronic probes for weakly-coupled new forces, such as a dark force via a leptophobic dark V B -boson or a new C-violating, P-conserving force. The status of these experimental activities and their physics impacts will be discussed.

Patterns of C- and CP-violation in hadronic η and η′ three-body decays

“…The extracted coupling strengths of the underlying effective isoscalar and isotensor BSM operators from η → π + π − π 0 and the one of the isovector BSM operator from η → ηπ + π − may in the future be matched to fundamental BSM operators on the quark level, thus allowing to predict a corresponding scale for BSM physics [11][12][13][14][15]93]. We conclude that our framework opens a window to the systematic analysis of C-and CPviolation in η ( ) → π + π − π 0 and η → ηπ + π − Dalitz plots provided by future high-statistics experimental measurements [94][95][96][97][98].…”

Patterns of CP violation from mirror symmetry breaking in the η→π+π−π0 Dalitz plot

“…[32]. Other experiments find no evidence for a charge asymmetry and C violation [28,[32][33][34][35][36], and we note that new, high-statistics experiments are planned [37][38][39]. It is also possible to form asymmetries that probe the isospin of the C-violating final state: a sextant asymmetry A S , sensitive to the I ¼ 0 state [4,5], and a quadrant asymmetry A Q , sensitive to the I ¼ 2 final state [4,28].…”

“…New-physics contributions that differ in their isospin can thus be probed through the kinematic pattern they imprint in the Dalitz plot. Our method opens a new window on the study of C-and CP-violation in η → π þ π − π 0 decay, and it holds promise for the highstatistics experiments of the future [37][38][39].…”

Patterns of $C$- and $CP$-violation in hadronic $η$ and $η'$ three-body decays

“…The extracted coupling strengths of the underlying effective isoscalar and isotensor BSM operators from η → π + π − π 0 and the one of the isovector BSM operator from η ′ → ηπ + π − may in the future be matched to fundamental BSM operators on the quark level, thus allowing to predict a corresponding scale for BSM physics [11][12][13][14][15]93]. We conclude that our framework opens a window to the systematic analysis of C-and CP -violation in η (′) → π + π − π 0 and η ′ → ηπ + π − Dalitz plots provided by future high-statistics experimental measurements [94][95][96][97].…”