Parity Violation in Weak Nuclear Interactions

The treatment of parity violations in the weak nuclear interactions is discussed within the frameworks of both the Standard Model (SM) and the Generation Model (GM) of particle physics. It will be demonstrated that several important differences between these two models lead to the SM merely describing the parity violations, while the GM provides an understanding of the cause of the parity violations in weak nuclear interactions. The significant differences arising from several dubious assumptions made during the development of the SM, lead to very different conclusions concerning the nature of the parity violations in the two models. While the SM is able to describe the observed parity violations in terms of a “V-A” theory of the weak nuclear interactions, the GM is also able to demonstrate the cause of the observed parity violations: in the GM, the observed parity violations arise as a consequence of the negative intrinsic parity of both the W massive bosons, which mediate these so-called charge-changing (CC) weak nuclear interactions.

Study of parity violation inΛ^(+)_(c)→ΦρandΛ^(+)_(c)→ωρdecays

CP violation in baryonic decays has not been significantly observed.With large data events accumulated at e+e-colliders or the Large Hadron Collider,charmed baryon decays would provide a promising laboratory to test CP symmetry.In this study,we formulateΛ^(+)_(c)→ΦρandΛ^(+)_(c)→ωρdecays for the measurement of their asymmetry parameters in weak decays at the BESII or LHCb experiments.The polarization transfer is analyzed in the two processes of e+e-→Λ^(+)_(c)Λ^(-)_(c)andΛ^(o)_(b)→Λ^(+)_(c)π^(-),and the formulas for the joint angular distribution of these processes are provided.The sensitivity of the measurement of the asymmetry parameters of the above two decay processes is estimated for future experiments.

New insights to old problems

From the history of the θ-τ puzzle and the discovery of parity non-conservation in 1956, we review the current status of discrete symmetry violations in the weak interaction. Possible origin of these symmetry violations are discussed.

Δ contribution to the parity-violating nucleon-nucleon force

Because the nucleon may be excited and transformed into a virtual A resonance easily, we consider the decuplet contribution to the parity-violating （PV） nucleon-nucleon interaction in the chiral effective field theory. The effective PV nucleon-nucleon potential is derived without introducing any unknown coupling constants.

Phenomenological study of J/ψ→Ξ^(0)(Λπ^(0))ˉΞ^(0)(Λγ)decays

The measurement of decay parameters is one of the important goals of particle physics experiments,and the measurement serves as a probe to search for evidence of CP violation in baryonic decays.The experimental results will aid in advancing existing theoretical research and establishing new experimental objectives.In this study,we formulate the asymmetric parameters that characterize parity violation,and then derive formulas for the measurement of CP violation.The formulae for the joint angular distribution of the full decay chain as well as the polarization observable of Ξ^(0),Ξ¯^(0),Λ,and Λ¯are also provided for experiments.Lastly,we evaluated the sensitivity of two asymmetric parameters:αΞ0→Λπ0(abbreviated asαΞ0)andαΞ¯0→Λ¯γ(abbreviated asαΞ¯0)for future experimental measurements.

Measurement of PV asymmetry in +p→d+γ and ■+d→n+p

The measurement of parity-violating （PV） observables in few-nucleon system can shed light on our current understanding of the weak interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered： the capture of polarized slow neutrons on hydrogen （n ＋ p → d ＋ γ） at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons （γ ＋ d → n ＋ p） at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 ×10^-8 .The introduction of both experiments is presented.