Λ_c~+/(?)_c~- Three-body Decay Parameter Measurement

In 1964,the charge-parity(CP)violation has been observed in the study of K0 decay.The CP violation effect has been found in K meson system,B meson system and D meson system in succession are in accordance with the prediction of the standard model(SM).But the standard model does not explain the large asymmetry of matter and antimatter in the universe.Current experimental results show that the standard model is consistent with most experimental data at high accuracy,but its limitations are particularly obvious.For instance,in the standard model,CP violation is represented by an irreducible complex phase and does not include gravitational effects,it fails to interpret dark matter and dark energy.Therefore,it is generally believed that the standard model theory is only a valid theory under a certain energy scale.Motivated by the fact that contributions of beyond-the-SM virtual particles may alter the magnitude of CF violation with respect to the SM expectation,a number of theoretical analyses have been performed in recent years.Experimental measurements of CP violation parameters of Ac particles are mostly concentrated in the two-body decay process,and the measurements of asymmetric decay parameters and CP violation parameters of three-body decay are rarely involved.Based on an e+e-collision data sample corresponding to an integrated luminosity of 567 pb-1 taken at the center-of－mass energy of √s=4.6 GeV with the BESⅢ detector,we measure asymmetry parameters in process e+e-→ ∧c+∧c-→pK-π+pK+π-.Since the events are relatively clean at this energy point,the extra hadrons can be excluded.Through our analysis we obtain the asymmetry pa-rametera α∧c+=0.015±0.084±0.006 in process Ac+→pK-π+,and α∧c-=-0.054±0.081±0.013in process ∧c→pK+π-.Meanwhile,CP violation parameter of Ac three-body decay can be obtained through the two parameters previously obtained as A=-0.568±1.615±0.08.In all measurements the first errors are statistical and the second are systematic.