Study Of Hyperon Radiative Decay At BES?

Hyperon radiative decay represents processes with effective s to d quark transitions,involving weak,electromagnetic,and strong interactions in the Feynman diagrams.This process is ideal for studying the double quark exchange mechanism and testing Hara's theorem.In this paper,based on the Beijing Spectrometer(BESIII)operating at the Beijing Electron Positron Collider(BEPCII),the radiative decays of ? and E+hyperons were studied using 10 billion J/? data collected by BESIII.In the study of ? radiative decay,the double-tag(DT)technique was used for event selection.Using the J/???? process,single-tag ? was reconstructed via the ???+p process,and double-tag A was reconstructed via the ???n process.To suppress the high background caused by the annihilation effect of the antineutrons(neutrons),a machine-learning model based on multi-input variables was used to distinguish the photon candidates sources,which significantly improved the signal significance.In this analysis,for the first time,we directly.measured the absolute branching fraction of the ???n decay,and the result was 0.846 ± 0.039sTat.± 0.052syst.× 10-3.Moreover,? hyperons generated by J/???? decay were polarized,based on which we could measure the ???n decay parameter,estimate the parity violation degree in the ? radiative decay,and test Hara's theorem We determined the decay parameter of the ???n process for the first time,and the result was-0.160±0.101stat.± 0.046syst..In the study of ?+ radiative decay,the DT technique was used for event selection and the J/???+/?-process was Dsed for signal reconstruction.Herein,we directly measured the absolute branching fraction of ?+??p decay for the first time,and the result was(1.013 ± 0.023stat.±0.016syt.)× 10-3.The decay parameter of the?+??p process was determined to be-0.608±0.053stat.± 0.025syst..In the experiments,two charge-parity(CP)violating observables were formed through the branching fractions and the decay parameters of the charge-conjugated channels of the ? and ?+ radiative decays.Moreover,no evidence of the CP violation was found under the current precision.The measured results of hyperon radiative decay at BESIII were considerably smaller than those of the existing fixed-target experiments.To understand the difference between the measured results of the electron-positron collider experiment and fixed-target experiment and provide more accurate input parameters for the theoretical models,it is necessary to perform a systematic experimental study of the hyperon radiative decay.The measurement error of the current BESIII experiment was dominated by statistical error.In order to improve the precision,the high-luminosity Super Tau-Charm Factory(STCF)experiment would be an optimal experimental choice to study hyperon radiative decay.The proposed luminosity of the STCF accelerator is two orders of magnitude higher than that of BEPCII.In addition,the center-of-mass of collision energy was between 2 and 7 GeV.Approximately 3.4 trillion J/? data will be collected per year,improving the accuracy of the hyperon radiative decay measurement by at least an order of magnitude,which is essential in testing related theories.The Offlline Software of Super Tau-Charm Facility has been preliminarily developed with a detector geometry management system and a full detector simulation algorithm in the pre-research stage.Currently,the software is playing an important role in the work of optimizing the STCF detector.