Research On The Improvement Of The Identification Of Heavy Component Of Cosmic Ray Based On Directed Cherenkov Light

After more than 100 years from the first observations of cosmic rays,the cosmic rays have greatly promoted the development of particle physics and astrophysics.However,the origin,the acceleration and the propagation of cosmic rays still remain central unresolved problems in astrophysics.Measurements of energy spectra for individual elements are very important to resolve the questions of the origin,the acceleration and propagation of cosmic rays.However,the measurements of high energy cosmic rays are based on the ground experiments,the composition reconstruction depends on the interaction model.Large High Altitude Air Shower Observatory(LHAASO)is an experiment built by Chinese scientists dedicated to the study of the origin of cosmic rays,is built at4410m above sea level near the Daocheng village,in Sichuan province,China.LHAASO is a hybrid array,which contains KM2A array,WCDA array and WFCTA array.The WFCTA is an important part of LHAASO.One of WFCTA aims is to measure of energy spectra for individual elements precisely.In this paper,we proposed a new method which is based on the characteristics of direct Cherenkov Light(DC-light)to discriminate the heavy nuclei and combine with WCDA to improve the discrimination capability of heavy nuclei.DC-light emitted by the primary nucleus before the first nuclear interaction with the nucleus in the Earths,atmosphere,which is proportional to the square of the charge of primary particles,with a narrow Cherenkov angle(0.1~°~0.3~°).In the paper,those characteristics encourage us to define a new parameter R to discriminate heavy events from the other cosmic rays.Due to emissive mechanisms of DC-light,the selection method by R is independent of the hadronic interaction models.While the other parameters such as Dist,Length/Width depend on the hadronic interaction models.The method by the DC-light is also applied to the selection of heavy nuclei from other cosmic rays with the pixel size of WFCTA cameras in the process of MVA,to improve selection efficiency of heavy events effectively.The event rate of heavy nuclei obtained by R,Dist and Length/Width is 24%higher than that obtained only by the Dist and Length/Width.In the near future,the selection methods by the R could be applied to the LHAASO data analysis,to improve the discrimination capability and reconstruction accuracy of heavy nuclei.