Development Of LHAASO Raw Data Input And Output System

Particle physics is a science that studies the basic structure and basic int erac-tions of matter in the microcosm.At present,there are many large-scale particle experiment projects in China under construction,and the corresponding offline software systems are also under development.Large High Altitude Air Shower Observatory(LHAASO)is a major basic scientific research project in the field of cosmic ray researeh in China.Located in Haizi Mountain,Siechuan Province.China,at an altitude of 4,410 meters.construction began in 2017 and is expected to be completed in 2021.The LHAASO experiment uses a variety of detection methods consisting of three detector arrays.namely the kilometer-square array(KM2A),the water Cherenkov detector array(WCDA)and the wide-angle flu-orescence Cherenkov telescope array(WFCTA).The main physical goal of the LHAASO experiment is to accurately measure the gamma ray spectrum from 300 GeV to 20 PeV and explore the origin of high energy cosmic rays.The LHAASO experiment has the most sensitive ultra high-energy gammna-ray de-tection.the most sensitive very high-energy gamma ray survey,and the widest cosmic ray energy measurement range.This is due to the composite detector array of the LHAASO experiment,and the high-performance detector requires a complete offline data processing software system to fully function.The offline data processing software system performs the proceessing,analysis and manage-ment of experimental data and simulation data acquireed online based on an offline computing enviromnent.LHAASO's offline data processing software framework(LodeStar)is in the design and development plhase,providing a unified software foundation platform for LHAASO experiments,developing offline software such as raw data processing.data calibration.simulation.reconstrucetion and some common physies analysis tools,in which the data model and the data input and output services are used together by all offline software.At present.LodeStar has provided ROOT input and output system to realize the mutual conversion of transiet and persistent data model objects.The input service reads the persisteit data from the ROOT files into the memory and creates the data model object.while the output service will write the data model object to the ROOT files.For the raw data files generated by the online data acquisition system(DAQ),the raw data input and output services need to be provided and integrated with the ROOT input and output services.Raw data.processing is the first step in offline data processing,providing input for subsequent offline calibration,reconstruction,and physical analysis,playing an important role in the Pentire data.processing flow.Therefore,the development of raw data input and output systems is extremely important.The main content of this paper is to develop a general-purpose system for inputting and outputting raw data based on LodeStar.The system provides a data conversion service for processing raw data by user programs or other software modules.The raw data conversion service hides the complex structure of the raw data format,enabling the user program to obtain case information through a unified interface,greatly simplifying the access process of the raw data.The data conversion service pro-vides a variety of data decoding methods,and any decoding method can be called according to user requirements,so that the system can be flexibly used in multi-ple detector arrays of LHAASO,and can also provide reference for the raw data processing of other high energy physics experiments.