Study on the performance of YBJ preliminary carpet

The Sino-Italian collaboration YBJ-ARGO experiment is under construction at the Yang Bajing High Altitude Cosmic Ray Laboratory( Tibet, China, 4300m a. s. l. 606g/cm(2)). About 693m(2) of preliminary carpet detector have been instrumented and put into operation for calibration runs devoted to test the performance of the individual components and their integrated operation. Events collected with a "shower mode" trigger have been recorded to check the consistency of physics data. The performance and characteristics of a preliminary carpet detector are analyzed using its test run data at the high altitude conditions. Shower reconstruction algorithms are described together with the results after time offset correction. Results of the test run show the importance of the time correction for data analysis, and some results concerning detector calibration, azimuth angle distribution, zenith angle distribution and angular resolution are presented.