Development of Yangbajing air shower core detector for a new EAS hybrid experiment -

2) in Tibet, China. YAC works together with the Tibet air-shower array (Tibet-Ⅲ) and an underground water Cherenkov muon detector array (MD) as a hybrid experiment. Each YAC detector unit consists of lead plates of 3.5 cm thickness and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores. The burst size can be measured from 1 MIP (Minimum Ionization Particle) to 10⁶ MIPs. The first phase of this experiment, named "YAC-Ⅰ", consists of 16 YAC detectors each with a size of 40 cm×50 cm and distributed in a grid with an effective area of 10 m². YAC-Ⅰ is used to check hadronic interaction models. The second phase of the experiment, called "YAC-Ⅱ", consists of 124 YAC detectors with coverage of about 500 m². The inner 100 detectors of 80 cm× 50 cm each are deployed in a 10×10 matrix with a 1.9 separation; the outer 24 detectors of 100 cm×50 cm each are distributed around these to reject non-core events whose shower cores are far from the YAC-Ⅱ array. YAC-Ⅱ is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of protons, helium and iron nuclei between 5×10¹³ eV and 10¹⁶ eV, covering the "knee" and also connected with direct observations at energies around 100 TeV. We present the design and performance of YAC-Ⅱ in this paper."> Development of Yangbajing air shower core detector for a new EAS hybrid experiment -

[1]
Amenomori M et al. (Tibet ASγ collaboration). Astrophys. J., 2008, 678(2): 1165[2] Hrandel J R. Astropart. Phys., 2003, 19(2): 193[3] Huang J et al. Astropart. Phys., 2003, 18(6): 637[4] Amenomori M et al. (Tibet ASγ collaboration). Phys. Lett. B, 2006, 632(1): 58[5] Yoon Y S et al. Astrophys. J., 2011, 728(2): 122[6] Ahn H S et al. Astrophys. J., 2009, 707(1): 593[7] Wefel J P et al. Proc. of 29th Int. Cosmic Ray Conf., 2005, 3: 105[8] Kalmykov N N, Ostapchenko S S, Pavlov A I. Nucl. Phys. B-Proc. Suppl., 1997, 52(3): 17[9] Ahn E J et al. Phys. Rev. D, 2009, 80: 094003[10] Ranft J. Phys. Rev. D, 1995, 51: 64[11] Pierog T et al. 2013, arXiv:1306.0121[hep-ph][12] Ostapchenko S S. Phys. Rev. D, 2011, 83: 014018[13] Katayose Y et al. Proc. of 29th Int. Cosmic Ray Conf., 2005, 8: 157[14] Amenomori M et al. (Tibet ASγ collaboration). Proc. of 32nd Int. Cosmic Ray Conf., 2011, 1: 153[15] Amenomori M et al. (Tibet ASγ collaboration). Proc. of 32nd Int. Cosmic Ray Conf., 2011, 3: 290[16] LIU J S et al. Proc. of 33rd Int. Cosmic Ray Conf., 2013[17] ZHAI L M et al. Proc. of 33rd Int. Cosmic Ray Conf., 2013