Study of EAS Local Muon Density Spectrum and the Knee in the Energy Spectrum of Primary Cosmic Rays

  • With the extensive air shower (EAS) array at Mt. Liang Wang (735 g·cm2,245°N,102.9° E,Kunming China) it is able to measure the muon density spectrum at a fixed distance from the core of EAS in the knee region. The spectra at two different fixed core distances (25m≤core distance<30m,30m≤core distance<35m) were obtained from 4.4×104events collected in 1994 with criteria 5×104≤size≤1.6×107 and 10°≤θ<30° that show obvious kinks. Monte Carlo simulations for the EAS development and detection with same selection criteria in the array triggering and the analysis procedure have been performed in order to relate the local muon densities to primary energy. As a result,we have deduced that the average position of the knee (Eknee) is at about 1.7×1015eV and the average difference of the slopes of the primary energy spectrum before and after the knee (Δγ) is about 0.43. This work corroborates the first result (Eknee=5PeV,Δγ=0.3) reported by KASCADE. It authenticates reliably the existence of the knee at the primary energy spectrum by another composition of EAS - muon composition (more direct than electron composition). Based on the results obtained by two experiments,the difference of slopes of cosmic ray primary energy spectrum before and after the knee is close to 0.4 that is accepted widely,while the energy of the knee is different from the accepted 3PeV.
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  • [1] . LUO GuangXuan,TAN YouHeng,ZHANG ChunSheng et al.High Energy Phys.and Nucl.Phys.,1995,19(9):769—774(in Chinese)(罗光宣,谭有恒,张春生等.高能物理与核物理,1995,199):769—774) 2. Haungs A , Antoni T , Apel W D et al.Cosmic Ray Energy Spectrumaround the Kneeby Muon Density Measurements at KASCADE .In:D .Kieda,M .Salamon, B .Dingus.26th Inte rnational Cosmic Ray Conference.Utah:26th ICRC Conference Committee,1999 3. GAO X Y ,Leung K C ,Yang H T et al.ANew Underground Muon Detectoron Mt.Liang Wang.24th International Cosmic Ray Conference,Vol.1.Roma,1995,978—981 4. Ng L K ,GAO X Y ,YANG Z T et al.New Gamma ray Observatory on Mt. Liang Wang.In:R .J. Protheroe.21st International Cosmic Ray Conference,Vol.4.Australia,1990,286—289 5. GAO XiaoYu,Leung K C ,YANG HongTao et al.The EAS Muon Detection on Mt. Liang Wang.In:ZHU QingQi.CCAST- WL Workshop Series,Vol.48.Beijing:CCAST (World Laboratory)Workshop,1995,121—128(in Chinese)(高晓宇,Leung K C ,杨洪涛等.梁王山站EAS的μ子探测.见:朱清棋编辑.CCAST –WL Workshop Series,48卷.北京:CCAST(World Laboratory)Workshop,1995,121—128) 6. ZHA Min,CHUENG Tsang,DING LinKai et al.Chinese Physics Letters,1999,16(8):622—624 7. Cheung T ,JING GuiRu,GAO XiaoYu et al.EAS Muon Lateral Distribution and Primary Cosmic Ray.7th National Cosmic Ray and Astrophysics Conference Paper.Yunnan,1996(in Chinese)(张增,荆贵菇,高晓宇等.EAS中μ子横向分布与初级宇宙线.第七届全国宇宙线和天体物理会议论文集.云南,1996) 8. Cheung T ,ZHU Q Q .A Monte Carlo Generator of Mini jet Model for the Simulation of Hadron Multiproduction.24th International Cosmic Ray Conference,Vol.1Roma;1995,143—146
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LIU Jun, GENG Qing-Xi, YANG Hong-Tao, LIU Chang-Qin, ZHANG Pin, GAO Xiao-Yu, JING Cai-Liu, ZHA Min, JING Gui-Ru, ZHU Qing-Qi, Cheung T and Ng L. Study of EAS Local Muon Density Spectrum and the Knee in the Energy Spectrum of Primary Cosmic Rays[J]. Chinese Physics C, 2003, 27(2): 109-112.
LIU Jun, GENG Qing-Xi, YANG Hong-Tao, LIU Chang-Qin, ZHANG Pin, GAO Xiao-Yu, JING Cai-Liu, ZHA Min, JING Gui-Ru, ZHU Qing-Qi, Cheung T and Ng L. Study of EAS Local Muon Density Spectrum and the Knee in the Energy Spectrum of Primary Cosmic Rays[J]. Chinese Physics C, 2003, 27(2): 109-112. shu
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Received: 2002-04-09
Revised: 1900-01-01
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Study of EAS Local Muon Density Spectrum and the Knee in the Energy Spectrum of Primary Cosmic Rays

    Corresponding author: LIU Jun,
  • Cosmic Ray Research Institute of Yunnan University,Kunming 650091, China2 Institute of High Energy Physics,CAS,Beijing 100039,China3 City University of Hong Kong,Hong Kong,China4 Hong Kong Institute of Education,Hong Kong,China

Abstract: With the extensive air shower (EAS) array at Mt. Liang Wang (735 g·cm2,245°N,102.9° E,Kunming China) it is able to measure the muon density spectrum at a fixed distance from the core of EAS in the knee region. The spectra at two different fixed core distances (25m≤core distance<30m,30m≤core distance<35m) were obtained from 4.4×104events collected in 1994 with criteria 5×104≤size≤1.6×107 and 10°≤θ<30° that show obvious kinks. Monte Carlo simulations for the EAS development and detection with same selection criteria in the array triggering and the analysis procedure have been performed in order to relate the local muon densities to primary energy. As a result,we have deduced that the average position of the knee (Eknee) is at about 1.7×1015eV and the average difference of the slopes of the primary energy spectrum before and after the knee (Δγ) is about 0.43. This work corroborates the first result (Eknee=5PeV,Δγ=0.3) reported by KASCADE. It authenticates reliably the existence of the knee at the primary energy spectrum by another composition of EAS - muon composition (more direct than electron composition). Based on the results obtained by two experiments,the difference of slopes of cosmic ray primary energy spectrum before and after the knee is close to 0.4 that is accepted widely,while the energy of the knee is different from the accepted 3PeV.

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