LHAASO 的事例重建和物理分析 马欣华 2016 年高能物理计算与软件会 1

内容 1.LHAASO 的观测对象 2.LHAASO 的事例重建 3.LHAASO 的物理分析 2

primary cosmic rays (nuclei + gamma rays) single particle – time – position – direction – energy – component statistics – components – spectrum – imaging (anisotropy) – variation Crab Nebula 3

Extensive Air Showers single secondary particle (γ,e,μ,Č,h…) – time – position – direction – energy (> E th ) – component statistics ： – time – direction – core position – size – age Peter K.F. Grieder, Extensive Air Showers, Springer,

Extensive Air Showers 大气层可看成是量能器的簇射 介质， shower features: I.longitudinal development II.lateral development at one altitude longitudinal development lateral development Peter K.F. Grieder, Springer,

Main Array 1km 2 : 5242 electro-magnetic component detectors, every 15 m 1146  –detectors, every 30 m Water Cherenkov Detectors 80,000 m 2 CR Detectors: 18 wide field view Cherenkov telescopes Shower core detector array LHAASO 6 neutron detector array: 500 neutron detectors

LHAASO detection longitudinal development WFCTA: Č(F) lateral development KM2A : e(γ),μ WCDA: e,μ SCDA: γ family at core → π0 (PRISMA: thermal neutrons → π+π-) 7

events in detectors signal ：单元探测器采样，计数 工作模式： light(S,Č,F) → PMT → pulse → ADC or FADC background – outside detectors 在高海拔，问题更突出  cosmic radiation (single μ, small shower, …)  ground & atmosphere radiation – inside detectors  electronics noise  abnormal detectors 8

1.LHAASO 的观测对象 2.LHAASO 的事例重建 3.LHAASO 的物理分析 9

longitudinal development Wide Field Cherenkov Telescope Array (WFCTA) 10 Hillas-parameter based analysis

Hillas Parameters Xmax Energy reconstruction + μ (KM2A-MD) Atmospheric Fluorescence

lateral development at one altitude shower 的位置、时间 → 方向 shower 的位置、粒子数 → 芯位、 size 、 age Peter K.F. Grieder, Springer,

one KM^2 Array (KM2A) ED ： ~5000 plastic scintillators+fibers, distance :15m ， size: 1m×1m×2cm ， 0.5cm lead plate as γ converter, MD ： ~1200 water Č detectors, distance:30m ， size:6m×6m ， 2.8m dirt overburden 13

Water Cherenkov Detector Array (WCDA) Water depth: 4.5m Cell size: 5X5m 2 Total cell: 3600 Total area: 90,000m 2 Time resolution: <2ns Low energy threshold 150m Proton Gamma 14

PRImary Spectrum Measurement Array (PRISMA) 热中子探测 441 en-detectors to measure both thermal neutrons and electrons near core 5 m en-detectors Yu.V. Stenkin and J.F. Vald´es-Galicia,Modern Physics Letters A, Vol. 17, No. 26 (2002)

前锋面拟合：最小二乘法 前锋面到达阵列时，第 i 个 hit 的坐标为 (x i, y i, t i ) 三个未知参量： θ,φ,t 0 α 为锥面因子， α=h/r ， ARGO 取 0.03 ns/m 方向余弦 l=sinθcosφ, m=sinθsinφ, c: 光速 w: 权重（ N,r 的函数） r i : 探测器到 core 的距离 平面： 锥面： rh Peter K.F. Grieder, Springer, 重建方法：以 KM2A 为例

lateral distribution: Nishimura 西村 -Kamata 蒲田 -Greisen (NKG) function ρ e ( 电子数 /m 2 ) ：在 r 处的粒子数密度 r(m) ：到簇射芯位的距离 N e : size ( 电子数，大小 ) R M (m): Molière 半径 s: age ( 年龄 ) (NKG 函数限制 s<2.25) Γ ： gamma 函数 17 横向分布最大似然法拟合

改进重建的目标：提高阵列性能 以 KM2A 为例 gamma ： 30TeV~0.75km 2 Effective area gamma ： 30TeV~27% 100TeV~21% E nergy resolution gamma 18

Core Position resolution gamma ： 30TeV~8m 100TeV~6m Angular resolution gamma ： 30TeV~0.5° 100TeV~0.3° 19

γ/CR discrimination: γ CR 20

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1.LHAASO 的观测对象 2.LHAASO 的事例重建 3.LHAASO 的物理分析 22

LHAASO Physical Motivation To solve the problem of comic ray origin  TeV gamma ray astronomy (1) energy spectrum measurement of gamma ray sources, to search for Pevatron (2) all sky survey for new TeV gamma ray sources  1TeV-1EeV cosmic ray composition and energy spectrum measurement 23

 Other cosmic ray topics: anisotropy moon shadow → p-/p+ ratio …  topics in other fields : Solar physics Geophysics Dark Matter indirect search, Quantum gravity … LHAASO Physical Motivation (2) 24

TeV gamma ray astronomy （以 SNR 为例） 找源：全天区扫描 能谱分析：等天顶角法、等赤纬法等 物理模型拟合：宇宙线的产生、加速、传播， gamma ray 的产生、传播 25

 SNR Sky map in galactic coordinates (zenith angle <45°) 1) SNRs: 294 (107 in the view of LHAASO), in the GeV and TeV energy band~ 36 (15 in the view of LHAASO) 2) TeV UNID: 36 (15 in the view of LHAASO) 3) Supperbubble: 2 (1 in the view of LHAASO) 26

SNR models the unified model: gamma ray is generated in the environmental gas of SNR the accumulative diffusion model : gamma ray is generated by interaction between SNR and molecular clouds 27  to give the final judgment for acceleration mechanism  to find Pevatron W51C Age=30kyr D~4.3kpc W51C ~3%Crab

cosmic ray composition and energy spectrum measurement 能量确定 成份区分 – 直接挑选 – unfolding 计算流强 物理模型拟合 28

1TeV–1EeV accurate measurement in SIX orders with only ONE array – LHAASO  to remove systematic uncertainties from measurements of different detectors  to build a bridge from direct measurement at lower energy to measurements at the highest energy (Auger, etc.) 29 1 st knee 2 nd knee

ARGO-YBJ: Multi-parameter Analysis Bartoli et al., the ARGO-YBJ Collaboration and the LHAASO Collaboration, Knee of the cosmic hydrogen and helium spectrum below 1 PeV measured by ARGO-YBJ and a Cherenkov telescope of LHAASO, B. PHYSICAL REVIEW D 92, (2015) 30

总结 LHAASO 包含了多种探测器，事例重建聚焦于簇射参数的分析 计算，已有初步的重建方法和程序, 下一步需要对其规范化, 形 成官方统一的版本，对各种探测手段的充分有效的利用是关键； 需要的计算、存储资源 – 模拟和数据 – 多种版本 – 不同的物理目标 – 不同的理论模型 31