Quark jet versus gluon jet: fully-connected neural networks with high-level features  

作　　者：Hui Luo Ming-Xing Luo Kai Wang Tao Xu GuoHuai Zhu 

机构地区：[1]Graduate School of China Academy of Engineering Physics,Beijing 100193,China [2]Zhejiang Institute of Modem Physics and Department of Physics,Zhejiang University,Hangzhou 310027,China [3]Institut fiir Theoretische Physik,Universitat Hamburg Luruper Chaussee 149,Hamburg D- 22761,Germany

出　　处：《Science China(Physics,Mechanics & Astronomy)》2019年第9期49-59,共11页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the German Science Foundation (DFG) within the Collaborative Research Center 676 “Particles, Strings and the Early Universe”;the Recruitment Program of Global Youth Experts of China;supported in part by the National Natural Science Foundation of China (Grant Nos. 11135006, 11275168, 11422544, 11375151, and 11535002);the Zhejiang University Fundamental Research Funds for the Central Universities (Grant No. 2017QNA3007)

摘　　要：Jet identification is one of the fields in high energy physics that machine learning has begun to make an impact. More often than not, convolutional neural networks are used to classify jet images with the benefit that essentially no physics input is required.Inspired by a recent work by Datta and Larkoski, we study the classification of quark/gluon-initiated jets based on fully-connected neural networks(FNNs), where expert-designed physical variables are taken as input. FNNs are applied in two ways: trained separately on various narrow jet transverse momentum pTJbins;trained on a wide region of pTJ∈[200, 1000] GeV. We find their performances are almost the same. The performance is better when the pTJis larger. Jet discrimination with FNN is studied on both particle and detector level data. The results based on particle level data are comparable with those from deep convolutional neural networks, while the significance improvement characteristic(SIC) from detector level data would at most decrease by 15%.We also test the performance of FNNs with the full set or subsets of jet observables as input features. The FNN with one subset consisting of fourteen observables shows nearly no degradation of performance. This indicates that these fourteen expert-designed observables could have captured the most necessary information for separating quark and gluon jets.Jet identification is one of the fields in high energy physics that machine learning has begun to make an impact. More often than not, convolutional neural networks are used to classify jet images with the benefit that essentially no physics input is required.Inspired by a recent work by Datta and Larkoski, we study the classification of quark/gluon-initiated jets based on fully-connected neural networks(FNNs), where expert-designed physical variables are taken as input. FNNs are applied in two ways: trained separately on various narrow jet transverse momentum pTJbins; trained on a wide region of pTJ∈ [200, 1000] GeV. We find their performances are almost the same. The performance is better when the pTJis larger. Jet discrimination with FNN is studied on both particle and detector level data. The results based on particle level data are comparable with those from deep convolutional neural networks, while the significance improvement characteristic(SIC) from detector level data would at most decrease by 15%.We also test the performance of FNNs with the full set or subsets of jet observables as input features. The FNN with one subset consisting of fourteen observables shows nearly no degradation of performance. This indicates that these fourteen expert-designed observables could have captured the most necessary information for separating quark and gluon jets.

关 键 词：standard model simulation QUARK-GLUON jets MACHINE learning 

分 类 号：N[自然科学总论]