Polarization study of a boosted W boson decaying hadronically at the LHC with jet substructures and a multivariate analysis

Abstract

The study of the polarization of heavy particles is an important branch of research in today’s collider physics. The massive W boson has two types of polarization states, which usually are studied via the angular distribution of its decay products. We present a jet substructure-based study on the polarization of a boosted W boson decaying hadronically, which forms a fat jet, in pp collision at the s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s}$$\\end{document} = 14 TeV at the LHC. Two different methods, viz.N-subjettiness and Soft Drop, were used to find the subjets, which are approximately considered to be the two hadronic decay products of W, inside boosted W jets. These subjets were then used to calculate two variables pθ=|E1-E2|/pTW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_\ heta =|E_1-E_2|/p_T^W$$\\end{document} and zj=max(pT1,pT2)/pTW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_j=\\max (p_{T_1},p_{T_2})/p_T^W$$\\end{document}, where the subscripts 1 and 2 are for two subjets and W represents the reconstructed W jet. We then prepared the templates for longitudinally and transversely polarized W. These templates were used to extract the fractions of different W polarization in a mixed sample with relatively good accuracy.