Searching for the axion-like particles at the collider

by Daohan Wang (Institute of theoretical physics, CAS)

Thursday 25 Nov 2021, 16:00 → 16:30 Australia/Sydney

Axion-like particles (ALPs) appear in various new physics models with spontaneous global symmetry breaking. Possible ALP masses and couplings to SM particles range over many orders of magnitude. The ALP searching strategies varies greatly for different regions in the ALP coupling-mass parameter space. This talk aims to search for axion-like particles (ALP) and probe the parameter space of the ALP model at the HL-LHC. First, motivated by the extensive searches for the vector-like fermionic top-partners at the LHC, an axion-like pseudoscalar particle production associated with a top quark as a exotic decay channel of top-partner will be discussed based on Boost Decision Tree (BDT) techniques. This part of the talk relates to the ALP mass range of 50 GeV to 300 GeV. The second part of the talk focus on the ALP mass range of 0.3 GeV to 10 GeV. Motivated by the fact that the cosmology and astrophysics bounds are so far quite weak when the ALP mass lies in the range of MeV to GeV, searching for such light ALPs through the ALP-strahlung process with ALP decaying to a pair of collimated photons at the LHC will be discussed based on jet substructure variables analysis and jet images notion. Two different algorithms will be introduced using classical machine learning method BDT and modern machine learning method convolutional neural network (CNN).  Besides, some ongoing researches and future research plans about sub-GeV ALP and axion will also be discussed.