Multi-differential Jet Substructure Measurement in High Q2 ep collisions with HERA-II Data

The radiation pattern within quark- and gluon-initiated jets (jet substructure) is used extensively as a precision probe of the strong force as well as for optimizing event generators for nearly all tasks in high energy particle and nuclear physics. A detailed study of modern jet substructure observables, jet angularities, in electron-proton collisions is presented using data recorded using the H1 detector at HERA. The measurement is unbinned and multi-dimensional, using machine learning to correct for detector effects. Training these networks was enabled by the use of a large number of GPUs in the Perlmutter supercomputer at Berkeley Lab. The particle jets are reconstructed in the laboratory frame, using the kT jet clustering algorithm. Results are reported at high transverse momentum transfer Q²>150~GeV², and inelasticity $0.2 < y < 0.7$. The analysis is also performed in sub-regions of Q², thus probing scale dependencies of the substructure variables. The data are compared with a variety of predictions and point towards possible improvements of such models.