Neural network biased corrections: Cautionary study in background corrections for quenched jets

Abstract

Jets clustered from heavy ion collision measurements combine a dense background of particles with those actually resulting from a hard partonic scattering. The background contribution to jet transverse momentum ($p_T$) may be corrected by subtracting the collision average background; however, the background inhomogeneity limits the resolution of this correction. Many recent studies have embedded jets into heavy ion backgrounds and demonstrated a markedly improved background correction is achievable by using neural networks (NNs) trained with aspects of jet substructure which are used to map measured jet $p_{\mathrm{T}}$ to the embedded truth jet $p_{\mathrm{T}}$. However, jet quenching in heavy ion collisions modifies jet substructure, and correspondingly biases the NNs' background corrections. This study investigates those biases by using simulations of jet quenching in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}/c$ with hydrodynamically modeled quark-gluon plasma (QGP) evolution. To demonstrate the magnitude of the effect of such biases in measurement, a leading jet nuclear modification factor ($R_{\mathrm{AA}}$) is calculated and reported using the NN background correction on jets quenched utilizing a brick of QGP.

9 pages, 10 figures, and 14 additional figures in 10 page appendix