Exploring hidden sectors with two-particle angular correlations at future $e^{+}e^{-}$ colliders

Abstract: Future $e^+e^-$ colliders are called to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and discovering physics beyond the SM (BSM). This study scrutinises two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected correlation structures in these distributions could be a hint for new physics perturbing the QCD partonic cascade and modifying azimuthal and (pseudo)rapidity correlation. Using \textsc{Pythia8} and detector fast simulation tools we study unexpected structures arising in the two-particle angular correlation function, including selection cuts and detector effects. We have chosen the QCD-like Hidden Valley (HV) scenario as implemented in \textsc{Pythia8}, with relatively light $v$-quarks ($\lesssim 100$~GeV), to illustrate the potential of this method.