  Future $e^+e^-$ colliders are called to play a fundamental role in measuring
Standard Model (SM) parameters with unprecedented precision and the discovery
of physics beyond the SM (BSM). This study focus on a QCD-like Hidden Valley
(HV) scenario, with relatively light v-quarks ($\lesssim 100$ GeV), perturbing
the QCD partonic cascade and increasing azimuthal and (pseudo)rapidity
correlations of final-state SM hadrons. Using Pythia8 and detector fast
simulation tools we study $ridge$-$like$ structures arising in the two-particle
angular correlation function, including selection cuts and detector effects.
