Exploring Hidden Sectors with Two-Particle Angular Correlations at Future <i>e</i>⁺<i>e</i>⁻ Colliders

Future <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow></semantics></math></inline-formula> colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected correlation structures in these distributions is considered to be a hint for new physics perturbing the QCD partonic cascade and thereby modifying azimuthal and (pseudo)rapidity correlations. Using <span style="font-variant: small-caps;">Pythia8</span> Monte Carlo generator and fast simulation, including selection cuts and detector effects, we study potential structures in the two-particle angular correlation function. We adopt the QCD-like Hidden Valley (HV) scenario as implemented in <span style="font-variant: small-caps;">Pythia8</span> generator, with relatively light HV <i>v</i>-quarks (below about 100 GeV), to illustrate the potential of this method.