Lin C.-WChen Y.-CLee Y.-JChang PBelle collaboration.PAO-TI CHANG2022-04-252022-04-25202118248039https://www.scopus.com/inward/record.uri?eid=2-s2.0-85105526733&partnerID=40&md5=425b1453317c3cb05ff30a2edc91eee9https://scholars.lib.ntu.edu.tw/handle/123456789/606615The enhancement of charged-particle pairs with large pseudorapidity difference and small azimuthal angle difference, often referred to as the “ridge signal”, is a phenomenon widely observed in high multiplicity proton-proton, proton-ion and deutron-ion collisions, which is not yet fully understood. In heavy-ion collisions, the hydrodynamic expansion of the Quark-Gluon Plasma is the most popular explanation of the ridge signal. Measurements in the e+e- collision system, without the complexities introduced by hadron structure in the initial state, can be a new opportunity to examine the formation of a ridge signal. The first measurement of two-particle angular correlation functions in high multiplicity e+e- collisions at vs = 10.52 GeV is reported. About 31.5 fb-1 hadronic e+e- annihilation data collected by the Belle detector at KEKB are used in this study. Two-particle angular correlation functions are measured over the full azimuth and large pseudorapidity intervals which are defined by either the electron beam axis or the event thrust as a function of charged particle multiplicity. The measurement in the event thrust analysis, with mostly quark and anti-quark pairs determining the reference axis, is sensitive to soft gluon emissions associated with the outgoing (anti-)quarks. No significant ridge signal is observed with analyses performed in either coordinate system. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various e+e- event generators and expected to provide new constraints to the phenomenological models in the low collision energy regime. ? Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).Colliding beam accelerators; Germanium compounds; Ion sources; Angular correlations; Charged particle multiplicities; Co-ordinate system; Heavy ion collision; Hydrodynamic expansion; Low collision energy; Phenomenological models; Quark-gluon plasma; Heavy ionsconference paper2-s2.0-85105526733