Speaker
Description
The first measurement of two-particle angular correlation functions is reported in high-multiplicity $e^{+} e^{-}$ collisions recorded at $\sqrt{s}=10.52$ and $10.58$ GeV with the Belle detector at KEKB. The main goal of this measurement based on high-statistics low energy data is to search for the long-range (large pseudorapidity difference $\Delta\eta$) near-side (small azimuthal angle difference $\Delta\phi$) ``ridge signal'', which is a widely observed phenomenon in high multiplicity $pp$ and $pA$ collisions but not yet fully understood. A previous analysis of the ALEPH archived data from hadronic $Z$ decays, which is limited by the available statistics, has shown no significant long-range correlation signal in the correlation function. We report the two-particle angular correlation function measured for the first time at Belle energies. In addition to this search for a flow-like signal in the unexplored high-statistics Belle data, our measurements are compared to the predictions from PYTHIA and HERWIG event generators, which could provide new constraints to the phenomenological models.
