Inclusive hadron production in upsilon decays and in nonresonant electron-positron annihilation at 10.49 GeV

Measurements of single-particles inclusive spectra and two-particle correlations in decays of the UPSILON(1S) resonance and in nonresonant annihilations of electrons and positrons at center-of-mass energy 10.49 GeV suggest baryon and antibaryon are more likely to be correlated at long range in upsilon decay than in continuum events.

Abstract

We report measurements of single-particle inclusive spectra and two-particle correlations in decays of the \ensuremath{\Upsilon}(1S) resonance and in nonresonant annihilations of electrons and positrons at center-of-mass energy 10.49 GeV, just below BB\ifmmode\bar\else\textasciimacron\fi{} threshold. These data were obtained using the CLEO detector at the Cornell Electron Storage Ring (CESR) and provide information on the production of \ensuremath{\pi}, K, \ensuremath{\rho}, ${K}^{\mathrm{*}}$, \ensuremath{\varphi}, p, \ensuremath{\Lambda}, and \ensuremath{\Xi} in quark and gluon jets. The average multiplicity of hadrons per event for upsilon decays (compared with continuum annihilations) is 11.4 (10.5) pions, 2.4 (2.2) kaons, 0.6 (0.5) ${\ensuremath{\rho}}^{0}$, 1.2 (0.8) ${K}^{\mathrm{*}}$, 0.6 (0.4) protons and antiprotons, 0.15 (0.08) \ensuremath{\varphi}, 0.19 (0.07) \ensuremath{\Lambda} and \ensuremath{\Lambda}\ifmmode\bar\else\textasciimacron\fi{}, and 0.016 (0.005) ${\ensuremath{\Xi}}^{\mathrm{\ensuremath{-}}}$ and \ensuremath{\Xi}\ifmmode\bar\else\textasciimacron\fi{} $^{+}$. We have also seen evidence for \ensuremath{\eta} and ${f}^{0}$ production. The most significant differences between upsilon and continuum final states are (1) the inclusive energy spectra fall off more rapidly with increasing particle energy in upsilon decays, (2) the production of heavier particles, especially baryons, is not as strongly suppressed in upsilon decays, and (3) baryon and antibaryon are more likely to be correlated at long range in upsilon decay than in continuum events.