Inclusive neutral vector meson production in hadronicZ 0 decays

Abstract

Results are reported of a study of neutral vector meson production in multihadronic Z 0 decays in the OPAL experiment at LEP. Pions and kaons have been identied by specic ionisation energy loss and K and K + K mass spectra have been tted, in bins of the scaled momentum variable x p , t o combinations of resonance signals and non-resonant backgrounds. Rates are given for K (892) 0 and (1020), and production cross sections are compared to the predictions of Monte Carlo models. Overall multiplicities have been determined as 0:76 0:07 0:06 K (892) 0 and 0:086 0:015 0:010 (1020) per hadronic Z 0 decay (the quoted errors are respectively statistical and systematic). Momentum dependent distortions of the mass spectra, possibly associated indirectly with Bose-Einstein eects, have prevented reliable measurement of the (770) 0 cross section in this study.

Production of the ρ(770)0 meson in pp and Pb-Pb collisions at sAcharya1, Acosta2, Adamová3 et al. 2019Phys. Rev. CSelf Cite302210View full textAdd to dashboardCite

“…Previous measurements showed that ρ 0 -meson peaks reconstructed in the π + π − decay channel are distorted: the central value (mass) was shifted to lower values by tens of MeV/c 2 . This phenomenon was studied in detail at LEP [2][3][4][5] and was also observed at RHIC [6].…”

“…Due to its very short lifetime (τ ∼ 1.3 fm/c) the ρ(770) 0 meson is well suited to study various properties of the interaction dynamics in nucleon-nucleon and heavy-ion collisions [1]. Previous measurements at the Large Electron-Positron Collider (LEP) [2][3][4][5] and the Relativistiv Heavy Ion Collider (RHIC) [6] showed that properties of ρ(770) mesons reconstructed in the two-pion decay channel are modified in highenergy hadronic interactions and e + e − annihilation. At low momentum, reconstructed ρ(770)-meson peaks were found to be significantly distorted from the p-wave Breit-Wigner shape.…”

Indication for π+π− scattering in p + p collisions at GeV

“…At CERN-LEP, OPAL, ALEPH and DELPHI the ρ 0 was measured in inclusive e + e − reactions at √ s = 90 GeV [9][10][11][12]. Even though OPAL never reported the value of the ρ 0 mass, OPAL reported a shift on the position of the ρ 0 peak by approximately −70 MeV/c 2 at low x p , where x p is the ratio between the meson and the beam energies, and no shift at high x p (x p ∼ 1) [9,10]. OPAL also reported a shift in the position of the ρ ± peak from −10 to −30 MeV/c 2 , which was consistent with the ρ 0 measurement [11].…”

“…Bose-Einstein correlations were used to describe the shift on the position of the ρ 0 peak. However, high (even unphysical) chaocity parameters (λ ∼ 2.5) were needed [9,10,12]. .…”

“…In this paper, we will show that phase space does not account for the ρ(770) 0 mass shift measured at RHIC [1], CERN-LEBC-EHS [8] and CERN-LEP [9][10][11][12] and conclude that there are significant scattering interactions in p + p collisions.…”