Determination of the number of ψ(3686) events at BESIII

Abstract

The numbers of ψ(3686) events accumulated by the BESIII detector for the data taken during 2009 and 2012 are determined to be (107.0±0.8)×10 6 and (341.1±2.1)×10 6 , respectively, by counting inclusive hadronic events, where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is (448.1±2.9)×10 6 .

Study of two-photon decays of pseudoscalar mesons via J/ψ radiative decays

“…where P represents the pseudoscalar meson, N obs is the number of observed signal events determined from the fit to the γγ mass spectra, N bkg is the number of peaking background events, N ψð3686Þ is the total number of ψð3686Þ events [19], ε is the MC determined detection efficiency and Bðψð3686Þ → π þ π − J=ψ) is the branching fraction of ψð3686Þ → π þ π − J=ψ [7]. The product branching fractions of J=ψ → γðπ 0 ; η; η 0 Þ → 3γ, are then determined to be ð3.57 AE 0.12 AE 0.16Þ × 10 −5 , ð4.42 AE 0.04 AE 0.18Þ × 10 −4 and ð1.26 AE 0.02 AE 0.05Þ × 10 −4 , respectively, as summarized in Table I.…”

“…At present, the sample of 4.48 × 10 8 ψð3686Þ events [19] (1.06 × 10 8 events in 2009 and 3.41 × 10 8 in 2012) collected by the BESIII detector offers the opportunity to study the two-photon decays of pseudoscalar mesons in J=ψ radiative decay in ψð3686Þ → π þ π − J=ψ events. While the number of J=ψ events from the BESIII ψð3686Þ → π þ π − J=ψ data samples is much smaller than that of the direct BESIII e þ e − → J=ψ samples, the direct J=ψ samples have a large background from the e þ e − → γγ process.…”

Search for hc→π+π−J/ψ<

“…In order to validate the event selection criteria, we calculate the branching fraction Bðψð3686Þ → ηJ=ψÞ and compare it with a previous BESIII measurement [24], where η is reconstructed via two photons and only the first set of the data sample of ð107.0 AE 0.8Þ million ψð3686Þ taken in 2009 [14] was used. In our calculation, the yield of ψð3686Þ → ηJ=ψ; η → π 0 π þ π − is obtained by counting events in the η signal region and subtracting the events in the η sideband region.…”

“…An experimental measurement is desirable to distinguish between these calculations. In this paper, we perform a search for the hadronic transition h c → π þ π − J=ψ using a data sample consisting of ð448.1 AE 2.9Þ million ψð3686Þ events [14] collected at a center-of-mass energy of 3.686 GeV, corresponding to the peak of ψð3686Þ resonance. Considering kinematic limitation and parity conservation, the angular momentum between the two-pion system (in a relative S-wave) and J=ψ should be P-wave, and the transition rate of h c → π þ π − J=ψ is suppressed.…”

Studying χc1 → ηπ+π− decays at BESIII

“…This analysis is performed on (447.5±2.9)×10 6 ψ(3686) events [10,11], produced in the e + e − collisions at the Beijing Electron and Positron Collider (BEPCII), and collected by the BESIII detector [12]. The transition ψ(3686) → γχ c1 is identified from the energy of the radiated photon.…”