Search for Invisible Decays ofηandη′inJ/ψ→ϕηand

M. Ablikim¹,

J. Z. Bai²,

Y. Ban³

et al.

Abstract

Using a data sample of 58 x 10(6) J/psi decays collected with the Beijing Spectrometer II detector at the Beijing Electron Positron Collider, searches for invisible decays of eta and eta' in J/psi to phi eta and phi eta' are performed. The phi signals, which are reconstructed in K+K- final states, are used to tag the eta and eta' decays. No signals are found for the invisible decays of either eta or eta', and upper limits at the 90% confidence level are determined to be 1.65 x 10(-3) for the ratio B(eta-->invisible)/B(eta --> gamma gamma) and 6.69 x 10(-2) for B(eta' --> invisible)/B(eta' --> gammagamma). These are the first searches for eta and eta' decays into invisible final states.

Line shape and D(*)D¯(*Yu1, Wu2, Bayar3 et al. 2019Phys. Rev. D81400View full textAdd to dashboardCite

“…[15], which in our case are M ψ , g ψe + e − , A and R. M ψ is of course very close to the nominal mass of the ψ(3770), g ψe + e − determines the strength of the cross section, A is related to the width of the resonance, and R determines the fall down of the resonance shape above the resonance peak. The parameters are fitted to the data of the cross section for e + e − → DD [12][13][14].…”

“…[11] were based on a particular quark model. , [13], [14]) for the cross section of e + e − → D 0D0 reaction, using the form factor of Eq. (34) and the parameters in Table II.…”

“…This is a reasonable number, but in view of the results in Table V with the former fit, we can settle the value of Z within 0.80 ∼ 0.85, which is a reasonable range of uncertainty. , [13], [14]) using the form factor of Eq. (33).…”

“…The asymmetry of the ψ(3770) peak observed in the e + e − → DD reactions [12][13][14] has been the subject of the intense discussion (see Ref. [15] for a recent review).…”

“…Cross section of e + e − → D + D − fitted to the experimental data (•[12],[13],[14]) using the form factor of Eq. (34).…”