Observation of ψ(3686)→nn¯ and improved measurement of

Abstract

We observe the decay ψð3686Þ → nn for the first time and measure ψð3686Þ → pp with improved accuracy by using 1.07 × 10 8 ψð3686Þ events collected with the BESIII detector. The measured branching fractions are Bðψð3686Þ → nnÞ ¼ ð3.06 AE 0.06 AE 0.14Þ × 10 −4 and Bðψð3686Þ → ppÞ ¼ ð3.05 AE 0.02 AE 0.12Þ × 10 −4. Here, the first uncertainties are statistical, and the second ones are systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey 1 þ α cos 2 θ, we determine the α parameters to be α nn ¼ 0.68 AE 0.12 AE 0.11 and α pp ¼ 1.03 AE 0.06 AE 0.03 for ψð3686Þ → nn and ψð3686Þ → pp, respectively.

Study of the process e+e−→pp¯

“…energies between 3.773 and 4.6 GeV to determine the detection efficiency ϵ R . The MC events are produced with proton angular distributions described by the function 1 þ C cos 2 θ with C ¼ 0.595 AE 0.012 AE 0.015 for J=ψ [51] and C ¼ 1.03 AE 0.06 AE 0.03 for ψð3686Þ [52]. The branching fractions of J=ψ → pp and ψð3686Þ → pp are calculated for each data sample individually.…”

Observation ofψ(3686)→pp¯η′and improved measurement ofAblikim1, Ачасов2, Ahmed3 et al. 2019Phys. Rev. DSelf Cite9020View full textAdd to dashboardCite

“…Similarly, using the results in Ref. [33], we determine the ratio Γðψð3686Þ→ppη 0 Þ Γðψð3686Þ→ppÞ ¼ ð3.61 AE 0.33 AE 0.24Þ%, where common systematic uncertainties of proton's tracking, PID, and number of ψð3686Þ events have been cancelled. This ratio will helpful for future studies of the nucleon and N Ã pole contributions in ψð3686Þ baryonic decays.…”

Rescattering effects in antiproton-induced exclusive J/$ \psi$ and $ \psi^{{\prime}}_{}$ production on the deuteron

“…J/ψ -0.089 1.79 · 10 −3 92.9 ± 2.8 (2.121 ± 0.029) · 10 −3 0.595 ± 0.012 ± 0.015 [29,30] ψ ′ -0.259 1.35 · 10 −3 294 ± 8 (2.88 ± 0.10) · 10 −4 1.03 ± 0.06 ± 0.03 [30,31] Figs. 2a,b show the imaginary part of matrix element, Eq.…”

“…CT effects on the charmonium propagation are introduced by replacing σ tot ψn → σ eff ψN (p ψ , |z|) in Eq. (31). For simplicity, we will disregard CT effects on the slope B ψn , since its value is not fixed by any experimental data.…”