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Register a new userNucleon pole contributions in $J/psito N bar{N} pi$, $p bar{p} eta$, $p bar{p} eta^{prime}$ and $p bar{p} omega$ decays
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Nucleon pole contributions in $J/psi to N bar N pi$, $p bar p eta$, $p bar p eta^{prime}$ and $p bar{p} omega$ decays are re-studied. Different contributions due to PS-PS and PS-PV couplings in the $pi$-N interaction and the effects of $NNpi$ form factors are investigated in the $J/psi to N bar N pi$ decay channel. It is found that when the ratio of $|F_0| /|F_M|$ takes small value, without considering the $NNpi$ form factor, the difference between PS-PS and PS-PV couplings are negligible. However, when the $NNpi$ form factor is included, this difference is greatly enlarged. The resultant decay widths are sensitive to the form factors. As a conclusion, the nucleon-pole contribution as a background is important in the $J/psito Nbar{N}pi$ decay and must be accounted. In the $J/psito Nbar{N}eta$ and $Nbar{N}eta$ decays, its contribution is less than 0.1% of the data. In the $J/psito Nbar{N}omega$ decay, it provides rather important contribution without considering form factors. But the contribution is suppressed greatly when adding the off-shell form factors. Comparing these results with data would help us to select a proper form factor for such kind of decay.
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We observe the process $psi(3686) to p bar{p} eta^{prime}$ for the first time, with a statistical significance higher than 10$sigma$, and measure the branching fraction of $J/psi to p bar{p} eta^{prime}$ with an improved accuracy compared to earlier studies. The measurements are based on $4.48 times 10^8$ $psi(3686)$ and $1.31 times 10^{9}$ $J/psi$ events collected by the BESIII detector operating at the BEPCII. The branching fractions are determined to be $B(psi(3686) to p bar{p} eta^{prime}) = (1.10pm0.10pm0.08)times10^{-5}$ and $B(J/psi to p bar{p} eta^{prime})=(1.26pm0.02pm 0.07)times10^{-4}$, where the first uncertainties are statistical and the second ones systematic. Additionally, the $eta-eta^{prime}$ mixing angle is determined to be $-24^{circ} pm 11^{circ}$ based on $psi(3686) to p bar{p} eta^{prime}$, and $-24^{circ} pm 9^{circ}$ based on $J/psi to p bar{p} eta^{prime}$, respectively.
In this work, the triangle singularity mechanism is investigated in the $psi(2S) to p bar{p} eta / p bar{p} pi^0$ process. The triangle loop composed by $J/psi$, $eta$ and $p$ has a singularity in the physical kinematic range for the $psi(2S) to p bar{p} eta / p bar{p} pi^0$ process, and it would generate a very narrow peak in the invariant mass spectrum of $peta (pi)$ around $1.56387$ GeV, which is far away from both the threshold and relative resonances. In these processes, all the involved vertices are constrained by the experimental data. Thus, we can make a precise model independent prediction here. It turns out that the peak in the $peta$ invariant mass spectrum is visible, while it is very small in the $ppi^0$ invariant mass spectrum. We expect this effect shown in $p bar{p} eta$ final state can be observed by the Beijing Spectrometer (BESIII) and Super Tau-Charm Facility (STCF) in the future.
Using a sample of $1.06 times 10^{8}$ $psi(2S)$ events collected with the BESIII detector at BEPCII, the decay $psi(2S) to p bar{p}eta$ is studied. A partial wave analysis determines that the intermediate state N(1535) with a mass of $1524pm5^{+10}_{-4}$ MeV/$c^2$ and a width of $130^{+27+57}_{-24-10}$ MeV/$c^2$ is dominant in the decay; the product branching fraction is determined to be $B(psi(2S) to N(1535)bar{p})times B(N(1535)to peta)+c.c. = (5.2pm0.3^{+3.2}_{-1.2})times 10^{-5}$. Furthermore, the branching fraction of $psi(2S) to eta p bar{p}$ is measured to be $(6.4pm0.2pm0.6)times 10^{-5}$.
The decay $J/psi rightarrow omega p bar{p}$ has been studied, using $225.3times 10^{6}$ $J/psi$ events accumulated at BESIII. No significant enhancement near the $pbar{p}$ invariant-mass threshold (denoted as $X(pbar{p})$) is observed. The upper limit of the branching fraction $mathcal{B}(J/psi rightarrow omega X(pbar{p}) rightarrow omega p bar{p})$ is determined to be $3.9times10^{-6}$ at the 95% confidence level. The branching fraction of $J/psi rightarrow omega p bar{p}$ is measured to be $mathcal{B}(J/psi rightarrow omega p bar{p}) =(9.0 pm 0.2 (text{stat.})pm 0.9 (text{syst.})) times 10^{-4}$.
The first observation of the decay $eta_{c}(2S) to p bar p$ is reported using proton-proton collision data corresponding to an integrated luminosity of $3.0rm , fb^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $eta_{c}(2S)$ resonance is produced in the decay $B^{+} to [cbar c] K^{+}$. The product of branching fractions normalised to that for the $J/psi$ intermediate state, ${cal R}_{eta_{c}(2S)}$, is measured to be begin{align*} {cal R}_{eta_{c}(2S)}equivfrac{{mathcal B}(B^{+} to eta_{c}(2S) K^{+}) times {mathcal B}(eta_{c}(2S) to p bar p)}{{mathcal B}(B^{+} to J/psi K^{+}) times {mathcal B}(J/psito p bar p)} =~& (1.58 pm 0.33 pm 0.09)times 10^{-2}, end{align*} where the first uncertainty is statistical and the second systematic. No signals for the decays $B^{+} to X(3872) (to p bar p) K^{+}$ and $B^{+} to psi(3770) (to p bar p) K^{+}$ are seen, and the 95% confidence level upper limits on their relative branching ratios are % found to be ${cal R}_{X(3872)}<0.25times10^{-2}$ and ${cal R}_{psi(3770))}<0.10$. In addition, the mass differences between the $eta_{c}(1S)$ and the $J/psi$ states, between the $eta_{c}(2S)$ and the $psi(2S)$ states, and the natural width of the $eta_{c}(1S)$ are measured as begin{align*} M_{J/psi} - M_{eta_{c}(1S)} =~& 110.2 pm 0.5 pm 0.9 rm , MeV, M_{psi(2S)} -M_{eta_{c}(2S)} =~ & 52.5 pm 1.7 pm 0.6 rm , MeV, Gamma_{eta_{c}(1S)} =~& 34.0 pm 1.9 pm 1.3 rm , MeV. end{align*}
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