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Register a new userObservation of $e^+e^- rightarrow omega chi_{c1,2}$ near $sqrt{s}$ = 4.42 and 4.6 GeV
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Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $sqrt{s} >$ 4.4 GeV, the processes $e^+e^- rightarrow omega chi_{c1,2}$ are observed for the first time. With an integrated luminosity of $1074 pb^{-1}$ near $sqrt{s} =$ 4.42 GeV, a significant $omega chi_{c2}$ signal is found, and the cross section is measured to be $(20.9 pm 3.2 pm 2.5)pb$. With $567 pb^{-1}$ near $sqrt{s} =$ 4.6 GeV, a clear $omega chi_{c1}$ signal is seen, and the cross section is measured to be $(9.5 pm 2.1 pm 1.3) pb$, while evidence is found for an $omega chi_{c2}$ signal. The first errors are statistical and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the $omega chi_{c2}$ cross section, an enhancement is seen around $sqrt{s} =$ 4.42 GeV. Fitting the cross section with a coherent sum of the $psi(4415)$ Breit-Wigner function and a phase space term, the branching fraction $mathcal{B}(psi(4415)toomegachi_{c2})$ is obtained to be of the order of $10^{-3}$.
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Using data samples of 89.5~fb$^{-1}$, 711.0~fb$^{-1}$, and 121.4~fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at center-of-mass energies 10.52 GeV, 10.58 GeV, and 10.867 GeV, respectively, we study the exclusive reactions $e^+e^-togammachi_{cJ}$ ($J = 0,~1,~2$) and $e^+e^-togammaeta_c$. A significant $gamma chi_{c1}$ signal is observed for the first time at $sqrt{s}=10.58$ GeV with a significance of $5.1sigma$ including systematic uncertainties. No significant excesses for $gamma chi_{c0}$, $gamma chi_{c2}$, and $gamma eta_c$ final states are found, and we set 90% credibility level upper limits on the Born cross sections ($sigma_{rm B}$) at 10.52 GeV, 10.58 GeV, and 10.867~GeV. Together with cross sections measured by BESIII at lower center-of-mass energies, the energy dependency of $sigma_{rm B}(e^+e^-togammachi_{c1})$ is obtained.
Using $4.479 times 10^{8}$ $psi(3686)$ events collected with the BESIII detector, we search for the decays $psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}$ and $chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi$. The decays $psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}$ and $chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi$ are observed for the first time. The measured branching fractions are $mathcal{B}(psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}) = (11.7 pm 2.5 pm 1.0)times10^{-4}$, $(8.6 pm 0.3 pm 0.6)times10^{-4}$, $(6.9 pm 0.5 pm 0.6)times10^{-4}$, and $mathcal{B}(chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi) = (1.51 pm 0.30 pm 0.13)times10^{-4}$, $(3.73 pm 0.09 pm 0.25)times10^{-3}$, $(2.48 pm 0.08 pm 0.16)times10^{-3}$. The ratios of the branching fractions $frac{mathcal{B}(psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2})}{mathcal{B}(psi(3686) rightarrow gammachi_{c0,1,2})}$ and $frac{mathcal{B}(chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi)}{mathcal{B}(chi_{c0,1,2} rightarrow gamma J/psi)}$ are also reported.
The $e^+e^- to pi^+ pi^- pi^0 chi_{bJ}$ ($J=0,~1,~2$) processes are studied using a 118~fb$^{-1}$ data sample collected at a center-of-mass energy of 10.867 GeV, in the $Upsilon(10860)$ energy range, with the Belle detector. The $pi^+ pi^- pi^0 chi_{b1}$, $pi^+pi^-pi^0chi_{b2}$, $omegachi_{b1}$ signals and the evidence of $omegachi_{b2}$ are observed for the first time and the cross sections are measured. No significant $pi^+pi^-pi^0chi_{b0}$ or $omegachi_{b0}$ signal is observed and 90% confidence level upper limits on the cross sections for these two processes are obtained. In the $pi^+pi^-pi^0$ invariant mass spectrum, significant non-$omega$ signals are also observed. We search for the $X(3872)$-like state with a hidden $bbar{b}$ component (named $X_b$) decaying into $omega Upsilon(1S)$; no significant signal is observed with a mass between $10.55$ and $10.65$ GeV/$c^2$.
The cross section of the process $e^{+} e^{-} rightarrow K^{+} K^{-}$ is measured at a number of center-of-mass energies $sqrt{s}$ from 2.00 to 3.08 GeV with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results provide the best precision achieved so far. A resonant structure around 2.2 GeV is observed in the cross section line shape. A Breit-Wigner fit yields a mass of $M=2239.2 pm 7.1 pm 11.3$~and a width of $Gamma=139.8pm12.3pm20.6$ MeV, where the first uncertainties are statistical and the second ones are systematic. In addition, the time-like electromagnetic form factor of the kaon is determined at the individual center-of-mass energy points.
The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e+e- annihilation the product of two interference fragmentation functions is measured. We report nonzero asymmetries for pairs of charge-ordered pi+pi- pairs, which indicate a significant interference fragmentation function in this channel. The results are obtained from a 672 fb-1 data sample that contains 711 times 106 pi+pi- pairs and was collected at and near the ?(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e- collider.
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