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Register a new userObservation of an alternative $chi_{c0}(2P)$ candidate in $e^+ e^- rightarrow J/psi D bar{D}$
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We perform a full amplitude analysis of the process $e^+ e^- rightarrow J/psi D bar{D}$, where $D$ refers to either $D^0$ or $D^+$. A new charmoniumlike state $X^*(3860)$ that decays to $D bar{D}$ is observed with a significance of $6.5sigma$. Its mass is ($3862^{+26}_{-32}{}^{+40}_{-13}$) MeV/$c^2$ and width is ($201^{+154}_{-67}{}^{+88}_{-82}$) MeV. The $J^{PC}=0^{++}$ hypothesis is favored over the $2^{++}$ hypothesis at the level of $2.5sigma$. The analysis is based on the 980 $mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB.
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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.
In two recent reactions by Belle producing $Dbar D$ and $Dbar D^*$ meson pairs, peaks above threshold have been measured in the differential cross sections, possibly indicating new resonances in these channels. We want to study such reactions from the point of view that the $D$ meson pairs are produced from already known or predicted resonances below threshold. Our study shows that the peak in the $Dbar D^*$ production is not likely to be caused by the X(3872) resonance, but the peak seen in $Dbar D$ invariant mass can be well described if the $Dbar D$ pair comes from the already predicted scalar X(3700) resonance.
Several intermediate states of the reaction channels $e^{+}e^{-} rightarrow pi^{+} pi^{-} D^{0} bar{D}^{0}$ and $e^{+}e^{-} rightarrow pi^{+} pi^{-} D^{+}D^{-}$ are studied using the data samples collected with the BESIII detector at center-of-mass energies above 4.08 GeV. For the first time in this final state, a $psi(3770)$ signal is seen in the $Dbar{D}$ invariant mass spectrum, with a statistical significance of $5.2sigma$ at $sqrt{s} = 4.42$ GeV. There is also evidence for this resonance at $sqrt{s}$ = 4.26 and 4.36 GeV with statistical significance of 3.2$sigma$ and 3.3$sigma$, respectively. In addition, the Born cross section of $e^{+}e^{-}to pi^{+}pi^{-}psi(3770)$ is measured. The proposed heavy-quark-spin-symmetry partner of the $X(3872)$, the state $X_{2}(4013)$, is also searched for in the $Dbar{D}$ invariant mass spectra. No obvious signal is found. The upper limit of the Born cross section of the process $e^{+}e^{-}to rho^{0}X_{2}(4013)$ combined with the branching fraction is measured. Also, the processes $e^{+}e^{-}to D_{1}(2420)bar{D} + c.c.$ are investigated. The neutral mode with $D_{1}(2420)^{0}to D^{0}pi^{+}pi^{-}$ is reported with statistical significance of 7.4$sigma$ at $sqrt{s} = 4.42$ GeV for the first time, and evidence with statistical significance of 3.2$sigma$ and 3.3$sigma$ at $sqrt{s}$ = 4.36 and 4.60 GeV is seen, respectively. No evident signal for the process $e^{+}e^{-}to D_{1}(2420)^{0}bar{D}^{0} + c.c., D_{1}(2420)^{0}to D^{*+}pi^{-}$ is reported. Evidence for $e^{+}e^{-}to D_{1}(2420)^{+}D^{-} +~c.c., D_{1}(2420)^{+}to D^{+}pi^{+}pi^{-}$ is reported with statistical significance of 3.1$sigma$ and 3.0$sigma$ at $sqrt{s}$ = 4.36 and 4.42 GeV, respectively.
We analyze two recent reactions of Belle, producing $Dbar D$ and $Dbar D^*$ states that have an enhancement of the invariant $Dbar D$, $Dbar D^*$ mass distribution close to threshold, from the point of view that they might be indicative of the existence of a hidden charm scalar and an axial vector meson states below $Dbar D$ or $Dbar D^*$ thresholds, respectively. We conclude that the data is compatible with the existing prediction of a hidden charm scalar meson with mass around 3700 MeV, though other possibilities cannot be discarded. The peak seen in the $Dbar D^*$ spectrum above threshold is, however, unlikely to be due to a threshold enhancement produced by the presence, below threshold, of the hidden charm axial vector meson X(3872).
We observe $D^0-bar{D}^0$ mixing in the decay $D^0rightarrow K^+pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x}^2 = (0.09pm0.22)times 10^{-3}$ and $y = (4.6pm3.4)times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53pm0.13)times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.
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