to be published in the proceedings of DIS-2009, XVIIth. International Workshop on Deep-Inelastic Scattering and Related Subjects, Madrid, Spain, April 26-30, 2009
Since the discovery of the X(3872) in 2003 the B-factory experiments BaBar and Belle have been driving forces in the spectroscopy of new charmonium-like states. In this article the latest results on the decays X(3872) -> D0 D*0bar and X(3872) -> psi gamma, where psi stands for J/psi or psi(2S), are presented and analyses of Z(4430)+ -> psi pi+ and Z(4050/4250)+ -> chi_c1 pi+ are discussed.
Charm and charmonium physics have gained renewed interest in the past decade. Recent spectroscopic observations strongly motivate these studies. Among the several possible reactions, measurements in proton-antiproton annihilation play an important role, complementary to the studies performed at B-factories. The fixed target PANDA experiment at FAIR (Darmstadt, Germany) will investigate fundamental questions of hadron and nuclear physics in the interactions of antiprotons with nucleons and nuclei. With reaction rates as large as 2*10^7 interactions/s, and a mass resolution 20 times better as co…
Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the long-awaited ${\mathcal O}(α_s^2)$ correction for the exclusive double charmonium production process at $B$ factories, {\it i.e.}, $e^+e^-\to J/ψ+η_c$ at $\sqrt{s}=10.58$ GeV. For the first time, we confirm that NRQCD factorization does hold at next-to-next-to-leading-order (NNLO) for exclusive double charmonium production. It is found that including the NNLO QCD correction considerably reduces the renormalization scale dependence, and also implies the reasonable perturbative convergence behavior for this process. O…
Search for charmonium and charmonium-like states in Υ(2S) radiative decays
Using a sample of 158 million Υ(2S) events collected with the Belle detector, charmonium and charmonium-like states with even charge parity are searched for in Υ(2S) radiative decays. No significant χ_{cJ} or η_c signal is observed and the following upper limits at 90% confidence level (C.L.) are obtained: BR(Υ(2S) \to γχ_{c0})< 1.0 \times 10^{-4}, BR(Υ(2S) \to γχ_{c1})<3.6 \times 10^{-6}, BR(Υ(2S) \to γχ_{c2})<1.5 \times 10^{-5}, and BR(Υ(2S) \to γη_c)< 2.7 \times 10^{-5}. No significant signal of any charmonium-like state is observed, and we obtain the limits \BR (Υ(2S) \to γX(3872)) \times …
With about 12 fb$^{-1}$ collected XYZ data sets, BESIII continues the exploration of the exotic charmonium-like states. In this talk, recent results on the measurements of the spin-parity determination of $Z_{\rm c}(3900)$, as well as on line-shapes of $e^+e^- \rightarrow J/ψ\,ππ, h_{\rm c}ππ, ψ(2S)\,π^0π^0/π^+π^-$, and $π^+ D^0 D^{*-}$ from open charm are discussed. Also, the recent observation of $e^+ e^- \rightarrow ϕχ_{c1/2}$ at $\sqrt(s)=4.6$ GeV is reported.
Cross sections of the process $e^+e^-\toπ^0π^0 J/ψ$ at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4 $fb^{-1}$ of data samples collected with the BESIII detector operating at the BEPCII collider facility. A fit to the measured energy-dependent cross sections confirms the existence of the charmonium-like state $Y(4220)$. The mass and width of the $Y(4220)$ are determined to be $(4220.4\pm2.4\pm2.3)$ ${\rm MeV}/c^{2}$ and $(46.2\pm4.7\pm2.1)$ MeV, respectively, where the first uncertainties are statistical and the second systematic. The mass a…
Search for Charmonium(-like) states decaying into the $Ω^-\barΩ^+$ final states
School of Physical Science and Technology, Lanzhou University（兰州大学物理科学与技术学院）；Frontiers Science Center for Rare Isotopes, Lanzhou University（兰州大学稀有同位素前沿科学中心）
The recent results on Charmonium and Charmonium-like states at BESIII are reviewed, including the observation of $\rm Z_{cs}(3985)$ state, the study of the new decay modes of $ψ_2(3823)$ state, observation of resonance structure in $\rm e^+e^- \to π^+π^-ψ_2(3823)$ process, the study of the $\rm e^+e^- \to K^+K^-J/ψ$ process, cross section measurement of $\rm e^+e^- \to ωπ^0$ and $ωη$ process, branching fraction measurement of $ψ(3686)\to\barΣ^0Λ+ c.c.$ process. Decay channels for $χ_{cJ} \to Λ\barΛ$, $χ_{cJ} \to Λ\barΛη$, $ψ(3686) \to Λ\barΛω$ and $η_c(2S)\to3(π^+π^-)$ are also discussed. The …
The beauty hadron decays is unique laboratory to study charmonium and charmonium-like states, such as the $χ_{c1}(3872)$ meson, other exotic states and the tensor D-wave $ψ_2(3823$) states. However the nature of many exotic charmonium-like candidates are still unknown. The most recent LHCb results related to b-hadron decays to charmonium states and obtained using large data samples collected during the Run 1 and Run 2 periods are presented. This includes the most precise determination of the mass and width of the $χ_{c1}(3872)$ state using the $B^{+} \to J/ψπ^{+}π^{-}K^{+}$ decays, observation…
Inspired by the first observation of a vector charmonium-like state $Y(4626)$ decaying to a meson pair $D_{s}^{+}D_{s1}(2536)^{-}$, which could be viewed as a $P$-wave scalar-scalar $[cs][\bar{c}\bar{s}]$ tetraquark state, we predict a potential vector charmonium-like state $Y$ with $P$-wave scalar-scalar $[cq][\bar{c}\bar{q}]$ configuration. The corresponding mass spectrum of $Y$ state is calculated to be $4.33^{+0.16}_{-0.23}~\mbox{GeV}$ in the framework of QCD sum rules. We suggest that the predicted $Y$ state could be looked for in an open-charm $e^{+}e^{-}\rightarrow\bar{D}D_{1}(2420)+c.c…
Very recently LHCb reported the evidence of a new charged charmonium-like structure in the $J/ψπ^-$ invariant mass spectrum near 4600 MeV. In this work we investigate this structure together with three other charged charmonium-like states, the $Z_c(3900)$, $Z_c(4020)$, and $Z_c(4430)$. Our results suggest that the two higher states can be established as the first radial excitations of the two lower ones, all of which have the quantum numbers $J^{PC}=1^{+-}$. We propose to search for more relationship among exotic hadrons in order to better understand them.
