Observation of the ^1P_1 State of Charmonium

We report the observation of the $X(3823)$ in the process $e^+e^-\to \pi^+\pi^-X(3823) \to \pi^+\pi^-\gamma\chi_{c1}$ with a statistical significance of $6.2\sigma$, in data samples at center-of-mass energies $\sqrt{s}=$4.230, 4.260, 4.360, 4.420 and 4.600~GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the $X(3823)$ is $(3821.7\pm 1.3\pm 0.7)$~MeV/$c^2$, where the first error is statistical and the second systematic, and ...

The hyperfine splitting for the 2S charmonium state is calculated and the predicted number is $\Delta_{\rm HF}(2S) = 57 \pm 8$ MeV, being by derivation the lower bound of this splitting. It results in $M(\eta_c(2S))= 3630 \pm 8$ MeV, which is smaller by two standard deviations than found in the Belle experiment \cite{ref.01}, but close to the $\eta_c(2S)$ mass observed by the same group in the experiment $e^+e^- \to J/\psi \eta_c$ \cite{ref.06} where $M(\eta_c(2S)) = 3622 \pm...

During the last few years there has been a renaissance in charm and charmonium spectroscopy with higher precision measurements at the $\psi^{'}$ and $\psi(3770)$ coming from BESII and CLEOc and many new discoveries coming from B-factories. In this paper, I review some new results on "classical" charmonium and $e^+ e^- \to$ hadrons using B-factory Initial State Radiation and two photon events.

We present a study of the P-wave spin -triplet charmonium chi_{cJ} decays (J=0,1,2) into pi^0 pi^0 pi^0 pi^0. The analysis is based on 106 million \psiprime decays recorded with the BESIII detector at the BEPCII electron positron collider. The decay into the pi^0 pi^0 pi^0 pi^0 hadronic final state is observed for the first time. We measure the branching fractions B(chi_{c0} -> pi^0 pi^0 pi^0 pi^0)=(3.34 +- 0.06 +- 0.44)*10^{-3}, B(chi_{c1} -> pi^0 pi^0 pi^0 pi^0)=(0.57 +- 0....

In this work, we calculate the $h_c(^1P_1)$ production rate at the LHC to leading order of the strong coupling constant, for both color-singlet and -octet mechanisms. Numerical results show that a considerable number of $h_c$ events with moderate transverse momentum $p_T$ will be produced in the early run of the LHC, which will supply a good opportunity to further study the nature of this P-wave spin-singlet charmonium state.

We systematically investigate the mass spectrum and two-body open-charm strong decays of charmonium states in a coupled-channel model where the $^3P_0$ quark-antiquark pair creation mechanism is employed. The results of masses, mass shifts, proportions of the $c\bar{c}$ component, and open-charm decay widths are provided. The $S$-$D$ wave mixing angles and di-electric decay widths for vector mesons are also presented. Based on our results, we find that the $\psi(3770)$, $\psi...

Using a sample of 9.7 million B meson pairs collected with the CLEO detector, we study B decays to the chi_c1 and chi_c2 charmonia states, which are reconstructed via their radiative decays to J/psi. We first measure the branching fraction for inclusive chi_c1 production in B decays to be Br(B->chi_c1 X)=(4.14+-0.31+-0.40)*10^-3, where the first uncertainty is statistical and the second one is systematic. We derive the branching fractions for direct chi_c1 and chi_c2 producti...

During the last few years there has been a renaissance in charm and charmonium spectroscopy with higher precision measurements at the $\psi^{'}$ and $\psi(3770)$ coming from BESII and CLEOc and many new discoveries coming from B-factories. In this paper, I will review the status of $\psi(3770)$ and below.

In this paper, we present a new experimental progress in brief on the recent observation of the charged charmonium-like state Z_c(4020)^{+/-} states and its iso-spin partner Z_c(4020)^{0} in pi pi hc process at the BESIII experiment. The charged Z_{c}(4020) is its decay into \pi^{+/-} hc final state, and carries electric charge, thus it contains at least four quarks. The observation of both charge and neutral state makes Z_{c}(4020) the first iso-spin triplet Z_{c} state obse...

Using decays to $\phi$-meson pairs, the inclusive production of charmonium states in $b$-hadron decays is studied with $pp$ collision data corresponding to an integrated luminosity of $3.0fb^{-1}$, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by $B_C\equiv B(b\to CX)\times B(C\to\phi\phi)$ the inclusive branching fraction of a $b$ hadron to a charmonium state $C$ that decays into a pair of $\phi$ mesons, ratios $R^{C1}_{C2}\equiv B_{C1}...