A Comprehensive Study of the Radiative Decays of $J/psi$ and $psi(2S)$ to Pseudoscalar Meson Pairs, and Search for Glueballs

Using 53 pb$^{-1}$ of $e^+e^-$ annihilation data taken at $sqrt{s}=3.686$ GeV, a comprehensive study has been made of the radiative decays of samples of 5.1 million $J/psi$ and 24.5 million $psi(2S)$ into pairs of pseudoscalar mesons, $pi^+pi^-$, $pi^0pi^0$, $K^+K^-$, $K_S^0K_S^0$, and $etaeta$. Product branching fractions for the radiative decays of $J/psi$ and $psi(2S)$ to scalar resonances $f_0(1370,1500,1710,2100, text{and} 2200)$, and tensor resonances $f_2(1270,1525, text{and} 2230)$ have been determined, and are discussed in relation to predicted glueballs. For $psi(2S)$ radiative decays the search for glueballs has been extended to masses between 2.5 GeV and 3.3 GeV.

Precision Measurement of the Mass of the $D^{*0}$ Meson and the Binding Energy of the $X(3872)$ Meson as a $D^0overline{D^{*0}}$ Molecule

A precision measurement of the mass difference between the $D^0$ and $D^{*0}$ mesons has been made using 316~pb$^{-1}$ of $e^{+}e^{-}$ annihilation data taken at $sqrt{s}=4170$~MeV using the CLEO-c detector. We obtain $Delta M equiv M(D^{*0})-M(D^0) =142.007pm0.015$(stat)~$pm$~0.014(syst)~MeV, as the average for the two decays, $D^0to K^-pi^+$ and $D^0to K^-pi^+pi^-pi^+$. The new measurement of $Delta M$ leads to $M(D^{*0})=2006.850pm0.049$~MeV, and the currently most precise measurement of the binding energy of the ``exotic meson X(3872) if interpreted as a $D^0D^{*0}$ hadronic molecule, $E_{b}(text{X}(3872))equiv M(D^0D^{*0})-M(text{X}(3872))=3pm192$ keV.

First Measurements of Timelike Form Factors of the Hyperons, Lambda0, Sigma0, Sigma+, Xi0, Xi-, and Omega-, and Evidence of Diquark Correlations

Using 805 pb^-1 of e+e- annihilation data taken with the CLEO-c detector at psi(3770), sqrt{s}=3770 MeV, we report the first measurements of the electromagnetic form factors of the Lambda0, Sigma0, Sigma+, Xi0, Xi-, and Omega- hyperons for the large timelike momentum transfer of |Q^2|=14.2 GeV^2. The form factors for the different hyperons are found to vary by nearly a factor two. It is found that |G_M(Lambda0)|=1.66(24) x |G_M(Sigma0)|. The Lambda0 and Sigma0 hyperons have the same uds quark content, but differ in their isospin, and therefore the spin of the $ud$ quark pair. It is suggested that the spatial correlation implied by the singlet spin--isospin configuration in the Lambda0 is an example of strong diquark correlations in the Lambda0, as anticipated by Jaffe and Wilczek. Improved measurements of the branching fractions of psi(2S) -> p pbar and hyperon--antihyperon pairs are also reported.

High precision measurement of the masses of the $D^0$ and $K_S$ mesons

Using 580 pb$^{-1}$ of $e^+e^-$ annihilation data taken with the CLEO--c detector at $psi(3770)$, the decay $D^0(overline{D}^0)to K^pmpi^mp pi^+pi^-$ has been studied to make the highest precision measurement of $D^0$ mass, $M(D^0)=1864.845pm0.025pm0.022pm0.053$ MeV, where the first error is statistical, the second error is systematic, and the third error is due to uncertainty in kaon masses. As an intermediate step of the present investigation the mass of the $K_S$ meson has been measured to be $M(K_S)=497.607pm0.007pm0.015$ MeV. Both $M(D^0)$ and $M(K_S)$ are the most precise single measurements of the masses of these mesons.

First Measurement of the Electromagnetic Form Factor of the Neutral Kaon at a Large Momentum Transfer and the Effect of $SU(3)$ Breaking

At large momentum transfers the photon interacts with the charges and spins of the constituent partons in a hadron. It is expected that the neutral kaon can acquire finite electromagnetic form factors because its wave function is affected by the order of magnitude difference between the mass of the strange quark and that of the down quark, or flavor $SU(3)$ breaking. We report on the first measurement of the form factor of neutral kaons at the large timelike momentum transfer of $|Q^2|=17.4$ GeV$^2$ by measuring the cross section for $e^+e^-to K_SK_L$ at $sqrt{s}=4.17$ GeV using CLEO-c data with an integrated luminosity of 586 pb$^{-1}$. We obtain $F_{K_SK_L}(17.4~textrm{GeV}^2)=5.3times10^{-3}$, with a 90% C.L. interval of $(2.9-8.2)times10^{-3}$. This is nearly an order of magnitude smaller than $F_{K^+K^-}(17.4~textrm{GeV}^2)=(44pm1)times10^{-3}$, and indicates that the effect of $SU(3)$ breaking is small. In turn, this makes it unlikely that the recently observed strong violation of the pQCD prediction, $F_{pi^+pi^-}(|Q^2|)/F_{K^+K^-}(|Q^2|)=f_pi^2/f_K^2$, which is based on the assumption of similar wave functions for the pions and kaons, can be attributed to $SU(3)$ breaking alone.

Observation of the Charged Hadron $Z_c^{pm}(3900)$ and Evidence for the Neutral $Z_c^0(3900)$ in $e^+e^-to pipi J/psi$ at $sqrt{s}=4170$ MeV

Using 586 pb$^{-1}$ of $e^+e^-$ annihilation data taken with the CLEO-c detector at $sqrt{s}=4170$ MeV, the peak of the charmonium resonance $psi(4160)$, we analyze the decay $psi(4160)to pi^+pi^- J/psi$, and report observation of the charged state $Z_c^pm(3900)$ decaying into $pi^pm J/psi$ at a significance level of $>5 sigma$. We obtain $M(Z_c^pm)=3886pm4(text{stat})pm 2(text{syst})$ MeV and $Gamma(Z_c^pm)=37pm4(text{stat})pm 8(text{syst})$ MeV, which are in good agreement with the results for this resonance obtained by the BES III and Belle Collaborations in the decay of the resonance Y(4260). We also present first evidence for the production of the neutral member of this isospin triplet, $Z_c^0(3900)$ decaying into $pi^0J/psi$ at a $3.5sigma$ significance level.

First Measurements of Exclusive Hadronic Decays of Upsilon(1S) and Upsilon(2S)

Using data taken with the CLEO III detector, 1.09 fb-1 at Upsilon(1S), and 1.28 fb-1 at Upsilon(2S), branching fractions have been measured for the first time for exclusive decays of each resonance into one hundred different final states consisting of 4 to 10 light hadrons, pions, kaons, and protons. Significant strength is found in 73 decay modes of Upsilon(1S) and 17 decay modes of Upsilon(2S), with branching fractions ranging from 0.3x10^-5 to 110x10^-5. Upper limits at 90% confidence level are presented for the other decay modes.

Observation of eta_b(2S) in Upsilon(2S) -> gamma eta_b(2S), eta_b(2S) -> hadrons, and Confirmation of eta_b(1S)

The data for 9.3 million Upsilon(2S) and 20.9 million Upsilon(1S) taken with the CLEO III detector has been used to study the radiative population of states identified by their decay into twenty six different exclusive hadronic final states. In the Upsilon(2S) decays an enhancement is observed at a ~5 sigma level at a mass of 9974.6+-2.3(stat)+-2.1(syst) MeV. It is attributed to eta_b(2S), and corresponds to the Upsilon(2S) hyperfine splitting of 48.7+-2.3(stat)+-2.1(syst) MeV. In the Upsilon(1S) decays, the identification of eta_b(1S) is confirmed at a ~3 sigma level with M(eta_b(1S)) in agreement with its known value.

First Measurement of the Form Factors in the Decays D0 to rho- e+ nu_e and D+ to rho0 e+ nu_e

Using the entire CLEO-c psi(3770) to DDbar event sample, corresponding to an integrated luminosity of 818 pb^-1 and approximately 5.4 x 10^6 DDbar events, we measure the form factors for the decays D0 to rho- e+ nu_e and D+ to rho0 e+ nu_e for the first time and the branching fractions with improved precision. A four-dimensional unbinned maximum likelihood fit determines the form factor ratios to be: V(0)/A_1(0) = 1.48 +- 0.15 +- 0.05 and A_2(0)/A_1(0)= 0.83 +- 0.11 +- 0.04. Assuming CKM unitarity, the known D meson lifetimes and our measured branching fractions we obtain the form factor normalizations A_1(0), A_2(0), and V(0). We also present a measurement of the branching fraction for D^+ to omega e^+ nu_e with improved precision.

Observation of the Dalitz Decay $D_{s}^{*+} to D_{s}^{+} e^{+} e^{-}$

Using 586 $textrm{pb}^{-1}$ of $e^{+}e^{-}$ collision data acquired at $sqrt{s}=4.170$ GeV with the CLEO-c detector at the Cornell Electron Storage Ring, we report the first observation of $D_{s}^{*+} to D_{s}^{+} e^{+} e^{-}$ with a significance of $5.3 sigma$. The ratio of branching fractions $calB(D_{s}^{*+} to D_{s}^{+} e^{+} e^{-}) / calB(D_{s}^{*+} to D_{s}^{+} gamma)$ is measured to be $[ 0.72^{+0.15}_{-0.13} (textrm{stat}) pm 0.10 (textrm{syst})]%$, which is consistent with theoretical expectations.