Review of Recent Measurements of Meson and Hyperon Form Factors

A review of recent precision measurements of the electromagnetic form factors of the mesons, pion and kaon, and the hyperons, $Lambda^0$, $Sigma^0$, $Sigma^+$, $Xi^-$, $Xi^0$, $Omega^-$, at large timelike momentum transfers is presented. Evidence is found for diquark correlations in $Lambda^0$, $Sigma^0$ hyperons.

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 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.