The Particle Data Group decided to split the $\eta(1440)$ into two states, called $\eta_L$ and $\eta_H$. The $\eta(1295)$ and the $\eta_H$ are supposed to be the radial excitations of the $\eta$ and $\eta'$, respectively. The $\eta_L$ state cannot be accomodated in a quark model; it cannot be a $q\bar q$ state, however, it might be a glueball. In this contribution it is shown that that the $\eta(1295)$ does not have the properties which must be expected for a radially excited state. The splitting of the $\eta(1440)$ is traced to a node in the wave function of a radial excitation. Hence the two peaks, $\eta_L$ and $\eta_H$, originate from one resonance which is interpreted here as first radial excitation of the $\eta$.
Four separate experiments, observing the OZI forbidden disconnected reaction pi- p -> phi phi n with increasing statistics were consistent. These experiments very selectively completely broke down the OZI suppression by 3 phi phi resonances with IG JPC = 0+ 2++ in the observed mass region 2.038 to 2.600 GeV. The only viable proposed explanation has been that the IG JPC = 0+ 2++ Glueball expected in this mass region caused the hard glue in the disconnection to resonate and very selectively breakdown the OZI suppression for its quantum numbers only. Recently a p p central production spin analysis found the f2(1950) had a dominant decay mode f2(1270) pi pi. We consider if it is related to the phi phi resonances, and find that it likely is.
Gluon jets with a mean energy of 22 GeV and purity of 95% are selected from hadronic Z0 decay events produced in e+e- annihilations. A subsample of these jets is identified which exhibits a large gap in the rapidity distribution of particles within the jet. After imposing the requirement of a rapidity gap, the gluon jet purity is 86%. These jets are observed to demonstrate a high degree of sensitivity to the presence of color reconnection, i.e. higher order QCD processes affecting the underlying color structure. We use our data to test three QCD models which include a simulation of color reconnection: one in the Ariadne Monte Carlo, one in the Herwig Monte Carlo, and the other by Rathsman in the Pythia Monte Carlo. We find the Rathsman and Ariadne color reconnection models can describe our gluon jet measurements only if very large values are used for the cutoff parameters which serve to terminate the parton showers, and that the description of inclusive Z0 data is significantly degraded in this case. We conclude that color reconnection as implemented by these two models is disfavored. The signal from the Herwig color reconnection model is less clear and we do not obtain a definite conclusion concerning this model. In a separate study, we follow recent theoretical suggestions and search for glueball-like objects in the leading part of the gluon jets. No clear evidence is observed for these objects.
Recent data on B->p pbar K, K0 pi pi and K Kbar K hint at a $\sim 2.3$ GeV object recoiling against a kaon. This could be the narrow state observed in J/\psi -> gamma xi. Nonobservation in p pbar annihilation implies ${\cal B}(\xi \to p\bar p) \sim$ few $\times 10^{-3}$, consistent with eta_c and J/\psi decays, but there are actual hints in p pbar -> phi phi and p p-> p pi^+ pi^- pi^+ pi^- p. Simple modeling shows ${\cal B}(B \to \xi K){\cal B}(\xi \to p\bar p) \sim 1\times 10^{-6}$, appearing as a spike in the $p\bar p$ spectrum, with $\sim$ 30 events per 100 fb$^{-1}$; modes such as K K_s K_s, K phi phi, K4 pi (K f_2 pi pi) etc. should be explored. The underlying dynamics of g* -> g xi is analogous to g* -> g etaprime or gluon fragmentation. Discovery of sizable B -> xi K could be useful for CP violation studies.
Using 13.3 fb^{-1} of e^+e^- data recorded with the CLEO II and CLEO II.V detector configurations at CESR, we have searched for f_J(2220) decays to K^0_{S} K^0_{S} in untagged two-photon interactions. We report an upper limit on the product of the two-photon partial width and the branching fraction, Gamma_gamma gamma cdot B (f_J(2220) to K^0_{S} K^0_{S}) of less than 1.1 eV at the 95% C.L: systematic uncertainties are included. This dataset is four times larger than that used in the previous CLEO publication.
A lower bound of 135 MeV for the width of the \xi meson is obtained from analyzing the pp and pbar-p interactions by use of Regge theory. The pp data exclude a narrow \xi as the latter would lead to total pbar-p cross sections far exceeding the measured ones. The broad width explains why the \xi may not be seen in pbarp-p experiments.
The $J/\Psi$ and $\Psi'$ experiments at the Beijing Electron Positron Collider (BEPC) play a unique role in many aspects of light hadron spectroscopy, such as hunting for glueballs and hybrids, extracting $u\bar u+d\bar d$ and $s\bar s$ components of mesons, and studying excited nucleons and hyperons, i.e., $N^*$, $\Lambda^*$, $\Sigma^*$ and $\Xi^*$ resonances. Physics objectives, recent results and future prospects of light hadron spectroscopy at BEPC are presented.
The K0sK0s final state in two-photon collisions is studied with the L3 detector at LEP using data collected at centre-of-mass energies from 91 GeV to 202 GeV. The mass spectrum is dominated by the formation of the f_2'(1525) tensor meson in the helicity two state. The two-photon width times the branching ratio is measured to be Gamma_{gamma gamma}(f_2'(1525))Br(f_2'(1525)->KKbar) = 0.076 +- 0.006 +- 0.011 keV. Clear evidence for destructive f_2(1270)-a_2(1320) interference is observed. In addition a clear signal for f_J(1750) is observed. The study of the decay angular distribution in the 1750 MeV mass region shows that the spin two helicity two wave is dominant. No signal is observed in the region around 2.2 GeV. The upper limit for the two-photon partial width of the \xi(2230) tensor glueball candidate of Gamma_{gamma gamma}(\xi(2230))Br(\xi(2230)->K0sK0s)<1.4 eV at 95% C.L. is derived. The production of Lambda-Lambdabar pairs in two-photon collisions is also studied. The cross section is compared to quark-diquark model predictions.
The production and decay properties of the f0(1370), f0(1500), f0(2000) and f2(1950) have been studied in central pp interactions at 450 GeV/c. The dPT, phi and |t| distributions of these resonances are presented. For the J = 0 states, the f0(1370) and f0(2000) have similar dPT and phi dependences. These are different to the dPT and phi dependences of the f0(980), f0(1500) and f0(1710). For the J = 2 states the f2(1950) has different dependences to the f2(1270) and f2'(1520). This shows that the dPT and phi dependences are not just J phenomena.
The reactions pp -> pf (X0) ps, where X0 is observed decaying to pi0pi0pi0pi0, pi+pi-pi0pi0 and pi+pi-pi+pi-, have been studied at 450 GeV/c. There is evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870) in the pi+pi-pi0pi0 and pi+pi-pi+pi- final states. The f2(1950) is consistent with being a single resonance with a dominant f2(1270)pipi decay mode. The f0(1370) is found to decay dominantly to rho-rho while the f0(1500) is found to decay to rho-rho and sigma-sigma.
The reactions pp -> pf (X0) ps, where X0 is observed decaying to eta etaprime and etaprime etaprime, have been studied at 450 GeV/c. This is the first time that these channels have been observed in central production and only the second time that the etaprime etaprime channel has been observed in any production mechanism. In the eta etaprime channel there is evidence for the f0(1500) and a peak at 1.95 GeV. The etaprime etaprime channel shows a peak at threshold which is compatible with having JPC = 2++ and spin projection JZ = 0.
Data taken with the ALEPH detector at LEP1 have been used to search for gamma gamma production of the glueball candidates f0(1500) and fJ(1710) via their decay to pi+pi-. No signal is observed and upper limits to the product of gamma gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) < 0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV at 95% confidence level.
Lattice QCD and other theoretical models predict that the 0(-+), 2(++) and 2(-+) glueballs have masses in the range of 2.0 to 2.4 GeV. For resonances in such an energy range, three-body decay modes are expected to be large. The strategy for looking for these glueballs and the newest results from studying Crystal Barrel data on the three-body annihilation of proton-antiproton in flight are presented.
The CLEOII detector at the Cornell e+ e- storage ring CESR has been used to search for the two-photon production of the $f_J(2220)$ decaying into pi+ pi-. No evidence for a signal is found in data corresponding to an integrated luminosity of 4.77/fb and a 95% CL upper limit on $\Gamma_{two-photon} * BR{pi+ pi-}$ of 2.5 eV is set. If this result is combined with the BES Collaboration's measurement of $f_J(2220) -> pi+ pi-$ in radiative $J/\psi$ decay, a 95% CL lower limit on the stickiness of the $f_J(2220)$ of 73 is obtained. If the recent CLEO result for $\Gamma_{two-photon} * BR{\K_S K_S}$ is combined with the present result, the stickiness of the $f_J(2220)$ is found to be larger than 102 at the 95% CL. These results for the stickiness (the ratio of the probabilities for two-gluon coupling and two-photon coupling) provide further support for a substantial neutral parton content in the $f_J(2220)$.
The Crystal Barrel Collaboration observes scalar meson resonances in $\bar p p$ annihilation. Based on the measurements and partial wave analyses these are candidates for the $^3$P$_0$ groundstate nonet. The supernummerary $f_0(1500)$ resonance is identified as a scalar groundstate glueball. Important information for its characterization comes from the decay pattern into pseudoscalar and scalar mesons. Data on kaonic decays in the mass region up to 1700 MeV are now avaible at Crystal Barrel. New analysis results are presented.
We use the CLEO detector at the Cornell electron-positron storage ring, CESR, to search for the two-photon production of the glueball candidate f_J(2220) in its decay to K_s K_s. We present a restrictive upper limit on the product of the two-photon partial width and the K_s K_s branching fraction. We use this limit to calculate a lower limit on the stickiness, which is a measure of the two-gluon coupling relative to the two-photon coupling. This limit on stickiness indicates that the f_J(2220) has substantial glueball content.