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Is f0(1500) a scalar glueball

Following the discovery of two new scalar mesons, f0(1370) and f0(1500) at the Low Energy Antiproton Ring at CERN, we argue that the observed properties of this pair are incompatible with them both being QQ mesons. We show instead that f0(1500) is compatible with the ground state glueball expected around 1500 MeV mixed with the nearby states of the 0 ++ Q ¯

The Effect of Confinement Size on Nuclear Structure Functions

Abstract We consider the differences in the structure function of a heavy nucleus, such as iron, compared to a light nucleus. We investigate, in the context of QCD, a suggestion that these differences arise as a result of differences in the scale of confinement of the nuclear constituents. This results in a simple relationship between heavy and light nucleus structure functions which is in reasonable agreement with experiment if the confinement size in iron is around 10–20% greater than in a free nucleon.

Scalar mesons in φ radiative decay: Their implications for spectroscopy and for studies of CP violation at φ factories

Existing predictions for the branching ratio for φ → KKγ via φ → Sγ (where S denotes one of the scalar mesons f0(975) and a0(980)) vary by several orders of magnitude. Given the importance of these processes for both hadron spectrocoopy and CP-violation studies at φ factories (where φ → K0K0γ poses a possible background problem), this state of affairs is very undesirable. We show that the variety of predictions is due in part to errors and in part to errors and in part to differences in modelling. The latter variation leads us to argue that the radiative decays of these scalar states are interesting in their own right and may offer unique insights into the nature of the scalar mesons. As a byproduct we find that the branching ration for φ → K0K0γ is ≲ 0(10−) and will pose no significant background to proposed studies of CP violation.

Consistent analysis of the spin content of the nucleon

Abstract The recent measurements of lepton nucleon scattering with polarised neutron and deuteron targets are analysed together with the previous polarised proton data in a mutually consistent way. The detailed x-dependence of the polarisation asymmetry in the valence region is shown to be in agreement with historical predictions based on quark models. The Bjorken sum rule is shown to be confirmed at the 1 σ level and estimates of the spin content of the nucleon Δq are extracted. While the average value of Δq from the three experiments comes out to be 0.41 ± 0.05 (to be compared with the naive quark model theoretical expectation of 0.58) this experimental average value is more than one standard deviation from the value obtained from any individual experiment. This inconsistency can be overcome by allowing arbitrary higher twist contributions but the resulting precision is poor, Δq= 0.38 ± 0.48.

Q anti-Q G Hermaphrodite Mesons in the MIT Bag Model

Abstract We suggest that hybrid (q q g) mesons could exist with rather light masses. The spectrum of the ground state nonets, J PC = (0, 1, 2) −+ ; 1 −− is calculated in the MIT bag model including O(α s ) energy shifts. We discuss hadronic transitions among these states, consider their possible production at LEAR and SPEAR and indicate some interesting decay signatures.

Evidence for a scalar glueball

Abstract We show that the newly discovered scalar meson f0(1500) at LEAR has properties compatible with the lightest scalar glueball predicted by lattice QCD and incompatible with a Q Q state. We suggest that decays of glueballs are into pairs of glueballs (including η, η′ or (ππ)s) or by mixing with nearby Q Q states. The partial widths of f0(1500) are in accord with this hypothesis, tests of which include characteristic radiative decays to γφ, γω, γϱ and the prediction of a further scalar state, f′0(1500 – 1800) which couples strongly to K K , ηη and ηη′.

On the Nuclear Dependence of Electroproduction

Abstract We discuss the theoretical description of electroproduction with nuclear targets. Models which convolute the probability for finding light constituents within the nucleus with their electroproduction cross sections are found to large corrections. Instead it is desirable to determine directly the nuclear quark and gluon distributions. We consider ways in which they may be estimated in QCD and their reliability. We present a detailed estimate for the expected A dependence of these distributions.

The production and decay of hybrid mesons by flux-tube breaking

Abstract An analytic calculation of the breaking of excited chromoelectric flux tubes is performed in an harmonic oscillator approximation and applied to predict the dynamics of all J PC low-lying gluonic excitations of mesons (hybrids). Widths, branching ratios and production dynamics of some recently discovered J PC = 1 −+ ,0 −+ and 1 −− mesons are found to be in remarkable agreement with these results. We introduce the selection rules that can be used to understand the systematics of numerical decay calculations and we find possible significant breaking of these rules for specific channels that may enable enhanced production and detection of hybrids.An analytic calculation of the breaking of excited chromoelectric flux-tubes is performed in an harmonic oscillator approximation and applied to predict the dynamics of all

Determining the gluonic content of isoscalar mesons

J^{PC}

Glueball-qq filter in central hadron production

low-lying gluonic excitations of mesons (hybrids). Widths, branching ratios and production dynamics of some recently discovered