Unquenching the scalar glueball

Computations in the quenched approximation on the lattice predict the lightest glueball to be a scalar in the 1.5-1.8 GeV region. Here we calculate the dynamical effect the coupling to two pseudoscalars has on the mass, width and decay pattern of such a scalar glueball. These hadronic interactions allow mixing with the $q \overline q$ scalar nonet, which is largely fixed by the well-established K_0^*(1430). This non-perturbative mixing means that, if the pure gluestate has a width to two pseudoscalar channels of ~100 MeV as predicted on the lattice, the resulting hadron has a width to these channels of only ~30 MeV with a large eta-eta component. Experimental results need to be reanalyzed in the light of these predictions to decide if either the f_0(1500) or an f_0(1710) coincides with this dressed glueball.Comment: 12 pages, LaTex, 3 Postscript figure

Strange Decays of Nonstrange Baryons

The strong decays of excited nonstrange baryons into the final states Lambda K, Sigma K, and for the first time into Lambda(1405) K, Lambda(1520) K, Sigma(1385) K, Lambda K*, and Sigma K*, are examined in a relativized quark pair creation model. The wave functions and parameters of the model are fixed by previous calculations of N pi and N pi pi, etc., decays. Our results show that it should be possible to discover several new negative parity excited baryons and confirm the discovery of several others by analyzing these final states in kaon production experiments. We also establish clear predictions for the relative strengths of certain states to decay to Lambda(1405) K and Lambda(1520) K, which can be tested to determine if a three-quark model of the Lambda(1405) K is valid. Our results compare favorably with the results of partial wave analyses of the limited existing data for the Lambda K and Sigma K channels. We do not find large Sigma K decay amplitudes for a substantial group of predicted and weakly established negative-parity states, in contrast to the only previous work to consider decays of these states into the strange final states Lambda K and Sigma K.Comment: 25 pages, 8 figures, RevTe

On the Mechanism of Open-Flavor Strong Decays

Open-flavor strong decays are mediated by $q\bar q$ pair production, which is known to occur dominantly with \3p0 quantum numbers. The relation of the phenomenological \3p0 model of these decays to ``microscopic" QCD decay mechanisms has never been clearly established. In this paper we investigate $q\bar q$ meson decay amplitudes assuming pair production from the scalar confining interaction (sKs) and from one gluon exchange (OGE). sKs pair production predicts decay amplitudes of approximately the correct magnitude and D/S amplitude ratios in $b_1\to\omega\pi$ and $a_1\to\rho\pi$ which are close to experiment. The OGE decay amplitude is found to be subdominant in most cases, a notable exception being $^3$P$_0\to{}^1$S$_0+{}^1$S$_0$. The full sKs~+~OGE amplitudes differ significantly from \3p0 model predictions in some channels and can be distinguished experimentally, for example through an accurate comparison of the D/S amplitude ratios in $b_1\to\omega\pi$ and $a_1\to\rho\pi$.Comment: 44 pages, 22 eps figures, RevTex, complete postscript file available at http://csep2.phy.ornl.gov/theory_group/people/barnes/pubs/abs.p

Quark--antiquark states and their radiative transitions in terms of the spectral integral equation. {\Huge II.} Charmonia

In the precedent paper of the authors (hep-ph/0510410), the $b\bar b$ states were treated in the framework of the spectral integral equation, together with simultaneous calculations of radiative decays of the considered bottomonia. In the present paper, such a study is carried out for the charmonium $(c\bar c)$ states. We reconstruct the interaction in the $c\bar c$-sector on the basis of data for the charmonium levels with $J^{PC}=0^{-+}$, $1^{--}$, $0^{++}$, $1^{++}$, $2^{++}$, $1^{+-}$ and radiative transitions $\psi(2S)\to\gamma\chi_{c0}(1P)$, $\gamma\chi_{c1}(1P)$, $\gamma\chi_{c2}(1P)$, $\gamma\eta_{c}(1S)$ and $\chi_{c0}(1P)$, $\chi_{c1}(1P)$, $\chi_{c2}(1P)\to\gamma J/\psi$. The $c\bar c$ levels and their wave functions are calculated for the radial excitations with $n\le 6$. Also, we determine the $c\bar c$ component of the photon wave function using the $e^+e^-$ annihilation data: $e^+e^- \to J/\psi(3097)$, $\psi(3686)$, $\psi(3770)$, $\psi(4040)$, $\psi(4160)$, $\psi(4415)$ and perform the calculations of the partial widths of the two-photon decays for the $n=1$ states: $\eta_{c0}(1S)$, $\chi_{c0}(1P)$, $\chi_{c2}(1P)\to\gamma\gamma$, and $n=2$ states: $\eta_{c0}(2S)\to\gamma\gamma$, $\chi_{c0}(2P)$, $\chi_{c2}(2P)\to \gamma\gamma$. We discuss the status of the recently observed $c\bar c$ states X(3872) and Y(3941): according to our results, the X(3872) can be either $\chi_{c1}(2P)$ or $\eta_{c2}(1D)$, while Y(3941) is $\chi_{c2}(2P)$.Comment: 24 pages, 9 figure

Relativistic two-photon and two-gluon decay rates of heavy quarkonia

The decay rates of $c\bar{c}$ and $b\bar{b}$ through two-photon or two-gluon annihilations are obtained by using totally relativistic decay amplitudes and a sophisticated quantum-chromodynamic potential model for heavy quarkonia. Our results for the photonic and gluonic widths of the 1S0, 3P0, and the 3P2 states are in excellent agreement with the available experimental data. The procedures and mathematical techniques used by us for the treatment of the fermion-antifermion bound states are also applicable to other decay processes.Comment: 15 pages, RevTeX, PostScript available at http://gluon.physics.wayne.edu/wsuhep/jim/predecay.p

Pseuduscalar Heavy Quarkonium Decays With Both Relativistic and QCD Radiative Corrections

We estimate the decay rates of $\eta_c\rightarrow 2\gamma$, $\eta_c'\rightarrow 2\gamma$, and $J/\psi\rightarrow e^+ e^-$, $\psi^\prime\rightarrow e^+e^-$, by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired interquark potential are used to calculate the wave functions and decay widths for these $c\bar{c}$ states. We find that the relativistic correction to the ratio $R\equiv \Gamma (\eta_c \rightarrow 2\gamma)/ \Gamma (J/ \psi \rightarrow e^+ e^-)$ is negative and tends to compensate the positive contribution from the QCD radiative correction. Our estimate gives $\Gamma(\eta_c \rightarrow 2\gamma)=(6-7) ~keV$ and $\Gamma(\eta_c^\prime \rightarrow 2\gamma)=2 ~keV$, which are smaller than their nonrelativistic values. The hadronic widths $\Gamma(\eta_c \rightarrow 2g)=(17-23) ~MeV$ and $\Gamma(\eta_c^\prime \rightarrow 2g)=(5-7)~MeV$ are then indicated accordingly to the first order QCD radiative correction, if $\alpha_s(m_c)=0.26-0.29$. The decay widths for $b\bar b$ states are also estimated. We show that when making the assmption that the quarks are on their mass shells our expressions for the decay widths will become identical with that in the NRQCD theory to the next to leading order of $v^2$ and $\alpha_s$.Comment: 14 pages LaTex (2 figures included

Radiative Decays of Excited Vector Mesons

Radiative decays of the $1^3S_1$ radial and $1^3D_1$ orbital excitations of the $\rho$, $\omega$ and $\phi$ are calculated in the quark model, using wave functions obtained variationally from the Hamiltonian with standard quark-model parameters. The larger radiative widths should be measurable at new high-intensity facilities being proposed, and in some cases may be measurable in data from existing experiments. The radiative decays are a strong discriminator between the $1^3S_1$ and $1^3D_1$ excitations, and can also be used to provide unique information about the decay products.Comment: 23 pages, 6 figure

Application of Jain and Munczek's bound-state approach to gamma gamma-processes of pi0, eta_c and eta_b

We point out the problems affecting most quark--antiquark bound state approaches when they are faced with the electromagnetic processes dominated by Abelian axial anomaly. However, these problems are resolved in the consistently coupled Schwinger-Dyson and Bethe-Salpeter approach. Using one of the most successful variants of this approach, we find the dynamically dressed propagators of the light u and d quarks, as well as the heavy c and b quarks, and find the Bethe-Salpeter amplitudes for their bound states pi0, eta_c and \eta_b. Thanks to incorporating the dynamical chiral symmetry breaking, the pion simultaneously appears as the (pseudo)Goldstone boson. We give the theoretical predictions for the gamma-gamma decay widths of pi0, eta_c and eta_b, and for the pi0 gamma* -> gamma transition form factor, and compare them with experiment. In the chiral limit, the axial-anomaly result for pi0->gamma-gamma is reproduced analytically in the consistently coupled Schwinger-Dyson and Bethe-Salpeter approach, provided that the quark-photon vertex is dressed consistently with the quark propagator, so that the vector Ward-Takahashi identity of QED is obeyed. On the other hand, the present approach is also capable of quantitatively describing systems of heavy quarks, concretely eta_c and possibly eta_b, and their gamma-gamma decays. We discuss the reasons for the broad phenomenological success of the bound-state approach of Jain and Munczek.Comment: RevTeX, 37 pages, 7 eps figures, submitted to Int. J. Mod. Phys.

The newly observed open-charm states in quark model

Comparing the measured properties of the newly observed open-charm states D(2550), D(2600), D(2750), D(2760), D_{s1}(2710), D_{sJ}(2860), and D_{sJ}(3040) with our predicted spectroscopy and strong decays in a constituent quark model, we find that: (1) the D(2\,^1S_0) assignment to D(2550) remains open for its too broad width determined by experiment; (2) the D(2600) and $D_{s1}(2710)$ can be identified as the 2\,^3S_1-1\,^3D_1 mixtures; (3) if the D(2760) and D(2750) are indeed the same resonance, they would be the D(1\,^3D_3); otherwise, they could be assigned as the D(1\,^3D_3) and $D^\prime_2(1D)$, respectively; (4) the $D_{sJ}(2860)$ could be either the $D_{s1}(2710)$'s partner or the D_s(1\,^3D_3); and (5) both the $D_{s1}(2P)$ and $D^\prime_{s1}(2P)$ interpretations for the $D_{sJ}(3040)$ seem likely. The $E1$ and $M1$ radiative decays of these sates are also studied. Further experimental efforts are needed to test the present quarkonium assignments for these new open-charm states.Comment: 26 pages,7 figures, journal versio

The Decay ηc→γγ\eta_c \rightarrow \gamma \gamma : A Test for Potential Models

We use a simple perturbation theory argument and measurements of charmonium leptonic widths $\Gamma (\psi_{NS} \rightarrow e^+e^-)$ to estimate the ratio \mbox{$R_\circ \equiv {\vert \Psi _{\eta_{c1S}}(0) \vert}^2 /{\vert\Psi_{\psi_{1 S}}(0)\vert}^2$} in the general context of non- relativistic potential models. We obtain $R_\circ = 1.4 \pm 0.1$. We then apply well known potential model formulas, which include lowest order QCD corrections, to find $\Gamma (\eta_c \rightarrow \gamma \gamma )/\Gamma (\psi_{1S} \rightarrow e^+e^-) \approx 2.2\pm 0.2$. The central value for $\Gamma (\psi_{1S} \rightarrow e^+ e^-)$in the 1992 Particle Data Tables then leads to a (non relativistic) prediction $\Gamma (\eta_c \rightarrow \gamma \gamma )\approx 11.8\pm 0.8$ keV. This prediction is in good agreement with a recent measurement by the ARGUS collaboration, is consistent with a recent measurement by the L3 collaboration but is significantly higher than several earlier measurements and than previous theoretical estimates, which usually assume $R_\circ =1$. The correction to $R_\circ =1$ is estimated to be smaller but nonnegligible for the $b\bar b$ system. Using the current central measurement for $\Gamma (\Upsilon_{1S}\rightarrow e^+e^-)$ we find $\Gamma (\eta_b\rightarrow \gamma \gamma )\approx 0.58\pm 0.03$ keV. A rough estimate of relativistic corrections reduces the expected two photon rates to about 8.8 keV and 0.52 keV for the $\eta_c$ and $\eta_b$ mesons respectively. Such correctionsComment: Estimates of likely relativistic corrections to the results have been adde