Model-independent Study of Magnetic Dipole Transitions in Quarkonium

We study magnetic dipole (M1) transitions between two quarkonia in the framework of non-relativistic effective field theories of QCD. Relativistic corrections of relative order v^2 are investigated in a systematic fashion. Non-perturbative corrections due to color-octet effects are considered for the first time and shown to vanish at leading order. Exact, all order expressions for the relevant 1/m and 1/m^2 operators are derived. The results allow us to scrutinize several potential model claims. In particular, we show that QCD excludes both contributions to the anomalous magnetic moment of the quarkonium induced by low-energy fluctuations and contributions to the magnetic dipole operators of the type induced by a scalar potential. Finally, we apply our results to the transitions J/psi -> eta_c gamma, Upsilon(1S) -> eta_b gamma, Upsilon(2S) -> eta_b(2S) gamma, Upsilon(2S) -> eta_b gamma, eta_b(2S) -> Upsilon(1S) gamma, h_b(1P) -> chi_{b0,1}(1P) gamma and chi_{b2}(1P) -> h_b(1P) gamma by assuming these quarkonium states in the weak-coupling regime. Our analysis shows that the J/psi -> eta_c gamma width is consistent with a weak-coupling treatment of the charmonium ground state, while such a treatment for the hindered transition Upsilon(2S) -> eta_b gamma appears difficult to accommodate within the CLEO III upper limit.Comment: 44 pages, 8 figures; typos corrected, one reference added; to appear in Physical Review

The static force in background perturbation theory

The static force $F_B(r)$ and the strong coupling $\alpha_F(r)$, which defines the gluon-exchange part of $F_B(r)$, are studied in QCD background perturbation theory (BPT). In the region r\la 0.6 fm $\alpha_F(r)$ turns out to be essentially smaller than the coupling $\alpha_B(r)$ in the static potential. For the dimensionless function $\Phi_B(r) = r^2 F_B(r)$ the characteristic values $\Phi_B(r_1) =1.0$ and $\Phi_B(r_0)=1.65$ are shown to be reached at the following $Q\bar Q$ separations: $r_1\sqrt{\sigma} =0.77, r_0\sqrt{\sigma} =1.09$ in quenched approximation and $r_1\sqrt{\sigma}=0.72, r_0\sqrt{\sigma}=1.04$ for $n_f =3$. The numbers obtained appear to be by only 8% smaller than those calculated in lattice QCD while the values of the couplings $\alpha_F(r_1)$ and $\alpha_F(r_0)$ in BPT are by $\sim 30$ and $50$ larger than corresponding lattice couplings. With the use of the BPT potential good description of the bottomonium spectrum is obtained.Comment: 21 pages, 1 figure. To be publised in Phys. Atom. Nucl. dedicated to the 70-th birthday of Yu.A. Simono

NRQCD Analysis of Bottomonium Production at the Tevatron

Recent data from the CDF collaboration on the production of spin-triplet bottomonium states at the Tevatron p \bar p collider are analyzed within the NRQCD factorization formalism. The color-singlet matrix elements are determined from electromagnetic decays and from potential models. The color-octet matrix elements are determined by fitting the CDF data on the cross sections for Upsilon(1S), Upsilon(2S), and Upsilon(3S) at large p_T and the fractions of Upsilon(1S) coming from chi_b(1P) and chi_b(2P). We use the resulting matrix elements to predict the cross sections at the Tevatron for the spin-singlet states eta_b(nS) and h_b(nP). We argue that eta_b(1S) should be observable in Run II through the decay eta_b -> J/psi + J/psi.Comment: 20 pages, 3 figure

Study of the f2(1270)f_2(1270), f2′(1525)f_2'(1525), f0(1370)f_0(1370) and f0(1710)f_0(1710) in the J/ψJ/\psi radiative decays

In this paper we present an approach to study the radiative decay modes of the $J/\psi$ into a photon and one of the tensor mesons $f_2(1270)$, $f'_2(1525)$, as well as the scalar ones $f_0(1370)$ and $f_0(1710)$. Especially we compare predictions that emerge from a scheme where the states appear dynamically in the solution of vector meson--vector meson scattering amplitudes to those from a (admittedly naive) quark model. We provide evidence that it might be possible to distinguish amongst the two scenarios, once improved data are available.Comment: The large Nc argument improved; version published in EPJA

Study of B→D∗∗πB\to D^{**} \pi decays

We investigate the production of the novel $P$-wave mesons $D^{*}_{0}$ and $D^{\prime}_{1} (D_{1})$, identified as $J^{P}=0^+$ and $1^+$, in heavy $B$ meson decays, respectively. With the heavy quark limit, we give our modelling wave functions for the scalar meson $D^{*}_{0}$. Based on the assumptions of color transparency and factorization theorem, we estimate the branching ratios of $B\to D^{*}_{0} \pi$ decays in terms of the obtained wave functions. Some remarks on $D^{(\prime)}_{1}$ productions are also presented.Comment: 16 pages, 2 figures, Revtex4, to be published in Phys. Rev.

Study of the J/ψ→ϕ(ω)f2(1270)J/\psi \to \phi (\omega) f_2(1270), J/ψ→ϕ(ω)f2′(1525)J/\psi \to \phi (\omega) f'_2(1525) and J/ψ→K∗0(892)Kˉ2∗0(1430)J/\psi \to K^{*0}(892) \bar{K}^{* 0}_2(1430) decays

We present an approach to study the decay modes of the $J/\psi$ into a vector meson and a tensor meson, taking into account the nature of the $f_2(1270)$, $f'_2(1525)$, $\bar{K}^{* 0}_2(1430)$ resonances as dynamically generated states from the vector meson-vector meson interaction. We evaluate four ratios of partial decay widths in terms of a flavor dependent OZI breaking parameter and the results obtained compare favorably with experiment. The fit to the data is possible due to the particular strength and sign of the couplings of the resonances to pairs of vector mesons given by the theory, thus providing a nontrivial test for the idea of these tensor states as dynamically generated from the vector-vector interaction.Comment: published versio

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

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair