Radiative Transitions In Charmonium Research Articles

Radiative transitions in charmonium from lattice QCD

The coupling of various charmonium mesons to a photon is studied using lattice QCD, giving access to radiative form factors and transitions, and probing the mesons’ structure. Methods are developed which allow the robust determination of amplitudes, including those involving an excited state as well as multiple form factors, for a range of kinematics. These are applied in dynamical lattice QCD calculations using the distillation technique to compute the underlying three-point correlation functions. Form factors and amplitudes involving the low-lying charmonia, ηc, J/ψ, χc0 and ηc′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\eta}_c^{\\prime } $$\\end{document}, are calculated, demonstrating the methods and providing the first dynamical lattice QCD results for some quantities.

Charmonium radiative transitions, meson and glueball particle properties with the effective strong coupling

The particle properties of conventional mesons and scalar glueball, radiative transitions of charmonium excited states χcJ (J = 0, 1, 2) are studied in the framework of relativistic quark models with infrared confinement by taking into account the mass dependence of the effective strong coupling. A specific behaviour of the mass-dependent strong coupling with a freezing point αs (0) = 1.032 has been revealed. The spectrum and leptonic (weak) decay constants of conventional mesons have been calculated in good agreement with the latest experimental data. New estimates on the scalar glueball mass, ’radius’ and gluon condensate value have been obtained. Dominant radiative transitions of the charmonium orbital excitations χcJ → J/ψ + γ have been studied and the partial decay widths have been estimated with reasonable accuracy.

Angular distributions in the radiative decays of the $$^3\varvec{D}_3$$ 3 D 3 state of charmonium originating from polarized $$\varvec{\bar{p}p}$$ p ¯ p collisions

Using the helicity formalism, we calculate the combined angular distribution function of the two gamma photons (\(\gamma _1\) and \(\gamma _2\)) and the electron (\(e^-\)) in the triple cascade process \(\bar{p}p\rightarrow {}^3D_3\rightarrow {}^3P_2+\gamma _1\rightarrow (\psi +\gamma _2) +\gamma _1 \rightarrow (e^- + e^+) +\gamma _2 +\gamma _1\), when \(\bar{p}\) and \(p\) are arbitrarily polarized. We also derive six different partially integrated angular distribution functions which give the angular distributions of one or two particles in the final state. Our results show that by measuring the two-particle angular distribution of \(\gamma _1\) and \(\gamma _2\) and that of \(\gamma _2\) and \(e^-\), one can determine the relative magnitudes as well as the relative phases of all the helicity amplitudes in the two charmonium radiative transitions \({}^3D_3\rightarrow {}^3P_2+\gamma _1\) and \(^3P_2\rightarrow \psi +\gamma _2\).

Effects of heavy meson loops on heavy quarkonium radiative transitions

Radiative transitions between charmonium states offer an insight into the internal structure of heavy quark bound states within QCD. In this work, we systematically investigate the coupled-channel effects of intermediate charmed mesons to charmonium radiative transitions utilizing an effective Lagrangian approach. Our results show that the coupled-channel effects of these decays under the open charm thresholds are relatively weak, while the coupled-channel effects of the excited P-wave states close to the charmed pairs thresholds are relatively important.

Radiative transitions in charmonium fromNf=2twisted mass lattice QCD

We present a study for charmonium radiative transitions: $J/\psi\rightarrow\eta_c\gamma$, $\chi_{c0}\rightarrow J/\Psi\gamma$ and $h_c\rightarrow\eta_c\gamma$ using $N_f=2$ twisted mass lattice QCD gauge configurations. The single-quark vector form factors for $\eta_c$ and $\chi_{c0}$ are also determined. The simulation is performed at a lattice spacing of $a= 0.06666$ fm and the lattice size is $32^3\times 64$. After extrapolation of lattice data at nonzero $Q^2$ to 0, we compare our results with previous quenched lattice results and the available experimental values.

Exotic and excited-state radiative transitions in charmonium from lattice QCD

We compute, for the first time using lattice QCD methods, charmonium radiative transition rates involving states of high spin and exotics. Utilizing a large basis of interpolating fields we are able to project out various excited-state contributions to three-point correlators computed on quenched anisotropic lattices. In the first lattice QCD calculation of the exotic ${1}^{\ensuremath{-}+}$ ${\ensuremath{\eta}}_{c1}$ radiative decay, we find a large partial width $\ensuremath{\Gamma}({\ensuremath{\eta}}_{c1}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\gamma})\ensuremath{\sim}100\text{ }\text{ }\mathrm{keV}$. We find clear signals for electric dipole and magnetic quadrupole transition form factors in ${\ensuremath{\chi}}_{c2}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\gamma}$, calculated for the first time in this framework, and study transitions involving excited $\ensuremath{\psi}$ and ${\ensuremath{\chi}}_{c1,2}$ states. We calculate hindered magnetic dipole transition widths without the sensitivity to assumptions made in model studies and find statistically significant signals, including a nonexotic vector hybrid candidate ${Y}_{\mathrm{hyb}?}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}\ensuremath{\gamma}$. As well as comparison to experimental data, we discuss in some detail the phenomenology suggested by our results and the extent to which it mirrors that of quark-potential models, and make suggestions for the interpretation of our results involving exotic quantum numbered states.

Radiative transitions in charmonium from lattice QCD

Radiative transitions between charmonium states offer an insight into the internal structure of heavy-quark bound states within QCD. We compute, for the first time within lattice QCD, the transition form-factors of various multipolarities between the lightest few charmonium states. In addition, we compute the experimentally unobservable, but physically interesting vector form-factors of the $\eta_c, J/\psi$ and $\chi_{c0}$. To this end we apply an ambitious combination of lattice techniques, computing three-point functions with heavy domain wall fermions on an anisotropic lattice within the quenched approximation. With an anisotropy $\xi=3$ at $a_s \sim 0.1 \mathrm{fm}$ we find a reasonable gross spectrum and a hyperfine splitting $\sim 90 \mathrm{MeV}$, which compares favourably with other improved actions. In general, after extrapolation of lattice data at non-zero $Q^2$ to the photopoint, our results agree within errors with all well measured experimental values. Furthermore, results are compared with the expectations of simple quark models where we find that many features are in agreement; beyond this we propose the possibility of constraining such models using our extracted values of physically unobservable quantities such as the $J/\psi$ quadrupole moment. We conclude that our methods are successful and propose to apply them to the problem of radiative transitions involving hybrid mesons, with the eventual goal of predicting hybrid meson photoproduction rates at the GlueX experiment.

Radiative transitions in a unitarized meson model.

Radiative transitions in charmonium and bottomonium are calculated in a unitarized meson model, and an analysis of the results and the validity of common approximations is given. The results for charmonium indicate the need for relativistic corrections in our model; those for bottomonium agree very well with experiment (as far as they are available).

3 S 1−3 D 1 mixing and E1 radiative transitions in charmonium

The radiative transitions ψ′→γ+χ J and χ J →γ+ψ are studied in the quark model with the ψ and ψ′ interpreted conventionally as3 S 1 $$c\bar c$$ states and the χ J as3 P J $$c\bar c$$ states. In particular, the effect of3 S 1−3 D 1 mixing on the decay widths is calculated. The photon angular distributions in these decays are also studied and are found to be a more sensitive test of3 D 1 admixtures in the Ψ states. The3 D 1 content of the Ψ is found to be large but the estimate is very sensitive to the photon angular distributions. More precise measurements could help to explain the large ψ″ leptonic width.