Precise determination of decay rates for ${\eta }_c\to \gamma \gamma$, $J/\psi \to \gamma {\eta }_c$ and $J/\psi \to {\eta }_c{e}^{+}{e}^{-}$ from lattice QCD

Abstract

We calculate the decay rates for ${\eta }_c\to \gamma \gamma$, $J/\psi \to \gamma {\eta }_c$ and $J/\psi \to {\eta }_c{e}^{+}{e}^{-}$ in lattice QCD with $u$, $d$, $s$ and $c$ quarks in the sea for the first time. We improve significantly on previous theory calculations to achieve accuracies of 1--2\%, giving lattice QCD results that are now more accurate than the experimental values. In particular our results transform the theoretical picture for ${\eta }_c\to \gamma \gamma$ decays. We use gluon field configurations generated by the MILC collaboration that include $n_f=2+1+1$ flavours of Highly Improved Staggered (HISQ) sea quarks at four lattice spacing values from 0.15 fm to 0.06 fm and with sea u/d masses down to their physical value. We also implement the valence $c$ quarks using the HISQ action. We find $\Gamma ({\eta }_c\to \gamma \gamma )=6.788(45{)}_{\text{fit}}(41{)}_{\text{syst}}\mathrm{keV}$, in good agreement with experimental results using $\gamma \gamma \to {\eta }_c\to K\overline{K}\pi$ but in 4$\sigma$ tension with the Particle Data Group global fit result; we suggest this fit is revisited. We also calculate $\Gamma (J/\psi \to \gamma {\eta }_c)=2.219(17{)}_{\text{fit}}(18{)}_{\text{syst}}(24{)}_{\text{expt}}(4{)}_{\text{QED}}\mathrm{keV}$, in good agreement with results from CLEO, and predict the Dalitz decay rate $\Gamma (J/\psi \to {\eta }_c{e}^{+}{e}^{-})=0.01349(21{)}_{\text{latt}}(13{)}_{\text{QED}}\mathrm{keV}$. We use our results to calibrate other theoretical approaches and to test simple relationships between the form factors and $J/\psi$ decay constant expected in the nonrelativistic limit.

arXiv comment26 pages, 19 figures. Updated Figure 7, added 3 references and made further small changes to clarify the presentation. Further small changes to text, version accepted by Physical Review D

References in corpus (49)

• Highly Improved Staggered Quarks on the Lattice, with Applications to Charm Physics
• Properties of heavy quarkonia and B_c mesons in the relativistic quark model
• High-precision scale setting in lattice QCD
• Light pseudoscalar decay constants, quark masses, and low energy constants from three-flavor lattice QCD
• Lattice QCD ensembles with four flavors of highly improved staggered quarks
• $B$- and $D$-meson leptonic decay constants from four-flavor lattice QCD
• Quarkonia and their transitions
• Constrained Curve Fitting
• Twisted Boundary Conditions in Lattice Simulations
• Scaling studies of QCD with the dynamical HISQ action
• Radiative Transitions in Charmonium from Lattice QCD
• Vus from pi and K decay constants in full lattice QCD with physical u, d, s and c quarks
• High-precision quark masses and QCD coupling from $n_f=4$ lattice QCD
• Precision tests of the J/ψ from full lattice QCD: mass, leptonic width and radiative decay rate to η_c
• Neutral B-meson mixing from full lattice QCD at the physical point
• Charmonium spectrum and their electromagnetic transitions with higher multipole contributions
• Model-independent Study of Magnetic Dipole Transitions in Quarkonium
• Observation of eta_c^{prime} Production in gamma gamma Fusion at CLEO
• J/psi and psi(2S) Radiative Transitions to eta_c
• Two Photon Decays of Charmonia from Lattice QCD
• Lattice QCD study of the radiative decays $J/\psi \to {\eta }_c\gamma$ and $h_c\to {\eta }_c\gamma$
• Charmonium properties from lattice QCD + QED: hyperfine splitting, $J/\psi$ leptonic width, charm quark mass and $a_{\mu }^c$
• Lattice study of semileptonic form factors with twisted boundary conditions
• Spin Dependence of Heavy Quarkonium Production and Annihilation Rates: Complete Next-to-Next-to-Leading Logarithmic result
• Studying Hadronic Structure of the Photon in Lattice QCD
• Charmonium decays: J/psi --> e+e- and eta_c --> gamma gamma
• Measurement of the gamma gamma* --> eta_c transition form factor
• Improved determination of Heavy Quarkonium magnetic dipole transitions in pNRQCD
• Lattice QCD form factor for $B_s\to D_s^{\ast }l\nu$ at zero recoil with non-perturbative current renormalisation
• Radiative transitions in charmonium from $N_f=2$ twisted mass lattice QCD
• Search for gammagamma -> eta_b in e+e- collisions at LEP2
• Matching lattice and continuum axial-vector and vector currents with NRQCD and HISQ quarks
• Next-to-next-to-leading-order QCD corrections to hadronic width of pseudoscalar quarkonium
• Improved determination of inclusive electromagnetic decay ratios of heavy quarkonium from QCD
• Observation of J/psi --> 3 gamma
• Measurement of $J/\psi \to \gamma {\eta }_{\mathrm{c}}$ decay rate and ${\eta }_{\mathrm{c}}$ parameters at KEDR
• Renormalising vector currents in lattice QCD using momentum-subtraction schemes
• Bottomonium precision tests from full lattice QCD: hyperfine splitting, ${\rm Y}$ leptonic width and $b$ quark contribution to $e^{+}{e}^{-}\to$ hadrons
• Evidence for ${\eta }_c\to \gamma \gamma$ and Measurement of $J/\psi \to 3\gamma$
• Two Photon Decays of ${\eta }_c$ from Lattice QCD
• Photon Structure Functions from Quenched Lattice QCD
• Resummation of QCD Corrections to the eta_c Decay Rate
• New puzzle in charmonium decays
• Study of the electromagnetic Dalitz decays $\psi ({\rm Y})\to {\eta }_c({\eta }_b)l^{+}{l}^{-}$
• Inclusive decays of ${\eta }_c$ and ${\eta }_b$ at NNLO with large $n_f$ resummation
• Ward Identity of the Vector Current and the Decay Rate of ${\eta }_c\to \gamma \gamma$ in Lattice QCD
• A Lattice Study of the Two-photon Decay Widths for Scalar and Pseudo-scalar Charmonium
• Observation of the Dalitz Decay $D_s^{\ast +}\to D_s^{+}{e}^{+}{e}^{-}$
• Study of the radiative decay $J/\psi \to {\eta }_c+\gamma$ in light cone sum rules

Cited by in corpus (11)

• Improved evaluation of the electroweak contribution to muon $g-2$
• Hadronic light-by-light scattering in the anomalous magnetic moments of electron and $\tau$
• Exclusive photon-fusion production of even-spin resonances and exotic QED atoms in high-energy hadron collisions
• Observation of the charmonium decay ${\eta }_c\to \gamma \gamma$ in $J/\psi \to \gamma {\eta }_c$
• Lattice study of $J/\psi \to \gamma {\eta }_c$ using a method without momentum extrapolation
• Self-consistent analysis for the ${\eta }_c\to \gamma \gamma$ process
• Constraints on axion-like particles using lattice QCD calculations of the rate for $J/\psi \to \gamma a$
• Color-octet nonrelativistic QCD matrix elements for heavy quarkonium decays in the refined Gribov-Zwanziger theory
• Study of the Magnetic Dipole Transition of $J/\psi \to \gamma {\eta }_c$ via ${\eta }_c\to p\bar{p}$
• Radiative Decays of Vector Mesons with Light-Cone Sum Rules
• Line shape of the $J\psi \to \gamma {\eta }_c$ decay