Colour-octet contributions to exclusive charmonium decays

Abstract

We investigate the theoretical uncertainties of $P$-wave charmonium decays into two pions, ${\chi }_{\stackrel{¸}{J}}\to {\pi }^{+}{\pi }^{-}$, ${\pi }^0{\pi }^0$. Constraining the pion distribution-amplitude from the recent precise data on $F_{\pi \gamma }(Q^2)$, we find an order-of-magnitude discrepancy between data and prediction. The disagreement persists even after inclusion of transverse degrees of freedom and Sudakov suppressions. We propose the colour-octet mechanism as the solution to the puzzle. The colour-octet decay contribution arising from the higher Fock component $|\c \cbar \g >$ of the ${\chi }_{\stackrel{¸}{J}}$ wave function is actually not power suppressed with respect to the usual colour-singlet decay arising from the dominant $|\c \cbar >$ Fock state. An explicit calculation yields an agreement with the data for a very reasonable value for the single extra non-perturbative parameter.

12 pages Latex, 3 PS-files of figures, uses macros 'amstex' and 'psfig'; also available by anonymous ftp from ftp://wpts0.physik.uni-wuppertal.de/pub/bolz/pwav/

References in corpus (6)

• Rigorous QCD Analysis of Inclusive Annihilation and Production of Heavy Quarkonium
• The $\pi \gamma$ transition form factor and the pion wave function
• Meson-Photon Transition Form Factors
• An update on ${\chi }_c$ Decays: Perturbative QCD versus Data
• The pion form factor: Sudakov suppressions and intrinsic transverse momentum
• A perturbative approach to $B$ decays into two $\pi$ mesons

Cited by in corpus (28)

• The two-gluon components of the eta and eta' mesons to leading-twist accuracy
• A possible hadronic excess in psi(2S) decay and rho-pi puzzle
• An Explanation for the rho-pi Puzzle of J/psi and psi' Decays
• Implications of light-quark admixtures on charmonium decays into meson pairs
• A perturbative approach to the eta_c-gamma transition form factor
• Corrections For Two Photon Decays of chi_{c0} and chi_{c2} and Color Octet Contributions
• Study of the P-wave charmonium state χ_{cJ} in ψ(2S) decays
• New Measurement of Exclusive Decays of the chi_c0 and chi_c2 to Two-Meson Final States
• Measurement of ${\chi }_{cJ}$ decaying into $p\bar{n}{\pi }^{-}$ and $p\bar{n}{\pi }^{-}{\pi }^0$
• Colour Octet Contribution in Exclusive P-Wave Charmonium Decay into Proton-Antiproton
• First Evidence of Lambda Lambda-bar in χ_cJ Decays
• Observation of χ_{cJ} decaying into the p\bar{p}K^{+}K^{-} final state
• Observation of $K^{\ast }(892{)}^0{\bar{K}}^{\ast }(892{)}^0$ in ${\chi }_{cJ}$ Decays
• First Observation of Exclusive chi_cJ Decays to Two Charged and Two Neutral Hadrons
• Exclusive charmonium decays
• Narrow width of a glueball decay into two mesons
• First Measurements of ${\chi }_{cJ}\to {\Sigma }^{-}{\bar{\Sigma }}^{+}(J=0,1,2)$ Decays
• Colour octet contribution to exclusive P-wave charmonium decay into nucleon-antinucleon
• First observations of $\psi (2S)$ and ${\chi }_{cJ}(1P)$ decays to four-body final states $h^{+}{h}^{-}{K}_S^0{K}_S^0$
• Color Octet Contribution in Exclusive P-Wave Charmonium Decay
• Recent Psi(2S) Results at BES
• Radiative decays ${\chi }_{cJ}\to V\gamma$ within the QCD factorisation framework
• Twist-3 contributions to $\gamma \gamma \to {\pi }^{+}{\pi }^{-},K^{+}{K}^{-}$ processes in perturbative QCD approach
• The two-pseudoscalar-meson decay of ${\chi }_{cJ}$ with twist-3 corrections
• Power counting in exclusive quarkonium decays
• Exclusive decays ${\chi }_{cJ}\to K^{\ast }(892)K$ within the effective field theory framework
• Precise Measurement of the ${\chi }_{c0}$ Resonance Parameters and Branching Fractions of ${\chi }_{c0,c2}\to {\pi }^{+}{\pi }^{-}/K^{+}{K}^{-}$
• Observation of ${\chi }_{cJ}\to p\bar{p}{K}_S^0{K}^{-}{\pi }^{+}+c.c.$