On the Spin of the X(3872)

Abstract

Whether the much studied X(3872) is an axial or tensor resonance makes an important difference to its interpretation. A recent paper by the BaBar collaboration raised the viable hypothesis that it might be a 2-+ state based on the 3 pions spectrum in the X -> J/psi omega decays. Furthermore, the Belle collaboration published the 2 pions invariant mass and spin-sensitive angular distributions in X -> J/psi rho decays. Starting from a general parametrization of the decay amplitudes for the axial and tensor quantum numbers of the X, we re-analyze the whole set of available data. The level of agreement of the two spin hypotheses with data is interpreted with a rigorous statistical approach based on Monte Carlo simulations in order to be able to combine all the distributions regardless of their different levels of sensitivity to the spin of the X. Our analysis returns a probability of 5.5% and 0.1% for the agreement with data of the 1++ and 2-+ hypotheses, respectively, once we combine the whole information (angular and mass distributions) from both channels. On the other hand, the separate analysis of J/psi rho (angular and mass distributions) and J/psi omega (mass distribution) indicates that the 2-+ assignment is excluded at the 99.9% C.L. by the former case, while the latter excludes at the same level the 1++ hypothesis. There are therefore indications that the two decay modes behave in a different way.

12 pages, 9 figures, 2 tables. Added angular distributions, which lead to different conclusions

References in corpus (15)

• Diquark-Antidiquarks with Hidden or Open Charm and the Nature of X(3872)
• Low-energy Universality and the New Charmonium Resonance at 3870 MeV
• Interference and binding effects in decays of possible molecular component of X(3872)
• Analysis of the Quantum Numbers $J^{PC}$ of the X(3872) Particle
• Rho-omega mixing, vector meson dominance and the pion form-factor
• Is the X(3872) Production Cross Section at Tevatron Compatible with a Hadron Molecule Interpretation?
• Evidence for the decay X(3872) --> J/psi omega
• Bounds on the width, mass difference and other properties of X(3872) --> pi+pi-J/psi decays
• Production of the X(3872) at the Tevatron and the LHC
• Measurement of the Dipion Mass Spectrum in X(3872) -> J/Psi Pi+ Pi- Decays
• On the hidden charm state at 3872 MeV
• Heavy quark spin selection rule and the properties of the X(3872)
• Remarks on the quantum numbers of X(3872) from the invariant mass distributions of the rho J/psi and omega J/psi final states
• Angular distributions in $J/\psi (\rho ,\omega )$ states near threshold
• Strong Couplings of X(3872)_{J=1,2} and a New Look at J/psi Suppression in Heavy Ion Collisions

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• Isospin breaking, coupled-channel effects, and X(3872)
• Amplitude analysis and the nature of the Zc(3900)
• Exotic Heavy Quarkonium Spectroscopy: A Mini-review
• Novel approaches in Hadron Spectroscopy
• XYZ spectroscopy at electron-hadron facilities: Exclusive processes
• Hunting for tetraquarks in ultra-pheripheral heavy ion collisions
• Charmonium spectrum with a Dirac potential model in the momentum space
• One-pion exchange in the X(3872) revisited
• Hamiltonian, Path Integral and BRST Formulations of Large N Scalar $QC{D}_2$ on the Light-Front and Spontaneous Symmetry Breaking