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# Observation of $e^+e^-$ Annihilation into the $\boldmath{C=+1}$ Hadronic Final States $\rho^0\rho^0$ and $\phi\rho^0$

Abstract : We report the first observation of $e^+e^-$ annihilations into states of positive $C$-parity, namely $\rho^0 \rho^0$ and $\phi\rho^0$. The two states are observed in the $\pip\pim\pip\pim$ and $K^+K^-\pip\pim$ final states, respectively, in a data sample of 225~$fb^{-1}$ collected by the $BaBar$~experiment at the $PEP-II$ $e^+e^-$ storage rings at energies near $\sqrt{s} ~=$ 10.58~$GeV$. The distributions of $\cos\theta^*$, where $\theta^*$ is the center-of-mass polar angle of the $\phi$ meson or the forward $\rho^0$ meson, suggest production by two-virtual-photon annihilation. We measure cross sections within the range $|\cos\theta^*| ~<~ 0.8$ of $\sigma(\e^+e^- \to \rho^0 \rho^0) ~=~$20.7 \pm 0.7 (\mathrm{stat})\pm 2.7(\mathrm{syst}) ~\mathrm{fb} and \sigma(\e^+e^- \to \phi \rho^0) \~=~$5.7\pm 0.5(\mathrm{stat}) \pm 0.8(\mathrm{syst}) ~\mathrm{fb}$.
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http://hal.in2p3.fr/in2p3-00084065
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Submitted on : Friday, January 19, 2007 - 11:51:56 AM
Last modification on : Sunday, June 26, 2022 - 11:45:58 AM

### Citation

B. Aubert, R. Barate, M. Bona, D. Boutigny, F. Couderc, et al.. Observation of $e^+e^-$ Annihilation into the $\boldmath{C=+1}$ Hadronic Final States $\rho^0\rho^0$ and $\phi\rho^0$. Physical Review Letters, American Physical Society, 2006, 97, pp.112002. ⟨10.1103/PhysRevLett.97.112002⟩. ⟨in2p3-00084065⟩

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