Jul 20 – 27, 2011
Alpes Congrès - Alpexpo
Europe/Paris timezone

First observation of the $h_b$(1P) and $h_b$(2P) bottomonium states and study of $\Upsilon$(5S) to Bottomonium decays

Jul 22, 2011, 11:45 AM
Bayard (Alpes Congrès - Alpexpo)


Alpes Congrès - Alpexpo

Parallel session talk QCD


Jean Wicht


We report the observation of the $h_b(1P)$ and $h_b(1P)p$ spin-singlet bottomonium states produced in the reaction $e^+e^-\to h_b(1P)n\pi^+\pi^-$ with significances of $5.5\,\sigma$ and $11.2\,\sigma$, respectively. We find that $M[h_b(1P)]=(9898.25\pm 1.06^{+1.03}_{-1.07})\,\mathrm{MeV}/c^2$ and $M[h_b(1P)p]=(10259.76\pm0.64^{+1.43}_{-1.03})\,\mathrm{MeV}/c^2$, which correspond to measurements of the P-wave hyperfine splittings$\Delta M_{m HF}=(1.62\pm1.52)\,\mathrm{MeV}/c^2$ and $(0.48^{+1.57}_{-1.22})\,\mathrm{MeV}/c^2$, respectively. We also report measurements of the cross sections for $e^+e^-\to h_b(1P)n\pi^+\pi^-$ relative to the cross section for the $e^+e^-\to\Upsilon(2S)\pi^+\pi^-$ reaction and examine the Dalitz plots of $\Upsilon$(5S)$\to \Upsilon$(nS)$\pi^+\pi^-$ and $\Upsilon$(5S)$\to h_b$(mP)$\pi^+\pi^-$ decays and search for resonant substructure. These results are obtained from a $121.4\,{\rm fb}^{-1}$ data sample collected with the Belle detector near the $\Upsilon(5S)$ resonance at the KEKB asymmetric-energy $e^+e^-$ collider.

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