# Europhysics Conference on High-Energy Physics 2011

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

## Study of rare $\Upsilon(2S)$ transitions to charmonia and lower bottomonia with the Belle detector

Jul 22, 2011, 11:30 AM
15m
Bayard (Alpes Congrès - Alpexpo)

### Bayard

#### Alpes Congrès - Alpexpo

Parallel session talk QCD

Umberto Tamponi

### Description

We report a search for the rare hadron transitions $\Upsilon(2S) \to \eta,$ $\pi^0 \Upsilon(1S)$ from 158 million $\Upsilon(2S)$ decays collected with the Belle detector at KEK. The $\eta$'s are detected via their $\pi^0 \pi^+ \pi^-$ and $\gamma\gamma$ decay modes. The $\Upsilon(1S)$'s are detected via their exclusive decays to dileptons. A major challenge is represented by the discrimination of these rare transitions from peaking backgrounds due to the dominant decay modes: $\Upsilon(2S) \to \pi\pi \Upsilon(1S)$ and $\Upsilon(2S) \to \gamma \chi_{bJ} \to\Upsilon(1S)$. New branching ratio measurements on the two photon cascades via $\chi_{bJ}$ states will be discussed. The $\chi_{cJ}$ is detected in $\gamma J/\psi$ final states, and $\eta_c$ in hadronic final states. The X(3872) is searched for in $J/\psi \pi^+\pi^-$ and $J/\psi \pi^+\pi^-\pi^0$ final states, The X(3915) in $J/\psi \pi^+\pi^-$. We also searched for the Y (4140) and X(4350) in $J/\psi \phi$ mode. No significant signals of radiative transitions from $\Upsilon(2S)$ to charmonia and XYZ states have been found. Upper limits on all related branching ratios will be given.

### Presentation materials

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