# EPS HEP 2013 Stockholm

17-24 July 2013
KTH and Stockholm University Campus
Europe/Stockholm timezone

### Support

20 Jul 2013, 10:11
15m
E1 (KTH Campus)

### E1

#### KTH Campus

Talk presentation QCD

### Speakers

Damir Becirevic (CNRS et Universite Paris Sud) Damir Becirevic (Unknown)

### Description

A long standing problem of theoretical estimate of the $J/\psi \to \eta_c \gamma$ decay amplitude has been solved recently by means of QCD on the latice. We describe and explain the progress and discuss the new results that are also a challenge to experimenters. We also discuss several other decay modes of charmonia, including the very first estimate of $\eta_c(2S)\to J/\psi \gamma$ that was theoretically very challenging. Our result suggests the rate of the latter to be large enough to be measured in experiments. We make contact of our findings with various (semi-)analytic, QCD based, descriptions of the same modes.

### Primary author

Damir Becirevic (CNRS et Universite Paris Sud)

### Co-author

Mr Francesco Sanfilippo (Laboratorie de Physique Théorique, Université Paris Sud, France)

 Slides