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preprints:2000:ttp00-22 [2016/03/17 11:03] (current)
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 +====== TTP00-22 Kinematic Effects in Radiative Quarkonia Decays ====== 
 +   <​hidden TTP00-22 ​ Kinematic Effects in Radiative Quarkonia Decays > Non-relativistic QCD (NRQCD) predicts colour octet contributions to be 
 + ​significant not only in many production processes of heavy quarkonia but 
 + also in their radiative decays. We investigate the photon energy 
 + ​distributions in these processes in the endpoint region. There the velocity 
 + ​expansion of NRQCD breaks down which requires a resummation of an infinite 
 + class of colour octet operators to so-called shape functions. We model these 
 + ​non-perturbative functions by the emission of a soft gluon cluster in the 
 + ​initial state. We found that the spectrum in the endpoint region is poorly 
 + ​understood if the values for the colour octet matrix elements are taken as 
 + large as indicated from NRQCD scaling rules. Therefore the endpoint region 
 + ​should not be taken into account for a fit of the strong coupling constant 
 + at the scale of the heavy quark mass. 
 + </​hidden>​ 
 +|**Stefan Wolf** ​ |  
 +|**  Phys. Rev.  D63 074020 2001  **  | 
 +| {{preprints:​2000:​ttp00-22.pdf|PDF}} {{preprints:​2000:​ttp00-22.ps|PostScript}} [[http://​arxiv.org/​abs/​hep-ph/​0010217|arXiv]] ​  | 
 +| |