Institute for Theoretical Particle Physics (TTP)


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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}} {{|PostScript}} [[|arXiv]]   | 
 +| |