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preprints:2002:ttp02-43 [2016/03/17 11:03] (current)
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 +====== TTP02-43 The radiative return at phi- and B-factories:​ small-angle photon emission at next to leading order ====== 
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 +   <​hidden TTP02-43 ​ The radiative return at phi- and B-factories:​ small-angle photon emission at next to leading order >   The radiative return offers the unique possibility for a measurement of the 
 + cross section of electron--positron annihilation into hadrons over a wide range 
 + of energies. The large luminosity of present phi- and B-factories easily 
 + ​compensates for the additional factor of alpha due to the emission of a hard 
 + ​photon. Final states with photons at large angles can be easily identified. The 
 + rate for events with collinear photons, however, is enhanced by a large 
 + ​logarithm and allows, in particular at lower energies, for a complementary 
 + ​measurement. 
 +  The Monte Carlo generator PHOKHARA, which includes next to leading order 
 + ​corrections from virtual and real photon emission, has been extended from large 
 + ​photon angles into the collinear region, using recent results for the virtual 
 + ​corrections. In addition, the present version includes final state radiation 
 + for muon and pion pair production and final states with four pions. 
 + ​Implications for the experimental analysis at three typical energies, 1.02, 4 
 + and 10.6 GeV, are presented: the magnitude of these new corrections is studied, 
 + ​possibilities for the separation of initial and final state radiation are 
 + ​proposed,​ and the differences with respect to the previous treatment based on 
 + ​structure functions are investigated. 
 + </​hidden>​ 
 +|**H. Czyz, A. Grzelinska, J. H. K"uhn, G. Rodrigo** ​ |  
 +|**  Eur. Phys. J. C  27 563-575 2003  **  | 
 +| {{preprints:​2002:​ttp02-43.pdf|PDF}} {{preprints:​2002:​ttp02-43.ps|PostScript}} [[http://​arxiv.org/​abs/​hep-ph/​0212225|arXiv]] ​  | 
 +| |