


Campanario Pallás, Francisco; Czyz, Henryk; Gluza, Janusz; Gunia, Michal; Riemann, Tord; Rodrigo García, Germán Vicente; Yundin, Valery


This document is a artículoDate2014


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http://hdl.handle.net/10550/44447


KLOE and Babar have an observed discrepancy of 2% to 5% in the invariant pion pair production cross section. These measurements are based on approximate NLO mu(+)mu()gamma cross section predictions of the Monte Carlo event generator PHOKHARA7.0. In this article, the complete NLO radiative corrections to mu(+)mu()gamma production are calculated and implemented in the Monte Carlo event generator PHOKHARA9.0. Numerical reliability is guaranteed by two independent approaches to the real and the virtual corrections. The novel features include the contribution of pentagon diagrams in the virtual corrections, which form a gaugeinvariant set when combined with their box diagram partners. They may contribute to certain distributions at the percent level. Also the real emission was complemented with twophoton final state emission contributions not included in the generator PHOKHARA7.0. We demonstrate that the numerical influence reaches, for realistic chargeaveraged experimental setups, not more than 0.1% at KLOE and 0.3% at BaBar energies. As a result, we exclude the approximations in earlier versions of PHOKHARA as origin of the observed experimental discrepancy.


Campanario Pallás, Francisco Czyz, Henryk Gluza, Janusz Gunia, Michal Riemann, Tord Rodrigo García, Germán Vicente Yundin, Valery 2014 Complete QED NLO contributions to the reaction e(+)e() > mu(+)mu()gamma and their implementation in the event generator PHOKHARA Journal Of High Energy Physics 02 2 1141 11427 

http://dx.doi.org/10.1007/JHEP02(2014)114
