Bremsstrahlung simulation in K→πl ± ν l (γ) decays
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In physics simulation chains, the PHOTOS Monte Carlo program is often used to simulate QED effects in decays of intermediate particles and resonances.
The program is based on an exact multiphoton phase space. In general, the matrix element is obtained from iterations of a universal kernel and approximations are involved. To evaluate the program’s precision, it is necessary to formulate and implement within the generator the exact matrix element, which depends on the decay channel. Then, all terms necessary for non-leading logarithms are taken into account. In the present letter we focus on the decay K→πl ± ν l and tests of the PHOTOS Monte Carlo program. We conclude that there is a 0.2 % relative precision in the implementation of the hard photon matrix element into the emission kernel, including the case where approximations are used.
KeywordsMatrix Element Virtual Correction Semileptonic Decay Real Emission Collinear Singularity
We would like to thank Tomasz Przedzinski for help in obtaining the numerical results presented in this paper and Brigitte Bloch-Devaux for help in improving the paper readability. We would like to thank the referee of EPJC for identifying an error in our handling of formula (14) of Ref. .
Work of Q. Xu is supported by China–Poland inter-governmental cooperation grant 34-13, National Natural Science Foundation of China under Grant No. 11147023, and Zhejiang Provincial Natural Science Foundation of China under Grant No. LQ12A05003.
Work of ZW is supported in part by the Polish Ministry of Science and Higher Education grant No. 1289/B/H03/2009/37.
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