# Differences

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+ | ====== TTP00-16 Four Pion Final States with Tagged Photons at Electron Positron Colliders ====== | ||

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+ | <hidden TTP00-16 Four Pion Final States with Tagged Photons at Electron Positron Colliders > A Monte Carlo generator has been constructed to simulate the reaction | ||

+ | e^+ e^- \to \gamma + 4 \pi, where the photon is assumed to be observed | ||

+ | in the detector. Isospin relations between the amplitudes governing | ||

+ | tau decays into four pions and electron positron annihilation into | ||

+ | four pions respectively have been found which allow to determine all | ||

+ | four modes after the amplitude for the \pi^+ \pi^- 2 \pi^0 channel has | ||

+ | been fixed. The kinematic breaking of these isospin relations as a | ||

+ | consequence of the \pi^- -- \pi^0 mass difference has also been | ||

+ | investigated. The program is constructed in analogy to an earlier one | ||

+ | simulating e^+ e^- \to \gamma + 2 \pi. However, it does not include | ||

+ | final state radiation from the charged pions. Additional collinear | ||

+ | photon radiation has been incorporated with the technique of structure | ||

+ | functions. Predictions are presented for cms energies of 1GeV, 3GeV | ||

+ | and 10GeV, corresponding to the energies of DAPHNE, BEBC and of | ||

+ | B-meson factories. Using this program it is demonstrated that, even | ||

+ | after applying realistic cuts, the event rates are sufficiently high | ||

+ | to allow for a precise measurement of R(Q^2) in the region of Q | ||

+ | between approximately 1GeV and 2.5GeV. The model predictions are | ||

+ | compared to recent data from electron positron colliders and agreement | ||

+ | is obtained within the relatively large errors. | ||

+ | </hidden> | ||

+ | |**H. Czyz and J.H. K\"uhn** | | ||

+ | |** Eur. Phys. J. C 18 497-509 2001 ** | | ||

+ | | {{preprints:2000:ttp00-16.pdf|PDF}} {{preprints:2000:ttp00-16.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/0008262|arXiv]] | | ||

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