# Evidence for an excess of soft photons in hadronic decays of Z$^0$

Abstract : Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/- 0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.
Type de document :
Article dans une revue
European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2006, 47, pp.273-294. <10.1140/epjc/s2006-02568-8>

http://hal.in2p3.fr/in2p3-00025986
Contributeur : Sylvie Flores <>
Soumis le : mardi 25 avril 2006 - 12:40:43
Dernière modification le : mercredi 4 janvier 2017 - 16:22:55

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### Citation

J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, et al.. Evidence for an excess of soft photons in hadronic decays of Z$^0$. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2006, 47, pp.273-294. <10.1140/epjc/s2006-02568-8>. <in2p3-00025986>

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