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.

37 pages, 9 figures, Accepted by Eur. Phys. J. C

Cited by in corpus (10)

• Possible studies at the first stage of the NICA collider operation with polarized and unpolarized proton and deuteron beams
• Observation of the Muon Inner Bremsstrahlung at LEP1
• Soft photon bremsstrahlung at next-to-leading power
• High-energy $\pi \pi$ scattering without and with photon radiation
• Soft-photon radiation in high-energy proton-proton collisions within the tensor-Pomeron approach: Bremsstrahlung
• Central exclusive diffractive production of a single photon in high-energy proton-proton collisions within the tensor-Pomeron approach
• On the stability of the open-string QED neutron and dark matter
• On the question of quark confinement in the Abelian U(1) QED gauge interaction
• QED meson description of the anomalous particles at ~17 and ~38 MeV
• Soft photon production from real-time dynamics of jet fragmentation