Browsing by Author "HADES collaboration (100 authors)"
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- Associate K^0 production in p+p collisions at 3.5 GeV: The role of Delta(1232)++Publication . HADES collaboration (100 authors); Blanco, A.; Fonte, P.; Lopes, L.; Mangiarotti, A.
An exclusive analysis of the four-body final states Λ+p+π++K0 and Σ0+p+π++K0 measured with HADES for p+p collisions at a beam kinetic energy of 3.5 GeV is presented. The analysis uses various phase space variables, such as missing mass and invariant mass distributions, in the four-particle event selection (p,π+,π+,π−) to find cross sections of the different production channels, contributions of the intermediate resonances Δ++ and Σ(1385)+, and corresponding angular distributions. A dominant resonant production is seen, where the reaction Λ+Δ+++K0 has a cross section about ten times higher (29.45±0.08−1.46+1.67±2.06μb) than the analogous nonresonant reaction (2.57±0.02−1.98+0.21±0.18μb). A similar result is obtained in the corresponding Σ0 channels with 9.26±0.05−0.31+1.41±0.65μb in the resonant and 1.35±0.02−1.35+0.10±0.09μb in the nonresonant reactions.
- Searching a Dark Photon with HADESPublication . HADES collaboration (100 authors); Blanco, A.; Fonte, P.; Lopes, L.; Mangiarotti, A.We present a search for the e+e- decay of a hypothetical dark photon, also names U vector boson, in inclusive dielectron spectra measured by HADES in the p (3.5 GeV) + p, Nb reactions, as well as the Ar (1.756 GeV/u) + KCl reaction. An upper limit on the kinetic mixing parameter squared epsilon^{2} at 90% CL has been obtained for the mass range M(U) = 0.02 - 0.55 GeV/c2 and is compared with the present world data set. For masses 0.03 - 0.1 GeV/c^2, the limit has been lowered with respect to previous results, allowing now to exclude a large part of the parameter region favoured by the muon g-2 anomaly. Furthermore, an improved upper limit on the branching ratio of 2.3 * 10^{-6} has been set on the helicity-suppressed direct decay of the eta meson, eta-> e+e-, at 90% CL.