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The cross section for ep → e bb̄X in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel bb̄ → eeX ′ is selected by identifying the semielectronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q2 ≤ 1GeV, the inelasticity 0.05 ≤ y ≤ 0.65 and(More)
The φ-meson production cross section is measured for the first time at a subthreshold energy of 1.93 AGeV in Ni+Ni central collisions. The φ data were obtained within the acceptance of the CDC/Barrel subsystem of FOPI. For a sample of 4.7 · 10 central events, after background subtraction, 23 candidates were observed. Extensive GEANT simulations of the(More)
Glass resistive-plate counters (GRPC) with multistrip anodes are possible candidates as ToF detectors for FOPI [1, 2]. Here we present further results obtained with protons of 1.5 GeV at the SIS. All counters have center anodes with strips read out at both ends and altogether six 1 mm thick plates and four gaps of 0.3 mm. Both outermost plates are connected(More)
The Phase I FOPI data evidence for highly central Au + Au collisions at 100, 150 and 250 A·MeV systematically larger mean kinetic energies for He fragments relative to the H values [1]. The EOS Collaboration find the same trend with somewhat larger size [2]. Microscopic transport models [3] and hybrid hydrodynamical models, including pure Coulomb repulsion(More)
The incident energy at which the azimuthal distributions in semi-central heavy ion collisions change from in-plane to out-of-plane enhancement – Etran is studied as a function of mass of emitted particles, their transverse momentum and centrality for Au+Au collisions. The analysis is performed in a reference frame rotated with the sidewards flow angle(More)
We present measurements of the excitation function of elliptic flow at midrapidity in Au+Au collisions at beam energies from 0.09 to 1.49 GeV per nucleon. For the integral flow, we discuss the interplay between collective expansion and spectator shadowing for three centrality classes. A complete excitation function of transverse momentum dependence of(More)
The production of neutron rich matter in relativistic nuclear collisions would give access to the information on the symmetry energy at high densities and thus on the isospin dependence of the equation of state at such densities. This information is crucial for understanding basic astrophysics aspects such as the origin of elements, the structure of rare(More)
The characteristics of a symmetric multigap resistive plate chamber with multistrip readout electrode, recently developed by us, continued to be investigated. Studies of the time resolution, efficiency, average charge and dark rate as a function of applied voltage and the influence of the angle of incidence of the detected particle on these observables have(More)
Experimental data on K+ meson and proton sideward flow measured with the FOPI detector at SIS/GSI in the reactions Ru + Ru at 1.69A GeV and Ni + Ni at 1.93A GeV are presented. The K+ sideward flow is found to be anti-correlated (correlated) with the one of protons at low (high) transverse momenta. When compared to the predictions of a transport model, the(More)
Cluster production is investigated in central collisions of Ca+Ca, Ni+Ni, 96Zr+96Zr, 96Ru+96Ru, Xe+CsI and Au+Au reactions at 0.4A GeV incident energy. We find that the multiplicity of clusters with charge Z ≥ 3 grows quadratically with the system’s total charge and is associated with a mid-rapidity source with increasing transverse velocity fluctuations.(More)