Non-destructive neutron radiography and tomography were applied to investigate the internal structure of a ceramic vessel lid originating from the medieval settlement of Otrar (Turkestan region, Kazakhstan). Tomographic reconstruction confirmed the presence of a freely movable spherical element located inside the lid. Quantitative analysis of the reconstructed three-dimensional volume allowed determination of the sphere’s geometrical parameters, with a calculated volume of 1.12(3) mm3 and a diameter of 1.29(1) mm. Neutron attenuation profiles show identical characteristics for the lid and the internal sphere, implying the same ceramic material.
The NA64 experimental setup is a universal detector designed to test a wide range of models beyond the Standard Model. Some of these models predict the existence of light dark matter particles, whose presence can be inferred from indirect evidence. The NA64 experiment is searching for such particles, specifically the dark photon A 1pt ' —a vector mediator between ordinary and dark matter. This paper focuses on simulating a specific dark photon production channel: the decay of a ρ^0 meson into a dark photon, which subsequently decays into dark matter particles.
Previously developed two-center approach for calculations of electron–positron pair creation in collisions of two identical heavy nuclei is extended to nonsymmetric collisions where the colliding nuclei differ from each other. The time-dependent Dirac equation for the positron wave function is solved numerically with the help of the generalized pseudospectral method in modified prolate spheroidal coordinates and Crank–Nicolson algorithm for time propagation. For the case of the asymmetric U^92 + -Cm^96 + collisions, we calculate total probabilities of electron–positron pair creation, as well as angle-integrated and angle-resolved energy distributions of the emitted positrons. Characteristic signatures of the supercritical regime are found in total probabilities and energy distributions. The angular distributions show high degree of isotropy.
Two narrow resonant structures at 6.9 and 7.2 GeV, as well as a broad structure near the di- J 1pt / 1ptψ production threshold, have recently been observed by the LHCb [1], ATLAS [2], and CMS [3] collaborations in the di- J 1pt / 1ptψ and J 1pt / 1ptψ + ψ (2S) invariant-mass spectra with four muons in the final state. This suggests the existence of fully heavy tetraquark candidates with a ccc̅c̅ quark configuration: X(6900) , X(7200) , and X(6500) . However, their quantum properties have not yet been confirmed [4]. This report presents an amplitude analysis for the di- J 1pt / 1ptψ and J 1pt / 1ptψ + ψ (2S) channels with 4μ and 4μ + 2π in final states, aimed at studying the properties of these exotic resonances. By performing a simultaneous fit to the mass and angular distributions, the masses and widths of the observed structures are determined under the hypothesis of two interfering states with J^P = 0^ + for both. The comparisons with other spin–parity hypotheses for X(6900) are also presented.
This paper describes hardware implementation of pulse shape discrimination algorithm into the current detector electronics with no need in major upgrade. According to this algorithm modeling and calculations of signal amplitude, time, photon and hadron contributions into the waveform are presented.
