The GAPS experiment was designed to study the antimatter component in cosmic rays with a specific focus on antideuterons, antiprotons and low-energy anti-helium nuclei (< 0.25 GeV / n). The first identification of antideuterons in cosmic rays would be a strong hint of new physics, exploring a wide range of theoretical models of Dark Matter (DM) together with more exotic sources. Secondary production of antideuteron and anti-helium by interaction between cosmic rays and interstellar medium is significantly suppressed at low energies with respect to the production of DM candidates. GAPS was proposed to NASA for a series of long-duration flights (around 100 total days) with stratospheric balloon from Antarctica. In 2019, the start of the integration phase of the various detectors is expected, while in the summer of 2020 everything will be transported to the American base of McMurdo. The launch is scheduled for the austral summer of 2020-2021. The GAPS antiparticle identification approach is truly innovative. In fact, it will provide a nearly background free technique of identifying antideuterons by using three different methods of detection for every event. Initially, a plastic time of flight (TOF) system tags the particle and records the velocity. This will distinguish antideuterons from lighter particles, such as antiprotons. The particle then slows down and stops in the Si(Li) tracker, forming an excited exotic atom. This atom then de-excites and releases both X-rays and a pion star.Si(Li) wafers (with 50 ns time resolution and 2 keV energy resolution) will be crucial in the process of particle identification; the X-ray energy only depends on the mass and charge of the particle, therefore its signature precisely determine the type of antiparticle detected as it makes transitions to lower states. Finally, the pion star (the third layer of detection) provides greater background suppression.
The INFN (Trieste, Rome Tor Vergata, Bergamo, Florence, Naples, Pavia) contribution to the project concerns the design and implementation of ASICs for the DAQ of silicon detectors. In addition, the Italian groups will contribute to the development of software for simulation, data-structure and analysis, as well as the future data analysis itself and interpretation of results.