MANTRA - Measuring Anti-Neutron: Tagging and Reconstruction Algorithm for frontier experiments

Abstract:

We propose a method to measure the energy of anti-neutrons (n-bar's) produced in high-energy physics (HEP) experiments with an energy up to few GeV. At present, large amounts of data are being collected by several high energy physics experiments, and the possibility of studying a wealth of new reactions and still unexplored reaction mechanisms could open an effective method to reliably measure their energy and kinematics be devised, exploiting at no additional cost the current experimental set-ups. The so developed method will be released as a tool exploitable for HEP community which could be used in data analysis for several kinds of measurements in which n-bar's play a fundamental role, such as nucleon and hyperon form factors, charmed mesons decays and anti-deuteron production.

Anti-neutrons are not reconstructed by the tracking systems due to their immediate annihilation, but they can produce annihilation stars in electromagnetic calorimeters (EMC) which can form self-contained hadronic showers consisting mainly of pions and hadrons resulting the inelastic interactions on the latter in the surrounding material . While neutral pions decay into two photons, which trigger electromagnetic showers completely contained in a relatively small number of EMC crystals, charged particles usually lose only a fraction of their energy and can easily escape the calorimeter. The signature from n-bar annihilation in the EMC can be distinguished from the signatures due to photons and other neutral particles due to the characteristic shape of the shower. When the n-bar annihilation products are neutral pions only, the total deposited energy can be used to determine its energy. However, if charged pions are produced the energy cannot be reconstructed only with the EMC since the shower can escape the calorimeter in the backward (backsplash) or forward direction; these particles can interact with the detectors placed before or behind the EMC, and the time signal can be used to estimate the n-bar energy.
The combination of the time information and the information from the EMC, together with the development of Artificial Intelligence techniques, will allow the n-bar's to be identified and their energy and momentum to be measured. The developed method will be tested with experimental data from the experiments BESIII and Belle II, carried out at e+e- colliders, and will be released as a general software tool for High Energy Physics experiments with similar features, to be used in all the analyses where n-bar's detection plays a fundamental role requiring a complete reconstruction.

Thanks to the knowledge and experiences in the proponents units, on software reconstruction techniques, particles identification, n-bar physics and physics analysis techniques, together with the skills developed in different collaborations and experimental environments, we consider the finalization of the project to be feasible well within the indicated time schedule.