Speaker
Description
The Mu2e experiment, which is currently under construction at the Fermilab Muon Campus, will search for the charged-lepton flavor violating (CLFV) neutrino-less conversion of a negative muon into an electron in the field of a nucleus. The conversion process results in a monochromatic electron with an energy of 104.97 MeV, and observations of a signal would require physics beyond the Standard Model. Aim of the experiment is to reach a sensitivity four orders of magnitude better than previous experiments .
The primary beam will start with the Fermilab Booster, supplying 8 GeV kinetic energy protons on a tungsten target. To reduce beam-related backgrounds, a pulsed structure (200 ns wide pulses spaced at 1700 ns intervals) is used. The muon beam will be formed through a sophisticated magnetic system composed of three consecutive solenoids, and will hit an aluminum target with the goal to examine $\sim 10^{18}$ stopped muons in three years of running.
In order to reach the desired sensitivity, the control of the backgrounds is a crucial issue, resulting in the need of very reliable Monte Carlo predictions. Extensive code-code comparison between GEANT4, version 11.01 with different hadron interaction models, FLUKA, version 2021 and MCNP, version 6.1 have been therefore performed in several cases, both for beam-related and cosmic rays-related backgrounds:
(a) double-differential distributions and yield of antiprotons produced from 8 GeV protons on a simplified tungsten target, to evaluate the background produced from the antiprotons that are back-scattered and transported through the transport solenoid;
(b) double-differential distributions and yield of charged pions from 8 GeV protons on tungsten and tantalum targets, with a comparison with available experimental data in the latter case;
(c) transmission of O(1) GeV neutrons, which are the main expected component of cosmic background, by 1 m of concrete;
(d) absorption of O(100) MeV neutral kaons by 1 m of concrete.
All the results of this comparison, which show in some cases relevant differences that can be ascribed to the different hadronic models used in the Monte Carlo codes, will be presented and discussed, together with their impact on the experiment.