Properties of straw tubes for the tracking detector of the COMET experiment

Abstract COMET (Coherent Muon to Electron Transition, J-PARC, Japan) is one of the experiments that studies extensions of the Standard Model (SM) of elementary particle physics. The main purpose of the COMET experiment is to search for charged lepton flavor violating neutrinoless conversion of muons into electrons in the field of a nucleus ( μ - e conversion, μ - N → e- N). The goal is to achieve a sensitivity to the branching ratio superior to 10−17, that four orders of magnitude smaller than the present limit. In the experiment a straw detector will be used to measure the momentum of the signal electrons from the μ - e conversion. In order to satisfy the requirements of the momentum measurements, we plan to develop a planar tracking device consisting of thin-wall straws made with an extremely light material to reduce multiple scattering and that is capable of operation in vacuum. Research the mechanical properties of straws will allow us to choose their optimal tension, to estimate the influence of the temperature and humidity, to assess the straws service life in the experiment, which we define as the tension relaxation time to the minimum working value.