Speaker
Description
The COMET experiment at J-PARC aims to search for a lepton-flavour violating process of muon to electron conversion, with a branching-ratio sensitivity of $10^{−17}$. The expected signal of this process is monochromatic 105 MeV single electron. To distinguish such a low energy signal, a material budget of detector is essential since the detection accuracy is primarily limited by multiple scattering.
To realize the required low material detector, a vacuum-compatible ultra-thin-wall straw tracker, 20$\mu$m-thick Mylar straw with 70nm Al cathode, has been developed employing ultrasonic-welding technique. This was reported in VCI2016, and the detector performances such as detection efficiency and intrinsic spacial resolutions were reported in VCI2019. In parallel to 20$\mu$m straw production, further thinner straw, 12$\mu$m-thick, was developed for the COMET upgrade, ie. COMET Phase-II. Details of R&D on 12$\mu$m straw were reported in VCI2022.
In the process of developing the 12$\mu$m straw, it became clear that it would be fundamentally difficult to make it any thinner using the current straw manufacturing method based on ultrasonic welding. Our R&D showed that the limit is around 10-12$\mu$m. Then, the brand-new extremely light straw was developed with a nonwoven graphite-textile. This was enabled by a collaboration with the nano-tech textile science.
In VCI2025, detailed R&D of the brand-new nonwoven graphite straw will be presented, in addition to the R&D status of the 12$\mu$m-thick straw.
| Primary experiment | COMET |
|---|
