COMET Phase-I Technical Design Report

Abstract

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminium nucleus (µ−e conversion, µ − N → e − N); a lepton flavor violating process. The experimental sensitivity goal for this process in the Phase-I experiment is 3.1 × 10 −15 , or 90 % upper limit of branching ratio of 7 × 10 −15 , which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the µ−e conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

Leptoquarks facing flavour tests and $b\to s\ell\ell$ after Moriond 2021

“…In particular, B → Kτ µ and τ → φµ decays are promising channels at Belle II. Additionally, the predicted range of neutrinoless µ − e in Aluminium will be (almost) fully probed by COMET and Mu2e [10].…”

“…Points complying with all imposed constraints (explaining R ( * ) K,D and respecting all experimental bounds) are marked in yellow. Notice that most of the currently preferred parameter space can be probed by the upcoming experiments COMET and Mu2e [10], both dedicated to searching for neutrinoless µ − e conversion in Aluminium.…”

A combined explanation of the $B$-meson decay anomalies with a single vector leptoquark

“…In the right panel of Figure 2 we show the sample points in the plane of the most constraining observables 𝐾 𝐿 → 𝜇 ± 𝑒 ∓ and neutrinoless 𝜇 − 𝑒 conversion. It can be seen that a large portion of the parameter space is already excluded (blue points), while the remaining (preferred) region (orange points) is well within the reach of the upcoming cLFV-dedicated experiments COMET [9] and Mu2e [10].…”

“…Being a 𝐵-factory, it aims not only to scrutinise the 𝐵-anomalies, but also to produce copious amounts of charmed mesons and 𝜏 leptons, allowing to reach an unprecedented precision and sensitivity on related flavour processes in Contrary to many other attempts in the literature, we do not neglect any coupling in order to comply with cLFV bounds; all couplings are a priori assumed to be non-vanishing. COMET [9]/Mu2e [10] and Mu3e [11]. The blue, orange and green lines respectively denote the 90%-range around the respective best-fit points, for leptoquark masses of 1.5, 2.5 and 3.5 TeV.…”

“…Figure 3:Predicted ranges for several 𝑏 → 𝑠𝜏𝜏 and cLFV observables to be investigated at Belle II[13], COMET[9]/Mu2e[10] and Mu3e[11]. The blue, orange and green lines respectively denote the 90%-range around the respective best-fit points, for leptoquark masses of 1.5, 2.5 and 3.5 TeV.…”