A method is presented for completely distinguishing between charged kaons and charged pions by using their charged muon (plus neutrino) decays (with neutrinos undetected) for meson laboratory momenta up to 1000 MeV/c. When either a charged kaon or a charged pion decays into a muon and a neutrino, momentum-energy (four-momentum) conservation will be used to provide unique "kinematic trajectories" for distinguishing kaon decays from pion decays when the change in three-momentum of the muon from that of either parent kaon or pion is measured (or simulated). Ina magnetic field, observation of a tracked particle showing a "kink" and/or a change in helicity indicates the decay of the parent particle into a similarly charged muon product. Unique kinematic separation between each parent kaon and parent pion is possible for each parent particle's momentum up to 1000 MeV/c. Curvature-radius of the helical path in a magnetic field is used to determine each charged particle's momentum, whether it be a kaon, a pion or a muon. A weak field is adequate for making this determination since momentum (curvature radius) need only be measured to an accuracy of about 10%. Monte Carlo calculations of the kineatic trajectories have been carried out for primary meson momenta between 0 and 1000 MeV/c and for a range of emission angles (or "kinks") between 0° and 180°. Monte Carlo results from these in-flight decay kinematic calculations show a complete separation is possible for pion decays from kaon decays for laboratory momenta up to 1000 MeV/c because these two classes of meson decays cluster into completely separated 2-D regions of difference-momentum (x)muon-angle space. The most difficult region for separating primary particles occurs for small-kink decays within less than 5°. Decay halflife and time dilation require an efficient time projection chamber to be fairly large, because kaons are strongly favored over pions at the higher laboratory momenta and for the smaller time projection chamber geometries.
Braithwaite, Wilfred J. and Braithwaite, Edwin S.
"Separating K+/- from Pi+/- using In-Flight Decays to Mu+/- + Nu,"
Journal of the Arkansas Academy of Science: Vol. 51
, Article 8.
Available at: https://scholarworks.uark.edu/jaas/vol51/iss1/8