Decay vertex reconstruction and 3-dimensional lifetime determination at BESIII

Abstract

This paper focuses mainly on the vertex reconstruction of resonance particles with a relatively long lifetime such as K0S, Λ, as well as on lifetime measurements using a 3-dimensional fit. The kinematic constraints between the production and decay vertices and the decay vertex fitting algorithm based on the least squares method are both presented. Reconstruction efficiencies including experimental resolutions are discussed. The results and systematic errors are calculated based on a Monte Carlo simulation.

Precision measurements of the e+e−→KS0Kuemmel1, Luo2, Zhou3 et al. 2019Phys. Rev. D8010View full textAdd to dashboardCite

“…Their distances of closest approach to the IP must be within 25 cm and 20 cm along the beam direction and in the transverse plane, respectively. Then primary and secondary vertex fits [27] are performed, and the decay length of the secondary vertex is required to be greater than twice its uncertainty. The invariant mass of…”

First observation of the decay χcJ→Σ+p¯Ablikim1, Ачасов2, Adlarson3 et al. 2019Phys. Rev. D2000View full textAdd to dashboardCite

“…The K 0 S candidate is reconstructed with a pair of oppositely charged pions. To suppress events from combinatorial background contributions, we require that the π þ π − pair is produced at a common vertex [18].…”

First measurement of e+e−→pKS0Ablikim1, Ачасов2, Ahmed3 et al. 2018Phys. Rev. D10050View full textAdd to dashboardCite

“…A charged track is identified as a pion by using the combined TOF and dE=dx information. To suppress random combinatorial backgrounds, we require that the π þ π − pair satisfies a secondary vertex fit [28], and the decay length, which is the distance between production and decay vertexes, is required to be greater than twice its resolution. If there is more than one π þ π − combination in an event, the one with the smallest χ 2 of the secondary vertex fit is retained.…”