The butterfly drift chamber geometry: An optimal four-plane drift chamber for use in a high track multiplicity environment

Abstract

This paper presents the arguments which have led to the definition of the butterfly geometry adopted for the construction of the large drift chambers for the European hybrid spectrometer. The main characteristic of this geometry is the quasi-invariance of its 4-plane wire pattern under a change of perspective. As a consequence track impact reconstruction can be performed with acceptable ambiguity rates even in presence of high track multiplicities with large angels of incidence. Its expected performance is compared with the performance of the well known y- u- ν- y-staggered geometry in a given context of application.