Beam momentum scan with Pb+Pb collisions

This document presents the request of the NA61/SHINE Collaboration at the CERN SPS to perform a new beam momentum scan with Pb+Pb collisions. The new data are needed to: (i) significantly extend previous studies of collective effects due to strong and electromagnetic interactions, (ii) improve measurements of event-by-event fluctuations and (iii) perform the first measurements of open charm production in central Pb+Pb collisions at the SPS energies. \end{enumerate} The charm production measurements require an upgrade of the NA61/SHINE facility by a high-precision vertex detector. The feasibility and expected performance of the proposed detector are presented.