ALICE forward rapidity upgrades

Abstract

Two forward rapidity upgrades of the ALICE apparatus at the LHC are presented: the Muon Forward Tracker (MFT) and the Fast Interaction Trigger (FIT). Their designs are driven by physics performance studies, which have been done using MC simulations. Several prototypes have been tested. Currently the detector design phase has ended. The final layouts, geometries and expected performance figures are presented. The latest developments from the test of the prototypes are discussed. The MFT will improve the performance of the ALICE Muon Spectrometer by adding vertexing capabilities to the system. The elementary component of the MFT is a Monolithic Active Pixel Sensor (MAPS), using the TowerJazz 0.18 µm technology called ALPIDE. ALPIDE has been developed by the ALICE collaboration for upgrades of the Inner Tracking System and the MFT. The MFT will consist of five detection planes forming a cone-like structure located between the interaction point and the frontal absorber of the Muon Spectrometer. The quality of track matching between the MFT and the Muon Spectrometer has been evaluated using Monte Carlo simulations. The same simulations were also used to extract the pointing accuracy of reconstructed muon tracks, which defines the resolution of the reconstructed vertex position. FIT has both online and offline functionalities. It will send online luminosity feedback to the LHC and it will generate minimum-bias and centrality-based triggers for ALICE. It is also expected to provide the offline information on the precise collision time for the Time-Of-Flight detector, as well as on forward multiplicity, centrality and event plane for Pb-Pb collisions. It will be composed of two Cherenkov detector arrays, surrounding the beam pipe on both sides of the interaction point, and one scintillator ring. The arrays will use Micro Channel Plate (MCP-PMT) technology to detect Cherenkov light and sectors of the scintillator ring will be optically coupled with Fine Mesh PMTs. The arrays provide good time response, while the scintillator ring allows for larger active area coverage. The extensive simulations verify the performance of the detector in terms of centrality and event-plane resolution. Additionally, the test results of the prototype of a single Cherenkov detector module, installed in ALICE, are presented.