ALICE upgrades for Run 4 and Run 5

TL;DR

ALICE plans significant upgrades for Run 4 and Run 5, including a new Inner Tracking System with bent pixel sensors, a Forward Calorimeter for small-x gluon measurements, and the ALICE 3 detector with advanced silicon sensors for broad physics exploration.

Contribution

This paper presents detailed upgrade plans for ALICE, introducing innovative detector technologies like bent pixel sensors and a comprehensive ALICE 3 detector for enhanced physics capabilities.

Findings

Development of bent pixel sensors for reduced material budget.

Design of the new Forward Calorimeter (FoCal) for small-x gluon studies.

Conceptualization of the ALICE 3 detector with monolithic silicon sensors.

Abstract

In view of Run 4 at the LHC, presently scheduled from 2029 onwards, ALICE is pursuing several upgrades to further extend its physics reach. In order to improve heavy-flavor hadron and dielectron measurements which rely on secondary vertexing, a reduction of the material budget of the innermost layers of the Inner Tracking System is needed. This can be achieved with bent pixel sensors, arranged in half-cylinder shapes with integrated power lines and data buses, allowing to get rid of most of the supporting structure and of the water cooling. Moreover, a new Forward Calorimeter (FoCal), covering pseudorapidities of $3.2<\eta<5.8$, has been proposed to measure small-x (down to $10^{-6}$) gluon distributions via prompt photon production. The FoCal will be composed of a highly granular Si+W electromagnetic calorimeter combined with a conventional sampling hadronic calorimeter, and will significantly enhance the scope of ALICE for inclusive and correlation measurements with mesons, photons, and jets. For Run 5 and beyond, the ALICE 3 project has been proposed. It consists of a novel compact detector based on monolithic silicon sensors, with ultra-thin layers near the vertex, high readout rate capabilities, superb pointing resolution, excellent tracking and particle identification over a large acceptance. Such a detector enables a rich physics program, ranging from electromagnetic probes at ultra-low transverse momenta to precision physics in the charm and beauty sector. For particle identification, a sequence of detector systems is foreseen: a combination of a Time-Of-Flight system, a Ring-Imaging Cherenkov detector, an electromagnetic calorimeter, a muon identifier, and a dedicated forward detector for ultra-soft photons. In these proceedings, the upgrade plans will be shown together with the status of R\&D on ITS3 and FoCal and with the concepts and requirements of ALICE 3.