  A forward electromagnetic and hadronic calorimeter (FoCal) was proposed as an
upgrade to the ALICE experiment, to be installed during LS3 for data-taking in
2027--2029 at the LHC. The FoCal extends the scope of ALICE, which was designed
for the comprehensive study of hot and dense partonic matter, by adding new
capabilities to explore the small-$x$ parton structure of nucleons and nuclei.
The primary objective of the FoCal is high-precision inclusive measurement of
direct photons and jets, as well as coincident gamma-jet and jet-jet
measurements, in pp and p--Pb collisions. These measurements by FoCal
constitute an essential part of a comprehensive small-$x$ program at the LHC
down to $x\sim10^{-6}$ and over a large range of $Q^2$ with a broad array of
complementary probes, comprising -- in addition to the photon measurements by
FoCal and LHCb -- Drell-Yan and open charm measurements planned by LHCb, as
well as photon-induced reactions performed by all LHC experiments.
