Orateur
Description
Direct photon measurement in heavy-ion collisions provides a valuable set of observables to study the hot QCD medium since these photons are produced at different stages of the collision and escape the medium unaffected. In proton-proton collisions, the direct photon yield at high transverse momentum ($p_\text{T}$) is fed by hard scattering processes (prompt photons) but also fragmentation of high-$p_\text{T}$ partons. Their measurement allows one to test pQCD calculations and can constrain parton distribution functions. The access to the prompt photon production can be achieved experimentally with isolation techniques.
In heavy-ion collisions (e.g., proton-lead and lead-lead), the high-$p_\text{T}$ component provides information on the initial parton dynamics and parton densities in nuclei, whereas the low-$p_\text{T}$ component (below $3\,\text{GeV}/c$) of the direct photon production could be dominated by thermal radiation from the hot and dense matter formed, carrying information on its space-time evolution and temperature. The study of isolated photons and their correlations (with hadrons and jets) is also a very promising observable to study the medium-induced parton energy loss in hadron collisions.
In this talk, we will present the latest ALICE results on direct (isolated) photons and their correlations in different collision systems.
| Choix de session parallèle | 1.3 Physique nucléaire: physique hadronique et QCD |
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