Speaker
Description
Ultra-peripheral collisions (UPCs) at the LHC offer a clean and controlled environment to study photon-induced interactions in the absence of hadronic interactions from collision with nuclear overlap. The ALICE experiment has established a comprehensive UPC physics program spanning QCD, electroweak, and nuclear structure studies.
The photoproduction of light vector mesons, such as $\rho^{0}$, $\phi$, and $K^{*0}$, has gained renewed interest, especially in the context of soft QCD and azimuthal anisotropy. In Pb--Pb and Xe--Xe collisions, coherent $\rho^{0}$ photoproduction shows signatures of impact-parameter-dependent modulation and quantum interference at femtoscopic scales.
New Run~3 data enable further differential studies, e.g.\ in $|t|$, the momentum transfer from the target nucleus and electromagnetic dissociation (EMD) classes, allowing improved sensitivity to nuclear shadowing and initial-state geometry. ALICE has also reported measurements of inclusive charm and strangeness photoproduction in Run~3, revealing insights into photonuclear particle production mechanisms.
ALICE is also advancing the study of exclusive multi-hadron final states and investigating baryon-to-meson ratios in inclusive UPCs to explore potential collective behavior in small systems. In the electroweak sector, photon-photon interactions ($\gamma\gamma \rightarrow \tau^{+}\tau^{-}$) are being exploited to probe the anomalous magnetic moment of the tau lepton.
Looking ahead, the upcoming FoCal detector upgrade will allow access to gluon distributions down to Bjorken-$x \sim 10^{-6}$ via direct photon and vector meson production at forward rapidity, significantly extending the UPC program in Run~4.
This talk will provide a comprehensive perspective on the current status, recent breakthroughs, and future opportunities in UPC physics at ALICE.
