Speaker
Description
Gluon nuclear PDFs still have large uncertainties in the small-x ($x$<10^{-3}) and small virtuality $Q^2<$50 (GeV/c)$^{2}$ region. Yields from particles coming from these gluons obtained in nuclear collisions are suppressed relative to $p$+$p$ collisions because of initial-state effects such as shadowing, energy loss and gluon saturation. Precise measurement of yields coming from small-x, small-$Q^2$ gluons are essential to understand these effects which have a significant contribution to the suppressions observed in A+A collisions at RHIC and LHC. The inverse Compton process $q+q\rightarrow \gamma+q \rightarrow \gamma+h$ is one of the few which can access and provide information on the gluon $x$ and $Q^2$ in the region where nPDFs are not well constrained. The LHCb detector can measure photons through the Electromagnetic Calorimeter or photon conversion to dielectrons in the pseudorapidity range 2$<\eta<$5, covering $x>5\times 10^{-6}$ and $Q^2>2$GeV$^2$ in the case of inverse Compton processes. This unique coverage allow us to search for the gluon saturation scale, the transition between dilute and saturated gluons, predicted by the Color-Glass Condensate effective theory. This presentation will show the status of the isolated $\gamma+$hadron correlation analysis using data collected in $p$+Pb and Pb+$p$ collisions at 8.16 TeV and $p$+$p$ collisions at 8 TeV. New techniques will also be presented to identify isolated photons and subtract the large background from neutral meson decays.
