Hadron quenching in cold nuclear medium from fully coherent energy loss

In high-energy proton-nucleus (pA) collisions, multiple rescatterings in the cold nuclear target induce many soft gluons that have a long formation time, resulting in the modification of hadron production rates due to fully coherent energy loss (FCEL). The FCEL effect, a significant cold nuclear matter effect, is particularly manifest in hadron production at forward rapidity. Therefore, it is crucial to understand the qualitative and quantitative role of the FCEL effect for the quenching of forward hadron production rates before introducing any other nuclear effects, such as nuclear parton distribution functions, whose information could eventually be affected by FCEL.

This talk will review the FCEL effect, emphasizing that the induced single soft gluon spectrum controls the FCEL effect. We will then show theoretical predictions based on the FCEL effect with collider data on light hadron and heavy flavor (D-meson, J/Ψ) production of low transverse momentum in pA collisions. The last part of this talk will discuss recent progress on the induced gluon spectrum for 2→2 partonic processes beyond leading logarithmic (LL) accuracy, including richer physics than the LL case. In particular, we will show that nontrivial color transitions of a produced parton pair can happen in pA collisions. Application of the induced spectrum beyond LL accuracy to phenomenology will also be discussed.