in Cu$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV'
---

Introduction
============

Experiments at the Relativistic Heavy Ion Collider (RHIC) [@Arsene:2004fa; @Back:2004je; @Adams:2005dq; @Adcox:2004mh] and later at the Large Hadron Collider (LHC) [@CMS:2012aa; @Abelev:2012hxa; @Aad:2012vca; @Gunji:2016uqe] established the formation of quark-gluon plasma (QGP) in relativistic collisions of heavy ions (). One of the most important tools to investigate the properties of this new medium are identified hadrons at high transverse momenta ($>$5), because they are leading fragments [@jacob1978large] of jets from hard-scattered partons, which, before fragmentation, interacted with the QGP [@Baier:2000mf]. The differential cross section of high-$p_T$ hadron production in elementary $p$+$p$ collisions can be derived using next-to-leading-order perturbative-quantum-chromodynamics formalism [@Owens:1986mp; @Adare:2007dg]:

$$\begin{aligned}
\label{eqcs}
d\sigma_{pp\rightarrow hX}\approx\sum_{abcd}\int 
dx_a dx_b dz_c f_{a/p}(x_a)\otimes f_{b/p}(x_b) \\ 
\otimes \  d\sigma_{ab\rightarrow cd} \otimes D_{c\rightarrow h}(z_c), \nonumber\end{aligned}$$

where $x_{a,b}$ is the initial momentum fraction carried by partons $a$ and $b$, $z_c$ is the final-state momentum fraction of the hadron $h$, $f_{a/p}$ and $f_{b/p}$ are the parton distribution functions (PDFs), $d\sigma_{ab\rightarrow cd}$ is the differential cross section of the initial partons hard scattering, $D_{c\rightarrow h}$ is the fragmentation function (FF) of the hard scattered parton to the final-state hadron.

There are two classes of nuclear effects, which modify the high-$p_T$ hadron 