Large-$p_T$ Inclusive ${\pi }^0$ Production in Heavy-Ion Collisions at RHIC and LHC

We present results for the large-$p_T$ inclusive ${\pi }^0$ production in p-p and A-A collisions at RHIC and LHC energies. We include the full next-to-leading order radiative corrections, $O({\alpha }_s^3)$, and nuclear effects such as parton energy loss and nuclear shadowing. We find the next-to-leading order corrections and the parton energy loss effect to be large and $p_T$ dependent, while the nuclear shadowing effects are small ($<10$). We calculate the ratio of prompt photons to neutral pions produced in heavy ion collisions and show that at RHIC energies this ratio increases with $p_T$ approaching one at $p_T\sim 8$ GeV, due to the large suppression of ${\pi }^0$ production. We show that at the LHC, this ratio has a steep $p_T$ dependence and approaches 25% effect at $p_T\sim 40$ GeV. We discuss theoretical uncertainties inherent in our calculation, such as choice of the renormalization, factorization and fragmentation scales and the K-factors which signify the size of higher-order corrections.