  Collinear factorized perturbative QCD model predictions are compared for p+Pb
at 4.4A TeV to test nuclear shadowing of parton distribution at the Large
Hadron Collider (LHC). The nuclear modification factor (NMF),
R_{pPb}(y=0,p_T<20 GeV/c) = dn_{p Pb} /(N_{coll}(b)dn_{pp}), is computed with
electron-nucleus (e+A) global fit with different nuclear shadow distributions
and compared to fixed Q^2 shadow ansatz used in Monte Carlo Heavy Ion Jet
Interacting Generator (HIJING) type models. Due to rapid DGLAP reduction of
shadowing with increasing Q^2 used in e+A global fit, our results confirm that
no significant initial state suppression is expected (R_{pPb} (p_T) = 1 \pm
0.1) in the p_T range 5 to 20 GeV/ c. In contrast, the fixed Q^2 shadowing
models assumed in HIJING type models predict in the above p_T range a sizable
suppression, R_{pPb} (p_T) = 0.6-0.7 at mid-pseudorapidity that is similar to
the color glass condensate (CGC) model predictions. For central (N_{coll} = 12)
p+ Pb collisions and at forward pseudorapidity (\eta = 6) the HIJING type
models predict smaller values of nuclear modification factors (R_{pPb}(p_T))
than in minimum bias events at mid-pseudorapidity (\eta = 0). Observation of
R_{pPb}(p_T= 5-20 GeV/c) less than 0.6 for minimum bias p+A collisions would
pose a serious difficulty for separating initial from final state interactions
in Pb+Pb collisions at LHC energies.
