Collinear factorized perturbative quantum chromodynamics (pQCD) model predictions are compared for $p+{rm Pb}$ at 5.02$A$ TeV to test nuclear shadowing of parton distribution at the Large Hadron Collider (LHC). The pseudorapidity distribution the nuc
lear modification factor (NMF), $R_{p{rm Pb}}(y=0,p_T<20;{rm GeV}/{it c}) = dn_{p{rm Pb}} /(N_{rm coll}(b)dn_{pp})$ and the pseudorapidity asymmetry $Y_{asym}^{h}(p_T)=R^h_{pPb}(p_T, eta<0)/R^h_{pPb}(p_T,eta>0)$ are computed using {small HIJING/B=B v2.0 model} and a pQCD improved parton model kTpQCD_v2.0 which embedded generalized parton distribution functions (PDFs). These results are updated calculations of those presented in Phys. Rev. C {bf 85}, 024903 (2012).
We study the effect of strong longitudinal color fields (SCF) in p+p reactions up to Large Hadron Collider energies in the framework of the HIJING/BBbar v2.0 model that combines (collinear factorized) pQCD multiple minijet production with soft longit
udinal string excitation and hadronization. The default vacuum string tension, kappa0 = 1 GeV/fm, is replaced by an effective power law energy dependent string tension, that increases monotonically with center-of-mass energy. The exponent 0.06 is found sufficient to reproduce well the energy dependence of multiparticle observables in RHIC, Tevatron, as well as recent LHC data. This exponent is found to be only half of that predicted by the Color Glass Saturation model, lambda(CGC)=0.115, where gluon fusion multiparticle production mechanisms are assumed. In HIJING/BBbar v2.0, the rapid growth of central-rapidity density with energy is due to the interplay of copious minijet production and increasing SCF contributions. The large (strange)baryon-to-meson ratios measured at Tevatron energies are well described. A significant enhancement of these ratios is predicted up to the highest LHC energy (14 TeV). The effect of JJbar loops and SCF on baryon-anti-baryon asymmetry and its relation to baryon number transport is also discussed.
