The production of π±, K±, p and p̄ in p–Pb collisions at sNN = 5.02 TeV

In this study, we are reporting comprehensive results on [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] production in the transverse momentum range of [Formula: see text] 4 GeV/c at midrapidity of [Formula: see text] 0.5 GeV/c, in p–Pb collisions at [Formula: see text] = 5.02 TeV. HIJING 1.0 and UrQMD 3.4 event generators are used to perform simulations and the results are compared with the ALICE and RHIC data. It is observed from the comparison that the yields for the baryons are more complex compared to the mesons and the complexity in baryons is due to the striping dynamics (spectators, leading particles of projectiles) of inner nucleus protons and neutrons. Though all the mesons could be produced during the interaction, they have maximum longitudinal momentum [Formula: see text]; baryons and mesons could be produced as a result of decay of massive baryon-resonances. Yields for the [Formula: see text] mesons are greater than the yield for the [Formula: see text] mesons. These are the well-known results from the RHIC data, which stated that the Cronin Effect is mainly due to [Formula: see text] mesons that can be produced as a result of multi-particle inner nucleus cascade. There exists the regions where yields for the [Formula: see text] mesons and baryons are same that may be due to the appearance of parton nature. The code used in simulation includes the parton dynamics earlier than it is included in the experiment.

Comparison study of the pT distributions of the charged particles in p–Pb interactions at LHC energies

Transverse momentum [Formula: see text] distributions of primary charged particles were compared to simulations using the Ultra Relativistic Quantum Molecular Dynamics (UrQMD) transport model and the HIJING 1.0 model in minimum bias p–Pb collisions at [Formula: see text] in the pseudorapidity [Formula: see text] regions: [Formula: see text], [Formula: see text] and [Formula: see text] and in the transverse momentum range [Formula: see text]. The simulated distributions were then compared with the ALICE data and it was observed that UrQMD predicts systematically higher yields than HIJING 1.0. Both codes cannot describe the experimental data in the range of [Formula: see text], though in the region of [Formula: see text] the model predictions are very close to the experimental results for particles with [Formula: see text], [Formula: see text]. The ratio of the yield at forward pseudorapidity to that at [Formula: see text] was also studied. It was observed that the predictions of the models depend on [Formula: see text]. In the experiment there is no essential difference of yields for particles from the intervals of [Formula: see text], [Formula: see text] and [Formula: see text]. The differences are significant for the models where the ratios are systematically less than 1. This means that the results are not connected to a medium effect but reflect the Cronin effect. We are led to conclude that the codes cannot take into account satisfactorily the leading effect due to the asymmetric p–Pb fragmentation.

Energy conservation in high-pT nuclear reactions

The Cronin effect, which is nuclear enhancement of high-pT hadron production in pA collisions was successfully predicted prior the measurements at RHIC and LHC. The restrictions imposed by energy conservation lead to spectacular effects. Energy deficit becomes an issue for hadron production in pA collisions at large xL and/or large xT toward the kinematic bounds xL, T = 1. It leads to a suppression, which has been indeed observed for hadrons produced at forward rapidities and large pT. Intensive energy dissipation via gluon radiation by a highly virtual parton produced with large pT, makes this process impossible to continue long. Color neutralization and creation of a colorless dipole must occur promptly. When this happens inside a hot medium created in AA collisions, attenuation of dipoles, rather than induced energy loss, becomes a dominant mechanism for suppression of high-pT hadrons.

APPLIED HIGH ENERGY QCD

This review stresses the theoretical elements that underlie a wide range of phenomenological studies of high-energy QCD, which include both soft and hard processes. After a brief introduction to the basics of QCD, various aspects of QCD-based phenomenology are covered: color transparency, hadronization of color charges, Regge phenomenology, parton model, Bjorken scaling and its violation, DGLAP evolution equation, BFKL formalism, GLR-MQ evolution equation and saturation. In the last part of the review, we employ the light-cone dipole formalism to describe deep inelastic lepton scattering, Drell — Yan processes, direct photon production, diffraction, quark and gluon shadowing in nuclei, the Cronin effect and nuclear broadening.

PARTICLE PRODUCTION AT RHIC FROM QUARK RECOMBINATION

Particle production at RHIC is discussed within the framework of quark recombination model. After a short introduction on the anomalies discovered at RHIC, we will first present the basic physics ideas common for all the quark recombination models and different implementations in different research groups. Then the main focus turns to the approach of Oregon group. Feynman and Field's independent fragmentation process is re-interpreted in the quark recombination model. In this approach, hard partons with high virtuality evolves into a shower of semihard partons by radiating gluons which can convert into quark-antiquark pairs. Then different fragmentation functions can be rewritten in terms of only a few shower parton distributions within the recombination model. By fitting the data on the fragmentation functions, the shower parton distributions can be determined and then can be used in other processes together with the assumed exponential distributed soft parton distributions. Applications to the particle production at RHIC for both Au + Au and d + Au collisions in mid-rapidity are discussed. In particular, the suppression for meson production in central Au + Au collisions and Cronin effect in d + Au collisions are naturally explained within the recombination models. Finally, strange particle production is briefly discussed.