Proton Production in d+Au Collisions and the Cronin Effect

Proton production in the intermediate p_T region in d+Au collisions is studied in the parton recombination model. The recombination of soft and shower partons is shown to be important in central collisions, but negligible in peripheral collisions. It is found that the large nuclear modification factor for proton production can be well reproduced by a calculation of the 3-quark recombination process.Comment: 4 RevTeX pages + 2 eps figure

Solvable Lattice Gas Models with Three Phases

Phase boundaries in p-T and p-V diagrams are essential in material science researches. Exact analytic knowledge about such phase boundaries are known so far only in two-dimensional (2D) Ising-like models, and only for cases with two phases. In the present paper we present several lattice gas models, some with three phases. The phase boundaries are either analytically calculated or exactly evaluated.Comment: 5 pages, 6 figure

Relating Meson and Baryon Fragmentation Functions by Shower-Parton Recombination

We relate the fragmentation functions of partons into mesons and baryons in the framework of recombination of shower partons. The results are in reasonable agreement with the data. The implication is that the meson and baryon fragmentation functions are not independent when hadronization of the shower partons are taken into account. The conclusion therefore closes a conceptual gap in the system of fragmentation functions whose $Q^2$ evolution has been more extensively studied than their interrelationship.Comment: 10 pages in LaTex + 3 figures in ep

Proton enhancement at large p_T at LHC without structure in associated-particle distribution

The production of pions and protons in the $p_T$ range between 10 and 20 GeV/c for Pb+Pb collisions at LHC is studied in the recombination model. It is shown that the dominant mechanism for hadronization is the recombination of shower partons from neighboring jets when the jet density is high. Protons are more copiously produced than pions in that $p_T$ range because the coalescing partons can have lower momentum fractions, but no thermal partons are involved. The proton-to-pion ratio can rise beyond 20. When such a high $p_T$ hadron is used as a trigger particle, there will not be any associated particles that are not in the background.Comment: Revised version with new material adde

Hadron Production in the Trans-fragmentation Region in Heavy-Ion Collisions

We study the production of hadrons in Au+Au collisions in the region $0.6<x_F<1.2$, which we refer to as the trans-fragmentation region (TFR), since it corresponds roughly to $\eta'>0$, where $\eta'=\eta-y_{\rm beam}$, depending on $p_T$. We show how hadrons can be produced in that region when the hadronization process is parton recombination. The inclusive $x$-distributions for proton and pion production are calculated with momentum degradation taken into account. The results show that the proton yield is significantly higher than that of the pions in the TFR. Without particle identification the existing data cannot be used for comparison with our result on the $p/\pi$ ratio. Without $p_T$ determination it is not feasible to relate the $x$ distribution to the experimental $\eta'$ distribution. Nevertheless, on theoretical grounds we have shown why the production of hadrons in the TFR is not forbidden by momentum conservation.Comment: 23 pages in LaTeX + 6 figures in ep