Dijet correlations at RHIC, leading-order ktk_t-factorization approach versus next-to-leading order collinear approach

We compare results of $k_t$-factorization approach and next-to-leading order collinear-factorization approach for dijet correlations in proton-proton collisions at RHIC energies. We discuss correlations in azimuthal angle as well as correlations in two-dimensional space of transverse momenta of two jets. Some $k_t$-factorization subprocesses are included for the first time in the literature. Different unintegrated gluon/parton distributions are used in the $k_t$-factorization approach. The results depend on UGDF/UPDF used. For collinear NLO case the situation depends significantly on whether we consider correlations of any two jets or correlations of leading jets only. In the first case the $2 \to 2$ contributions associated with soft radiations summed up in the $k_t$-factorization approach dominate at $\phi \sim \pi$ and at equal moduli of jet transverse momenta. The collinear NLO $2 \to 3$ contributions dominate over $k_t$-factorization cross section at small relative azimuthal angles as well as for asymmetric transverse momentum configurations. In the second case the NLO contributions vanish at small relative azimuthal angles and/or large jet transverse-momentum disbalance due to simple kinematical constraints. There are no such limitations for the $k_t$-factorization approach. All this makes the two approaches rather complementary. The role of several cuts is discussed and quantified.Comment: 26 pages, 17 figure

Nonphotonic electrons at RHIC within ktk_t-factorization approach and with experimental semileptonic decay functions

We discuss production of nonphotonic electrons in proton-proton scattering at RHIC. The distributions in rapidity and transverse momentum of charm and bottom quarks/antiquarks are calculated in the $k_t$-factorization approach. We use different unintegrated gluon distributions from the literature. The hadronization of heavy quarks is done by means of Peterson and Braaten et al. fragmentation functions. The semileptonic decay functions are found by fitting recent semileptonic data obtained by the CLEO and BABAR collaborations. We get good description of the data at large transverse momenta of electrons and find a missing strength concentrated at small transverse momenta of electrons. Plausible missing mechanisms are discussed.Comment: 16 pages, 11 figure

The Reduction of Flavins by Borohydride: 3,4-Dihydroflavin

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66296/1/j.1432-1033.1969.tb00621.x.pd

Solution of the Kwiecinski evolution equations for unintegrated parton distributions using the Mellin transform

The Kwiecinski equations for the QCD evolution of the unintegrated parton distributions in the transverse-coordinate space (b) are analyzed with the help of the Mellin-transform method. The equations are solved numerically in the general case, as well as in a small-b expansion which converges fast for b Lambda_QCD sufficiently small. We also discuss the asymptotic limit of large bQ and show that the distributions generated by the evolution decrease with b according to a power law. Numerical results are presented for the pion distributions with a simple valence-like initial condition at the low scale, following from chiral large-N_c quark models. We use two models: the Spectral Quark Model and the Nambu--Jona-Lasinio model. Formal aspects of the equations, such as the analytic form of the b-dependent anomalous dimensions, their analytic structure, as well as the limits of unintegrated parton densities at x -> 0, x -> 1, and at large b, are discussed in detail. The effect of spreading of the transverse momentum with the increasing scale is confirmed, with growing asymptotically as Q^2 alpha(Q^2). Approximate formulas for for each parton species is given, which may be used in practical applications.Comment: 18 pages, 6 figures, RevTe

kt - factorization and CCFM - the solution for describing the hadronic final states - everywhere ?

The basic ideas of kt-factorization and CCFM parton evolution is discussed. The unintegrated gluon densities, obtained from CCFM fits to the proton structure function data at HERA are used to predict hadronic final state cross sections like jet production at HERA, but also comparisons with recent measurements of heavy quark production at the Tevatron are presented. Finally, the kt-factorization approach is applied to Higgs production at high energy hadron hadron colliders and the transverse momentum spectrum of Higgs production at the LHC is calculated.Comment: to be published in MPLA, replaced with new reference

Towards system optimum: Finding optimal routing strategies in time dependent networks for large-scale evacuation problems

Disaster and evacuation planning crucially depend on good routing strategies. This article compares two different routing strategies in a multi-agent simulation of a large real world evacuation scenario. The first approach approximates a Nash equilibrium where every evacuee adopts an individually optimal routing strategy regardless of what this solution imposes on others. The second approach approximately minimizes the total travel time in the system, which requires to enforce cooperative behavior of the evacuees. Both approaches are analyzed in terms of the global evacuation dynamics and on a detailed geographic level