Measuring Double Parton Distributions in Nucleons at Proton-Nucleus Colliders

We predict a strong enhancement of multijet production in proton-nucleus collisions at collider energies, as compared to a naive expectation of a cross section $\propto A$. The study of the process would allow to measure, for the first time, the double parton distribution functions in a nucleon in a model independent way and hence to study both the longitudinal and the transverse correlations of partons.Comment: 12 pages, 2 figure

Elastic constants and dynamics in nematic liquid crystals

In this paper we present molecular dynamics calculations of the Frank elastic constants, and associated time correlation functions, in nematic liquid crystals. We study two variants of the Gay-Berne potential, and use system sizes of half a million molecules, significantly larger than in previous studies of elastic behaviour. Equilibrium orientational fluctuations in reciprocal (k-) space were calculated, to determine the elastic constants by fitting at low k; our results indicate that small system size may be a source of inaccuracy in previous work. Furthermore the dynamics of the Gay-Berne nematic were studied by calculating time correlation functions of components of the order tensor, together with associated components of the velocity field, for a set of wave vectors k. Confirming our earlier work, we found exponential decay for splay and twist correlations, and oscillatory exponential decay for the bend correlation. In the present work, we confirm similar behaviour for the corresponding velocity components. In all cases the decay rates, and oscillation frequencies, were found to be accurately proportional to k-squared for small k, as predicted by the equations of nematodynamics. However, the observation of oscillatory bend fluctuations, and corresponding oscillatory shear flow decay, is in contradiction to the usual assumptions appearing in the literature, and in standard texts. We discuss the advantages and drawbacks of using large systems in these calculations

Membrane Technology for the Recovery of Lignin: A Review

Citation: Humpert, D., Ebrahimi, M., & Czermak, P. (2016). Membrane Technology for the Recovery of Lignin: A Review. Membranes, 6(3), 13. doi:10.3390/membranes6030042Utilization of renewable resources is becoming increasingly important, and only sustainable processes that convert such resources into useful products can achieve environmentally beneficial economic growth. Wastewater from the pulp and paper industry is an unutilized resource offering the potential to recover valuable products such as lignin, pigments, and water [1]. The recovery of lignin is particularly important because it has many applications, and membrane technology has been investigated as the basis of innovative recovery solutions. The concentration of lignin can be increased from 62 to 285 g.L-1 using membranes and the recovered lignin is extremely pure. Membrane technology is also scalable and adaptable to different waste liquors from the pulp and paper industry

Production of J/ψJ/\psi-pairs at HERA-N⃗\vec{{\rm N}}

The production of $J/\psi$-pairs as a possible measure of the polarized gluon distribution $\Delta G(x)$ is studied for proton--nucleon collisions at \sqrt{s} =40\;\mbox{GeV}^2 (HERA-$\vec{{\rm N}}$). Possibilities of reconstructing the helicity state of at least one of the $J/\psi$'s are critically reviewed. The observation of production asymmetries in the single polarized mode of HERA-$\vec{{\rm N}}$ is found to be not feasible.Comment: 8 pages, LATeX, 3 figures availabe as .uu-fil

High-pTp_T ψψ\psi\psi production as signals for Double Parton scattering at hadron colliders

We present an analysis of the \psi\psi production from double parton (DP) sacttering and single parton (SP) scattering in the large p_T region via color-octet gluon fragmentation. We find that at the Tevatron the DP \psi\psi production is at the edge of the detectability at present, and at the LHC the DP cross section will dominate over the SP cross section in the lower p_T(min) region (i.e., p_T(min)<7GeV). We also conclude that the color-octet mechanism is of crucial importance to the double j/psi production at high energy hadron colliders.Comment: Revtex, 12 pages, 3 Postscript figure

Scale Factor in Double Parton Collisions and Parton Densities in Transverse Space

The scale factor $\sigma_{eff}$, which characterizes double parton collisions in high energy hadron interactions, is a direct manifestation of the distribution of the interacting partons in transverse space, in such a way that different distributions give rise to different values of $\sigma_{eff}$ in different double parton collision processes. We work out the value of the scale factor in a few reactions of interest, in a correlated model of the multi-parton density of the proton recently proposed.Comment: 10 pages, 2 figure

A double parton scattering background to Higgs boson production at the LHC

The experimental capability of recognizing the presence of b quarks in complex hadronic final states has addressed the attention towards final states with b\bar{b} pairs for observing the production of the Higgs boson at the LHC, in the intermediate Higgs mass range.We point out that double parton scattering processes are going to represent a sizeable background to the process.Comment: 9 pages, 2 figure

Double parton distributions in the leading logarithm approximation of perturbative QCD

Recent CDF measurements of the inclusive cross section for a double parton scattering attach a great importance to any theoretical calculations of two-particle distribution functions. Using a parton interpretation of the leading logarithm diagrams of perturbative QCD theory, generalized Lipatov-Altarelli-Parisi-Dokshitzer equations for the two-parton distributions are re-obtained. The solutions of these equations are not at all the product of two single-parton distributions what is usually applied to the current analysis as ansatz.Comment: 8 pages, LaTe

Signals for Double Parton Scattering at the Fermilab Tevatron

Four double-parton scattering processes are examined at the Fermilab Tevatron energy. With optimized kinematical cuts and realistic parton level simulation for both signals and backgrounds, we find large samples of four-jet and three-jet+one-photon events with signal to background ratio being 20\%-30\%, and much cleaner signals from two-jet+two-photon and two-jet+$e^+e^-$ final states. The last channel may provide the first unambiguous observation of multiple parton interactions, even with the existing data sample accumulated by the Tevatron collider experiments.Comment: 7 pages, plain LaTeX, 2 tables, no figures. A compressed PS file is available by anonymous ftp at ftp://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-945.ps.

Double parton scatterings in b-quark pairs production at the LHC

A sizable rate of events where two pairs of b-quarks are produced contemporarily is foreseen at the CERN LHC, as a consequence of the large parton luminosity. At very high energies both single and the double parton scatterings contribute to the process, the latter mechanisms, although power suppressed, giving the dominant contribution to the integrated cross section.Comment: 17 pages, 6 figure