Migration of a Carbon Adatom on a Charged Single-Walled Carbon Nanotube

We find that negative charges on an armchair single-walled carbon nanotube (SWCNT) can significantly enhance the migration of a carbon adatom on the external surfaces of SWCNTs, along the direction of the tube axis. Nanotube charging results in stronger binding of adatoms to SWCNTs and consequent longer lifetimes of adatoms before desorption, which in turn increases their migration distance several orders of magnitude. These results support the hypothesis of diffusion enhanced SWCNT growth in the volume of arc plasma. This process could enhance effective carbon flux to the metal catalyst

Can one improve the Froissart bound?

We explain why we hope that the Froissart bound can be improved, either qualitatively or, more likely, quantitatively, by making a better use of unitarity, in particular elastic unitarity. In other instances (Gribov's theorem) elastic unitarity played a crucial role. A preliminary requirement for this is to work with an appropriate average of the cross-section, to make the problem well defined. This is possible, without destroying the Lukaszuk--Martin bound.Comment: 4 pages, latex with AIP style, Talk given at "Diffraction 2008", Lalonde-les-Maures, France, September 2008. Missing square root restored p. 3. pi^2->pi corrected in eq. (1

Mechanisms of exclusive meson production at high energies

I discuss mechanisms of exclusive production of mesons at high energies. Some illustrative examples for the FNAL Tevatron and CERN LHC as well as for lower energies are shown.Comment: 5 pages, 6 figures based on a talk presented at Diffraction 2008, La Londe-les-Maures, France, September 200

The Color Dipole Picture and the Ratio of the Longitudinal to the Transverse Photoabsorption Cross Section

The transverse size of q q-bar fluctuations of a longitudinally polarized photon is reduced relative to the transerve size of q q-bar fluctuation of a transversely polarized photon. This implies a model-independent prediction of the ratio R(W2,Q2)=sigma_L/sigma_T=0.375, or, equivalently, F_L/F_2=0.27, for x=Q2/W2<<1 and Q2 sufficiently large, while R(W2,Q2)=0.50, if this effect is ignored. Experimental data from HERA confirm the transverse-size reduction.Comment: 6 pages, 2 figures, presented at Diffraction 200

Multipomeron Cuts and Hard Processes on Nuclei

With nuclear targets comes a new scale into the pQCD description of hard processes - the saturation scale. In the saturation regime, the familiar linear k_\perp-factorization breaks down and must be replaced by a nonlinear k_\perp-factorization, which accounts for absorptive and multiple scattering corrections to the hard process. Predictions for partial cross sections corresponding to a fixed number of cut Pomerons (the topological cross sections) can be obtained in a surprisingly straightforward manner. We discuss some applications to deep inelastic scattering.Comment: 4 pages, 2 figures, a talk given at Diffraction 2008: International Workshop On Diffraction In High Energy Physics; 9-14 Sep 2008, La Londe-les-Maures, Franc

ALICE diffractive physics in p-p and Pb-Pb collisions at the LHC

The ALICE detector is introduced and a double gap trigger is presented. The interest in studying double pomeron induced events both in proton-proton and in lead-lead reactions is discussed.Comment: 5 pages, 5 figures, to appear in proceedings conference Diffraction 2008, La Londe-les-Maures, France, sep 9-14, 200

The BSW Impact Picture 30 Years After

Thirty years ago Bourrely-Soffer-Wu (BSW) investigated an impact picture description of $p-p$ and $\bar p -p$ elastic scattering with success. For this anniversary, a short review of the main features of this picture will be presented with its evolution over the years. The future experiments at the LHC collider will provide decisive tests for the impact picture at high energy.Comment: 4 pages, 2 figures, Contribution to Diffraction 2008, International Workshop on Diffraction in High Energy Physics, La Londe-les-Maures, September 9-14 200

NLO Evolution of Color Dipoles in N = 4 SYM

The small-$x_B$ deep inelastic scattering in the saturation region is governed by the non-linear evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the BK equation for the evolution of color dipoles. I discuss recent calculation of the next-to-leading order evolution of color dipoles in QCD and ${\cal N}=4$ SYM.Comment: 4 pages, Prepared for the International Workshop on Diffraction in High-Energy Physics in La Londe-les-Maures, France, 9-14 September 200

Inclusive One Jet Production With Multiple Interactions in the Regge Limit of pQCD

DIS on a two nucleon system in the regge limit is considered. In this framework a review is given of a pQCD approach for the computation of the corrections to the inclusive one jet production cross section at finite number of colors and discuss the general results.Comment: 4 pages, latex, aicproc format, Contribution to the proceedings of "Diffraction 2008", 9-14 Sep. 2008, La Londe-les-Maures, Franc

Dynamic versus Static Structure Functions and Novel Diffractive Effects in QCD

Initial- and final-state rescattering, neglected in the parton model, have a profound effect in QCD hard-scattering reactions, predicting single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high centrality heavy ion collisions. I emphasize the importance of distinguishing between static observables such as the probability distributions computed from the square of the light-front wavefunctions versus dynamical observables which include the effects of rescattering.Comment: 8 pages, 1 figure. Presented at Diffraction 2008: International Workshop On Diffraction In High Energy Physics 9-14 Sep 2008, La Londe-les-Maures, Franc