Phenomenology on the QCD dipole picture revisited

We perform an adjust to the most recent structure function data, considering the QCD dipole picture applied to ep scattering. The structure function F2 at small x and intermediate Q2 can be described by the model containing an economical number of free-parameters, which encodes the hard Pomeron physics. The longitudinal structure function and the gluon distribution are predicted without further adjustments. The data description is effective, whereas a resummed next-to-leading level analysis is deserved.Comment: 18 pages, 6 figures. Version to be published in Eur. Phys. J.

Universality and tree structure of high energy QCD

Using non-trivial mathematical properties of a class of nonlinear evolution equations, we obtain the universal terms in the asymptotic expansion in rapidity of the saturation scale and of the unintegrated gluon density from the Balitsky-Kovchegov equation. These terms are independent of the initial conditions and of the details of the equation. The last subasymptotic terms are new results and complete the list of all possible universal contributions. Universality is interpreted in a general qualitative picture of high energy scattering, in which a scattering process corresponds to a tree structure probed by a given source.Comment: 4 pages, 3 figure

Geometric scaling as traveling waves

We show the relevance of the nonlinear Fisher and Kolmogorov-Petrovsky- Piscounov (KPP) equation to the problem of high energy evolution of the QCD amplitudes. We explain how the traveling wave solutions of this equation are related to geometric scaling, a phenomenon observed in deep-inelastic scattering experiments. Geometric scaling is for the first time shown to result from an exact solution of nonlinear QCD evolution equations. Using general results on the KPP equation, we compute the velocity of the wave front, which gives the full high energy dependence of the saturation scale.Comment: 4 pages, 1 figure. v2: references adde

Hamiltonian solutions of the 3-body problem in (2+1)-gravity

We present a full study of the 3-body problem in gravity in flat (2+1)-dimensional space-time, and in the nonrelativistic limit of small velocities. We provide an explicit form of the ADM Hamiltonian in a regular coordinate system and we set up all the ingredients for canonical quantization. We emphasize the role of a U(2) symmetry under which the Hamiltonian is invariant and which should generalize to a U(N-1) symmetry for N bodies. This symmetry seems to stem from a braid group structure in the operations of looping of particles around each other, and guarantees the single-valuedness of the Hamiltonian. Its role for the construction of single-valued energy eigenfunctions is also discussed.Comment: 25 pages, no figure. v2: some calculation details removed to make the paper more concise (see v1 for the longer version), minor correction in a formula in the section on quantization, references added; results and conclusions unchange

Macro and Micro Plastics Sorb and Desorb Metals and Act As A Point Source of Trace Metals To Coastal Ecosystems

Nine urban intertidal regions in Burrard Inlet, Vancouver, British Columbia, Canada, were sampled for plastic debris. Debris included macro and micro plastics and originated from a wide diversity of uses ranging from personal hygiene to solar cells. Debris was characterized for its polymer through standard physiochemical characteristics, then subject to a weak acid extraction to remove the metals, zinc, copper, cadmium and lead from the polymer. Recently manufactured low density polyethylene (LDPE), nylon, polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC) were subject to the same extraction. Data was statistically analyzed by appropriate parametric and non-parametric tests when needed with significance set at P < 0.05. Polymers identified in field samples in order of abundance were; PVC (39), LDPE (28), PS (18), polyethylene (PE, 9), PP (8), nylon (8), high density polyethylene (HDPE, 7), polycarbonate (PC, 6), PET (6), polyurethane (PUR, 3) and polyoxymethylene (POM, 2). PVC and LDPE accounted for 46% of all samples. Field samples of PVC, HDPE and LDPE had significantly greater amounts of acid extracted copper and HDPE, LDPE and PUR significantly greater amounts of acid extracted zinc. PVC and LDPE had significantly greater amounts of acid extracted cadmium and PVC tended to have greater levels of acid extracted lead, significantly so for HDPE. Five of the collected items demonstrated extreme levels of acid extracted metal; greatest concentrations were 188, 6667, 698,000 and 930 μgg-1 of copper, zinc, lead and cadmium respectively recovered from an unidentified object comprised of PVC. Comparison of recently manufactured versus field samples indicated that recently manufactured samples had significantly greater amounts of acid extracted cadmium and zinc and field samples significantly greater amounts of acid extracted copper and lead which was primarily attributed to metal extracted from field samples of PVC. Plastic debris will affect metals within coastal ecosystems by; 1) providing a sorption site (copper and lead), notably for PVC 2) desorption from the plastic i.e., the “inherent” load (cadmium and zinc) and 3) serving as a point source of acute trace metal exposure to coastal ecosystems. All three mechanisms will put coastal ecosystems at risk to the toxic effects of these metals

Total gluon shadowing due to fluctuation effects

We show a new physical phenomenon expected for the ratio R_{pA} of the unintegrated gluon distribution of a nucleus over the unintegrated gluon distribution of a proton scaled up by the atomic factor A^{1/3} in the fluctuation-dominated (diffusive scaling) region at high energy. We calculate the dependence of R_{pA} on the atomic number A, the rapidity Y and the transverse gluon momentum k_{\perp}. We find that R_{pA} exhibits an increasing gluon shadowing with growing rapidity, approaching 1/A^{1/3} at asymptotic rapidities which means total gluon shadowing, due to the effect of gluon number fluctuations or Pomeron loops. The increase of R_{pA} with rising gluon momentum decreases as the rapidity grows. In contrast, in the geometric scaling region where the effect of fluctuations is negligible, the ratio R_{pA} shows only partial gluon shadowing in the fixed-coupling case, basically independent on the rapidity and the gluon momentum.Comment: 12 pages, 1 figure; two plots and further explanations added; matches version accepted for publicatio

A novel homozygous R764H mutation in crumbs homolog 1 causes autosomal recessive retinitis pigmentosa.

PURPOSE: Retinitis pigmentosa (RP; MIM 268000) is a hereditary disease characterized by poor night vision and progressive loss of photoreceptors, eventually leading to blindness. This degenerative process primarily affects peripheral vision due to the loss of rods. Autosomal recessive RP (arRP) is clinically and genetically heterogeneous. It has been associated with mutations in different genes, including CRB1 (crumbs homolog 1). The aim of this study was to determine the causative gene in a Tunisian patient with arRP born to non-consanguineous parents. METHODS: Four accessible family members were included. They underwent full ophthalmic examination with best-corrected Snellen visual acuity, fundus photography and fluorescein angiography. Haplotype analysis was used to evaluate homozygosity in the family to 20 arRP loci. All exons and intron-exon junctions of candidate genes not excluded by haplotype analysis were PCR amplified and directly sequenced. RESULTS: The proband was a 43-year-old female patient. Best-corrected visual acuity was 20/63 (right eye) and 20/80 (left eye). Visual loss began during the third decade. Funduscopic examination and fluorescein angiography revealed typical advanced RP changes with bone spicule-like pigment deposits in the posterior pole and the midperiphery along with retinal atrophy, narrowing of the vessels, and waxy optic discs. Haplotype analysis revealed homozygosity with microsatellite markers D1S412 and D1S413 on chromosome 1q31.3. These markers flanked CRB1. Our results excluded linkage of all the other arRP loci/genes tested. Sequencing of the 12 coding exons and splice sites of CRB1 disclosed a homozygous missense mutation in exon 7 at nucleotide c. 2291G>A, resulting in an arginine to histidine substitution (p.R764H). CONCLUSIONS: R764H is a novel mutation associated with CRB1-related arRP. Previously, an R764C mutation was reported. Extending the mutation spectrum of CRB1 with additional families is important for genotype-phenotype correlations and characterization of the scope of mutation

Diffractive photon dissociation in the saturation regime from the Good and Walker picture

Combining the QCD dipole model with the Good and Walker picture, we formulate diffractive dissociation of a photon of virtuality Q^2 off a hadronic target, in the kinematical regime in which Q is close to the saturation scale and much smaller than the invariant mass of the diffracted system. We show how the obtained formula compares to the HERA data and discuss what can be learnt from such a phenomenology. In particular, we argue that diffractive observables in these kinematics provide useful pieces of information on the saturation regime of QCD.Comment: 17 pages, 7 figures, revte

Travelling waves and impact-parameter correlations

It is usually assumed that the high-energy evolution of partons in QCD remains local in coordinate space. In particular, fixed impact-parameter scattering is thought to be in the universality class of one-dimensional reaction-diffusion processes as if the evolutions at different points in the transverse plane became uncorrelated through rapidity evolution. We check this assumption by numerically comparing a toy model with QCD-like impact-parameter dependence to its exact counterpart with uniform evolution in impact-parameter space. We find quantitative differences, but which seem to amount to a mere rescaling of the strong coupling constant. Since the rescaling factor does not show any strong alpha_s-dependence, we conclude that locality is well verified, up to subleading terms at small alpha_s.Comment: 13 pages, 11 figures; corrected typo

Deep Inelastic Scattering in Conformal QCD

We consider the Regge limit of a CFT correlation function of two vector and two scalar operators, as appropriate to study small-x deep inelastic scattering in N=4 SYM or in QCD assuming approximate conformal symmetry. After clarifying the nature of the Regge limit for a CFT correlator, we use its conformal partial wave expansion to obtain an impact parameter representation encoding the exchange of a spin j Reggeon for any value of the coupling constant. The CFT impact parameter space is the three-dimensional hyperbolic space H3, which is the impact parameter space for high energy scattering in the dual AdS space. We determine the small-x structure functions associated to the exchange of a Reggeon. We discuss unitarization from the point of view of scattering in AdS and comment on the validity of the eikonal approximation. We then focus on the weak coupling limit of the theory where the amplitude is dominated by the exchange of the BFKL pomeron. Conformal invariance fixes the form of the vector impact factor and its decomposition in transverse spin 0 and spin 2 components. Our formalism reproduces exactly the general results predict by the Regge theory, both for a scalar target and for gamma*-gamma* scattering. We compute current impact factors for the specific examples of N=4 SYM and QCD, obtaining very simple results. In the case of the R-current of N=4 SYM, we show that the transverse spin 2 component vanishes. We conjecture that the impact factors of all chiral primary operators of N=4 SYM only have components with 0 transverse spin.Comment: 44+16 pages, 7 figures. Some correction