QCD Physics with ZEUS and H1 at HERA

A review is presented of recent results in QCD from the H1 and ZEUS experiments at HERA, emphasizing the use of higher order calculations to describe the data.Comment: 12 pages, 15 figures, invited review paper for Mod. Phys. Lett

Global analysis of fragmentation functions for pions and kaons and their uncertainties

We present new sets of pion and kaon fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either pions or kaons identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions without the need of non trivial flavor symmetry assumptions. The resulting sets are in good agreement with all data analyzed, which cover a much wider kinematical range than in previous fits. An extensive use of the Lagrange multiplier technique is made in order to assess the uncertainties in the extraction of the fragmentation functions and the synergy from the complementary data sets in our global analysis.Comment: 28 pages, 25 figure

Exclusive diffractive processes at HERA within the dipole picture

We present a simultaneous analysis, within an impact parameter dependent saturated dipole model, of exclusive diffractive vector meson (J/psi, phi and rho) production, deeply virtual Compton scattering and the total gamma* p cross section data measured at HERA. Various cross sections measured as a function of the kinematic variables Q^2, W and t are well described, with little sensitivity to the details of the vector meson wave functions. We determine the properties of the gluon density in the proton in both longitudinal and transverse dimensions, including the impact parameter dependent saturation scale. The overall success of the description indicates universality of the emerging gluon distribution and proton shape.Comment: 48 pages, 28 figures, the final version to appear in Physical Review

Effects of processing parameters on chemical and physical properties of enzymatically interesterified beef tallow–corn oil blends

The purpose of this study was to improve some physical and chemical characteristics of tallow through enzymatic interesterification process with corn oil and to investigate effects of process parameters on chemical and physical properties of obtained products. Full factorial design was constructed using blend ratio and reaction time as process parameters. Enzymatic interesterification was catalyzed with sn-1,3-specific lipase. Interesterified lipids have higher free fatty acid content and lower oxidative stability compared to initial blends. Interesterification did not cause trans-fatty acid formation and products mostly contained \u3b2 crystals. Solid fat content and slip melting point decreased up to 6 hr of interesterification; however, longer reaction times have negative effects on these parameters. Statistical analyses\u2019 results confirmed that reaction time is highly important for enzymatic interesterification. Practical applications: Some of interesterified lipids can be utilized as alternatives to margarines or butterfat due to their lower trans-fatty acid content and crystal morphology

Investigation of the coupling asymmetries at double-slit interference experiments

Double-slit experiments inferring the phase and the amplitude of the transmission coefficient performed at quantum dots (QD), in the Coulomb blockade regime, present anomalies at the phase changes depending on the number of electrons confined. This phase change cannot be explained if one neglects the electron-electron interactions. Here, we present our numerical results, which simulate the real sample geometry by solving the Poisson equation in 3D. The screened potential profile is used to obtain energy eigenstates and eigenvalues of the QD. We find that, certain energy levels are coupled to the leads stronger compared to others. Our results give strong support to the phenomenological models in the literature describing the charging of a QD and the abrupt phase changes.Comment: conference paper, 50th anniversary of Aharonov-Bohm effec

Impact of surface waterproofing products on the performance of brick masonry through the moisture exposure life-cycle

Moisture is one of the major causes of damage to building systems, affecting the hygrothermal performance and durability of building systems. Surface treatment products are available in the market that can influence the hygric performance of masonry facades under water exposure. These are of a wide range of chemical compositions, and they claim to waterproof the masonry surfaces while not diminishing vapour transmissibility. This paper presents and discusses the findings from a series of benchtests carried out to measure hydrophobicity, water absorption and water vapour transmission following the relevant codes for an appraisal of the hygric behaviour change in brick masonry induced by waterproofing through three distinct phases of the life-cycle of moisture exposure, i.e. first contact with water, wetting and drying. To this end, 4 waterproofing products including silane/siloxane blend liquid and cream, and acrylic and stearate-based liquids were selected for testing, along with 3 brick types common in the 50s and 60s to be representative of the majority of the UK building stock. The findings show that the treatment products indeed enhance the surface hydrophobicity and reduce water absorption while allowing water vapour transmission to differing degrees: silane/siloxane blend cream overall was found the most effective throughout the moisture-exposure life-cycle, with an average of ~96% reduction in water absorption and 18% of increase in water vapour resistance in comparison to the untreated case, followed by the stearate-based liquid with 57% reduction in water absorption and 12% increase in water vapour resistance. The acrylic-based product demonstrated good performance in hydrophobicity and water vapour transmission tests, however led to a comparatively higher water absorption capacity than the other treatment products with only ~40% reduction in comparison to the base-case. Finally, silane/siloxane blend liquid was found to lead to the lowest contact angle, demonstrating a lower-than-others capacity to developing surface hydrophobicity, and led to 35% reduction in water absorption and 28% increase in water vapour resistance, making it the poorest product in the dataset to lead to watertight and vapour open systems under water exposure. Based on the test results it was also deemed beneficial to use masonry specimens to account for its composite nature, rather than using results obtained from brick and mortar separately to infer the wall response under exposure

Geometrical Effects in Determination of Fickian Mass Diffusivity of Polymers

Hydrophilicity of polymers makes them prone to moisture absorption that leads to degradation of mechanical properties. Kinetics of moisture ingress needs to be fully characterized to perform reliable designs with polymeric materials. The rate of diffusion is the essential parameter in determining the time scale of the moisture uptake in polymeric materials. The model from which the diffusion coefficient is to be determined can be mathematically complex when the viscoelastic relaxation and diffusion time scales are comparable (i.e. Deborah Number ~ l). However, Fickian type of diffusion is shown to be adequate in modeling the moisture absorption into a broad range of polymers. Most methods for determining the diffusion coefficient are based on the solution of Fick's second law in semi-infinite and slab domains from which, a closed form solution has been adapted by the American Society of Testing and Materials (ASTM). However, those techniques either do not consider the errors due to finite sample dimension or the correction factors provided are not precise enough. In addition, fabrication of samples conforming ASTM standard (i.e. length or width to thickness ratio of 100 or greater) may not be practical due to difficulties in producing and testing very thin coupons. In this study, the solution of the Fickian diffusion equation for a three-dimensional rectangular domain is utilized to generate mass gain data for geometries with length to thickness ratios ranging from l to I 00. These data are then used to demonstrate the errors introduced by the two conventional methods used to determine the diffusion coefficient for sample dimensions deviating from an infinitely wide slab. After applying the correction factor suggested by ASTM, up to 13% error is observed in the diffusion coefficient. In order to improve the prediction of diffusion coefficient, a least square curve fit method, which yields accurate predictions regardless of the sample geometry, is proposed.YesPeer reviewed and presented at the 23rd Oklahoma AIAA/ASME Symposium

Non-isothermal phase-field simulations of laser-written in-plane SiGe heterostructures for photonic applications

Advanced solid-state devices, including lasers and modulators, require semiconductor heterostructures for nanoscale engineering of the electronic bandgap and refractive index. However, existing epitaxial growth methods are limited to fabrication of vertical heterostructures grown layer by layer. Here, we report the use of finite-element-method-based phase-field modelling with thermocapillary convection to investigate laser inscription of in-plane heterostructures within silicon-germanium films. The modelling is supported by experimental work using epitaxially-grown Si0.5Ge0.5 layers. The phase-field simulations reveal that various in-plane heterostructures with single or periodic interfaces can be fabricated by controlling phase segregation through modulation of the scan speed, power, and beam position. Optical simulations are used to demonstrate the potential for two devices: graded-index waveguides with Ge-rich (>70%) cores, and waveguide Bragg gratings with nanoscale periods (100–500 nm). Periodic heterostructure formation via sub-millisecond modulation of the laser parameters opens a route for post-growth fabrication of in-plane quantum wells and superlattices in semiconductor alloy films

Precision measurements of alphas at HERA

Recent determinations of alphas(Mz) from the H1 and ZEUS Collaborations using inclusive-jet cross-section measurements in neutral current deep inelastic scattering at high Q2 are presented. A combined value of alphas(mz)=0.1198 +- 0.0019 (exp.) +- 0.0026 (th.) was obtained from these measurements. The determinations of alphas at various scales clearly show the running of the coupling from HERA jet data alone and in agreement with the prediction of QCD.Comment: 5 pages, 4 figure

A global analysis of inclusive diffractive cross sections at HERA

We describe the most recent data on the diffractive structure functions from the H1 and ZEUS Collaborations at HERA using four models. First, a Pomeron Structure Function (PSF) model, in which the Pomeron is considered as an object with parton distribution functions. Then, the Bartels Ellis Kowalski Wusthoff (BEKW) approach is discussed, assuming the simplest perturbative description of the Pomeron using a two-gluon ladder. A third approach, the Bialas Peschanski (BP) model, based on the dipole formalism is then described. Finally, we discuss the Golec-Biernat-W\"usthoff (GBW) saturation model which takes into account saturation effects. The best description of all avaible measurements can be achieved with either the PSF based model or the BEKW approach. In particular, the BEKW prediction allows to include the highest $\beta$ measurements, which are dominated by higher twists effects and provide an efficient and compact parametrisation of the diffractive cross section. The two other models also give a good description of cross section measurements at small $x$ with a small number of parameters. The comparison of all predictions allows us to identify interesting differences in the behaviour of the effective pomeron intercept and in the shape of the longitudinal component of the diffractive structure functions. In this last part, we present some features that can be discriminated by new experimental measurements, completing the HERA program.Comment: 32 pages, 18 figure