Search

We present a systematic interpretation of vector boson scattering (VBS) and diboson measurements from the LHC in the framework of the dimension-six Standard Model Effective Field Theory (SMEFT). We consider all available measurements of VBS fiducial cross-sections and differential distributions from ATLAS and CMS, in most cases based on the full Run II luminosity, and use them to constrain 16 independent directions in the dimension-six EFT parameter space. Compared to the diboson measurements, we find that VBS provides complementary information on several of the operators relevant for the description of the electroweak sector. We also quantify the ultimate EFT reach of VBS measurements via dedicated projections for the High Luminosity LHC. Our results motivate the integration of VBS processes in future global SMEFT interpretations of particle physics data., Comment: 56 pages. Version 2: Fixed normalisation factor in the definition of the Wilson coefficients. Figures 3.11 and 4.8 replaced. References added

We quantify the impact of unpolarized lepton-proton and lepton-nucleus inclusive deep-inelastic scattering (DIS) cross section measurements from the future Electron-Ion Collider (EIC) on the proton and nuclear parton distribution functions (PDFs). To this purpose we include neutral- and charged-current DIS pseudodata in a self-consistent set of proton and nuclear global PDF determinations based on the NNPDF methodology. We demonstrate that the EIC measurements will reduce the uncertainty of the light quark PDFs of the proton at large values of the momentum fraction $x$, and, more significantly, of the quark and gluon PDFs of heavy nuclei, especially at small and large $x$. We illustrate the implications of the improved precision of nuclear PDFs for the interaction of ultra-high energy cosmic neutrinos with matter., 11 pages, 5 figures, In the context of the Electron-Ion collider yellow report

We review the current status of Parton Distribution Function (PDF) determinations for unpolarized and longitudinally polarized protons and for unpolarized nuclei, which are probed by high-energy hadronic scattering in perturbative Quantum Chromodynamics (QCD). We present the established theoretical framework, the experimental information, and the methodological aspects inherent to any modern PDF extraction. Furthermore, we summarize the present knowledge of PDFs and discuss their limitations in both accuracy and precision relevant to advance our understanding of QCD proton substructure and pursue our quest for precision in the Standard Model and beyond. In this respect, we highlight various achievements, discuss contemporary issues in PDF analyses, and outline future directions of progress., 34 pages, 5 figures, 2 tables; invited review submitted to Annual Review of Nuclear and Particle Science, Vol.70 (2020); version accepted for publication; various references updated; improved discussion on implications for astroparticle physics

We perform a combined analysis of inclusive electron scattering data from $A=3$ nuclei in the deep-inelastic and quasielastic scattering regions, using Monte Carlo analysis methods and the nuclear weak binding approximation to establish the range over which the data can be described within the same theoretical framework. Comparison with quasielastic $^3$He cross sections from SLAC and Jefferson Lab suggests that most features of the $x \gtrsim 1$ data can be reasonably well described in the impulse approximation with finite-$Q^2$ nuclear smearing functions for momentum transfers $Q^2 \gtrsim 1$ GeV$^2$. For the DIS region, we analyze the recent $^3$He to deuterium cross section ratio from the Jefferson Lab E03-103 experiment to explore the possible isospin dependence of the nuclear effects. We discuss the implications of this for the MARATHON experiment at Jefferson Lab, and outline how a Bayesian analysis of $^3$He, $^3$H and deuterium data can robustly determine the free neutron structure function., 45 pages, 14 figures

In this contribution we present a status report on the recent progress towards an analysis of nuclear parton distribution functions (nPDFs) using the NNPDF methodology. We discuss how the NNPDF fitting approach can be extended to account for the dependence on the atomic mass number $A$, and introduce novel algorithms to improve the training of the neural network parameters within the NNPDF framework. Finally, we present preliminary results of a nPDF fit to neutral current deep-inelastic lepton-nucleus scattering data, and demonstrate how one can validate the new fitting methodology by means of closure tests., 8 pages, 3 figures, to appear in the proceedings of Diffraction and Low-x 2018

Traditional international trade models explain the sources of comparative advantage and show how a country as a whole gains from trade and from terms-of-trade improvement. The traditional models assumed competitive market-determined outcomes with passive or benevolent government. Income-distribution consequences of trade policy were noted. The models did not address the politics of trade policy, the study of which requires two premises consistent with public-choice principles: (1) that political self-interest underlies policy decisions rather than benevolent-government social-welfare objectives, and (2) political decision makers prefer creation of politically assignable rents to non-assignable budgetary revenue or aggregate country-wide gains from free trade or terms-of-trade improvement. These two premises are acknowledged in the first-generation of models of politicized trade policy. A second generation of models includes the first but not the second premise. It is documented that public-choice premises have not always been included in mainstream economic models. The second-generation models devoid of the primacy of rents in trade-policy determination are mainstream for many members of the academic international trade community. The chapter explains how, by not including the political preference for rents over budgetary revenue, the second-generation models are at variance with the actual conduct of trade policy. Public-choice concepts are also used to re-evaluate a wide range of traditional trade-policy conclusions and recommendations. Empirical evidence is reviewed and interpreted.

We perform the first simultaneous extraction of unpolarized parton distributions and fragmentation functions from a Monte Carlo analysis of inclusive and semi-inclusive deep-inelastic scattering, Drell-Yan lepton-pair production, and single-inclusive $e^+ e^-$ annihilation data. We use data resampling techniques to thoroughly explore the Bayesian posterior distribution of the extracted functions, and use $k$-means clustering on the parameter samples to identify the configurations that give the best description across all reactions. Inclusion of the semi-inclusive data reveals a strong suppression of the strange quark distribution at parton momentum fractions $x \gtrsim 0.01$, in contrast with the ATLAS observation of enhanced strangeness in $W^\pm$ and $Z$ production at the LHC. Our study reveals significant correlations between the strange quark density and the strange $\to$ kaon fragmentation function needed to simultaneously describe semi-inclusive $K^\pm$ production data from COMPASS and inclusive $K^\pm$ spectra in $e^+ e^-$ annihilation from ALEPH and SLD, as well as between the strange and light antiquark densities in the proton., Comment: 6 pages, 4 figures; version to appear in Phys. Rev. D

Engineered electromagnetic surfaces (EES) are surfaces which can be fabricated on a thin layer of plastic using a low-cost printed electronics technology. These surfaces can be installed at strategic locations in indoor and outdoor propagation environments to improve the coverage or mitigate interference at millimeter-wave bands for 5G applications. Two methods used to embed uniform and non-uniform EESs into ray-tracing software tools are introduced along with a propagation prediction example for an outdoor scenario that incorporates EESs.

We perform the first global QCD analysis of polarized inclusive and semi-inclusive deep-inelastic scattering and single-inclusive $e^+e^-$ annihilation data, fitting simultaneously the parton distribution and fragmentation functions using the iterative Monte Carlo method. Without imposing SU(3) symmetry relations, we find the strange polarization to be very small, consistent with zero for both inclusive and semi-inclusive data, which provides a resolution to the strange quark polarization puzzle. The combined analysis also allows the direct extraction from data of the isovector and octet axial charges, and is consistent with a small SU(2) flavor asymmetry of the polarized sea., 5 pages, 4 figures

Ricardo’s contribution to trade theory is commonly identified with the single-factor model that bears his name. But Ricardo’s contribution to the theory of rent is also fundamental to the currently active literature on the political economy of trade policy. The multi-factor model often employed in this literature is thoroughly Ricardian.

We perform the first iterative Monte Carlo (IMC) analysis of fragmentation functions constrained by all available data from single-inclusive ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into pions and kaons. The IMC method eliminates potential bias in traditional analyses based on single fits introduced by fixing parameters not well constrained by the data and provides a statistically rigorous determination of uncertainties. Our analysis reveals specific features of fragmentation functions using the new IMC methodology and those obtained from previous analyses, especially for light quarks and for strange quark fragmentation to kaons.

A novel dual-band Frequency Selective Surface (FSS) using double meandered loops is designed to block the transmission of signals at 13 and 24 GHz, while allowing other portions of the RF spectrum to pass. The structure was fabricated using Printed Electronics (PE) technology and both simulated and measured results are reported.

We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at $x \gtrsim 0.1$. The study also provides the first determination of the flavor-separated twist-3 PDFs and the $d_2$ moment of the nucleon within a global PDF analysis., Comment: 54 pages, 18 figures, 6 tables; to appear in Phys. Rev. D

Design techniques have been developed to commercialize reflectarray designs. The use of low-cost, lossy materials in the design of traditional reflectarrays has been shown to substantially reduce their performance, precluding any competitiveness with solid reflectors. A novel design technique is presented that mitigates these losses and allows for performance on a par with commercial reflectors, while maintaining low costs. An atypical but highly successful radome material is also employed, with preliminary results showing ample environmental protection to allow the reflectarray to be used outdoors year-round, while still maintaining excellent electrical performance and low overall costs.

Polarizability has been shown to be a useful route for the calculation of the directivity-to-quality-factor ratio (D/Q) bound of electrically small antennas of arbitrary shape. We demonstrate that the same integral-equation-based moment method formulation used to determine the radiation patterns and input impedance of such antennas can also be used to estimate its polarizability, and hence D/Q bounds.

Several authors have described the use of subwavelength inter-element spacing as a means of improving the performance of reflectarray antennas. This paper examines the use of such a sub-wavelength lattice for improving the performance of sub-reflectarray antennas. This does not yet appear to have been done by others. In addition to studying the scattered field patterns of such sub-reflectarrays on their own, we also inspect their performance when they are used to illuminate a main-reflector, as would be the case in practice.

The spin-dependent cross sections for semi-inclusive lepton-nucleon scattering are derived in the framework of collinear factorization, including the effects of masses of the target and produced hadron at finite momentum transfer squared Q^2. At leading order the cross sections factorize into products of parton distribution and fragmentation functions evaluated in terms of new, mass-dependent scaling variables. The size of the hadron mass corrections is estimated at kinematics relevant for future semi-inclusive deep-inelastic scattering experiments., Comment: 28 pages, 12 figures, published version

I address a complex of globalization issues: the effect of globalization on the skill premium; on unemployment; on the ability of national governments to conduct independent social policies; the relative importance of globalization and exogenous technical change. A large empirical literature concludes that trade has played a relatively minor role, relative to skill-biased technical change, in the rise of the skill premium. This paper replaces the Stolper–Samuelson theorem's focus on inter-sectoral with attention to intra-sectoral relations between inputs. Specifically, I assume out-sourcing and unskilled labor are highly substitutable, equipment and skilled labor are complementary, production methods are flexible, and that the country undertaking out-sourcing has a significantly different structure from that providing it. Globalization then offers a simple and immediate possible explanation for prominent stylized facts regarding the skill premium and the presence of skill-biased technical change.

During the past half century, multilateral trade liberalization has reduced tariffs to historically low levels. The “Received Theory” of multilateral trade agreements, based solely on terms-of-trade externalities between national governments, offers an explanation that has become the conventional wisdom. But it is dramatically inconsistent with actual trade agreements. This paper offers an alternative explanation, based on intergovernmental political externalities, consistent with what we actually observe. With remarkably little necessary formal structure—in particular, no formal bargaining model—this framework (chosen to parallel actual experience) gives an immediate and transparent role to the basic characteristics of contemporary trade agreements: gradual liberalization, reciprocity, nondiscrimination, and multilateralism.

Virtually all current estimates of the maximum carboxylation rate ( V cmax ) of ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco) and the maximum electron transport rate ( J max ) for C 3 species implicitly assume an infinite CO 2 transfer conductance ( g i ). And yet, most measurements in perennial plant species or in ageing or stressed leaves show that g i imposes a significant limitation on photosynthesis. Herein, we demonstrate that many current parameterizations of the photosynthesis model of Farquhar, von Caemmerer & Berry ( Planta 149, 78‐90, 1980) based on the leaf intercellular CO 2 concentration ( C i ) are incorrect for leaves where g i limits photosynthesis. We show how conventional A‐C i curve (net CO 2 assimilation rate of a leaf ‐ A n ‐ as a function of C i ) fitting methods which rely on a rectangular hyperbola model under the assumption of infinite g i can significantly underestimate V cmax for such leaves. Alternative parameterizations of the conventional method based on a single, apparent Michaelis‐Menten constant for CO 2 evaluated at C i [ K m (CO 2 ) i ] used for all C 3 plants are also not acceptable since the relationship between V cmax and g i is not conserved among species. We present an alternative A‐C i curve fitting method that accounts for g i through a non-rectangular hyperbola version of the model of Farquhar et al . (1980). Simulated and real examples are used to demonstrate how this new approach eliminates the errors of the conventional A‐C i curve fitting method and provides V cmax estimates that are virtually insensitive to g i . Finally, we show how the new A‐C i curve fitting method can be used to estimate the value of the kinetic constants of Rubisco in vivo is presented

The internal conductance from intercellular spaces to the sites of carboxylation ( g i ) has only been measured in a few tree species and not in conifers, despite the fact it may impose a large limitation on photosynthesis. The present study provides the first estimates of g i for a coniferous species, and examines variation in g i with height and its relationships to anatomical, biochemical and physiological traits. Measurements were made on upper and lower canopy current-year needles of 50-year-old Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco). Needle thickness and specific leaf area decreased by 30% from the top to bottom of the canopy. These anatomical/morphological changes were accompanied by modest variation in allocation of N to chlorophyll and the chlorophyll a / b ratio. Allocation of N to Rubisco did not vary with height, but the ratio of Rubisco to chlorophyll did owing to the aforementioned changes in allocation to chlorophyll. The value of g i was estimated in one tree from concurrent measurements of carbon isotope discrimination and net photosynthesis. To examine the variation in g i among trees a second independent method based on day respiration and the difference between the chloroplastic and intercellular photocompensation points (photocompensation point method) was used. Estimates of g i obtained by the two methods agreed well with values varying between 0.14 and 0.20 mol m - 2 s - - 1 . It is estimated that g i limits photosynthesis by approximately 20% as compared to an approximately 30% stomatal limitation (under well-watered conditions). The value of g i scaled approximately with maximum rates of photosynthesis, which were significantly greater in upper canopy needles. Nevertheless, g i did not vary significantly with canopy height, owing to greater variability in g i than photosynthesis.

Even as the virtues of the free market are extolled daily, trade between national markets becomes increasingly managed. Such management has long been commonplace in international primary-product markets and in the trade of the now-unfashionable centrally-planned economies. But recent decades have seen the proliferation of management of the trade of manufactures between industrial (and newly industrializing) economies.