Lattice study of infrared behaviour in SU(3) gauge theory with twelve massless flavours
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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The Effects of Silicon and Niobium Concentration on the Solidification Behavior and Microstructure of Cast Monel Alloys
Cast Monel alloys are used in applications requiring a combination of good mechanical properties and excellent resistance to corrosion. Despite prevalent industrial use, relatively few studies have been conducted to investigate the relationships between composition, solidification behavior, and microstructure. Given that these alloys are used in the cast and welded conditions, these factors have a significant influence over the material properties. Here, in this work, microstructural characterization, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry were used to study how changes in Si and Nb concentrations affected the solidification path and microstructure of Monel alloys. It was found that increasing Nb concentration stabilized higher amounts of MC carbides and suppressed graphite formation during solidification. It was also found that the high nominal concentration and segregation of Si to the liquid led to the formation of Ni 31 Si 12 and other silicides via terminal eutectic reactions at the end of solidification. A pseudo-binary solidification diagram was constructed using experimental data and was applied to predict the mass fraction of solidified eutectic as a function of composition. The modeled microstructures were found to be in good agreement with experimentally measured phase fractions.
36 MATERIALS SCIENCE↗
Wilson loops in warped resolved deformed conifolds
We calculate quark-antiquark potentials using the relationship between the expectation value of the Wilson loop and the action of a probe string in the string dual. We review and categorise the possible forms of the dependence of the energy on the separation between the quarks. In particular, we examine the possibility of there being a minimum separation for probe strings which do not penetrate close to the origin of the bulk space, and derive a condition which determines whether this is the case. We then apply these considerations to the flavoured resolved deformed conifold background of Gaillard et al. (2010) . We suggest that the unusual behaviour that we observe in this solution is likely to be related to the IR singularity which is not present in the unflavoured case. - Highlights: > We calculate quark-antiquark potentials using the Wilson loop and the action of a probe string in the string dual. > We review and categorise the possible forms of the dependence of the energy on the separation between the quarks. > We look in particular at the flavoured resolved deformed conifold. > There appears to be unusual behaviour which seems likely to be related to the IR singularity introduced by flavours.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Quantifying the effect of tow architecture variability on the performance of biaxially braided composite tubes
Targeted experiments are performed with stereoscopic digital image correlation to quantify the effect of irregular braid structure on the local surface mechanical response of carbon-fiber reinforced epoxy composite tubes. Virtual models comparing both nonuniform and uniform tow structure of the outer braid of each specimen are integrated into numerical simulations similar to experiments. Experimental and numerical results agree well. Statistical tests are used to support correlations between as-manufactured braid variation ranges to local increases in stress up to 18% compared to an ideal, uniform structure in the elastic regime. Results support improved manufacturing and modeling efforts of defect sensitive braided composites.
36 MATERIALS SCIENCE↗
Interaction of Graphene Quantum Dots with Oligothiophene: A Comprehensive Theoretical Study
Graphene/polythiophene composites are widely used in a variety of optoelectronic devices and applications, e.g., as electrode materials in capacitors and solar cells, but the detailed molecular-level relationship between their structural and electronic properties is not well understood. We present a density functional theory study of these composites using model systems consisting of graphene nanosheets and nanoribbons sandwiched between oligothiophenes (up to 13 monomers in length). These systems are investigated by computing optical band gaps, UV–visible spectra, densities of states, and by analyzing noncovalent interactions in terms of the reduced density gradient. Frontier molecular orbital analysis reveals a significant decrease in the optical band gap upon increasing the concentration of graphene, which can be tuned by adjusting the proportion of graphene using larger nanoribbons. This finding has implications for device design in these materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A Meta-Generalized Gradient Approximation for the Cavity-Dependent Exchange-Correlation Interaction in Strongly Coupled Light–Matter Systems
Strong light–matter coupling in optical cavities enables the manipulation of chemical and physical properties without altering molecular composition. Theoretical modeling of such phenomena requires exchange-correlation (XC) functionals that account for both electron–electron and electron–photon (ep) interactions within quantum electrodynamical density functional theory (QEDFT). In this work, we develop a meta-generalized gradient approximation (meta-GGA) specifically targeting the cavity-dependent XC interaction in strongly coupled light–matter systems. This novel approximation is built upon a new semilocal polarizability approximation, which draws from the jellium-with-a-gap model, and can be extended to a “global hybrid” variant that goes beyond the isotropic model from previous approximations. The polarizability model yields significantly improved dispersion coefficients and benchmark calculations with the cavity-dependent XC functional demonstrate improved agreement with QED Hartree–Fock (QED-HF) reference energies. Application to the regioselectivity of brominated nitrobenzene intermediates reveals the functional’s capacity to capture cavity-induced energetic shifts. In conclusion, our results advance the Jacob’s ladder of functionals for QEDFT and provide a practical tool for modeling polaritonic chemistry.
Approximation↗
Assessing the Representation of Synoptic Variability Associated With California Extreme Precipitation in CMIP6 Models
Abstract Days of extreme precipitation over California are evaluated in Coupled Model Intercomparison Project Phase 6 (CMIP6) models and the ERA‐Interim reanalysis. In the current climate, the model spread in composited precipitation on extreme precipitation days is closely related to the magnitude of composited integrated vapor transport (IVT) across models, a proxy for the intensity of atmospheric rivers. Most models underestimate the magnitude of IVT associated with extreme precipitation, according to ERA‐Interim. This is due mostly to the contribution of moisture, which almost all models overestimate, while the contribution of lower‐tropospheric wind speed is generally closer to the reanalyses. Moreover, most models underestimate the variance in the latitude of maxima of numerous variables among days of extreme California precipitation. That is, in the general circulation models there is a lack of diversity in the latitude of the disturbances bringing winter precipitation to California. In the future climate, most models project a decrease in the frequency of southward‐displaced disturbances among California extreme precipitation days. Hence, the greatest increases in extreme precipitation are over northern California. However, the historical underestimate of the latitudinal variance of disturbances calls into question the reliability of these projections. This bias should be especially considered for dynamical downscaling efforts over the region.
Norris, Jesse↗
Jets and Heavy Flavors at HERA
Recent results on jet cross sections and heavy-flavor production in photoproduction and neutral current deep inelastic ep scattering from the H1 and ZEUS Collaborations are presented. The jet measurements are used to perform stringent tests of perturbative QCD, to extract precise values of the strong coupling and to constrain further the proton and photon parton distribution functions. The measurement of beauty and charm production at HERA is an important testing ground for perturbative QCD and can provide information on the structure of the proton.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Diffractive PDF fits and factorisation tests at HERA
A DGLAP next-to-leading-order QCD analysis to extract the diffractive parton distribution functions, using DIS inclusive and dijet diffractive HERA data, is presented. Predictions based on the extracted parton densities are compared to diffractive dijet photoproduction data to discuss factorisation.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Exclusive production of vector mesons in pp and pp-bar collisions
Protons and antiprotons at collider energies are a source of high energy Weizsaecker-Williams photons. This opens up a possibility to study at the LHC exclusive photoproduction of heavy vector mesons at energies much larger than possible at the HERA accelerator.We present selected results on the production of vector mesons {rho}, {omega}, {phi}, J/{Psi} and {Upsilon}. We show distributions in rapidity, transverse momentum of mesons and azimuthal angle between outgoing protons for RHIC, Tevatron and LHC energies. The absorption effects are discussed.The amplitude for {gamma}p{yields}Vp is calculated in a pQCD k{sub T}-factorization approach with an unintegrated gluon distribution constrained by inclusive deep-inelastic structure function. The total cross section for diffractive meson (virtual) photo-production as a function of energy and photon virtuality is calculated and compared to HERA data. We also discuss the ratio of the first radial excitation state (2S) to the ground state (1S) in diffractive J/{Psi} and {Upsilon} production.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
UHE neutrinos: higher twists, scales, saturation
It is shown that in the ultra-high energy neutrino interactions the higher twist corrections brought about by the non-conservation of the top-bottom current dramatically change the longitudinal structure function, F{sub L}. To the Double Leading Log Approximation simple and numerically accurate formulas for F{sub L} and {sigma}{sup {nu}N} are derived.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Prompt photon photoproduction at HERA with non-collinear parton dynamics
We investigate the prompt photon photoproduction at HERA within the framework of the k{sub T}-factorization approach to QCD. Our consideration is based on the off-shell matrix elements for the underlying partonic subprocesses and the Kimber-Martin-Ryskin (KMR) unintegrated parton densities in the proton. We also use the Ciafaloni-Catani-Fiorani-Marchesini (CCFM) unintegrated gluon as well as valence and sea quark distributions.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
The Photon Impact Factor for DIS at NLO: analytic result
Using the Operator Product Expansion for high-energy scattering processes, we compute the photon impact factor at next-to-leading order accuracy. We obtain an analytic expression as a linear combination of five independent conformal tensor structures.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Beyond cusp anomalous dimension from integrability in SYM{sub 4}
We study the first sub-leading correction O((ln s){sup 0}) to the cusp anomalous dimension in the high spin expansion of finite twist operators in N = 4 SYM theory. This term is still governed by a linear integral equation which we study in the weak and strong coupling regimes. In the strong coupling regime we find agreement with the string theory computations.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Overview of the PHENIX Longitudinal and Transverse Spin Physics Program
The PHENIX experiment uses polarized p+p collisions at RHIC to explore the spin structure of the proton. The p+p collisions, while complementary to deep inelastic lepton scattering experiments, offer distinct advantages for the determination of the helicity preferences of gluons, the flavor-dependence of sea antiquark polarizations, and parton transverse motion or spin orientation preferences inside polarized protons. The PHENIX experiment has been measuring the double longitudinal spin asymmetry of several inclusive probes to understand the gluon polarization in the allowed kinematic range. In addition, PHENIX experiment also has been studying the single spin asymmetries with a variety of final state particles in different kinematic regimes to shed light on the transverse spin structure. A brief overview is given of results to date and planned future directions.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
PHENIX Measurement of Parity-Violating Single Spin Asymmetry in W Production in p+p Collisions at 500 GeV
The flavor-separated polarized parton distribution functions for light quarks and anti-quarks in the proton can be studied in the production of W bosons in p+p collisions. The Ws are produced in processes like u+d-bar{yields}W{sup +} and u-bar+d{yields}W{sup -} and we observe the lepton (an electron or muon) from the decay channel W{sup {+-}}{yields}l{sup {+-}}{nu}. The electron energy spectrum from W decays measured with an integrated luminosity of approximately 10 pb{sup -1} will be shown, with a measurement of the electron single spin asymmetry in central rapidity.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Phenomenology of transverse-spin and transverse-momentum effects in hard processes
Some recent analyses of single-spin and azimuthal asymmetries in SIDIS and Drell-Yan processes, focusing in particular on Collins, Sivers and Boer-Mulders effects, are briefly reviewed. The perspectives for future phenomenological studies are also outlined.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗