A
bstract
We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and ...of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations — parton-level fixed order, shower-matched, merged — in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV
e
+
e
−
collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.
A
bstract
We compute the contribution of order
α
S
2
α
2
to the cross section of a top-antitop pair in association with at least one heavy Standard Model boson —
Z
,
W
±
, and Higgs — by including ...all effects of QCD, QED, and weak origin and by working in the automated M
ad
G
raph
5_
a
MC@NLO framework. This next-to-leading order contribution is then combined with that of order
α
S
3
α
, and with the two dominant lowest-order ones,
α
S
2
α
and
α
S
α
2
, to obtain phenomenological results relevant to a 8, 13, and 100 TeV
pp
collider.
A
bstract
We present the key features relevant to the automated computation of all the leading- and next-to-leading order contributions to short-distance cross sections in a mixed-coupling expansion, ...with special emphasis on the first subleading NLO term in the QCD+EW scenario, commonly referred to as NLO EW corrections. We discuss, in particular, the FKS subtraction in the context of a mixed-coupling expansion; the extension of the FKS subtraction to processes that include final-state tagged particles, defined by means of fragmentation functions; and some properties of the complex mass scheme. We combine the present paper with the release of a new version of M
ad
G
raph
5_
a
MC@NLO, capable of dealing with mixed-coupling expansions. We use the code to obtain illustrative inclusive and differential results for the 13-TeV LHC.
A
bstract
We study the production of jets in hadronic collisions, by computing all contributions proportional to
α
S
n
α
m
, with
n
+
m
= 2 and
n
+
m
= 3. These correspond to leading and ...next-to-leading order results, respectively, for single-inclusive and dijet observables in a perturbative expansion that includes both QCD and electroweak effects. We discuss issues relevant to the definition of hadronic jets in the context of electroweak corrections, and present sample phenomenological predictions for the 13-TeV LHC. We find that both the leading and next-to-leading order contributions largely respect the relative hierarchy established by the respective coupling-constant combinations.
In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical-chemical processes in porous media. The basic ...concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multifield problems in porous and fractured media for applications in geoscience and hydrology. To this purpose OGS is based on an object-oriented FEM concept including a broad spectrum of interfaces for pre- and postprocessing. The OGS idea has been in development since the mid-eighties. We provide a short historical note about the continuous process of concept and software development having evolved through Fortran, C, and C++ implementations. The idea behind OGS is to provide an open platform to the community, outfitted with professional software-engineering tools such as platform-independent compiling and automated benchmarking. A comprehensive benchmarking book has been prepared for publication. Benchmarking has been proven to be a valuable tool for cooperation between different developer teams, for example, for code comparison and validation purposes (DEVOVALEX and CO
2
BENCH projects). On one hand, object-orientation (OO) provides a suitable framework for distributed code development; however, the parallelization of OO codes still lacks efficiency. High-performance-computing efficiency of OO codes is subject to future research.
A
bstract
We present the calculation of the next-to-leading contribution of order
α
S
2
α
2
to the production of a Standard Model Higgs boson in association with a top-quark pair at hadron colliders. ...All effects of weak and QCD origin are included, whereas those of QED origin are ignored. We work in the M
ad
G
raph
5_
a
MC@NLO framework, and discuss sample phenomenological applications at a 8, 13, and 100 TeV
pp
collider, including the effects of the dominant next-to-leading QCD corrections of order
α
S
3
α
.
We compare two optical clocks based on the ^{2}S_{1/2}(F=0)→^{2}D_{3/2}(F=2) electric quadrupole (E2) and the ^{2}S_{1/2}(F=0)→^{2}F_{7/2}(F=3) electric octupole (E3) transition of ^{171}Yb^{+} and ...measure the frequency ratio ν_{E3}/ν_{E2}=0.932829404530965376(32), improving upon previous measurements by an order of magnitude. Using two caesium fountain clocks, we find ν_{E3}=642121496772645.10(8) Hz, the most accurate determination of an optical transition frequency to date. Repeated measurements of both quantities over several years are analyzed for potential violations of local position invariance. We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant α to 1.0(1.1)×10^{-18}/yr and of the proton-to-electron mass ratio μ to -8(36)×10^{-18}/yr. Using the annual variation of the Sun's gravitational potential at Earth Φ, we improve limits for a potential coupling of both constants to gravity, (c^{2}/α)(dα/dΦ)=14(11)×10^{-9} and (c^{2}/μ)(dμ/dΦ)=7(45)×10^{-8}.
We present the key features relevant to the automated computation of all the leading- and next-to-leading order contributions to short-distance cross sections in a mixed-coupling expansion, with ...special emphasis on the first subleading NLO term in the QCD+EW scenario, commonly referred to as NLO EW corrections. We discuss, in particular, the FKS subtraction in the context of a mixed-coupling expansion, the extension of the FKS subtraction to processes that include final-state tagged particles, defined by means of fragmentation functions, and some properties of the complex mass scheme. We combine the present paper with the release of a new version of MadGraph5_aMC@NLO, capable of dealing with mixed-coupling expansions. We use the code to obtain illustrative inclusive and differential results for the 13-TeV LHC.
The deformation behavior and corresponding microstructure evolution of a Mg
97Zn
1Y
2 (at.%) alloy with a long period stacking ordered (LPSO) structure subjected to hot compression were investigated. ...The peak stress at 573
K was about 190
MPa, and no macroscopic fracture took place up to a strain of about 60%. The mechanisms responsible for the mechanical performance of the Mg
97Zn
1Y
2 (at.%) alloy are discussed based on microstructural investigations using various electron microscopy techniques. The high strength at elevated temperature could be attributed to synergetic strengthening refinement of the LPSO via kinking and a limited fraction of dynamical recrystallization. Microcracks nucleated at the interfaces in the sandwich structure composed of LPSO and nanometer thick Mg slices could weaken the alloy at late stages of deformation, but their propagation could be limited within the individual kink band where the microcracks nucleated, which could ensure the capability of the alloy to resist premature or catastrophic fracture. Furthermore, lack of deformation twins in Mg grains effectively reduced the potential nucleation sites for cracks, which should be another reason for the good ductility of the alloy. These findings may provide or evoke insights into methods for optimizing the mechanical properties of Mg alloys.
► Direct or indirect mechanisms accounting for the enhancing nutrient bioavailability with biochar application are evaluated in the present study. ► Direct release form biochar is important for ...cations (e.g. K, Ca, Na, Mg) bioavailability with biochar addition. ► The SEM-EDX analysis indicated that mineral sorption on biochar surface influenced P sorption. ► The direct P release altered soil pH and changes of Fe, Al oxides and accumulation of Ca controlled P bioavailability with biochar application. ► The long term effect of P bioavailability with biochar application deserves further attention.
As a soil amendment and important bio-resources, biochar has been reported to increases in soil nutrient availability. However, the involved direct or indirect mechanisms are still not clear. In present study, we evaluated the effects of four biochar application rates (0, 1, 5 and 10%, w/w) on inorganic P fractions, available NO3−-N, NH4+-N, K, Na, Ca, Mg and of Fe, Al oxides in a sandy soil. To discern direct and indirect mechanisms, separately soil and biochar equivalent to the respective part in the mixture of soil and biochar were also studied. The results suggested that cations such as K, Ca, Na, Mg in mixture were mainly originated form biochar while inorganic N showed little effects form biochar regardless of direct or indirect mechanisms. P solubility with biochar application was more complex because they also affected by altering soil pH, changes of Fe and Al oxides, and direct P contributions from biochar. In addition, changes of Fe and Al oxides were complicated by altering soil pH, sorption on biochar, and direct release form biochar. In result, Fe and Al oxides showed no observable effects on P fractions in our soil type. Although P availability was enhanced due to the pH changes and direct release from biochar, the observed P availability was greatly lower than the predicted P availability because of the precipitation of large amount of Ca contained in biochar with soluble P in mixture. The results suggested that biochar application, resulting in pH changes and mineral sorption, can indirectly change nutrient bioavailability especially for P apart from direct release form biochar. The long term effect of P availability with biochar application deserves further attention for large-scale soil ecological restoration.
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