The forward Compton amplitude describes the process of virtual photon scattering from a hadron and provides an essential ingredient for the understanding of hadron structure. As a physical amplitude, ...the Compton tensor naturally includes all target mass corrections and higher twist effects at a fixed virtuality, Q2. By making use of the second-order Feynman-Hellmann theorem, the nucleon Compton tensor is calculated in lattice QCD at an unphysical quark mass across a range of photon momenta 3 ≲ Q2 ≲ 7 GeV2. This allows for the Q2 dependence of the low moments of the nucleon structure functions to be studied in a lattice calculation for the first time. The results demonstrate that a systematic investigation of power corrections and the approach to parton asymptotics is now within reach.
Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated ...structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here, we demonstrate how a novel implementation of the ...Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavors of degenerate mass quarks corresponding to mπ≈470 MeV. We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately 6 GeV2, with results for the ratio of the electric and magnetic form factors of the proton at our simulated quark mass agreeing well with experimental results.
The forward Compton amplitude describes the process of virtual photon scattering from a hadron and provides an essential ingredient for the understanding of hadron structure. As a physical amplitude, ...the Compton tensor naturally includes all target mass corrections and higher twist effects at a fixed virtuality, \(Q^2\). By making use of the second-order Feynman-Hellmann theorem, the nucleon Compton tensor is calculated in lattice QCD at an unphysical quark mass across a range of photon momenta \(3 \lesssim Q^2 \lesssim 7\) GeV\(^2\). This allows for the \(Q^2\) dependence of the low moments of the nucleon structure functions to be studied in a lattice calculation for the first time. The results demonstrate that a systematic investigation of power corrections and the approach to parton asymptotics is now within reach.
The partonic structure of hadrons plays an important role in a vast array of high-energy and nuclear physics experiments. It also underpins the theoretical understanding of hadron structure. Recent ...developments in lattice QCD offer new opportunities for reliably studying partonic structure from first principles. Here we report on the use of the Feynman-Hellmann theorem to study the forward Compton amplitude in the unphysical region. We demonstrate how this amplitude provides direct constraint on hadronic inelastic structure functions. The use of external momentum transfer allows us to study the \(Q^2\) evolution to explore the onset of asymptotic scaling and reveal higher-twist effects in partonic structure.
Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated ...structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here we demonstrate how a novel implementation of the Feynman-Hellmann ...method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavours of degenerate mass quarks corresponding to \(m_\pi \approx 470 \text{ MeV}\). We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately \(6 \text{ GeV}^2\), with results for \(G_E/G_M\) in the proton agreeing well with experimental results.
Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated ...structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here, we demonstrate how a novel implementation of the ...Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavors of degenerate mass quarks corresponding to $m_{π} ≈ 470$ MeV. We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately $6 GeV^2$, with results for the ratio of the electric and magnetic form factors of the proton at our simulated quark mass agreeing well with experimental results.
Specific repair of aging hair keratin Zur Wiesche, E. S.; Gassenmeier, T.; Fischer, D. ...
International journal of cosmetic science,
12/2009, Letnik:
31, Številka:
6
Journal Article
Recenzirano
IFSCC Magazine, 11 (2008) (4) 317–320
Winner of the Poster Award at the IFSCC Congress 2008, Barcelona, Spain.
A new method was developed to study aging effects on human hair keratin caused by ...shampooing, blow drying and sunlight. An automatic multiple process allowed reproducible simulation of the stress of approximately 100 Central European summer days in only 5 working days. Stress‐strain measurements showed a significant weakening of the hair structure due to simulated aging effects. A new keratin active containing peptides identical to those in human hair was developed. The new keratin active penetrates deeply into the cortex cells, which was demonstrated by means of fluorescence microscopy. Aging damage was successfully prevented by strengthening the hair structure.
Keywords: Hair keratin, hair strengthening, intermediate filament, keratin aging simulation, restructuring
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