排序方式: 共有31条查询结果,搜索用时 31 毫秒
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Göckeler M Horsley R Pleiter D Rakow PE Schäfer A Schierholz G Schroers W;QCDSF Collaboration 《Physical review letters》2004,92(4):042002
We perform a quenched lattice calculation of the first moment of twist-two generalized parton distribution functions of the proton, and assess the total quark (spin and orbital angular momentum) contribution to the spin of the proton. 相似文献
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Göckeler M Hägler P Horsley R Nakamura Y Pleiter D Rakow PE Schäfer A Schierholz G Stüben H Zanotti JM;QCDSF;UKQCD 《Physical review letters》2007,98(22):222001
We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72, 094020 (2005)], we predict that the Boer-Mulders function h(1/1), describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. 相似文献
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M. Göckeler R. Horsley H. Perlt P.E.L. Rakow A. Schäfer G. Schierholz A. Schiller 《The European Physical Journal C - Particles and Fields》2006,48(2):523-530
We consider the renormalisation of lattice QCD operators with one and two covariant derivatives related to the first and second
moments of generalised parton distributions and meson distribution amplitudes. Employing the clover fermion action we calculate
their non-forward quark matrix elements in one-loop lattice perturbation theory. For some representations of the hypercubic
group commonly used in simulations we determine the sets of all possible mixing operators and compute the matrices of the
renormalisation factors in one-loop approximation. We describe how tadpole improvement is applied to the results.
PACS 11.15.Ha; 12.38.Bx; 12.38.Gc
An erratum to this article can be found at 相似文献
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M. Göckeler Ph. Hägler R. Horsley D. Pleiter P. E. L. Rakow A. Schäfer G. Schierholz J. M. Zanotti 《Few-Body Systems》2005,36(1-4):111-118
We present recent results on generalized parton distributions from dynamical lattice QCD calculations. Our set of twelve different combinations of couplings and quark masses allows for a preliminary study of the pion mass dependence of the transverse nucleon structure. 相似文献
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QCDSFUKQCD Collaboration T. Bakeyev M. Gckeler R. Horsley D. Pleiter P. E. L. Rakow G. Schierholz H. Stüben 《Physics letters. [Part B]》2004,580(3-4):197-208
By considering the local vector current between nucleon states and imposing charge conservation, we determine its renormalisation constant and quark mass improvement coefficient for Symanzik O(a) improved Wilson fermions. The computation is first performed for quenched fermions (and for completeness also with unimproved fermions) and compared against known results. The two-flavour unquenched case is then considered. 相似文献
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Colorimetric sensor arrays for molecular recognition 总被引:1,自引:0,他引:1
The development of colorimetric sensor arrays for the detection of volatile organic compounds is reported. Using an array of chemo-responsive dyes, enormous discriminatory power is created in a simple device that can imaged easily with an ordinary flat-bed scanner. High sensitivities (ppb) have been demonstrated for the detection of biologically important analytes, including amines, carboxylic acids, and thiols. By the proper choice of dyes and substrate, the array can be made essentially non-responsive to changes in humidity. 相似文献
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R. Grün K. Obenauer P. Schläpfer P. Esenwein Grifzow und Rakow 《Fresenius' Journal of Analytical Chemistry》1937,111(5-6):218-219
Ohne Zusammenfassung 相似文献
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M. Göckeler Ph. Hägler R. Horsley Y. Nakamura D. Pleiter P. E. L. Rakow A. Schäfer G. Schierholz W. Schroers H. Stüben J. M. Zanotti 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):445-450
The QCDSF/UKQCD Collaboration has an ongoing program to calculate nucleon matrix elements with two flavours of dynamical O(a) improved Wilson fermions. Here we present recent results on the electromagnetic form factors, the quark momentum fraction
〈x〉 and the first three moments of the nucleon's spin-averaged and spin-dependent generalised parton distributions, including
preliminary results with pion masses as low as 320MeV. 相似文献