Search results for "quench"
showing 10 items of 306 documents
Lattice quark masses: a non-perturbative measurement
1998
We discuss the renormalization of different definitions of quark masses in the Wilson and the tree-level improved SW-Clover fermionic action. For the improved case we give the correct relationship between the quark mass and the hopping parameter. Using perturbative and non-perturbative renormalization constants, we extract quark masses in the $\MSbar$ scheme from Lattice QCD in the quenched approximation at $\beta=6.0$, $\beta=6.2$ and $\beta=6.4$ for both actions. We find: $\bar{m}^{\MSbar}(2 GeV)=5.7 \pm 0.1 \pm 0.8$ MeV, $m_s^{\MSbar}(2GeV)= 130 \pm 2 \pm 18 $ MeV and $m_c^{\MSbar}(2 GeV) = 1662\pm 30\pm 230$ MeV.
New results from lattice QCD: Non-perturbative renormalization and quark masses
1998
For the first time, we compute non-perturbatively, i.e. without lattice perturbation theory, the renormalization constants of two-fermion operators in the quenched approximation at $\beta=6.0$, 6.2 and 6.4 using the Wilson and the tree-level improved SW-Clover actions. We apply these renormalization constants to fully non-perturbatively estimate quark masses in the $\bar{MS}$ scheme from lattice simulations of both the hadron spectrum and the Axial Ward Identity in the quenched approximation. Some very preliminary unquenched Wilson results obtained from the gluon configurations generated by the T$\chi$L Collaboration at $\beta=5.6$ and $N_{f}=2$ are also discussed.
Geometrical volume effects in the computation of the slope of the isgur-wise function
1994
We use a method recently suggested for evaluating the slope of the Isgur-Wise function, at the zero-recoil point, on the lattice. The computations are performed in the quenched approximation to lattice QCD, on a $24^3 \times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved action for the fermions. We have found unexpectedly large finite-volume effects in such a calculation. These volume corrections turned out to be purely geometrical and independent of the dynamics of the system. After the study of these effects on a smaller volume and for different quark masses, we give approximate expressions that account for them. Using these approximations we find $\xi^\prime(1)=-1.7 \pm 0.2$ and $\…
Nonperturbative renormalization of quark bilinears
1998
We compute non-perturbatively the renormalization constants of quark bilinears on the lattice in the quenched approximation at three values of the coupling beta=6/g_0^2=6.0,6.2,6.4 using both the Wilson and the tree-level improved SW-Clover fermion action. We perform a Renormalization Group analysis at the next-to-next-to-leading order and compute Renormalization Group invariant values for the constants. The results are applied to obtain a fully non-perturbative estimate of the vector and pseudoscalar decay constants.
K--pipi amplitudes from lattice QCD with a light charm quark.
2006
4 pages, 1 figure.-- PACS nrs.: 12.38.Gc, 13.25.Es, 11.30.Rd.-- ISI Article Identifier: 000244420700019.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0607220
Charmonium dissociation and heavy quark transport in hot quenched lattice QCD
2012
We study the properties of charmonium states at finite temperature in quenched lattice QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above Tc. Our analysis suggests that the S wave states disappear at about 1.5 Tc. The charm diffusion coefficient is estimated and found to be approximately 1/{\pi}T at 1.5Tc {\leq} T {\leq} 3Tc.
Radiation processes in oxygen-deficient silica glasses: Is ODC(I) a precursor of E′-center?
2006
Abstract The accumulation of radiation-induced defects under non-destructive X-ray and destructive cathodoexcitation was studied in pure silica KS-4V glasses possessing an absorption band at 7.6 eV. The correspondence between the existence of this band and the creation of the E′-center by radiation was checked. Detection of induced defects was accomplished by measurement of the luminescence during irradiation, post irradiation afterglow or phosphorescence, induced optical absorption, and thermally stimulated luminescence. In all samples, these observed phenomena associated with charge trapping and recombination on the oxygen-deficient luminescence center. Others centers of luminescence were…
The Medium-Depending Fluorescence of Quadrupolar Donor-Acceptor-Donor Substituted Distyrylbenzenes with High Two-Photon Absorption Cross-Sections
2006
ABSTRACT1,4-Distyrylbenzenes with terminal dialkylamino groups and a central 2,5-disubstitution with electron-accepting groups were prepared via twofold Horner-olefination. These chromophores with a quadrupolar donor-acceptor-donor substitution and C2-symmetry absorb in the violet to green region of the visible spectrum exhibit large two-photon-absorption cross-sections when irrdiated in the NIR. Whereas a variation of the solvent polarity only slightly alters the absorption spectra, the fluorescence appears to be highly responsive. Besides a positive solvatochromism, the emission is very sensitive towards protonation. Quenching or appearance of new emitting species depends on the substitut…
Structure–property relationship of isomeric diphenylethenyl-disubstituted dimethoxycarbazoles
2015
Isomeric 3,6-dimethoxy- and 2,7-dimethoxycarbazoles containing diphenylethenyl moieties were synthesized by condensation of the appropriate dimethoxycarbazoles with diphenylacetaldehyde. The solid-state structures and the molecular order of the compounds were proven by X-ray crystallography. Both compounds were found to be capable of glass formation with comparable glass transition temperatures (70–71 °C). They exhibited high thermal stabilities, with the 5% weight loss temperatures exceeding 375 °C. The isomer having diphenylethenyl groups at C-3 and C-6 positions and methoxy groups at C-2 and C-7 positions (3a) exhibited aggregation-induced emission (AIE), while its counterpart having dip…
Size Reduction of CdSe/ZnS Core−Shell Quantum Dots Photosensitized by Benzophenone: Where Does the Cd(0) Go?
2011
The size of core-shell CdSe/ZnS quantum dots can be decreased by using the combined action of an n,π* aromatic ketone and UVA light. Energy-dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy techniques gave information on the photosensitization mechanism and the eventual destiny of Cd(2+) and Se(2-) core ions. Our data support the electron transfer from the BP ketyl radical to Cd(2+), leading to Cd(0) and H(+), as well as to the recovery of benzophenone. Elemental Cd remains on the core and, eventually, can be oxidized to CdO. In addition, Se(2-) counterions disperse inside the solution mainly attached to protonated amine ligands. The Se(2-) combines with H(+), leadin…