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W. Lee

Publications and source records attributed to W. Lee.

At least 37 records · Page 2Linked to original sources
arXiv2007

Effect of internal friction on transformation twin dynamics in SrxBa1-xSnO3 perovskite

The dynamics of transformation twins in SrxBa1-xSnO3 (x=0.6,0.8) perovskite has been studied by dynamical mechanical analysis in three-point bend geometry. This material undergoes phase transitions from orthorhombic to tetragonal and cubic structures on heating. The mechanical loss signatures of the transformation twins include relaxation and frequency-independent peaks in the orthorhombic and tetragonal phases, with no observed energy dissipation in the cubic phase. The macroscopic shape, orientation and relative displacements of twin walls have been calculated from bending and anisotropy energies. The mechanical loss angle and distribution of relaxation time are discussed in term of bending modes of domain walls.

cond-mat.mtrl-sci↗
arXiv2003

Calculating weak matrix elements using HYP staggered fermions

We present preliminary results of weak matrix elements relevant to CP violation calculated using the HYP (II) staggered fermions. Since the complete set of matching coefficients at the one-loop level became available recently, we have constructed lattice operators with all the $g^2$ corrections included. The main results include both $ΔI = 3/2$ and $ΔI = 1/2$ contributions.

hep-lat↗
arXiv2003

Comparison of Fat7-bar and HYP fat links

We study various methods of constructing fat links based upon the HYP (by Hasenfratz & Knechtli) and Fat7-bar (by W. Lee) algorithms. We present the minimum plaquette distribution for these fat links. This enables us to determine which algorithm is most effective at reducing the spread of plaquette values.

hep-lat↗
arXiv2001

Weak matrix elements for CP violation

We present preliminary results of matrix elements of four-fermion operators relevant to the determination of e and e'/e using staggered fermions.

hep-lat↗
arXiv2000

Measurement of the Cosmic Ray Energy Spectrum and Composition from 10^{17} to 10^{18.3} eV Using a Hybrid Fluorescence Technique

We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} eV and 10^{18} eV using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic ray intensity is changing f rom a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Fly's Eye measurements and supports the previously found steepening near 4 \times 10^{17} eV .

astro-ph↗
arXiv2000

Reply to Boglione and Pennington

In a recent article we presented an argument which, we believe, shows to be incorrect an estimate, by Boglione and Pennington, of corrections to the valence (quenched) approximation predictions for properties of the lightest scalar glueball. Boglione and Pennington's reply to our article, it appears to us, fails to address the specific technical issues we raised.

hep-ph↗
arXiv1999

A Multi-Component Measurement of the Cosmic Ray Composition Between 10^{17} eV and 10^{18} eV

The average mass composition of cosmic rays with primary energies between $10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum, $X_{max}$, and in the change in the muon density at a fixed core location, $ρ_μ(600m)$, as a function of energy. The composition has also been evaluated in terms of the combination of $X_{max}$ and $ρ_μ(600m)$. The results show that the composition is changing from a heavy to lighter mix as the energy increases.

astro-ph↗
arXiv1999

Scalar Quarkonium Masses and Mixing with the Lightest Scalar Glueball

We evaluate the continuum limit of the valence (quenched) approximation to the mass of the lightest scalar quarkonium state for a range of different quark masses and to the mixing energy between these states and the lightest scalar glueball. Our results support the interpretation of $f_0(1710)$ as composed mainly of the lightest scalar glueball.

hep-lat↗
arXiv1999

Order a improved renormalization constants

We impose the axial and vector Ward identities on local fermion bilinear operators in the Sheikholesalami-Wohlert discretization of fermions. From this we obtain all the coefficients needed to improve the theory at O(a), as well as the scale and scheme independent renormalization constants, Z_A, Z_V and Z_S/Z_P.

hep-lat↗
arXiv1999

Breakdown of Cluster Decomposition in Instanton Calculations of the Gluino Condensate

A longstanding puzzle concerns the calculation of the gluino condensate <{trλ^2\over 16π^2}> = cΛ^3 in N=1 supersymmetric SU(N) gauge theory: so-called weak-coupling instanton (WCI) calculations give c=1, whereas strong-coupling instanton (SCI) calculations give, instead, c=2[(N-1)!(3N-1)]^{-1/N}. By examining correlators of this condensate in arbitrary multi-instanton sectors, we cast serious doubt on the SCI calculation of <{trλ^2\over 16π^2}> by showing that an essential step --- namely cluster decomposition --- is invalid. We also show that the addition of a so-called Kovner-Shifman vacuum (in which <{trλ^2\over 16π^2}> = 0) cannot straightforwardly resolve this mismatch.

hep-th↗
arXiv1999

Coupling Constant and Quark Loop Expansion for Corrections to the Valence Approximation

For full QCD vacuum expectation values we construct an expansion in quark loop count and in powers of a coupling constant. The leading term in this expansion is the valence (quenched) approximation vacuum expectation value. Higher terms give corrections to the valence approximation. A test of the expansion is presented for moderately heavy quarks on a small lattice. We consider briefly an application of the expansion to quarkonium-glueball mixing.

hep-lat↗
arXiv1998

Continuum Limit of Scalar Masses and Mixing Energies

We evaluate the continuum limit of the valence approximation to the mass of scalar quarkonium and to the scalar quarkonium-glueball mixing energy for a range of different quark masses. Our results answer several questions raised by the proposed identification of $f_0(1710)$ as composed primarily of the lightest scalar glueball.

hep-lat↗
arXiv1998

Non-perturbative Renormalization Constants using Ward Identities

We extend the application of vector and axial Ward identities to calculate $b_A$, $b_P$ and $b_T$, coefficients that give the mass dependence of the renormalization constants of the corresponding bilinear operators in the quenched theory. The extension relies on using operators with non-degenerate quark masses. It allows a complete determination of the $O(a)$ improvement coefficients for bilinears in the quenched approximation using Ward Identities alone. Only the scale dependent normalization constants $Z_P^0$ (or $Z_S^0$) and $Z_T$ are undetermined. We present results of a pilot numerical study using hadronic correlators.

hep-lat↗
arXiv1998

Scalar Quarkonium Masses and Mixing with the Lightest Scalar Glueball

We evaluate the continuum limit of the valence (quenched) approximation to the mass of the lightest scalar quarkonium state, for a range of different quark masses, and to the mixing energy between these states and the lightest scalar glueball. Our results support the interpretation of $f_0(1710)$ as composed mainly of the lightest scalar glueball.

hep-lat↗
arXiv1998

Improved Error Estimate for the Valence Approximation

We construct a systematic mean-field-improved coupling constant and quark loop expansion for corrections to the valence (quenched) approximation to vacuum expectation values in the lattice formulation of QCD. Terms in the expansion are evaluated by a combination of weak coupling perturbation theory and a Monte Carlo algorithm.

hep-lat↗
arXiv1998

The Scalar Quarkonium Spectrum and Quarkonium-Glueball Mixing

We evaluate the valence approximation to the mass of scalar quarkonium and to the mixing energy between scalar quarkonium and the lightest scalar glueball for a range of different lattice sizes and quark masses. Our results support the identification of $f_0(1710)$ as the lightest scalar glueball.

hep-lat↗