119180642
More on volume dependence of spectral weight function
Spectral weight functions are easily obtained from two-point correlation functions and they might be used to distinguish single-particle from multi-particle states in a finite-volume lattice calculation, a problem crucial for many lattice QCD simulations. In previous studies, it is shown that the spectral weight function for a broad resonance shares the typical volume dependence of a two-particle scattering state i.e. proportional to $1/L^3$ in a large cubic box of size $L$ while the narrow resonance case requires further investigation. In this paper, a generalized formula is found for the spectral weight function which incorporates both narrow and broad resonance cases. Within L\"uscher's formalism, it is shown that the volume dependence of the spectral weight function exhibits a single-particle behavior for a extremely narrow resonance and a two-particle behavior for a broad resonance. The corresponding formulas for both $A^+_1$ and $T^-_1$ channels are derived. The potential application of these formulas in the extraction of resonance parameters are also discussed.
121608815
Mean-field calculations for the three-dimensional Holstein model
The electron-phonon Holstein model is studied in three spatial dimensions. It is argued that this model can be used to account for major features of the high-Tc BaPb1-xBixO3 and BaxK1-xBiO3 systems. Mean-field calculations are performed via a path integral representation of the model. Charge-density-wave order parameters and transition temperatures are obtained.
119942970
LATTICE STUDY OF SCALAR AND TENSOR GLUEBALLS
5274338
Calculating the I = 2 Pion Scattering Length Using Tadpole Improved Clover Wilson Action on Coarse Anisotropic Lattices
In an exploratory study, using the tadpole improved clover Wilson quark action on small, coarse and anisotropic lattices, the pipi scattering length in the I = 2 channel is calculated within quenched approximation. A new method is proposed which enables us to make chiral extrapolation of our lattice results without calculating the decay constant on the lattice. Finite volume and finite lattice spacing errors are analyzed and the results are extrapolated towards the infinite volume and continuum limit. Comparisons of our lattice results with the new experiment and the results from Chiral Perturbation Theory are made. Good agreements are found. (C) 2002 Elsevier Science B.V. All rights reserved.
6175444
TUNING THE TADPOLE IMPROVED CLOVER WILSON ACTION ON COARSE ANISOTROPIC LATTICES
Wilson quark action, with tadpole improved clover term added, is studied on coarse anisotropic lattices. The bare velocity of light parameter in this action is determined nonperturbatively using the pseudo-scalar and vector meson dispersion relations for various values of the gauge coupling β and bare quark mass parameter κ.
121803018
PRELIMINARY RESULTS FOR LIGHT HADRON MASSES FROM LATTICE QCD ON ASYMMETRIC LATTICES
16420888
MeV tau neutrino in a gauge-mediated supersymmetry breaking model
A supersymmetric model which naturally accommodates MeV tau neutrinos within the framework of gauge-mediated supersymmetry breaking is described. The lepton number violation is originally introduced in the messenger sector of the theory. A large slepton-Higgs mixing mass and a small lepton-higgsino mixing mass are generated at one loop. The scalar tau neutrino has a non-vanishing vacuum expectation value. This results in a non-zero vτ mass which is in the range of 1–10 MeV.
125180647
On the isolated singularity of a 7-space obtained by rolling Calabi-Yau threefolds through extremal transitions
119253117
SPACETIME NONCOMMUTATIVE EFFECT ON BLACK HOLE AS PARTICLE ACCELERATORS
We study the spacetime noncommutative effect on black hole as particle accelerators and, find that the particles falling from infinity with zero velocity cannot collide with unbound energy, either near the horizon or on the prograde ISCO when the noncommutative Kerr black hole is exactly extremal. Our results also show that the bigger of the spinning black hole's mass is the higher of center of mass energy that the particles obtain. For small and medium noncommutative Schwarzschild black hole, the collision energy depends on the black hole's mass.
119447810
Note on the slope parameter of the baryonic Lambda(b) ---> Lambda(c) Isgur-Wise function
Abstract Using the framework of the Heavy Quark Effective Theory we have re-analyzed the Isgur–Wise function describing semileptonic Λ b → Λ c decays in the QCD sum rule approach. The slope parameter of the Isgur–Wise function is found to be ρ 2 = 1.35 ± 0.13 , which is consistent with an experimental measurement and a lattice calculation. To O ( 1 / m b , 1 / m c ) of the heavy quark expansion the integrated Λ b decay width is used to extract the CKM matrix element V c b for which we obtain a value of | V c b | = 0.041 ± 0.004 ± 0.001 in excellent agreement with the value of | V c b | determined from semileptonic B → D ∗ decays.
118542460
Coherent Neutron Scattering in Polycrystalline Deuterium and its Implications for Ultracold Neutron Production
This paper presents a calculation of the neutron cross-sections in solid materials (used in practical neutron sources) with a large coherent scattering contribution. In particular, the dynamic structure function S(Q, !) of polycrystalline ortho-D2 is evaluated using a Monte-Carlo calculation that performs an average over scattering angles relative to crystal axes in random orientations. This method uses an analytical dispersion function with force constants derived from neutron scattering data of single crystal D2 in the framework of an axially symmetric force tensor. The resulting two dimensional map of S(Q, !) captures details of the phonon branches as well as the molecular rotations, that can be compared directly to data from inelastic neutron scattering on polycrystalline D2. This high resolution information is used to calculate the absolute cross-sections of production and upscattering loss of ultracold neutron (UCN). The resulting scattering cross-sections are significantly different, especially for UCN upscattering, from the previous predictions using the approach centered on the incoherent approximation.