The Quark Structure of Pentaquarks

Motivated by the possible observation of the $\Theta^+(1530)$, we study the quark structure of pentaquark states in quenched lattice QCD. The complete set of 19 local sources that have the proper symmetry for positive or negative parity isoscalar pentaquarks is constructed, as well as a nonlocal source composed of two displaced ``good'' diquarks. Quantitative structure information is determined from diagonalizing the 19-dimensional correlation matrix and from calculating the overlaps of sources with the lattice eigenstates. The volume dependence of the overlap is studied to differentiate between scattering and localized resonant states. The positive parity state has a small component of two ``good'' diquarks, and its energy is too much higher than the negative parity state to be a candidate for the $\Theta^+(1530)$.Comment: 6 pages, 3 figures Lattice 2005: Hadron Spectrum and Quark Masse

Optical Materials Activated with CeO2:Ln3+ Nanoparticles

Silica glasses and siliceous powders activated with CeO2:Ln3+ (Ln ¹ Ce) nanoparticles were synthesized by the sol-gel method and their structural and spectral-luminescent properties were investigated. It is shown that the main features of the Ln3+ ions are a high relative intensity of magnetic dipole transitions and sufficiently effective sensitization of their luminescence with labile photoreduced (Ce4+)- ions by means of superexchange mechanism or/and by transfer of electron

Confining string and P-vortices in the indirect Z(2) projection of SU(2) lattice gauge theory

We study the distribution of P-vortices near the confining string in the indirect Z(2) projection of SU(2) lattice gauge theory. It occurs that the density of vortices is constant at large distances and strongly suppressed near the line connecting the test quark-antiquark pair. This means that the condensate of P-vortices is broken inside the confining string. We also find that the width of the P-vortex density distribution is proportional to the logarithm of the distance between the quark and antiquark.Comment: 3 pages, 4 figures, Lattice2002(topology), 2 references added, minor change

Heavy quark potential in lattice QCD at finite temperature

Results of the study of lattice QCD with two flavors of nonperturbatively improved Wilson fermions at finite temperature are presented. The transition temperature for m_{\pi}/m_{\rho} \sim 0.8 and lattice spacing a \sim 0.12 fm is determined. A two-exponent ansatz is successfully applied to describe the heavy quark potential in the confinement phase.Comment: 3 pages, 1 figure, talk given at the 5th International Conference on Quark Confinement and the Hadron Spectrum, Gargnano, Italy, 10-14 Sep 200

Functional birefringent elements imprinted by femtosecond laser nanostructuring of multi-component glass

A decade ago, a new type of self-organization process was observed in the bulk of SiO2 glass after irradiation with ultrashort laser pulses [1]. Under certain irradiation conditions, highly ordered nanostructures with features smaller than 20 nm could be formed in the irradiated volume. The sub-wavelength arrangement of these structures results in form birefringence, which was recently exploited for demonstrating a variety of functional optical elements in silica glass [2]. Despite excellent physical and chemical properties of fused silica, the applications of this glass are limited due to the expensive manufacturing process associated with high melting temperature. Recently the evidence of laser-induced nanogratings in glasses other than SiO2 was reported, including GeO2 glass [3], binary titanium silicate glass (ULE, Corning) and multicomponent borosilicate glass (Borofloat 33, Schott) [4]. However, birefringence induced in borosilicate glass was more than one order of magnitude lower than in pure SiO2 glass

Pressure dependence of the Boson peak in glassy As2S3 studied by Raman Scattering

A detailed pressure-dependence study of the low-energy excitations of glassy As2S3 is reported over a wide pressure range, up to 10 GPa. The spectral features of Boson peak are analysed as a function of pressure. Pressure effects on the Boson peak are manifested as an appreciable shift of its frequency to higher values, a suppression of its intensity, as well as a noticeable change of its asymmetry leading to a more symmetric shape at high pressures. The pressure-induced Boson peak frequency shift agrees very well with the predictions of the soft potential model over the whole pressure range studied. As regards the pressure dependence of the Boson peak intensity, the situation is more complicated. It is proposed that in order to reach proper conclusions the corresponding dependence of the Debye density of states must also be considered. Employing a comparison of the low energy modes of the crystalline counterpart of As2S3 as well as the experimental data concerning the pressure dependencies of the Boson peak frequency and intensity, structural or glass-to-glass transition seems to occur at the pressure ~4 GPa related to a change of local structure. Finally, the pressure-induced shape changes of the Boson peak can be traced back to the very details of the excess (over the Debye contribution) vibrational density of states.Comment: To appear in J. Non-Cryst. Solids (Proceedings of the 5th IDMRCS, Lille, July 2005

Distinguishing exotic states from scattering states in lattice QCD

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.Includes bibliographical references (p. 91-95).This work explores the problem of distinguishing potentially interesting new exotic states in QCD from conventional scattering states using lattice QCD, and addresses the specific case of the search for localized resonances in a system of five quarks. We employ a complete basis of local interpolating operators, as well as a number of spatially distributed operators, to search for localized resonances in the system of five quarks. Motivated by initially promising experimental searches for the 8+(1540) pentaquark, we have set out to implement new approaches, both on the theoretical and computational side, to allow for calculations deemed infeasible by other groups searching for pentaquarks on the lattice. We restrict our system of five quarks to the quantum numbers of the O+(1540) pentaquark and get an insight into the structure of its states, calculate their energies and explore their properties. Finally, we use the obtained results to discriminate between scattering and exotic states. The calculation is performed in the quenched approximation with heavy Wilson fermions.by Dmitry Sigaev.Ph.D

Lead-germanate glasses and fibers: a practical alternative to tellurite for nonlinear fiber applications

We report on the fabrication of novel lead-germanate glasses and fibers. We have characterized these glasses in terms of their thermal properties, Raman spectra and refractive indices (both linear and nonlinear) and present them as viable alternatives to tellurite glasses for applications requiring highly nonlinear optical fibers. © 2013 Optical Society of America.H. Tilanka Munasinghe, Anja Winterstein-Beckmann, Christian Schiele, Danilo Manzani, Lothar Wondraczek, Shahraam Afshar V., Tanya M. Monro, and Heike Ebendorff-Heidepriemhttp://www.opticsinfobase.org/ome/abstract.cfm?URI=ome-3-9-1488&origin=searc