Demonstration of the temporal matter-wave Talbot effect for trapped matter waves

We demonstrate the temporal Talbot effect for trapped matter waves using ultracold atoms in an optical lattice. We investigate the phase evolution of an array of essentially non-interacting matter waves and observe matter-wave collapse and revival in the form of a Talbot interference pattern. By using long expansion times, we image momentum space with sub-recoil resolution, allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure

Azimuthal anisotropy at RHIC: the first and fourth harmonics

We report the first observations of the first harmonic (directed flow, v_1), and the fourth harmonic (v_4), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v_2) generated at RHIC. From the correlation of v_2 with v_1 it is determined that v_2 is positive, or {\it in-plane}. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 6 pages with 3 figures, as accepted for Phys. Rev. Letters The data tables are at http://www.star.bnl.gov/central/publications/pubDetail.php?id=3

Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at sNN=200\sqrt{s_{NN}} = 200 GeV

Identified mid-rapidity particle spectra of $\pi^{\pm}$, $K^{\pm}$, and $p(\bar{p})$ from 200 GeV p+p and d+Au collisions are reported. A time-of-flight detector based on multi-gap resistive plate chamber technology is used for particle identification. The particle-species dependence of the Cronin effect is observed to be significantly smaller than that at lower energies. The ratio of the nuclear modification factor ($R_{dAu}$) between protons $(p+\bar{p})$ and charged hadrons ($h$) in the transverse momentum range $1.2<{p_{T}}<3.0$ GeV/c is measured to be $1.19\pm0.05$(stat)$\pm0.03$(syst) in minimum-bias collisions and shows little centrality dependence. The yield ratio of $(p+\bar{p})/h$ in minimum-bias d+Au collisions is found to be a factor of 2 lower than that in Au+Au collisions, indicating that the Cronin effect alone is not enough to account for the relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from transverse momentum 1.8 GeV/c to 3. GeV/

Mid-rapidity anti-proton to proton ratio from Au+Au collisions at sNN=130 \sqrt{s_{NN}} = 130 GeV

We report results on the ratio of mid-rapidity anti-proton to proton yields in Au+Au collisions at \rts = 130 GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of $|y|<0.5$ and 0.4 $<p_t<$ 1.0 GeV/$c$, the ratio is essentially independent of either transverse momentum or rapidity, with an average of $0.65\pm 0.01_{\rm (stat.)} \pm 0.07_{\rm (syst.)}$ for minimum bias collisions. Within errors, no strong centrality dependence is observed. The results indicate that at this RHIC energy, although the $p$-\pb pair production becomes important at mid-rapidity, a significant excess of baryons over anti-baryons is still present.Comment: 5 pages, 3 figures, accepted by Phys. Rev. Let

Transverse-momentum ptp_t correlations on (η,ϕ)(\eta,\phi) from mean-ptp_{t} fluctuations in Au-Au collisions at sNN=\sqrt{s_{NN}} = 200 GeV

We present first measurements of the pseudorapidity and azimuth $(\eta,\phi)$ bin-size dependence of event-wise mean transverse momentum $$ fluctuations for Au-Au collisions at $\sqrt{s_{NN}} = 200$ GeV. We invert that dependence to obtain $p_t$ autocorrelations on differences $(\eta_\Delta,\phi_\Delta)$ interpreted to represent velocity/temperature distributions on ($\eta,\phi$). The general form of the autocorrelations suggests that the basic correlation mechanism is parton fragmentation. The autocorrelations vary strongly with collision centrality, which suggests that fragmentation is strongly modified by a dissipative medium in the more central Au-Au collisions relative to peripheral or p-p collisions. \\Comment: 7 pages, 3 figure

Photo-induced processes in silicate glasses exposed to IR femtosecond pulses

The optical properties variation in silicate glasses after exposure to high-power femtosecond laser radiation at 0.85 μm have been studied. The laser spectral line broadening leading to the supercontinuum generation in visible and UV spectral regions was observed in all studied glasses. Color center generation and intrinsic luminescence were found in boro- and alkali-silicate glasses. It is believed that these processes result from linear and/or two-photon absorption of the short-wavelength part of this supercontinuum which causes glass matrix ionization. No color center absorption in the visible region was observed in fused silica at irradiances up to the laser damage threshold. It was concluded that there is no significant ionization of fused silica under exposure to IR femtosecond laser pulses with irradiance below laser induced damage threshold. ©2004 Copyright SPIE - The International Society for Optical Engineering

The role of self-focusing in laser-induced breakdown of water caused by nano- and picosecond pulses

An experimental investigation of laser-induced breakdown of water and subthreshold phenomena using pulsed laser radiation in the nanosecond to picosecond region has been performed. It has been shown that self-focusing and suspended particles have a strong influence on laser-induced breakdown of water. A significant decrease in transmittance for an input irradiance 1 to 2 orders of magnitude less than the laser-induced breakdown threshold of water as observed, as well as a strong spot size dependence of this threshold. Besides the investigated processes result in a breakdown threshold of water for small spot sizes (∼2-4μm) that is nearly 10 times larger than that of glass due to a sharp increase in scattering from inhomogeneities formed as a result of self- focusing. For large spot sizes (∼20μm) the breakdown threshold of water is considerably less than for the same glasses (∼10-100 times) due to breakdown initiated by suspended particles. ©2004 Copyright SPIE - The International Society for Optical Engineering

Measurement Of The Induced Refractive Index In A Photothermorefractive Glass By A Liquid-Cell Shearing Interferometer

A liquid-cell shearing interferometer was developed to measure refractive-index variations (Δn) in transparent materials. The cell was filled with a liquid having a matched refractive index. The achieved resolution was better than 1/1000 of a fringe shift and resulted in a Δn measurement sensitivity down to 10-7for 1-mm-thick samples. A refractive-index increment in photothermorefractive glass of up to 5 × 10-6was observed after UV exposure at 325 nm. A refractive-index decrement of up to 1 × 10-3was observed after thermal development of the exposed sample. It was proved that photothermorefractive glass obeys the reciprocity law; i.e., Δn depends on the UV dosage but does not depend on the irradiance. © 2002 Optical Society of America

Theoretical Model Of Multiple-Shot Bulk Damage In Silicate Glasses Under Conditions Of Multiphoton Generation Of Color Centers

A model of multiple shot bulk damage under conditions of multiphoton excitation of glass matrix has been considered. It has been based on the nonsteady thermal self-focusing due to accumulation of color centers and increasing of absorption coefficient of medium at the wavelength of incident radiation. These representations have allowed to explain not only the shape of accumulation curves but the influence of spot size and color centers generation efficiency on the thresholds of single and multiple shot damage, and the influence of variable- valence impurity ions on the process\u27 characteristics too. ©2004 Copyright SPIE - The International Society for Optical Engineering