Ultrastable CO2 Laser Trapping of Lithium Fermions

We demonstrate an ultrastable CO2 laser trap that provides tight confinement of neutral atoms with negligible optical scattering and minimal laser-noise- induced heating. Using this method, fermionic 6Li atoms are stored in a 0.4 mK deep well with a 1/e trap lifetime of 300 sec, consistent with a background pressure of 10^(-11) Torr. To our knowledge, this is the longest storage time ever achieved with an all-optical trap, comparable to the best reported magnetic traps.Comment: 4 pages using REVTeX, 1 eps figur

Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag

We study the electrophoretic separation of polyelectrolytes of varying lengths by means of end-labeled free-solution electrophoresis (ELFSE). A coarse-grained molecular dynamics simulation model, using full electrostatic interactions and a mesoscopic Lattice Boltzmann fluid to account for hydrodynamic interactions, is used to characterize the drag coefficients of different label types: linear and branched polymeric labels, as well as transiently bound micelles. It is specifically shown that the label's drag coefficient is determined by its hydrodynamic size, and that the drag per label monomer is largest for linear labels. However, the addition of side chains to a linear label offers the possibility to increase the hydrodynamic size, and therefore the label efficiency, without having to increase the linear length of the label, thereby simplifying synthesis. The third class of labels investigated, transiently bound micelles, seems very promising for the usage in ELFSE, as they provide a significant higher hydrodynamic drag than the other label types. The results are compared to theoretical predictions, and we investigate how the efficiency of the ELFSE method can be improved by using smartly designed drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule

Fast shower simulation in the ATLAS calorimeter

The time to simulate pp collisions in the ATLAS detector is largely dominated by the showering of electromagnetic particles in the heavy parts of the detector, especially the electromagnetic barrel and endcap calorimeters. Two procedures have been developed to accelerate the processing time of electromagnetic particles in these regions: (1) a fast shower parameterisation and (2) a frozen shower library. Both work by generating the response of the calorimeter to electrons and positrons with Geant 4, and then reintroduce the response into the simulation at runtime. In the fast shower parameterisation technique, a parameterisation is tuned to single electrons and used later by simulation. In the frozen shower technique, actual showers from low-energy particles are used in the simulation. Full Geant 4 simulation is used to develop showers down to ~1 GeV, at which point the shower is terminated by substituting a frozen shower. Judicious use of both techniques over the entire electromagnetic portion of the ATLAS calorimeter produces an important improvement of CPU time. We discuss the algorithms and their performance in this paper

Mass measurements near the rr-process path using the Canadian Penning Trap mass spectrometer

The masses of 40 neutron-rich nuclides from Z = 51 to 64 were measured at an average precision of $\delta m/m= 10^{-7}$ using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a $^{252}$Cf spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical $r$ process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in $\beta$-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.Comment: 15 pages, 16 figures. v2 updated, published in Physical Review

Quantum computation with trapped polar molecules

We propose a novel physical realization of a quantum computer. The qubits are electric dipole moments of ultracold diatomic molecules, oriented along or against an external electric field. Individual molecules are held in a 1-D trap array, with an electric field gradient allowing spectroscopic addressing of each site. Bits are coupled via the electric dipole-dipole interaction. Using technologies similar to those already demonstrated, this design can plausibly lead to a quantum computer with $\gtrsim 10^4$ qubits, which can perform $\sim 10^5$ CNOT gates in the anticipated decoherence time of $\sim 5$ s.Comment: 4 pages, RevTeX 4, 2 figures. Edited for length and converted to RevTeX, but no substantial changes from earlier pdf versio

A white-light trap for Bose-Einstein condensates

We propose a novel method for trapping Bose-condensed atoms using a white-light interference fringe. Confinement frequencies of tens of kHz can be achieved in conjunction with trap depths of only a few micro-K. We estimate that lifetimes on the order of 10 s can be achieved for small numbers of atoms. The tight confinement and shallow depth permit tunneling processes to be used for studying interaction effects and for applications in quantum information.Comment: 10 pages with 3 figure

Contact Interactions and Resonance-Like Physics at Present and Future Colliders from Unparticles

High scale conformal physics can lead to unusual unparticle stuff at our low energies. In this paper we discuss how the exchange of unparticles between Standard Model fields can lead to new contact interaction physics as well as a pseudoresonance-like structure, an unresonance, that might be observable at the Tevatron or LHC in, e.g., the Drell-Yan channel. The specific signatures of this scenario are quite unique and can be used to easily identify this new physics given sufficient integrated luminosity.Comment: 20 pages, 10 figs; minor text changes, ref added; typos correcte

Toroidal optical dipole traps for atomic Bose-Einstein condensates using Laguerre-Gaussian beams

We theoretically investigate the use of red-detuned Laguerre-Gaussian (LG) laser beams of varying azimuthal mode index for producing toroidal optical dipole traps in two-dimensional atomic Bose-Einstein condensates. Higher-order LG beams provide deeper potential wells and tighter confinement for a fixed toroid radius and laser power. Numerical simulations of the loading of the toroidal trap from a variety of initial conditions is also given.Comment: 12 pages, 5 figures, submitted to Phys. Rev.