On timelike and spacelike hard exclusive reactions

We show to next-to-leading order accuracy in the strong coupling alpha_s how the collinear factorization properties of QCD in the generalized Bjorken regime relate exclusive amplitudes for spacelike and timelike hadronic processes. This yields simple space--to--timelike relations linking the amplitudes for electroproduction of a photon or meson to those for photo- or meso-production of a lepton pair. These relations constitute a new test of the relevance of leading twist analyzes of experimental data.Comment: v2: major text revision; results, references, and author added; v3: matches the published version Phys. Rev. D86, rapid communication

High temperature expansion applied to fermions near Feshbach resonance

We show that, apart from a difference in scale, all of the surprising recently observed properties of a degenerate Fermi gas near a Feshbach resonance persist in the high temperature Boltzmann regime. In this regime, the Feshbach resonance is unshifted. By sweeping across the resonance, a thermal distribution of bound states (molecules) can be reversibly generated. Throughout this process, the interaction energy is negative and continuous. We also show that this behavior must persist at lower temperatures unless there is a phase transition as the temperature is lowered. We rigorously demonstrate universal behavior near the resonance.Comment: 4 pages, 4 figures (3 color, 1 BW), RevTeX4; ver4 -- updated references, changed title -- version accepted for publication in Physical Review Letter

Quenching of hadron spectra in media

We determine how the yield of large transverse momentum hadrons is modified due to induced gluon radiation off a hard parton traversing a QCD medium. The quenching factor is formally a collinear- and infrared-safe quantity and can be treated perturbatively. In spite of that, in the $p_\perp$ region of practical interest, its value turns out to be extremely sensitive to large distances and can be used to unravel the properties of dense quark-gluon final states produced in heavy ion collisions. We also find that the standard modelling of quenching by shifting $p_\perp$ in the hard parton cross section by the mean energy loss is inadequate.Comment: 20 pp, 5 eps figure

Explanation of 100-fold reduction of spectral shifts for hydrogen on helium films

We show that helium film-mediated hydrogen-hydrogen interactions account for a two orders of magnitude discrepancy between previous theory and recent experiments on cold collision shifts in spin-polarized hydrogen adsorbed on a helium film. These attractive interactions also explain the anomalous dependence of the cold collision frequency shifts on the $^3$He covering of the film. Our findings suggest that the gas will become mechanically unstable before reaching the Kosterlitz-Thouless transition unless the experiment is performed in a drastically different regime, for example with a much different helium film geometry.Comment: 4+ pages, 1 figure (3 subfigures), revtex

Space Storable Rocket Technology (SSRT) basic program

The Space Storable Rocket Technology Program (SSRT) was conducted to establish a technology for a new class of high performance and long life bipropellant engines using space storable propellants. The results are described. Task 1 evaluated several characteristics for a number of fuels to determine the best space storable fuel for use with LO2. The results indicated that LO2-N2H4 is the best propellant combination and provides the maximum mission/system capability maximum payload into GEO of satellites. Task 2 developed two models, performance and thermal. The performance model indicated the performance goal of specific impulse greater than or = 340 seconds (sigma = 204) could be achieved. The thermal model was developed and anchored to hot fire test data. Task 3 consisted of design, fabrication, and testing of a 200 lbf thrust test engine operating at a chamber pressure of 200 psia using LO2-N2H4. A total of 76 hot fire tests were conducted demonstrating performance greater than 340 (sigma = 204) which is a 25 second specific impulse improvement over the existing highest performance flight apogee type engines

Heat flow in the postquasistatic approximation

We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model which corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model which corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale.Comment: 5 pages, 5 figure

Local versus global equilibration near the bosonic Mott-superfluid transition

We study the response of trapped two dimensional cold bosons to time dependent lattices. We find that in lattice ramps from 11 (superfluid, $\hbar/U_{\text{i}} = 3$ms, $\hbar/J_{\text{i}} = 45$ms) to 16 recoils (Mott, $\hbar/U_{\text{f}} = 2$ms, $\hbar/J_{\text{f}} = 130$ms) the local number fluctuations remains at their equilibrium values if ramps are slower than 3 ms. Global transport, however, is much slower (1s), especially in the presence of Mott shells. This separation of timescales has practical implications for cold atom experiments and cooling protocols.Comment: 4 pages, 4 figs. 6 subfigure

Small optic suspensions for Advanced LIGO input optics and other precision optical experiments

We report on the design and performance of small optic suspensions developed to suppress seismic motion of out-of-cavity optics in the Input Optics subsystem of the Advanced LIGO interferometric gravitational wave detector. These compact single stage suspensions provide isolation in all six degrees of freedom of the optic, local sensing and actuation in three of them, and passive damping for the other three

Generalized parton distributions and rapidity gap survival in exclusive diffractive pp scattering

We propose a new approach to the problem of rapidity gap survival (RGS) in the production of high-mass systems (H = dijet, heavy quarkonium, Higgs boson) in double-gap exclusive diffractive pp scattering, pp -> p + (gap) + H + (gap) + p. It is based on the idea that hard and soft interactions proceed over widely different time- and distance scales and are thus approximately independent. The high-mass system is produced in a hard scattering process with exchange of two gluons between the protons. Its amplitude is calculable in terms of the gluon generalized parton distributions (GPDs) in the protons, which can be measured in J/psi production in exclusive ep scattering. The hard scattering process is modified by soft spectator interactions, which we calculate in a model-independent way in terms of the pp elastic scattering amplitude. Contributions from inelastic intermediate states are suppressed. A simple geometric picture of the interplay of hard and soft interactions in diffraction is obtained. The onset of the black-disk limit in pp scattering at TeV energies strongly suppresses diffraction at small impact parameters and is the main factor in determining the RGS probability. Correlations between hard and soft interactions (e.g. due to scattering from the long-range pion field of the proton, or due to possible short-range transverse correlations between partons) further decrease the RGS probability. We also investigate the dependence of the diffractive cross section on the transverse momenta of the final-state protons ("diffraction pattern"). By measuring this dependence one can perform detailed tests of the interplay of hard and soft interactions, and even extract information about the gluon GPD in the proton. Such studies appear to be feasible with the planned forward detectors at the LHC.Comment: 26 pages, 17 figures, uses revtex