Relativistic Modification of the Gamow Factor

In processes involving Coulomb-type initial- and final-state interactions, the Gamow factor has been traditionally used to take into account these additional interactions. The Gamow factor needs to be modified when the magnitude of the effective coupling constant increases or when the velocity increases. For the production of a pair of particles under their mutual Coulomb-type interaction, we obtain the modification of the Gamow factor in terms of the overlap of the Feynman amplitude with the relativistic wave function of the two particles. As a first example, we study the modification of the Gamow factor for the production of two bosons. The modification is substantial when the coupling constant is large.Comment: 13 pages, in LaTe

Interference effects in f-deformed fields

We show how the introduction of an algeabric field deformation affects the interference phenomena. We also give a physical interpretation of the developed theory.Comment: 6 pages, Latex file, no figures, accepted by Physica Script

Driven interfaces in disordered media: determination of universality classes from experimental data

While there have been important theoretical advances in understanding the universality classes of interfaces moving in porous media, the developed tools cannot be directly applied to experiments. Here we introduce a method that can identify the universality class from snapshots of the interface profile. We test the method on discrete models whose universality class is well known, and use it to identify the universality class of interfaces obtained in experiments on fluid flow in porous media.Comment: 4 pages, 5 figure

Projections of Discovery Potentials from Expected Background

Background with certain uncertainties are usually known in searches of novel phenomena prior to the experiments are conducted at their design stage. We quantitatively study the projected sensitivities in terms of discovery potentials. These are essential for the optimizations of the experimental specifications as well as of the cost-effectiveness in various investment. Sensitivities in counting analysis are derived with complete Poisson statistics and its continuous approximation, and are compared with those using maximum likelihood analysis in which additional measurables are included as signatures. The roles and effects due to uncertainties in the background estimates are studied. Two expected features to establish positive effects are verified and quantified: (i) In counting-only experiments, the required signal strength can be derived with complete Poisson analysis, and the continuous approximation would underestimate the results. (ii) Incorporating continuous variables as additional constraints would reduce the required signal strength relative to that of counting-only analysis. The formulations are applied to the case on the experimental searches of neutrinoless double beta decay in which both ambient and two-neutrino background are considered.Comment: 13 pages, 10 figure

Clock synchronization with dispersion cancellation

The dispersion cancellation feature of pulses which are entangled in frequency is employed to synchronize clocks of distant parties. The proposed protocol is insensitive to the pulse distortion caused by transit through a dispersive medium. Since there is cancellation to all orders, also the effects of slowly fluctuating dispersive media are compensated. The experimental setup can be realized with currently available technology, at least for a proof of principle.Comment: 4 pages, 3 figure

Dissociation rates of J/psi's with comoving mesons - thermal vs. nonequilibrium scenario

We study J/psi dissociation processes in hadronic environments. The validity of a thermal meson gas ansatz is tested by confronting it with an alternative, nonequilibrium scenario. Heavy ion collisions are simulated in the framework of the microscopic transport model UrQMD, taking into account the production of charmonium states through hard parton-parton interactions and subsequent rescattering with hadrons. The thermal gas and microscopic transport scenarios are shown to be very dissimilar. Estimates of J/psi survival probabilities based on thermal models of comover interactions in heavy ion collisions are therefore not reliable.Comment: 12 pages, 6 figure

Lens Galaxy Properties of SBS1520+530: Insights from Keck Spectroscopy and AO Imaging

We report on an investigation of the SBS 1520+530 gravitational lens system and its environment using archival HST imaging, Keck spectroscopic data, and Keck adaptive-optics imaging. The AO imaging has allowed us to fix the lens galaxy properties with a high degree of precision when performing the lens modeling, and the data indicate that the lens has an elliptical morphology and perhaps a disk. The new spectroscopic data suggest that previous determinations of the lens redshift may be incorrect, and we report an updated, though inconclusive, value z_lens = 0.761. We have also spectroscopically confirmed the existence of several galaxy groups at approximately the redshift of the lens system. We create new models of the lens system that explicitly account for the environment of the lens, and we also include improved constraints on the lensing galaxy from our adaptive-optics imaging. Lens models created with these new data can be well-fit with a steeper than isothermal mass slope (alpha = 2.29, with the density proportional to r^-alpha) if H_0 is fixed at 72 km/s/Mpc; isothermal models require H_0 ~ 50 km/s/Mpc. The steepened profile may indicate that the lens is in a transient perturbed state caused by interactions with a nearby galaxy.Comment: 12 pages, 10 figures, submitted to Ap

Universality and Phase Diagram around Half-filled Landau Level

Gated GaAs/AlGaAs heterostructures were used to determine the low-temperature behavior of the two-dimensional electron gas near filling factor nu=1/2 in the disorder-magnetic-field plane. We identify a line on which sigma_{xy} is temperature independent, has value sigma_{xy}=0.5 (e^{2}/h), and a distinct line on which rho_{xy}=2 (h/e^{2}). The phase boundaries between the Hall insulator and the principal quantum Hall liquids at nu=1 and 1/3 show levitation of the delocalized states of the first Landau levels for electrons and composite fermions. Finally, the data suggest that there is no true metallic phase around nu=1/2.Comment: 7 pages (Revtex), 5 figure