Heavy flavor in heavy-ion collisions at RHIC and RHIC II

In the initial years of operation, experiments at the Relativistic Heavy Ion Collider (RHIC) have identified a new form of matter formed in nuclei-nuclei collisions at energy densities more than 100 times that of a cold atomic nucleus. Measurements and comparison with relativistic hydrodynamic models indicate that the matter thermalizes in an unexpectedly short time, has an energy density at least 15 times larger than needed for color deconfinement, has a temperature about twice the critical temperature predicted by lattice QCD, and appears to exhibit collective motion with ideal hydrodynamic properties - a "perfect liquid" that appears to flow with a near-zero viscosity to entropy ratio - lower than any previously observed fluid and perhaps close to a universal lower bound. However, a fundamental understanding of the medium seen in heavy-ion collisions at RHIC does not yet exist. The most important scientific challenge for the field in the next decade is the quantitative exploration of the new state of nuclear matter. That will require new data that will, in turn, require enhanced capabilities of the RHIC detectors and accelerator. In this report we discuss the scientific opportunities for an upgraded RHIC facility - RHIC II - in conjunction with improved capabilities of the two large RHIC detectors, PHENIX and STAR. We focus solely on heavy flavor probes. Their production rates are calculable using the well-established techniques of perturbative QCD and their sizable interactions with the hot QCD medium provide unique and sensitive measurements of its crucial properties making them one of the key diagnostic tools available to us.Comment: 96 pages, 53 figures. Accepted for publication in Physics Reports. Fixed typo in Fig. 15 captio

Enhanced carrier scattering rates in dilute magnetic semiconductors with correlated impurities

In III-V dilute magnetic semiconductors (DMSs) such as Ga$_{1-x}$Mn$_x$As, the impurity positions tend to be correlated, which can drastically affect the electronic transport properties of these materials. Within the memory function formalism we have derived a general expression for the current relaxation kernel in spin and charge disordered media and have calculated spin and charge scattering rates in the weak-disorder limit. Using a simple model for magnetic impurity clustering, we find a significant enhancement of the charge scattering. The enhancement is sensitive to cluster parameters and may be controllable through post-growth annealing.Comment: 4 pages, 3 figure

Violation of the `Zero-Force Theorem' in the time-dependent Krieger-Li-Iafrate approximation

We demonstrate that the time-dependent Krieger-Li-Iafrate approximation in combination with the exchange-only functional violates the `Zero-Force Theorem'. By analyzing the time-dependent dipole moment of Na5 and Na9+, we furthermore show that this can lead to an unphysical self-excitation of the system depending on the system properties and the excitation strength. Analytical aspects, especially the connection between the `Zero-Force Theorem' and the `Generalized-Translation Invariance' of the potential, are discussed.Comment: 5 pages, 4 figure

Anisotropic splitting of intersubband spin plasmons in quantum wells with bulk and structural inversion asymmetry

In semiconductor heterostructures, bulk and structural inversion asymmetry and spin-orbit coupling induce a k-dependent spin splitting of valence and conduction subbands, which can be viewed as being caused by momentum-dependent crystal magnetic fields. This paper studies the influence of these effective magnetic fields on the intersubband spin dynamics in an asymmetric n-type GaAs/AlGaAs quantum well. We calculate the dispersions of intersubband spin plasmons using linear response theory. The so-called D'yakonov-Perel' decoherence mechanism is inactive for collective intersubband excitations, i.e., crystal magnetic fields do not lead to decoherence of spin plasmons. Instead, we predict that the main signature of bulk and structural inversion asymmetry in intersubband spin dynamics is a three-fold, anisotropic splitting of the spin plasmon dispersion. The importance of many-body effects is pointed out, and conditions for experimental observation with inelastic light scattering are discussed.Comment: 8 pages, 6 figure

XUV Frequency Combs via Femtosecond Enhancement Cavities

We review the current state of tabletop extreme ultraviolet (XUV) sources based on high harmonic generation (HHG) in femtosecond enhancement cavities (fsEC). Recent developments have enabled generation of high photon flux (1014 photons/sec) in the XUV, at high repetition rates (>50 MHz) and spanning the spectral region from 40 nm - 120 nm. This level of performance has enabled precision spectroscopy with XUV frequency combs and promises further applications in XUV spectroscopic and photoemission studies. We discuss the theory of operation and experimental details of the fsEC and XUV generation based on HHG, including current technical challenges to increasing the photon flux and maximum photon energy produced by this type of system. Current and future applications for these sources are also discussed.Comment: invited review article, 38 page

About possible contribution of intrinsic charm component to inclusive spectra of charmed mesons

We calculate differential energy spectra ($x_F$-distributions) of charmed particles produced in proton-nucleus collisions, assuming the existence of intrinsic heavy quark components in the proton wave function. For the calculation, the recently proposed factorization scheme is used, based on the Color Glass Condensate theory and specially suited for predictions of a production of particles with large rapidities. It is argued that the intrinsic charm component can, if it exists, dominate in a sum of two components, intrinsic + extrinsic, of the inclusive spectrum of charmed particles produced in proton-nucleus collisions at high energies, in the region of medium $x_F$, $0.15 < x_F < 0.7$, and can give noticeable contribution to atmospheric fluxes of prompt muons and neutrinos.Comment: 10 pages, 4 figures. Version published in J. Phys. G

Potential for ultrafast dynamic chemical imaging with few-cycle infrared lasers

We studied the photoelectron spectra generated by an intense few-cycle infrared laser pulse. By focusing on the angular distributions of the back rescattered high energy photoelectrons, we show that accurate differential elastic scattering cross sections of the target ion by free electrons can be extracted. Since the incident direction and the energy of the free electrons can be easily changed by manipulating the laser's polarization, intensity, and wavelength, these extracted elastic scattering cross sections, in combination with more advanced inversion algorithms, may be used to reconstruct the effective single-scattering potential of the molecule, thus opening up the possibility of using few-cycle infrared lasers as powerful table-top tools for imaging chemical and biological transformations, with the desired unprecedented temporal and spatial resolutions.Comment: 16 pages, 6 figure