J/Psi and Psi' total cross sections and formation times from data for charmonium suppression in pApA collisions

The recent data for E866 experiment on the x_F dependence for charmonium suppression in pA collisions at 800 GeV are analyzed using a time- and energy-dependent preformed charmonium absorption cross section \sigma_{abs}^\psi(\tau,\sqrt{s}). For \sqrt{s}=10 GeV the initially (\tau=0) produced premeson has an absorption cross section of \sigma_{pr}~3mb. At the same energy but for \tau -> \infty one deduces for the total cross sections \sigma_{tot}^{J/Psi N}=(2.8\pm 0.3)mb, \sigma_{tot}^{J/Psi N}= (10.5\pm 3.6)mb. The date are compatible with a formation time \tau_{1/2}=0.6 fm/c.Comment: 13 pages of Latex including 2 figures; typos in the abstract are correcte

Leakage Effect on J/psi Pt Distributions in Different Centrality Bins for Pb-Pb Collisions at E/A=160 GeV

A transport approach including a leakage effect for J/psi's in the transverse phase space is used to calculate the ratios between the J/psi transverse momentum distributions in several centrality bins for Pb-Pb collisions at E/A = 160 GeV. From the comparison with the CERN-SPS data, where the centrality is characterized by the transverse energy Et, the leakage effect is extremely important in the region of high transverse momentum and high transverse energy, and both the threshold and the comover models can describe the ratio well for all centrality bins except the most central one (Et < 100 GeV), for which the comover model calculation is considerably better than the threshold one.Comment: 4 pages, 2 figures, REVTEX3.1, accepted for publication in Phys. Rev.

Scanning the Quark-Gluon Plasma with Charmonium

We suggest the variation of charmonium suppression with Feynman x_F in heavy ion collisions as a novel and sensitive probe for the properties of the matter created in such reactions. In contrast to the proton-nucleus case where nuclear suppression is weakest at small x_F, final state interactions with the comoving matter create a minimum at x_F=0, which is especially deep and narrow if a quark-gluon plasma is formed. While a particularly strong effect is predicted at SPS, at the higher RHIC energy it overlaps with the expected sharp variation with x_F of nuclear effects and needs comparison with proton-nucleus data. If thermal enhancement of J/\Psi production takes over at the energies of RHIC and LHC, it will form an easily identified peak, rather than dip in x_F dependence. We predict a steep dependence on centrality and suggest that this new probe is complementary to the dependence on transverse energy, and is more sensitive to a scenario of final state interactions.Comment: 5 pages including 3 figures. Stylistic and clarifying corrections are mad

Dielectric response effects in attosecond time-resolved streaked photoelectron spectra of metal surfaces

The release of conduction-band electrons from a metal surface by a sub-femtosecond extreme ultraviolet (XUV) pulse, and their propagation through the solid, provokes a dielectric response in the solid that acts back on the photoelectron wave packet. We calculated the (wake) potential associated with this photoelectron self-interaction in terms of bulk and surface plasmon excitations and show that it induces a considerable, XUV-frequency-dependent temporal shift in laser-streaked XUV photoemission spectra, suggesting the observation of the ultrafast solid-state dielectric response in contemporary streaked photoemission experiments.Comment: 4 pages and 4 figures, submitted to PR

Resonant Photoelectron Diffraction with circularly polarized light

Resonant angle scanned x-ray photoelectron diffraction (RXPD) allows the determination of the atomic and magnetic structure of surfaces and interfaces. For the case of magnetized nickel the resonant L2 excitation with circularly polarized light yields electrons with a dichroic signature from which the dipolar part may be retrieved. The corresponding L2MM and L3MM Auger electrons carry different angular momenta since their source waves rotate the dichroic dipole in the electron emission patterns by distinct angles

Nuclear Transparency in Heavy Ion Collisions at 14.6 GeV/nucleon

The probability of a projectile nucleon to traverse a target nucleus without interaction is calculated for central Si-Pb collisions and compared to the data of E814. The calculations are performed in two independent ways, via Glauber theory and using the transport code UrQMD. For central collisions Glauber predictions are about 30 to 50% higher than experiment, while the output of UrQMD does not show the experimental peak of beam rapidity particles.Comment: 9 pages, 4 figures. submitted to Nucl. Phys.