Correlations of Heavy Quarks Produced at Large Hadron Collider

We study the correlations of heavy quarks produced in relativistic heavy ion collisions and find them to be quite sensitive to the effects of the medium and the production mechanisms. In order to put this on a quantitative footing, as a first step, we analyze the azimuthal, transverse momentum, and rapidity correlations of heavy quark-anti quark ($Q\overline{Q}$) pairs in $pp$ collisions at $\cal{O}$($\alpha_{s}^{3}$). This sets the stage for the identification and study of medium modification of similar correlations in relativistic collision of heavy nuclei at the Large Hadron Collider. Next we study the additional production of charm quarks in heavy ion collisions due to multiple scatterings, {\it viz.}, jet-jet collisions, jet-thermal collisions, and thermal interactions. We find that these give rise to azimuthal correlations which are quite different from those arising from prompt initial production at leading order and at next to leading order.Comment: 26 pages, 15 figures. Three new figures added, comparison to experimental data included, abstract and discussion expande

Longitudinal muon spin relaxation in high purity aluminum and silver

The time dependence of muon spin relaxation has been measured in high purity aluminum and silver samples in a longitudinal 2 T magnetic field at room temperature, using time-differential \musr. For times greater than 10 ns, the shape fits well to a single exponential with relaxation rates of \lambda_{\textrm{Al}} = 1.3 \pm 0.2\,(\textrm{stat.}) \pm 0.3\,(\textrm{syst.})\,\pms and \lambda_{\textrm{Ag}} = 1.0 \pm 0.2\,(\textrm{stat.}) \pm 0.2\,(\textrm{syst.})\,\pms

EMail-Verteiler zur Distribution digitaler Informationen im Zentrum für ZMK-Münster

Auf der Basis verschiedener in HTML-Seiten integrierter PHP-Scripte können EMails an vordefinierte Zielgruppen, z.B. an alle Studenten, an alle Mitarbeiter einer Poliklinik oder auch an eine manuell selektierbare individuelle Liste von Personen geschickt werden. Der PHP-Server des Apache-Webserves sorgt für eine augenblickliche, schnelle Distribution ohne Abhängigkeit von Mail-Servern der Universität, persönlichen Providern oder lokalen EMail-Programmen. Digitale Verteiler sind herkömmlichen 'Snail-Mail'-Verteilern in Geschwindigkeit und Qualität weit überlegen und werden diese vermutlich bald vollständig ersetzen können

Anomalous mass dependence of radiative quark energy loss in a finite-size quark-gluon plasma

We demonstrate that for a finite-size quark-gluon plasma the induced gluon radiation from heavy quarks is stronger than that for light quarks when the gluon formation length becomes comparable with (or exceeds) the size of the plasma. The effect is due to oscillations of the light-cone wave function for the in-medium $q\to gq$ transition. The dead cone model by Dokshitzer and Kharzeev neglecting quantum finite-size effects is not valid in this regime. The finite-size effects also enhance the photon emission from heavy quarks.Comment: 8 pages, 3 figure

Direct growth of graphene on GaN via plasma-enhanced chemical vapor deposition under N₂ atmosphere

One of the bottlenecks in the implementation of graphene as a transparent electrode in modern opto-electronic devices is the need for complicated and damaging transfer processes of high-quality graphene sheets onto the desired target substrates. Here, we study the direct, plasma-enhanced chemical vapor deposition (PECVD) growth of graphene on GaN-based light-emitting diodes (LEDs). By replacing the commonly used hydrogen (H2) process gas with nitrogen (N2), we were able to suppress GaN surface decomposition while simultaneously enabling graphene deposition at lt;800 °C in a single-step growth process. Optimizing the methane (CH4) flow and varying the growth time between 0.5 h and 8 h, the electro-optical properties of the graphene layers could be tuned to sheet resistances as low as ∼1 kΩ/D with a maximum transparency loss of ∼12. The resulting high-quality graphene electrodes show an enhanced current spreading effect and an increase of the emission area by a factor of ∼8 in operating LEDs. © 2020 The Author(s)

Strange Particle Production in p+p, p+Pb and Pb+Pb Interactions from NA49

Recent NA49 results on Lambda, Antilambda, Xi- and Antixi+ production in minimum bias p+p and centrality selected p+Pb collisions at 158 GeV/c, and the results on Lambda, Antilambda, K+ and K- production in central Pb+Pb collisions at 40, 80 and 158 A GeV are discussed and compared with other available data. By comparing the energy dependence of Lambda and Antilambda production at mid-rapidity a striking similarity is observed between p+p and A+A data. This is also seen in the energy dependence of the Lambda/pi ratio. K+/pi at mid-rapidity is affected in a similar way, due to the associated production of K+ together with Lambda particles. The observed yields increase faster than the number of wounded nucleons when comparing p+Pb to p+p. As already observed in A+A collisions, the increase is larger for multistrange than for strange baryons and for baryons than for anti-baryons.Comment: 8 pages, 10 figures, To appear in proceedings of Strange Quark in Matter 2001-A Flavourspace Odyssey, Frankfurt am Main, Germany, 24-29. Sept. 200

Recent high pT measurements in STAR

After five years of data taking, the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory provides precise measurements of particle production at high transverse momentum in p-p, d-Au, and Au-Au collisions at sqrt(s) = 200 GeV. We review recent results on the flavor dependence of high pT particle suppression and hadron particle spectra at sqrt(s) = 62.4 GeV. New results on two-particle angular correlations for identified trigger particles and for low momentum associated charged hadrons in p-p and Au-Au as well as near-side $\Delta\eta$ correlations will be presented and discussed.Comment: 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, Calcutta. 8 pages, 10 figures, submitted to J. Phys. G: Nucl. Part. Phy