Flavor ordering of elliptic flows at high transverse momentum

Based on the quark coalescence model for the parton-to-hadron phase transition in ultra-relativistic heavy ion collisions, we relate the elliptic flow ($v_2$) of high \pt hadrons to that of high \pt quarks. For high \pt hadrons produced from an isospin symmetric and quark-antiquark symmetric partonic matter, magnitudes of their elliptic flows follow a flavor ordering as $(v_{2,\pi}=v_{2,N}) > (v_{2,\Lambda}=v_{2,\Sigma}) > v_{2,K} > v_{2,\Xi} > (v_{2,\phi}=v_{2,\Omega})$ if strange quarks have a smaller elliptic flow than light quarks. The elliptic flows of high \pt hadrons further follow a simple quark counting rule if strange quarks and light quarks have same high \pt spectrum and coalescence probability.Comment: 4 pages, 1 figure, revte

Timing performance of 30-nm-wide superconducting nanowire avalanche photodetectors

We investigated the timing jitter of superconducting nanowire avalanche photodetectors (SNAPs, also referred to as cascade switching superconducting single photon detectors) based on 30-nm-wide nanowires. At bias currents (IB) near the switching current, SNAPs showed sub 35 ps FWHM Gaussian jitter similar to standard 100 nm wide superconducting nanowire single-photon detectors. At lower values of IB, the instrument response function (IRF) of the detectors became wider, more asymmetric, and shifted to longer time delays. We could reproduce the experimentally observed IRF time-shift in simulations based on an electrothermal model, and explain the effect with a simple physical picture

Meson and baryon elliptic flow at high pT from parton coalescence

The large and saturating differential elliptic flow v2(pT) observed in Au+Au reactions at RHIC so far could only be explained assuming an order of magnitude denser initial parton system than estimated from perturbative QCD. Hadronization via parton coalescence can resolve this ``opacity puzzle'' because it enhances hadron elliptic flow at large pT relative to that of partons at the same transverse momentum. An experimentally testable consequence of the coalescence scenario is that v2(pT) saturates at about 50% higher values for baryons than for mesons. In addition, if strange quarks have weaker flow than light quarks, hadron v2 at high pT decreases with relative strangeness content.Comment: Talk at SQM2003 [7th Int. Conf. on Strangeness in Quark Matter (Atlantic Beach, NC, USA, Mar 12-17, 2003)] - 6 pages, 5 eps figs, IOP style file

Constraints on the Energy Content of the Universe from a Combination of Galaxy Cluster Observables

We demonstrate that constraints on cosmological parameters from the distribution of clusters as a function of redshift (dN/dz) are complementary to accurate angular diameter distance (D_A) measurements to clusters, and their combination significantly tightens constraints on the energy density content of the Universe. The number counts can be obtained from X-ray and/or SZ (Sunyaev-Zel'dovich effect) surveys, and the angular diameter distances can be determined from deep observations of the intra-cluster gas using their thermal bremsstrahlung X-ray emission and the SZ effect. We combine constraints from simulated cluster number counts expected from a 12 deg^2 SZ cluster survey and constraints from simulated angular diameter distance measurements based on the X-ray/SZ method assuming a statistical accuracy of 10% in the angular diameter distance determination of 100 clusters with redshifts less than 1.5. We find that Omega_m can be determined within about 25%, Omega_Lambda within 20%, and w within 16%. We show that combined dN/dz + D_A constraints can be used to constrain the different energy densities in the Universe even in the presence of a few percent redshift dependent systematic error in D_A. We also address the question of how best to select clusters of galaxies for accurate diameter distance determinations. We show that the joint dN/dz + D_A constraints on cosmological parameters for a fixed target accuracy in the energy density parameters are optimized by selecting clusters with redshift upper cut--offs in the range 0.5 < z < 1.Comment: LateX, 6 pages, 5 figures. Accepted for publication in The Astrophysical Journa

Rethinking the QCD collisional energy loss

It is shown that to leading order the collisional energy loss of an energetic parton in the hot quark gluon plasma reads $dE/dx \sim \alpha(m_D^2)T^2$, where the scale of the coupling is determined by the (parametrically soft) Debye screening mass. Compared to previous expressions derived by Bjorken and other authors, $dE^B/dx \sim \alpha^2 T^2 \ln(ET/m_D^2)$, the rectified result takes into account the running of the coupling, as dictated by quantum corrections beyond tree level. As one significant consequence, due to asymptotic freedom, the QCD collisional energy loss becomes independent of the jet energy in the limit $E \gg T$. It is advocated that this resummation improved perturbative result might be useful to (re-)estimate the collisional energy loss for temperatures relevant in heavy ion phenomenology.Comment: contribution to "Hot Quarks 2006", Villasimius, Italy, 15-20 May 200

Elliptic flow at large transverse momenta from quark coalescence

We show that hadronization via quark coalescence enhances hadron elliptic flow at large pT relative to that of partons at the same transverse momentum. Therefore, compared to earlier results based on covariant parton transport theory, more moderate initial parton densities dN/d\eta(b=0) ~ 1500-3000 can explain the differential elliptic flow v_2(pT) data for Au+Au reactions at s^1/2=130 and 200 AGeV from RHIC. In addition, v2(pT) could saturate at about 50% higher values for baryons than for mesons. If strange quarks have weaker flow than light quarks, hadron v_2 at high pT decreases with relative strangeness content.Comment: Minor changes, extended discussion. To appear in PR

Overview of Hard processes at RHIC: high-pt light hadron and charm production

An overview of the experimental results on high-pt light hadron production and open charm production is presented. Data on particle production in elementary collisions are compared to next-to-leading order perturbative QCD calculations. Particle production in Au+Au collisions is then compared to this baseline.Comment: 9 pages, 6 figures, Strange Quark Matter 200

Impact of solid waste disposal on nutrient dynamics in a sandy catchment

Groundwaters impacted by mature landfill leachate are generally enriched in ammonium. In order to assess the dynamics of ammonium exchanges between leachates and the water system inside a sandy permeable catchment we measured ammonium, nitrate and chloride concentrations in the stream and in sediment pore waters of the streambed of a landfill impacted aquifer. Geophysical investigation methods complemented the biogeochemical survey. The studied zone is a 23 km² catchment located in a coastal lagoon area sensitive to eutrophication risk. Ammonium concentrations in the river were up to 800 µmol l−1 during low water period in summer. Three surveys of the river chemistry showed a regular increase in ammonium, nitrate and chloride concentrations along a 1 km section of the watercourse, downstream the landfill, implying that the leachate plume exfiltrates along this section. Sediment cores collected within this section showed all an increase in ammonium concentrations with depth in pore waters as a consequence of the landfill leachate dispersion, as attested by a simultaneous increase in chloride concentrations. Nitrate enrichment in the river water was due to nitrification of ammonium at the interface between groundwater and streamwater. The apparent nitrification rate obtained was within values reported for turbid estuaries, although the river contained very little suspended particulate matter. Actually, pore water chemistry suggests that nitrification occurred for the most part in subsurface permeable sediments, rather than in stream water. The overall topographic, hydrological, geochemical, and geoelectrical data set permit to estimate the extension of the chloride and ammonium plume. The estimation of the apparent ammonium plume velocity is 23 m year−1 whereas the chloride plume velocity should be 50 m year−1. The river is the outlet of the impacted groundwaters. Considering that the input of ammonium from the landfill is balanced by the present day output via the river, the residence time of ammonium in the aquifer is between 7 and 18 years

Mechanism of action of VP1-001 in cryAB(R120G)-associated and age-related cataracts

PurposeWe previously identified an oxysterol, VP1-001 (also known as compound 29), that partially restores the transparency of lenses with cataracts. To understand the mechanism of VP1-001, we tested the ability of its enantiomer, ent-VP1-001, to bind and stabilize αB-crystallin (cryAB) in vitro and to produce a similar therapeutic effect in cryAB(R120G) mutant and aged wild-type mice with cataracts. VP1-001 and ent-VP1-001 have identical physicochemical properties. These experiments are designed to critically evaluate whether stereoselective binding to cryAB is required for activity.MethodsWe compared the binding of VP1-001 and ent-VP1-001 to cryAB using in silico docking, differential scanning fluorimetry (DSF), and microscale thermophoresis (MST). Compounds were delivered by six topical administrations to mouse eyes over 2 weeks, and the effects on cataracts and lens refractive measures in vivo were examined. Additionally, lens epithelial and fiber cell morphologies were assessed via transmission electron microscopy.ResultsDocking studies suggested greater binding of VP1-001 into a deep groove in the cryAB dimer compared with ent-VP1-001. Consistent with this prediction, DSF and MST experiments showed that VP1-001 bound cryAB, whereas ent-VP1-001 did not. Accordingly, topical treatment of lenses with ent-VP1-001 had no effect, whereas VP1-001 produced a statistically significant improvement in lens clarity and favorable changes in lens morphology.ConclusionsThe ability of VP1-001 to bind native cryAB dimers is important for its ability to reverse lens opacity in mouse models of cataracts

Shear viscosity and chemical equilibration of the QGP

We have investigated, in the frame work of the transport approach, different aspects of the QGP created in Heavy Ion Collisions at RHIC and LHC energies. The shear viscosity $\eta$ has been calculated by using the Green-Kubo relation at the cascade level. We have compared the numerical results for $\eta$ obtained from the Green-Kubo correlator with the analytical formula in both the Relaxation Time Approximation (RTA) and the Chapman-Enskog approximation (CE). From this comparison we show that in the range of temperature explored in a Heavy Ion collision the RTA underestimates the viscosity by about a factor of 2, while a good agreement is found between the CE approximation and Gree-Kubo relation already at first order of approximation. The agreement with the CE approximation supplies an analytical formula that allows to develop kinetic transport theory at fixed shear viscosity to entropy density ratio, $\eta/s$. We show some results for the build up of anisotropic flows $v_{2}$ in a transport approach at fixed shear viscosity to entropy density ratio, $\eta/s$. We study the impact of a T-dependent $\eta/s(T)$ on the generation of the elliptic flows at both RHIC and LHC. We show that the transport approach provides, in a unified way, a tool able to naturally describe the $v_{2}(p_{T})$ in a wide range of $p_{T}$, including also the description of the rise and fall and saturation of the $v_{2}(p_{T})$ observed at LHC. Finally, we have studied the evolution of the quark-gluon composition employing a Boltzmann-Vlasov transport approach that include: the mean fields dynamics, associated to the quasi-particle model, and the elastic and inelastic collisions for massive quarks and gluons. Following the chemical evolution from an initial gluon dominated plasma we predict a quark dominance close to $T_{C}$ paving the way to an hadronization via quark coalescence.Comment: 15 pages, 10 figures, Invited Talk given by S. Plumari at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS