Pi0 and Eta measurement with photon conversions in ALICE in proton-proton collisions at sqrt(s) = 7 TeV

We present a measurement of the Pi0 transverse momentum spectrum and of the Eta/Pi0 ratio in proton-proton collisions at sqrt(s) = 7 TeV at the CERN LHC. In this analysis the reconstruction of Pi0 and Eta mesons has been done via photon conversions in the central tracking system of ALICE. Therefore, this method is completely independent from the electromagnetic calorimeters. It makes the Pi0 (Eta) measurement possible down to pt = 0.4 (0.6) GeV/c with a very good resolution and a very small background. For 100 Mio. pp collisions the pt reach is 7 GeV/c. The results are compared to NLO pQCD calculations.Comment: Proceedings to talk at HardProbes 2010, 4 page

Effect of polarized gluon distribution on spin asymmetries for neutral and charged pion production

A longitudinal double spin asymmetry for \pi^0 production has been measured by the PHENIX collaboration. The asymmetry is sensitive to the polarized gluon distribution and is indicated to be positive by theoretical predictions. We study a correlation between behavior of the asymmetry and polarized gluon distribution in neutral and charged pion production at RHIC.Comment: 7 pages, 5 eps figures, section added, typos corrected. to be published in PR

Jet-Medium Interactions with Identified Particles

Identified particles have long been of great interest at RHIC in large part because of the baryon/meson differences observed at intermediate $p_T$ and the implications for hadronization via quark coalescence. With recent high statistics data identified particles are also now central to understanding the details of the jet-medium interactions and energy loss and hadron formation at intermediate and high $p_T$. In particular, high $p_T$ identified particle spectra along with two-particle correlations triggered with direct photons, neutral pions or electrons from heavy flavor decay with hadrons can provide information about how medium modifications to jet fragmentation depend on parton type. I will review recent results with identified particles both in heavy ion systems and the reference measurements in p+p collisions.Comment: Proceedings for Quark Matter 2009, Knoxville T

Physics of Large-x Nuclear Suppression

We discuss a common feature of all known reactions on nuclear targets - a significant suppression at large x. Simple interpretation of this effect is based on energy conservation restrictions in initial state parton rescatterings. Using the light-cone dipole approach this mechanism is shown to control variety of processes on nuclear targets: high-pT particle production at different rapidities as well as direct and virtual (Drell-Yan) photon production. We demonstrate universality and wide applicability of this mechanism allowing to describe large-x effects also at SPS and FNAL energies too low for the onset of coherent effects or shadowing.Comment: 4 pages, 6 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee. Only minor changes in tex

Scaling properties of high p_T inclusive hadron production

We analyze the scaling properties of inclusive hadron production in proton-proton and in heavy ion collisions from fixed target to collider energies. At large transverse momentum p_T, the invariant cross section exhibits a power-like behavior Ed^3\sigma/d^3p\propto p_T^{-n} at fixed transverse x, x_T=2p_T/\sqrt{s}, and fixed center-of-mass scattering angle \theta_{cm}. Knowledge of the exponent n allows one to draw conclusions about the production mechanisms of hadrons, which are poorly known, even at high p_T. We find that high-p_T hadrons are produced by different mechanisms at fixed-target and collider energies. For pions, higher-twist subprocesses where the pion is produced directly dominate at fixed target energy, while leading-twist partonic scattering plus fragmentation is the most important mechanism at collider energies. High-p_T baryons on the other hand appear to be produced by higher-twist mechanisms at all available energies. The higher-twist mechanism of direct proton production can be verified experimentally by testing whether high p_T protons are produced as single hadrons without accompanying secondaries. In addition, we find that medium-induced gluon radiation in heavy ion collisions can violate scaling.Comment: 14 pages, 3 figure

Nuclear parton distributions at next to leading order

We perform a next to leading order QCD global analysis of nuclear deep inelastic scattering and Drell-Yan data using the convolution approach to parameterize nuclear parton densities. We find both a significant improvement in the agreement with data compared to previous extractions, and substantial differences in the scale dependence of nuclear effects compared to leading order analyses.Comment: 9 pages, 10 figure

Overview and first results of the Wind and Storms Experiment (WASTEX): a field campaign to observe the formation of gusts using a Doppler lidar

Wind gusts are responsible for most damages in winter storms over central Europe, but capturing their small scale and short duration is a challenge for both models and observations. This motivated theWind and Storms Experiment (WASTEX) dedicated to investigate the formation of gusts during the passage of extratropical cyclones. The field campaign took place during the winter 2016–2017 on a former waste deposit located close to Karlsruhe in the Upper Rhine Valley in southwest Germany. Twelve extratropical cyclones were sampled during WASTEX with a Doppler lidar system performing vertical scans in the mean wind direction and complemented with a Doppler C-band radar and a 200m instrumented tower. First results are provided here for the three most intense storms and include a potential sting jet, a unique direct observation of a convective gust and coherent boundary-layer structures of strong winds

Quantum-noise-limited optical frequency comb spectroscopy

We achieve a quantum-noise-limited absorption sensitivity of 1.7/times10$^{-12}$ cm$^{-1}$ per spectral element at 400 s of acquisition time with cavity-enhanced frequency comb spectroscopy, the highest demonstrated for a comb-based technique. The system comprises a frequency comb locked to a high-finesse cavity and a fast-scanning Fourier transform spectrometer with an ultra-low-noise autobalancing detector. Spectra with a signal-to-noise ratio above 1000 and a resolution of 380 MHz are acquired within a few seconds. The measured absorption lineshapes are in excellent agreement with theoretical predictions.Comment: 18 pages, 4 figures; http://prl.aps.org/pdf/PRL/v107/i23/e23300

EPS09 - Nuclear PDFs and Their Uncertainties at NLO

In this talk, we present our recent next-to-leading order (NLO) nuclear parton distribution functions (nPDFs), which we call EPS09. As an extension to earlier NLO analyses, we supplement the deep inelastic scattering and Drell-Yan dilepton data by inclusive midrapidity pion measurements from RHIC in order to reduce the otherwize large freedom in the nuclear gluon densities. Our Hessian-type error analysis leading to a collection of nPDF error sets, is the first of its kind among the nPDF analyses.Comment: 4 pages, 4 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse