Beam Performance of Tracking Detectors with Industrially Produced GEM Foils

Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been tested extensively in particle beams at the Meson Test Beam Facility at Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They showed an efficiency in excess of 95% and spatial resolution better than 70 um. The influence of the angle of incidence of particles on efficiency and spatial resolution was studied in detail.Comment: 8 pages, 9 figures, accepted by Nuclear Instruments and Methods in Physics Research

Does the Sigma(1580)3/2- resonance exist?

Precise new data for the reaction $K^- p \to \pi^0 \Lambda$ are presented in the c.m. energy range 1565 to 1600 MeV. Our analysis of these data sheds new light on claims for the $\Sigma(1580){3/2}^-$ resonance, which (if it exists with the specified quantum numbers) must be an exotic baryon because of its very low mass. Our results show no evidence for this state.Comment: 4 pages, 4 figure

A Method to Polarize Stored Antiprotons to a High Degree

Polarized antiprotons can be produced in a storage ring by spin--dependent interaction in a purely electron--polarized hydrogen gas target. The polarizing process is based on spin transfer from the polarized electrons of the target atoms to the orbiting antiprotons. After spin filtering for about two beam lifetimes at energies $T\approx 40-170$ MeV using a dedicated large acceptance ring, the antiproton beam polarization would reach $P=0.2-0.4$. Polarized antiprotons would open new and unique research opportunities for spin--physics experiments in $\bar{p}p$ interactions

Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance

Differential cross sections for the process pi^- p -> gamma n have been measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations. A new three-parameter SAID fit yields 36 +/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.Comment: 14 pages, 8 figures, submitted to PR

Observation of the Charge Symmetry Breaking d + d -> 4He + pi0 Reaction Near Threshold

We report the first observation of the charge symmetry breaking d + d -> 4He + pi0 reaction near threshold at the Indiana University Cyclotron Facility. Kinematic reconstruction permitted the separation of 4He + pi0 events from double radiative capture 4He + gamma + gamma events. We measured total cross sections for neutron pion production of 12.7 +- 2.2 pb at 228.5 MeV and 15.1 +- 3.1 pb at 231.8 MeV. The uncertainty is dominated by statistical errors.Comment: 7 pages, 2 figures, plain Te

Highlights from the Pierre Auger Observatory

The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km$^2$ str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our X$_{max}$ data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201

A novel method for the absolute fluorescence yield measurement by AIRFLY

One of the goals of the AIRFLY (AIR FLuorescence Yield) experiment is to measure the absolute fluorescence yield induced by electrons in air to better than 10% precision. We introduce a new technique for measurement of the absolute fluorescence yield of the 337 nm line that has the advantage of reducing the systematic uncertainty due to the detector calibration. The principle is to compare the measured fluorescence yield to a well known process - the Cerenkov emission. Preliminary measurements taken in the BFT (Beam Test Facility) in Frascati, Italy with 350 MeV electrons are presented. Beam tests in the Argonne Wakefield Accelerator at the Argonne National Laboratory, USA with 14 MeV electrons have also shown that this technique can be applied at lower energies.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid, Spain, 16 - 20 September 200

Inclusive pi^0, eta, and direct photon production at high transverse momentum in p+p and d+Au collisions at sqrt(s_NN) = 200 GeV

We report a measurement of high-p_T inclusive pi^0, eta, and direct photon production in p+p and d+Au collisions at sqrt(s_NN) = 200 GeV at midrapidity (0 gamma gamma were detected in the Barrel Electromagnetic Calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The eta -> gamma gamma decay was also observed and constituted the first eta measurement by STAR. The first direct photon cross section measurement by STAR is also presented, the signal was extracted statistically by subtracting the pi^0, eta, and omega(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading order perturbative QCD calculations.Comment: 28 pages, 30 figures, 6 tables, the updated version that was accepted by Phys. Rev.

Strangeness Enhancement in Cu+Cu and Au+Au Collisions at \sqrt{s_{NN}} = 200 GeV

We report new STAR measurements of mid-rapidity yields for the $\Lambda$, $\bar{\Lambda}$, $K^{0}_{S}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, $\bar{\Omega}^{+}$ particles in Cu+Cu collisions at \sNN{200}, and mid-rapidity yields for the $\Lambda$, $\bar{\Lambda}$, $K^{0}_{S}$ particles in Au+Au at \sNN{200}. We show that at a given number of participating nucleons, the production of strange hadrons is higher in Cu+Cu collisions than in Au+Au collisions at the same center-of-mass energy. We find that aspects of the enhancement factors for all particles can be described by a parameterization based on the fraction of participants that undergo multiple collisions

Azimuthal anisotropy of K0s and Lambda prduction at mid-rapidity from Au+Au collisions at root s = 130 GeV

We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV at RHIC. The value of v2 as a function of transverse momentum of the produced particles pt and collision centrality is presented for both particles up to pt 3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.Comment: 6 pages, 4 figures, by the STAR collaboratio