Energy resolution of alpha particles in a microbulk Micromegas detector at high pressure Argon and Xenon mixtures

The latest Micromesh Gas Amplification Structures (Micromegas) are achieving outstanding energy resolution for low energy photons, with values as low as 11% FWHM for the 5.9 keV line of $^{55}$Fe in argon/isobutane mixtures at atmospheric pressure. At higher energies (MeV scale), these measurements are more complicated due to the difficulty in confining the events in the chamber, although there is no fundamental reason why resolutions of 1% FWHM or below could not be reached. There is much motivation to demonstrate experimentally this fact in Xe mixtures due to the possible application of Micromegas readouts to the Double Beta Decay search of $^{136}$Xe, or in other experiments needing calorimetry and topology in the same detector. In this paper, we report on systematic measurements of energy resolution with state-of-the-art Micromegas using a 5.5 MeV alpha source in high pressure Ar/isobutane mixtures. Values as low as 1.8% FWHM have been obtained, with possible evidence that better resolutions are achievable. Similar measurements in Xe, of which a preliminary result is also shown here, are under progress.Comment: 16 pages, 19 figures, version after referees comments. Accepted for publication in Nuclear Instruments and Methods

Micromegas in a Bulk

In this paper we present a novel way to manufacture the bulk Micromegas detector. A simple process based on the PCB (Printed Circuit Board) technology is employed to produce the entire sensitive detector. Such fabrication process could be extended to very large area detectors made by the industry. The low cost fabrication together with the robustness of the electrode materials will make it extremely attractive for several applications ranging from particle physics and astrophysics to medicineComment: 6 pages, 4 figure

Antimatter and Matter Production in Heavy Ion Collisions at CERN (The NEWMASS Experiment NA52)

Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. Together with previous data taking at a rigidity of -20 GeV/c we obtained 10^6 antiprotons 10^3 antideuterons and two antihelium3 without centrality requirements. We measured nuclei and antinuclei (p,d,antiprotons, antideuterons) near midrapidity covering an impact parameter range of b=2-12 fm. Our results strongly indicate that nuclei and antinuclei are mainly produced via the coalescence mechanism. However the centrality dependence of the antibaryon to baryon ratios show that antibaryons are diminished due to annihilation and breakup reactions in the hadron dense environment. The volume of the particle source extracted from coalescence models agrees with results from pion interferometry for an expanding source. The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide with each other and with the thermal freeze-out of hadrons.Comment: 12 pages, 8 figures, to appear in the proceedings of the conference on 'Fundamental Issues in Elementary Matter' Bad Honnef, Germany, Sept. 25-29, 200

Centrality dependence of K+ produced in Pb+Pb collisions at 158 GeV per nucleon

The NA52 collaboration searches for a discontinuous behaviour of charged kaons produced in Pb+Pb collisions at 158 A GeV as a function of the impact parameter, which could reveal a hadron to quark-gluon plasma (QGP) phase transition. The K+ yield is found to grow proportional to the number of participating ('wounded') nucleons N, above N=100. Previous NA52 data agree with the above finding and show a discontinuous behaviour in the kaon centrality dependence near N=100, marking the onset of strangeness enhancement -over e.g. p+A data at the same \sqrt{s}- in a chemically equilibrated phase.Comment: 2 pages, 2 figures, submitted to the XXXth International Conference on High Energy Physics, 27 July - 2 August, 2000, Osaka, Japa

QUARTET EXCITATION IN 20Ne MAY BE SEEN THROUGH THE DECAY IN 8Be + 12C

Les résultats préliminaires de 1'étude de 19F + p → 8Be + 12C et 16O + α → 8Be + 12C dans la region d'excitation de 20Ne 15,3 < Ex < 18,7 MeV semblent montrer que la plupart des niveaux trouvés sont 8 particule-4 trous et que les deux plus importantes résonances peuvent être la tête de bande du processus 12 particule-8 trous.Preliminary results of the study of 19F + p → 8Be + 12C and 16O + α → 8Be + 12C in the region of excitation of 20Ne 15.3 < Ex < 18.7 MeV show tentatively that most of the found levels are 8 particle-4 holes, and the two biggest resonances could be the head band of 12 particle-8 holes process

Search for significant background fluctuations in the EUSO-Balloon data

International audienceThe EUSO-Balloon instrument recorded data during a stratospheric flight in August 2014, to measure the UV background during a moonless night, from an altitude of ∼ 38 km, with a field of view of ±5.5 ◦ . In this paper, we report on the search for coherent fluctuations of this background over areas ranging from ∼ 1 km2 up to the entire field of view, on timescales from a few µs to ∼ 100µs. In addition to the expected laser track events induced by shootings from a helicopter flying in the field-of-view of EUSO-Balloon during part of the mission, three unidentified and significant events, probably related to human activity, are discussed

Ultra high energy cosmic ray detector KLYPVE on board the Russian Segment of the ISS

International audienceModified KLYPVE is a novel fluorescence detector of ultra high energy cosmic rays (UHECRs, energies & 50 EeV) to be installed on the Russian Segment of the International Space Station. The main goal of the experiment is to register arrival directions and energies of UHECRs but it will be able to register other transient events in the atmosphere as well. The main component of KLYPVE is a segmented two component optical system with a large entrance pupil and a wide field of view, which provides annual exposure approximately twice that of the Pierre Auger Observatory. The project is actively developed by a working group of the JEM-EUSO Collaboration led by Skobeltsyn Institute of Nuclear Physics at Moscow State University (Russia). The current status of KLYPVE with a focus on its scientific tasks, technical parameters and instruments is presented