| 1. |
- Schael, S, et al.
(författare)
-
Precision electroweak measurements on the Z resonance
- 2006
-
Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
-
Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
|
|
| 2. |
|
|
| 3. |
- Abdo, A. A., et al.
(författare)
-
FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE VELA PULSAR
- 2009
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 696:2, s. 1084-1093
-
Tidskriftsartikel (refereegranskat)abstract
- The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new gamma-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high-quality pulse profile, with some 32,400 pulsed photons at E >= 0.03 GeV, shows new features, including pulse structure as fine as 0.3 ms and a distinct third peak, which shifts in phase with energy. We examine the high-energy behavior of the pulsed emission; initial spectra suggest a phase-averaged power-law index of Gamma = 1.51(-0.04)(+0.05) with an exponential cutoff at E-c = 2.9 +/- 0.1 GeV. Spectral fits with generalized cutoffs of the form e(-(E/Ec)b) require b <= 1, which is inconsistent with magnetic pair attenuation, and thus favor outer-magnetosphere emission models. Finally, we report on upper limits to any unpulsed component, as might be associated with a surrounding pulsar wind nebula.
|
|
| 4. |
- Atwood, W. B., et al.
(författare)
-
THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION
- 2009
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 697:2, s. 1071-1102
-
Tidskriftsartikel (refereegranskat)abstract
- The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy gamma-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic gamma-ray background up to TeV energies, and (7) explore the discovery space for dark matter.
|
|
| 5. |
- Adriani, O., et al.
(författare)
-
Measurements of quasi-trapped electron and positron fluxes with PAMELA
- 2009
-
Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114, s. A12218-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents precise measurements of the differential energy spectra of quasi-trapped secondary electrons and positrons and their ratio between 80 MeV and 10 GeV in the near-equatorial region (altitudes between 350 km and 600 km). Latitudinal dependences of the spectra are analyzed in detail. The results were obtained from July until November 2006 onboard the Resurs-DK satellite by the PAMELA spectrometer, a general purpose cosmic ray detector system built around a permanent magnet spectrometer and a silicon-tungsten calorimeter.
|
|
| 6. |
- Greiner, J., et al.
(författare)
-
Gamma-ray burst investigation via polarimetry and spectroscopy (GRIPS)
- 2009
-
Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:1, s. 91-120
-
Tidskriftsartikel (refereegranskat)abstract
- The primary scientific goal of the GRIPS mission is to revolutionize our understanding of the early universe using gamma-ray bursts. We propose a new generation gamma-ray observatory capable of unprecedented spectroscopy over a wide range of gamma-ray energies (200 keV-50 MeV) and of polarimetry (200-1000 keV). The gamma-ray sensitivity to nuclear absorption features enables the measurement of column densities as high as 10(28)cm (-aEuro parts per thousand 2). Secondary goals achievable by this mission include direct measurements of all types of supernova interiors through gamma-rays from radioactive decays, nuclear astrophysics with massive stars and novae, and studies of particle acceleration near compact stars, interstellar shocks, and clusters of galaxies.
|
|
| 7. |
- Adriani, O., et al.
(författare)
-
Secondary electron and positron fluxes in the near-Earth space observed in the ARINA and PAMELA experiments
- 2009
-
Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 73:3, s. 364-366
-
Tidskriftsartikel (refereegranskat)abstract
- Secondary electron and positron fluxes in the energy range from 3 MeV to 7 GeV were measured with the ARINA and PAMELA spectrometers onboard the Resurs-DK satellite launched on June 15, 2006 into an elliptical orbit with an inclination of 70.4° and an altitude of 350-600 km. It is shown that positrons dominate over electrons by a factor of up to 4-5 in the geomagnetic equator region (L < 1.2 and B > 0.25).
|
|
| 8. |
- Adriani, O., et al.
(författare)
-
Positrons and electrons in primary cosmic rays as measured in the PAMELA experiment
- 2009
-
Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 73:5, s. 568-570
-
Tidskriftsartikel (refereegranskat)abstract
- The PAMELA experiment is being carried out on board the Russian satellite Resurs DK1 placed in the near-earth near-polar orbit on June 15, 2006. The apparatus comprising a silicon-strip magnetic spectrometer and an electromagnetic calorimeter allows measurement of electron and positron fluxes in cosmic rays in a wide energy interval from ∼100 MeV to hundreds of GeV. The high-energy electron and positron separation technique is discussed and the data on positron-to-electron ratio in primary cosmic rays up to E ≃ 10 GeV from the 2006 - 2007 measurements are reported in this work.
|
|
| 9. |
- Galper, A. M., et al.
(författare)
-
International Russian-Italian mission "Rim-Pamela
- 2009
-
Ingår i: Proceedings of the 13th Lomonosov Conference on Elementary Particle Physics. - : WORLD SCIENTIFIC. - 9812837582 - 9789812837585 ; , s. 199-206
-
Konferensbidrag (refereegranskat)abstract
- The successful launch of spacecraft "RESURS DK" 1 with precision magnetic spectrometer "PAMELA" onboard was executed at Baikonur cosmodrome 15 June 2006. The primary phase of realization of International Russian-Italian Project "RIM-PAMELA" with German and Swedish scientists' participation has begun since the launch of instrument "PAMELA" that has mainly been directed to investigate the fluxes of galactic cosmic rays. This report contains the main scientific Project's tasks and the conditions of science program's implementation after one year since exploration has commenced.
|
|
| 10. |
- Grishantseva, L. A., et al.
(författare)
-
Sub-cutoff electrons and positrons in the near Earth space
- 2009
-
Ingår i: 31st International Cosmic Ray Conference, ICRC 2009. - : University of Lodz.
-
Konferensbidrag (refereegranskat)abstract
- Precise spectra of electron and positron fluxes in energy range from 80 MeV to several GeV below the geomagnetic cutoff rigidity were obtained using data of the PAMELA spectrometer. It was launched on June 15th 2006 onboard the Resurs-DK satellite on an elliptical orbit (the inclination is 70°, the altitude is 350-610 km). The work presents measurements of secondary lepton fluxes produced in interactions of cosmic ray protons with the atmosphere in the near Earth space (out of the South Atlantic Anomaly). Latitudinal dependences are discussed. These results are particularly interesting for more accurate definition of electron/positron flux model in the Earth magnetosphere.
|
|
| 11. |
- Adriani, O., et al.
(författare)
-
The PAMELA space mission
- 2008
-
Ingår i: Astroparticle, Part. Space Phys., Detect. Med. Phys. Appl. - Proc. Conf.. - : WORLD SCIENTIFIC. - 9812819088 - 9789812819086 ; , s. 858-864
-
Konferensbidrag (refereegranskat)abstract
- The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) experiment, is a satellite-borne particle spectrometer. It was launched on 15th June 2006 from the Baikonur cosmodrome in Kazakhstan, is installed into the Russian Resurs-DK1 satellite. PAMELA is composed of a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. Among the PAMELA major objectives are the study of charged particles in the cosmic radiation, the investigation of the nature of dark matter, by mean of the measure of the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved. PAMELA has been in a nearly continuous data taking mode since llth July 2006. The status of the apparatus and performances will be presented.
|
|
| 12. |
- Boezio, M., et al.
(författare)
-
The first year in orbit of the pamela experiment
- 2007
-
Ingår i: Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007. - : Universidad Nacional Autonoma de Mexico. ; , s. 99-102
-
Konferensbidrag (refereegranskat)abstract
- On the 15th of June 2006, the PAMELA experiment mounted on the Resurs DK1 satellite, was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. PAMELA is a satellite-borne apparatus designed to study charged particles in the cosmic radiation, to investigate the nature of dark matter, measuring the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved, and to search for antinuclei with unprecedented sensitivity. The PAMELA apparatus comprises a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. We will present the status of the apparatus after one year in orbit. Furthermore, we will discuss the PAMELA in-flight performances.
|
|
| 13. |
- Boezio, M., et al.
(författare)
-
The PAMELA space experiment : First year of operation
- 2008
-
Ingår i: Journal of Physics, Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 110:6
-
Tidskriftsartikel (refereegranskat)abstract
- On the 15th of June 2006 the PAMELA experiment, mounted on the Resurs DK1 satellite, was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. PAMELA is a satellite-borne apparatus designed to study charged particles in the cosmic radiation, to investigate the nature of dark matter, measuring the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved, and to search for antinuclei with unprecedented sensitivity. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows charged particle identification over a wide energy range. © 2008 IOP Publishing Ltd.
|
|
| 14. |
- Casolino, M., et al.
(författare)
-
Cosmic-ray observations of the heliosphere with the PAMELA experiment
- 2006
-
Ingår i: Astrophysics. - : Elsevier BV. ; , s. 1848-1852
-
Konferensbidrag (refereegranskat)abstract
- The PAMELA experiment is a multi-purpose apparatus built around a permanent magnet spectrometer, with the main goal of studying in detail the antiparticle component of cosmic rays. The apparatus will be carried in space by means of a Russian satellite, due to launch in 2005, for a three year-long mission. The characteristics of the detectors composing the instrument, alongside the long lifetime of the mission and the orbital characteristics of the satellite, will allow to address several items of cosmic-ray physics. In this paper, we will focus on the solar and heliospheric observation capabilities of PAMELA.
|
|
| 15. |
- Casolino, M., et al.
(författare)
-
Magnetospheric and solar physics observations with the PAMELA experiment
- 2008
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 588:1-2, s. 243-246
-
Tidskriftsartikel (refereegranskat)abstract
- PAMELA is a satellite-borne experiment designed to make long duration measurements of the cosmic radiation in Low Earth Orbit. It is devoted to the detection of the cosmic-ray spectra in the 100 MeV-300 GeV range with primary scientific goal the measurement of antiproton and positron spectra over the largest energy range ever achieved. Other tasks include the search for antinuclei with unprecedented sensitivity and the measurement of the light nuclear component of cosmic rays. In addition, PAMELA can investigate phenomena connected with solar and Earth physics. The apparatus consists of: a Time of Flight system, a magnetic spectrometer, an electromagnetic imaging calorimeter, a shower tail catcher scintillator, a neutron detector and an anticoincidence system. In this work we present some measurements of galactic, secondary and trapped particles performed in the first months of operation.
|
|
| 16. |
- Papini, P., et al.
(författare)
-
In-flight performances of the PAMELA satellite experiment
- 2008
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 588:1-2, s. 259-266
-
Tidskriftsartikel (refereegranskat)abstract
- PAMELA is a satcllite-borne experiment designed to study with great accuracy charged particles in the cosmic radiation with a particular focus on antiparticles. The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June 15, 2006 in a 350 x 600 km orbit with an inclination of 70 degrees. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows charged particle identification over a wide energy range. In this work, the detector design is reviewed and the in-orbit performances in the first months after the launch are presented.
|
|
| 17. |
- Pearce, Mark, et al.
(författare)
-
PAMELA : a payload for antimatter matter exploration and light-nuclei astrophysics - status and first results
- 2007
-
Ingår i: 2007 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-11. - 9781424409228 ; , s. 42-47
-
Konferensbidrag (refereegranskat)abstract
- PAMELA is a satellite-borne experiment designed for precision studies of the charged cosmic radiation. The primary scientific goal is the study of the antimatter component of the cosmic radiation (antiprotons, 80 MeV - 190 GeV; and positrons, 50 MeV - 270 GeV) in order to search for evidence of dark matter particle annihilations. PAMELA will also search for primordial antinuclei (in particular, anti-helium), and test cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and studies of light nuclei and their isotopes. Concomitant goals include a study of solar physics and solar modulation during the 24th solar minimum by investigating low energy particles in the cosmic radiation; and a reconstruction of the cosmic ray electron energy spectrum up to several TeV thereby allowing a possible contribution from local sources to be studied. PAMELA is housed on-board the Russian Resurs-DK1 satellite, which was launched on June 15th 2006 in an elliptical (350-600 km altitude) orbit with an inclination of 70 degrees. PAMELA consists of a permanent magnet spectrometer, to provide rigidity and charge sign information; a Time-of-Flight and trigger system, for velocity and charge determination; a silicon-tungsten calorimeter, for lepton/hadron discrimination; and a neutron detector. An anticoincidence system is used offline to reject false triggers. In this article the PAMELA experiment and its status are reviewed. A preliminary discussion of data recorded in-orbit is also presented.
|
|
| 18. |
- Stozhkov, Y. I., et al.
(författare)
-
About Separation of Hadron and Electromagnetic Cascades in the Pamela Calorimeter
- 2005
-
Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 20:29, s. 6745-6748
-
Tidskriftsartikel (refereegranskat)abstract
- Results of calibration of the PAMELA instrument at the CERN facilities are discussed. In September, 2003, the calibration of the Neutron Detector together with the Calorimeter was performed with the CERN beams of electrons and protons with energies of 20-180 GeV. The implementation of the Neutron Detector increases a rejection factor of hadrons from electrons about ten times. The results of calibration are in agreement with calculations.
|
|
| 19. |
- Adriani, O., et al.
(författare)
-
An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV
- 2009
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 458:7238, s. 607-609
-
Tidskriftsartikel (refereegranskat)abstract
- Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium(1), which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars(2) and microquasars(3) or through dark matter annihilation(4), which would be 'primary sources'. Previous statistically limited measurements(5-7) of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply overmuch of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.
|
|
| 20. |
- Adriani, O., et al.
(författare)
-
Latest results from the Pamela experiment
- 2009
-
Ingår i: Proceedings of Science. ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- In this paper we present the latest results of the Pamela satellite experiment, focusing in particular on the p̄/p and the e +/(e+ +e-) ratios.
|
|
| 21. |
- Adriani, O., et al.
(författare)
-
The PAMELA space mission
- 2009
-
Konferensbidrag (refereegranskat)abstract
- The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) space mission has been launched on-board the Resurs-DK1 satellite on June 15(th) 2006 from the Baikonur cosmodrome, in Kazakhstan. PAMELA is a particle spectrometer designed to study charged particles in the cosmic radiation with special focus on the investigation of the nature of dark matter, by mean of the measure of the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved.
|
|
| 22. |
- Boezio, M., et al.
(författare)
-
PAMELA and indirect dark matter searches
- 2009
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 105023-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a review of the experimental results obtained by PAMELA in measuring the (p, (p) over bar ) and e(+/-) abundance in cosmic rays. In this context, we discuss the interpretation of the observed anomalous positron excess in terms of the annihilation of dark matter particles as well as in terms of standard astrophysical sources. Moreover we show the constraints on dark matter models from (p) over bar data.
|
|
| 23. |
- De Simone, N., et al.
(författare)
-
Comparison of models and measurements of protons of trapped and secondary origin with PAMELA experiment
- 2009
-
Ingår i: 31st International Cosmic Ray Conference, ICRC 2009. - : University of Lodz.
-
Konferensbidrag (refereegranskat)abstract
- PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: Antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of 10-8). The experiment, housed on board the Russian Resurs- DK1 satellite, was launched on June, 15th 2006 in a 350x600 km orbit with an inclination of 70 degrees. In this work we present the measurement of galactic and reentrant albedo proton spectra in the energy range between 100 MeV and 300 GeV. The galactic protons refer to the period 2006-2008, showing evidence of Solar modulation effects even during the solar minimum.
|
|
| 24. |
- Mocchiutti, E., et al.
(författare)
-
Precision studies of cosmic rays with the PAMELA satellite experiment
- 2009
-
Ingår i: 2009 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-5. - : IEEE. - 9781424439621 ; , s. 2125-2130
-
Konferensbidrag (refereegranskat)abstract
- The PAMELA satellite experiment was launched into low earth orbit on June 15th 2006. The combination of a permanent magnet silicon strip spectrometer, and a silicon-tungsten imaging calorimeter allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 200 GeV). A primary scientific goal is to search for dark matter particle annihilations by measuring the energy spectra of cosmic ray antiparticles. Latest results from the PAMELA experiment will be reviewed with a particular focus on cosmic ray antiprotons and positrons. The status of PAMELA measurements for other cosmic ray species will also be reviewed.
|
|
| 25. |
- Mocchiutti, E., et al.
(författare)
-
The PAMELA space experiment
- 2009
-
Ingår i: Proceedings of the 44th Rencontres de Moriond - 2009 Electroweak Interactions and Unified Theories, EW 2009. - : Gioi Publishers. ; , s. 317-324
-
Konferensbidrag (refereegranskat)abstract
- The 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations. PAMELA is also searching for primordial antinuclei (anti-helium) and testing cosmic-ray propagation models through precise measurements of the anti-particle energy spectrum and precision studies of light nuclei and their isotopes. Moreover, PAMELA is investigating phenomena connected with solar and earth physics.
|
|
| 26. |
- Mori, N., et al.
(författare)
-
Measurement of the He nuclei flux at high energies with the PAMELA experiment
- 2009
-
Ingår i: 31st International Cosmic Ray Conference, ICRC 2009. - : University of Lodz.
-
Konferensbidrag (refereegranskat)abstract
- The PAMELA experiment is a satellitebased apparatus launched in June 2006. Its core instrument is a magnetic spectrometer, whose high spatial resolution (∼ 3 micron) provides the discriminative power to separate particles and antiparticles. It can measure the momentum and the energy-loss rate of an incident particles, thus allowing to identify higher charges (up to Z ≃ 5). The main goal for PAMELA is a precise measurement of the light antimatter component in cosmic rays (antiprotons, positrons), with unprecedented statistics and over a largely unexplored energy range. The instrument characteristics and the large statistics allow to precisely measure absolute fluxes for various cosmic-ray species up to high energy. Here the He flux analysis above some GeV is presented.
|
|
| 27. |
- Papini, P., et al.
(författare)
-
Latest results from PAMELA
- 2009
-
Konferensbidrag (refereegranskat)abstract
- The PAMELA experiment is a satellite-borne apparatus designed to study charged particles in the cosmic radiation, with a particular focus on antiparticles. The detector is housed on the Resurs-DK1 satellite and it is taking data since June 2006. The main parts of the apparatus are a magnetic spectrometer, which is equipped with a silicon-microstrip tracking system and which is used to measure the rigidity and the charge of particles, and a silicon/tungsten electromagnetic calorimeter which provides particle identification. The main results about the antiparticles component of cosmic rays obtained during the first 500 days of data taking are summarized here.
|
|
| 28. |
- Picozza, P., et al.
(författare)
-
Dark Matter Research and the PAMELA Space Mission
- 2009
-
Ingår i: SOURCES AND DETECTION OF DARK MATTER AND DARK ENERGY IN THE UNIVERSE. - : AIP. ; , s. 141-150
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Bajkonur cosmodrome and since July 2006 it has been collected data. The core of the apparatus is a silicon-microstrip magnetic spectrometer combined with a time-of-flight system, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The overall devices allow precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectra in order to search for exotic sources, such as dark matter particle annihilation. PAMELA is also searching for primordial antinuclei ((He) over bar). Concomitant, but not secondary, goals are the measurements of light nuclei and their isotopes for studying the energy dependence of cosmic ray lifetimes in the Galaxy, the monitoring of the solar activity and the study of the radiation belts.
|
|
| 29. |
- Sparvoli, R., et al.
(författare)
-
Cosmic rays studies with the PAMELA space experiment
- 2009
-
Ingår i: Nuovo cimento della societa italiana de fisica. C, Geophysics and space physics. - 1124-1896 .- 1826-9885. ; 32:5-6, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- The instrument PAMELA, in orbit since June 15th, 2006 on board the Russian satellite Resurs DK1, is delivering to ground 16 Gigabytes of data per day. The apparatus is designed to study charged particles in the cosmic radiation, with a particular focus on antiparticles as a possible signature of dark matter annihilation in the galactic halo; the combination of a magnetic spectrometer and different detectors-indeed- allows antiparticles to be reliably identified from a large background of other charged particles. New results on the antiproton-to-proton and positron-to-all-electron ratios over a wide energy range (1-100GeV) have been recently released by the PAMELA Collaboration, and will be summarized in this paper. While the antiproton-to-proton ratio does not show particular differences from an antiparticle standard secondary production, in the positron-to-all-electron ratio an enhancement is clearly seen at energies above 10 GeV. Possible interpretations of this effect will be briefly discussed.
|
|
| 30. |
- Casolino, M., et al.
(författare)
-
Launch of the space experiment PAMELA
- 2008
-
Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 42:3, s. 455-466
-
Tidskriftsartikel (refereegranskat)abstract
- PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antimatter with a precision of the order of 10-8. The experiment, housed on board the Russian Resurs-DK I satellite, was launched on June 15th, 2006 in a 350 x 600 km orbit with all inclination of 70'. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, time-of-flight, and rigidity information. Lepton/hadron identification is performed by a silicon-tungsten calorimeter and a neutron detector placed at the bottom of the device. An anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the calorimeter, the neutron detector, and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we describe the experiment, its scientific objectives, and the performance in the first months after launch.
|
|
| 31. |
- Casolino, M., et al.
(författare)
-
Two years of flight of the Pamela experiment : Results and perspectives
- 2009
-
Ingår i: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 78:Suppl. A, s. 35-40
-
Tidskriftsartikel (refereegranskat)abstract
- PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of 10~8). The experiment, housed on board the Russian Resurs-DKl satellite, was launched on June, 15th 2006 in a 350 x 600 km orbit with an inclination of 70 degrees. In this work we describe the scientific objectives and the performance of PAMELA in its first two years of operation. Data on protons of trapped, secondary and galactic nature - as well as measurements of the December 13th 2006 Solar Particle Event - are also provided.
|
|
| 32. |
- Bonvicini, V., et al.
(författare)
-
Performance of the PAMELA Si-W imaging calorimeter in space
- 2009
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 160, s. 012039-
-
Tidskriftsartikel (refereegranskat)abstract
- The Payload for Antimatter-Matter Exploration and Light Nuclei Astrophysics (PAMELA), primarily designed to directly measure antiparticles (antiprotons and positrons) in the cosmic radiation, was launched successfully on June 15th, 2006, and, since then, it is in continuous data taking. The calorimeter of the PAMELA apparatus has been designed to identify antiprotons from an electron background and positrons from a background of protons with high efficiency and rejection power. It is a sampling silicon-tungsten imaging calorimeter, which comprises 44 single-sided silicon sensor planes (380 μm thick) interleaved with 22 plates of tungsten absorber (0.74 X0 each). It is the first silicon-tungsten calorimeter to be launched in space. In this work we present the in-orbit performance of the calorimeter, including the measured identification capabilities. The calorimeter provides a proton rejection factor of ∼105 while keeping a high efficiency in selecting electrons and positrons, thus fulfilling the identification power needed to reach the primary scientific objectives of PAMELA. We show also that, after almost two years of operation in space, the calorimeter is still performing nominally.
|
|
| 33. |
|
|
| 34. |
- Casolino, M., et al.
(författare)
-
Cosmic ray measurements with Pamela experiment
- 2009
-
Konferensbidrag (refereegranskat)abstract
- PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature hi a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of 10(-8)). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15(th) 2006 in a 350 X 600 km orbit with an inclination of 70 degrees. In this work we describe the scientific objectives awl the performance of PAMELA in its first two years of operation. Data oil protons of trapped, secondary and galactic nature - as well as measurements of the December 13(th) 2006 Solar Particle Event - are also provided.
|
|
| 35. |
- Abdo, A. A., et al.
(författare)
-
FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE VELA PULSAR
- 2009
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 696:2, s. 1084-1093
-
Tidskriftsartikel (refereegranskat)abstract
- The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new gamma-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high-quality pulse profile, with some 32,400 pulsed photons at E >= 0.03 GeV, shows new features, including pulse structure as fine as 0.3 ms and a distinct third peak, which shifts in phase with energy. We examine the high-energy behavior of the pulsed emission; initial spectra suggest a phase-averaged power-law index of Gamma = 1.51(-0.04)(+0.05) with an exponential cutoff at E-c = 2.9 +/- 0.1 GeV. Spectral fits with generalized cutoffs of the form e(-(E/Ec)b) require b <= 1, which is inconsistent with magnetic pair attenuation, and thus favor outer-magnetosphere emission models. Finally, we report on upper limits to any unpulsed component, as might be associated with a surrounding pulsar wind nebula.
|
|
| 36. |
- Atwood, W. B., et al.
(författare)
-
THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION
- 2009
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 697:2, s. 1071-1102
-
Tidskriftsartikel (refereegranskat)abstract
- The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy gamma-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic gamma-ray background up to TeV energies, and (7) explore the discovery space for dark matter.
|
|
| 37. |
- Lundquist, J., et al.
(författare)
-
The PAMELA Calorimeter Identification Capabilities
- 2005
-
Ingår i: Proceedings of the 29th International Cosmic Ray Conference, vol 3:OG1. ; , s. 305-308
-
Konferensbidrag (refereegranskat)abstract
- A silicon-tungsten imaging calorimeter has been designed, built and successfully integrated in the PAMELA satellite-bome apparatus. The main physics task of the experiment is the measurement of the flux of antiprotons, positrons and light nuclei in the cosmic radiation. The purpose of the calorimeter is to separate antiprotons and positrons from the vast background of cosmic-ray electrons and protons, respectively. In this work we present the identification capabilities of the calorimeter obtained using both Monte Carlo and test beam data. We show that the calorimeter can provide a proton rejection factor of about 105 while keeping a similar to 90% efficiency in selecting electrons and positrons. The PAMELA calorimeter is therefore able to provide the identification power needed to reach the primary scientific objectives of PAMELA.
|
|
| 38. |
|
|
| 39. |
- Cox, David G., et al.
(författare)
-
A comprehensive analysis of the androgen receptor gene and risk of breast cancer: results from the National Cancer Institute Breast and Prostate Cancer Cohort Consortium (BPC3)
- 2006
-
Ingår i: Breast Cancer Research. - : Springer Science and Business Media LLC. - 1465-5411 .- 1465-542X. ; 8:5
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction Androgens have been hypothesised to influence risk of breast cancer through several possible mechanisms, including their conversion to estradiol or their binding to the oestrogen receptor and/ or androgen receptor ( AR) in the breast. Here, we report on the results of a large and comprehensive study of the association between genetic variation in the AR gene and risk of breast cancer in the National Cancer Institute Breast and Prostate Cancer Cohort Consortium ( BPC3). Methods The underlying genetic variation was determined by first sequencing the coding regions of the AR gene in a panel of 95 advanced breast cancer cases. Second, a dense set of markers from the public database was genotyped in a panel of 349 healthy women. The linkage disequilibrium relationships ( blocks) across the gene were then identified, and haplotypetagging single nucleotide polymorphisms ( htSNPs) were selected to capture the common genetic variation across the locus. The htSNPs were then genotyped in the nested breast cancer cases and controls from the Cancer Prevention Study II, European Prospective Investigation into Cancer and Nutrition, Multiethnic Cohort, Nurses' Health Study, and Women's Health Study cohorts ( 5,603 breast cancer cases and 7,480 controls). Results We found no association between any genetic variation ( SNP, haplotype, or the exon 1 CAG repeat) in the AR gene and risk of breast cancer, nor were any statistical interactions with known breast cancer risk factors observed. Conclusion Among postmenopausal Caucasian women, common variants of the AR gene are not associated with risk of breast cancer.
|
|
| 40. |
- Orsi, S., et al.
(författare)
-
A second level trigger for the PAMELA satellite experiment
- 2006
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 25:1, s. 33-40
-
Tidskriftsartikel (refereegranskat)abstract
- The PAMELA space experiment will be launched on-board of a Russian Resurs DK1 satellite towards the end of 2005. The main scientific goal is the study of the antimatter component of the cosmic radiation. Three years of data taking will provide unprecedented statistics for antiprotons (80 MeV-190 GeV) and positrons (50 MeV-270 GeV) and will set the upper limit for the ratio He/He below 10(-8). PAMELA is built around a permanent magnet silicon spectrometer, surrounded by a plastic scintillator anticoincidence shield. An electromagnetic calorimeter is used for particle identification and energy measurements. If PAMELA data exceed the storage allowance on the satellite or the daily downlink quota (20 GB), a second level trigger may be activated by uplink from ground. Information from the anticoincidence system and from the calorimeter will be included in the second level trigger condition, providing a selective reduction of data. The second level trigger condition provides a reduction of data of similar to 60%, with a maximum systematic uncertainty in the proton (electron) spectra of 10% (3%). This uncertainty will be assessed during flight measuring one event every 10 without the second level trigger condition.
|
|
| 41. |
|
|
| 42. |
- Adriani, O., et al.
(författare)
-
New Measurement of the Antiproton-to-Proton Flux Ratio up to 100 GeV in the Cosmic Radiation
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5
-
Tidskriftsartikel (refereegranskat)abstract
- A new measurement of the cosmic-ray antiproton-to-proton flux ratio between 1 and 100 GeV is presented. The results were obtained with the PAMELA experiment, which was launched into low-Earth orbit on-board the Resurs-DK1 satellite on June 15th 2006. During 500 days of data collection a total of about 1000 antiprotons have been identified, including 100 above an energy of 20 GeV. The high-energy results are a tenfold improvement in statistics with respect to all previously published data. The data follow the trend expected from secondary production calculations and significantly constrain contributions from exotic sources, e. g., dark matter particle annihilations.
|
|
| 43. |
- Andersson, V., et al.
(författare)
-
Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)
- 2005
-
Ingår i: Proceedings of the 22nd Texas Symposium on Relativistic Astrophysics at Stanford. ; , s. 736-743
-
Konferensbidrag (refereegranskat)abstract
- We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (30-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO is designed to detect 10 % polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters and has a narrow field-of-view (~ 5 deg2) to reduce possible source confusion. A prototype instrument has been tested in the polarized soft gamma-ray beams at Advanced Photon Source (ANL) and at Photon Factory (KEK). On the results, the polarization dependence of EGS4 has been validated and that of Geant4 has been corrected.
|
|
| 44. |
- Boezio, Mirko, et al.
(författare)
-
The electron-hadron separation performance of the PAMELA electromagnetic calorimeter
- 2006
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 26:2, s. 111-118
-
Konferensbidrag (refereegranskat)abstract
- A silicon-tungsten sampling imaging calorimeter has been designed and built for thePAMELA satellite-borne experiment. The main physics goals of the experiment are themeasurement of the flux of antiprotons (80 MeV-190 GeV) and positrons (50 MeV-270 GeV) in the cosmic radiation. The calorimeter has been designed to identify antiprotons from an electron background and positrons in a background of protons with a high efficiency and rejection power. This work presents the electron-hadron separationcapabilities of the calorimeter as obtained using both Monte Carlo and test beam data.The calorimeter is found to have sufficient performance to reach the primary scientific objectives of PAMELA, providing a proton rejection factor of ∼105 while keeping a ∼90% efficiency in selecting electrons and positrons. From simulations, an electron rejection factor of ∼105 in antiproton measurements (∼90% antiproton identification efficiency) is demonstrated.
|
|
| 45. |
- Canzian, Federico, et al.
(författare)
-
Genetic polymorphisms of the GNRH1 and GNRHR genes and risk of breast cancer in the National Cancer Institute Breast and Prostate Cancer Cohort Consortium (BPC3).
- 2009
-
Ingår i: BMC cancer. - : Springer Science and Business Media LLC. - 1471-2407. ; 9, s. 257-
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Gonadotropin releasing hormone (GNRH1) triggers the release of follicle stimulating hormone and luteinizing hormone from the pituitary. Genetic variants in the gene encoding GNRH1 or its receptor may influence breast cancer risk by modulating production of ovarian steroid hormones. We studied the association between breast cancer risk and polymorphisms in genes that code for GNRH1 and its receptor (GNRHR) in the large National Cancer Institute Breast and Prostate Cancer Cohort Consortium (NCI-BPC3). METHODS: We sequenced exons of GNRH1 and GNRHR in 95 invasive breast cancer cases. Resulting single nucleotide polymorphisms (SNPs) were genotyped and used to identify haplotype-tagging SNPs (htSNPS) in a panel of 349 healthy women. The htSNPs were genotyped in 5,603 invasive breast cancer cases and 7,480 controls from the Cancer Prevention Study-II (CPS-II), European Prospective Investigation on Cancer and Nutrition (EPIC), Multiethnic Cohort (MEC), Nurses' Health Study (NHS), and Women's Health Study (WHS). Circulating levels of sex steroids (androstenedione, estradiol, estrone and testosterone) were also measured in 4713 study subjects. RESULTS: Breast cancer risk was not associated with any polymorphism or haplotype in the GNRH1 and GNRHR genes, nor were there any statistically significant interactions with known breast cancer risk factors. Polymorphisms in these two genes were not strongly associated with circulating hormone levels. CONCLUSION: Common variants of the GNRH1 and GNRHR genes are not associated with risk of invasive breast cancer in Caucasians.
|
|
| 46. |
|
|
| 47. |
- Kiss, Mózsi, et al.
(författare)
-
The PoGOLite balloon-borne soft gamma-ray polarimeter
- 2008
-
Ingår i: COOL DISCS, HOT FLOWS. - : AIP. ; , s. 225-232
-
Konferensbidrag (refereegranskat)abstract
- Linearly polarized radiation in the hard X-ray/soft gamma-ray band is expected from a large variety of astronomical sources. We discuss the importance of polarimetric studies for several classes of sources - pulsars, accreting black holes. magnetic neutron stars and jets from active galaxies - and then describe PoGOLite, a balloon-borne instrument which is currently under construction and will be able to measure the polarization of electromagnetic radiation from such extra-solar objects in the energy range 25-80 keV.
|
|
| 48. |
- Mocchiutti, E., et al.
(författare)
-
The PAMELA electromagnetic calorimeter : performances
- 2006
-
Ingår i: Calorimetry in High Energy Physics. - : American Institute of Physics (AIP). - 0735403643 ; , s. 159-166
-
Konferensbidrag (refereegranskat)abstract
- A sampling silicon-tungsten imaging calorimeter has been designed and built for the PAMELA satellite-borne experiment. The calorimeter has been designed to identify antiprotons from an electron background and positrons in a background of protons with a high efficiency and rejection power. In this work we present the identification capabilities of the calorimeter obtained using both Monte Carlo and test beam data. We show that the calorimeter provides a proton rejection factor of at least 105 while keeping a high efficiency in selecting electrons and positrons. Hence, the calorimeter will fulfill the identification power needed to reach the primary scientific objectives of PAMELA, that are the measurement of the flux of antiprotons, positrons and light isotopes in the cosmic radiation.
|
|
| 49. |
- Pearce, David A., et al.
(författare)
-
First evidence for a bipolar distribution of dominant freshwater lake bacterioplankton
- 2007
-
Ingår i: Antarctic Science. - 0954-1020 .- 1365-2079. ; 19:2, s. 245-252
-
Tidskriftsartikel (refereegranskat)abstract
- As a result of the recent application of DNA based technology to the investigation of maritime Antarctic freshwater lakes, patterns have begun to emerge in the bacterioplankton communities that dominate these systems. In this study, the bacterioplankton communities of five Antarctic and five Arctic freshwater lakes were assessed and compared with existing data in the literature, to determine whether emerging patterns in Antarctic lakes also applied to Arctic systems. Such a bipolar comparison is particularly timely, given the current interest in biogeography, the global distribution of microorganisms and the controversy over the global ubiquity hypothesis. In addition, it has recently been discovered that commonly encountered bacterial sequences, often originating from uncultivated bacteria obtained on different continents, form coherent phylogenetic freshwater clusters. In this study we encountered both identical sequences and sequences with a high degree of similarity among the bacterioplankton in lake water from both poles. In addition, Arctic freshwater lakes appeared to be dominated by some of the same groups of bacterioplankton thought to be dominant in Antarctic lakes, the vast majority of which represented uncultivated groups.
|
|
| 50. |
- Picozza, P., et al.
(författare)
-
PAMELA - A payload for antimatter matter exploration and light-nuclei astrophysics
- 2007
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 27:4, s. 296-315
-
Tidskriftsartikel (refereegranskat)abstract
- The PAMELA experiment is a satellite-borne apparatus designed to study charged particles in the cosmic radiation with a particular focus on antiparticles. PAMELA is mounted on the Resurs DK1 satellite that was launched from the Baikonur cosmodrome on June 15th 2006. The PAMELA apparatus comprises a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows antiparticles to be reliably identified from a large background of other charged particles. This paper reviewsthe design, space qualification and on-ground performance of PAMELA. The in-orbit performance will be discussed in future publications.
|
|
