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The study of antiprotons and positrons in cosmic rays with the PAMELA spectrometer

Science.gov (United States)

... Zinn, J., Hoerlin, H., and Petschek, AG, "The Motion of Bomb Debris Follow- ing the Starfish Test," Radiation Trapped in the Earth's Magnetic Field ...

CERN Document Server

PAMELA is a space telescope orbiting around the Earth since June 2006. The scientific objectives addressed by the mission are the measurement of the antiprotons and positrons spectra in cosmic rays, the hunt for anti-nuclei as well as the determination of light nuclei fluxes from Hydrogen to Oxygen in a wide energy range and with very high statistics. In this paper the charge discrimination capabilities of the PAMELA Time-Of-Flight system for light nuclei, determined during a beam test calibration, will be presented.

CERN Document Server

Recently PAMELA released their first results on the positron and antiproton ratios. Stimulated by the new data, we studied the cosmic ray propagation models and calculated the secondary positron and antiproton spectra. The low energy positron ratio can be consistent with data in the convection propagation model. Above $\\sim 10$ GeV PAMELA data shows a clear excess on the positron ratio. However, the secondary antiproton is roughly consistent with data. The positron excess may be a direct evidence of dark matter annihilation or decay. We compare the positron and anti-proton spectra with data by assuming dark matter annihilates or decays into different final states. The PAMELA data actually excludes quark pairs being the main final states, disfavors gauge boson final states. Only in the case of leptonic final states the positron and anti-proton spectra can be explained simultaneously. We also compare the decaying and ...

Energy Technology Data Exchange (ETDEWEB)

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.

CERN Document Server

A new calculation of the $\\bar{p}/p$ ratio in cosmic rays is compared to the recent PAMELA data. The good match up to 100 GeV allows to set constraints on exotic contributions from thermal WIMP dark matter candidates. We derive stringent limits on possible enhancements of the WIMP \\pbar flux: a $m_{\\rm WIMP}$=100 GeV (1 TeV) signal cannot be increased by more than a factor 6 (40) without overrunning PAMELA data. Annihilation through the $W^+W^-$ channel is also inspected and cross-checked with $e^+/(e^-+e^+)$ data. This scenario is strongly disfavored as it fails to simultaneously reproduce positron and antiproton measurements.

CERN Document Server

We provide a scenario in which a hidden U(1) gauge boson constitutes dark matter of the Universe and decays into the standard-model particles through a kinetic mixing with an $U(1)_{B-L}$ gauge boson. Interestingly, our model can naturally account for the steep rise in the positron fraction recently reported by PAMELA. Moreover, we find that due to the charge assignment of $U(1)_{B-L}$, only a small amount of antiprotons are produced in the decay, which is also consistent with the PAMELA and other observational data.

Energy Technology Data Exchange (ETDEWEB)

In the framework of the RIM (Russian Italian mission) program, PAMELA is the experiment devoted to the accurate measurement of the positron and antiproton spectra from the very low energy thresh-old of 100 MeV up to more than 50 GeV, and to hunt antinuclei with sensitivity better than 10{sup -7} in the helium/helium ratio. A permanent magnet equipped by microstrip silicon sensors, measures the particle momentum with MDR=400 GV/c on GF=25 cm{sup 2} sr. An accurate ToF system, a 19 X{sub o} deep imaging calorimeter, an aerogel Cherenkov counter and a TRD detector complement the spectrometer in order an efficient e{sup +-}/p{sup +-} separation and some light isotope identification capability. The PAMELA experiment will be carried out on a 700 km high polar orbit, on board of the Earth-observation meteor-3A satellite, to be launched at the end of 1988.

Energy Technology Data Exchange (ETDEWEB)

This paper described a newly developed chipper device for mounting on Claas Jaguar chipper harvesters for short rotation forestry harvesting. It was designed by the Agriculture Engineering Research Unit of the Agricultural Research Council in Rome, Italy. The new rotor has a lower number of blades compared to standard rotors and has a different cutting angle and drum insertion. This study evaluated the particle-size distribution of wood chips produced by standard rotors compared to those with the experimental rotor. The objective was to distinguish the particle size distribution of chips produced using the two types of chippers in order to evaluate the influence of wooden species in the chip formation process. Tests were conducted using 860 and 890 Claas Jaguar chipper harvesters, both equipped with standard and CRA-ING rotors. The experiment was conducted on poplar cultivations on biennial shift and on arboreal cultivations. Compared to traditional rotors, ...

CERN Document Server

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-DK1 satellite, was launched on June, 15 2006 in a $350\\times 600 km$ orbit with an inclination of 70 degrees. 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 ...

CERN Document Server

We investigate the signatures of antimatter in cosmic rays that would result from annihilations of the scalar dark matter candidate of the Inert Doublet Model. We consider three benchmark candidates, all consistent with the WMAP cosmic abundance and existing direct detection experiments, and confront the predictions of the model with the recent PAMELA, ATIC and HESS data. For a light IDM WIMP candidate, M_{DM} = 10 GeV, we argue that the positron and antiproton fluxes are large, but consistent with expected backgrounds, unless there is an enhancement in the local density of dark matter. For an IDM WIMP candidate with M_{DM} = 70 GeV, the contribution is lower than the expected backgrounds unless there is a large boost factor. However, the candidate is enable to explain the excesses observed by the recent experiments. Finally, for an IDM WIMP candidate with M_{DM}=10 TeV, it is possible to fit the PAMELA excess, while satisfying the anti-protons ...

CERN Document Server

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-DK1 satellite, was launched on June, 15, 2006 in a 350*600 km orbit with an inclination of 70 degrees. 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 ...

Energy Technology Data Exchange (ETDEWEB)

The Council for Research in Agriculture, Agricultural Engineering Research Unit (CRA-ING) in Rome, Italy has developed an innovative short-rotation forestry (SRF) harvesting system. The system involves a 2 step operation, notably the tree felling and inter-row windrowing performed by a feller windrower equipment; and subsequent chipping performed by a harvester equipped with a pick-up device. The low moisture content of the windrowed trees at harvesting time affects their physical qualities and mechanical strength throughout the chipping operation. The purpose of this study was to analyze the moisture losses of windrowed trees, in relation to the windrow location, on field storage and weather condition. In addition, the study characterized chips quality changes during on field storage by the 2 different harvesting systems. The innovative 2-step system was compared with the traditional 1-step harvesting system.

International Nuclear Information System (INIS)

In the future even more than in the past, nuclear power will be indispensable in the present industrialized countries and in those still under development. The safe, nonpolluting, and economic supply of energy to mankind in the future includes so many different problems that the technology of the high-temperature reactor at its present level of development, and with the possibilities is offers above and beyond those provided by other, established, technologies, does not have to mark the end of some old line of development, but rather should be seen as the starting point of a development offering promise for the future. It is for this very reason that the extensive, valuable knowledge and experience accumulated in the construction, operation, and decommissioning of the AVR and THTR plants, the development of the HTR module and other variants and, last, but not least, the valuable results of projects such as PNP, NFE, and HHT, must be preserved at the research centers and with former ...

CERN Document Server

Recent observations of a large excess of cosmic-ray positrons at high energies have raised a lot of interest in leptonic decay modes of dark matter particles. Nevertheless, dark matter particles in the Milky Way halo could also decay hadronically, producing not only a flux of antiprotons but also a flux of antideuterons. We show that for certain choices of parameters the antideuteron flux from dark matter decay can be much larger than the purely secondary flux from spallation of cosmic rays on the interstellar medium, while the total antiproton flux remains consistent with present observations. We show that if the dark matter particle is sufficiently light, the antideuteron flux from dark matter decay could even be within the reach of planned experiments such as AMS-02 or GAPS. Furthermore, we discuss the prospects to observe the antideuteron flux in the near future if the steep rise in the positron fraction reported by the PAMELA collaboration is interpreted in ...

International Nuclear Information System (INIS)

Inelastic scattering of #alpha#-particles in 22-24 MeV energy range on "1"8o o, "1"9f, "2"0Ne, "2"2Ne nuclei is investigated. Measurements of excitation functions were conducted for the beam of Leningrad University cyclo otron at several angles in 15-165 deg range of laboratory system with 2.5 deg spacing. The error of determining absolute cross sections equals +-20% for "2"2Ne and +-12% for other nuclei. Angular distributions have the differaction character, are similar in form for all nuclei, the values of differential cross- -sections don't exceed the rutherford values. The dependence of integral cross-sections on the energy of level excitation is similar to the exponential d dependence of cross-sections of production of the given element isotopes on the gergy difference of masses of final nuclear products in the reactions of deeply inelastic transfers with heavy ions. The observed isotopic effect in the value of cross-sections of elastic and inelastic #alpha#-particle scattering ...