a Payload for Antimatter Matter Exploration and Light nuclei Astrophysics

Transcription

1 a Payload for Antimatter Matter Exploration and Light nuclei Astrophysics

2 The triple ring system surrounding Supernova 1987A, as detected by the Hubble Space Telescope. A supernova remnant, the Crab nebula, as observed by the Very Large Telescope. Cosmic rays provide a unique probe of the most energetic processes in the Universe. Cosmic rays are particles which were produced during primordial nucleosynthesis or from supernova explosions. Most of the cosmic rays come from outside the solar system but from within the Milky Way. During the last ten million years they have been accelerated to nearly the speed of light, and traveled many times across the Galaxy, trapped by the galactic magnetic field. origin and propagation of cosmic rays A pictorial view of a supernova explosion and a conical section of the expanding cloud of ejected material. While astronomical observations of light from distant objects yield clues to the state of matter in our Galaxy and beyond, cosmic rays bring us a small but valuable sample of that matter itself. Through studies of the composition and energy spectra of cosmic rays, we are able to learn about the origin and evolution of material in our Galaxy and about fundamental physical processes that govern its dynamics. The space experiment PAMELA will perform a detailed survey of cosmic rays across a wide energy range, thus shedding light on the most intriguing puzzles in this field.

3 Matter-Antimatter asymmetry is another fundamental question that PAMELA will address. This question has important ramifications for both cosmology and particle physics. Although antiprotons and positrons can be produced in high-energy cosmic-ray collisions with the interstellar medium, heavy antinuclei, if discovered in cosmic rays, would provide an unambiguous signature of the existence of antimatter domains. According to the Big Bang theory, antihelium could originate in primordial gas which has not condensed into a star. Heavier antinuclei could only be produced by nucleosynthesis processes in antimatter stars. A cloud of positrons in the center of the Milky Way, seen by the Compton Gamma Ray Observatory. The positrons annihilate with electrons, thus emitting radiation - which can be detected. Jets of antimatter could be emitted by a massive black hole in the center of the Galaxy. antimatter in the Universe During its mission, PAMELA will measure the antiproton and positron components in cosmic rays with statistics never reached before by previous experiments, and will search for antinuclei with an unprecedent sensitivity. Nucleosynthesis in ordinary stars, producing heavy elements. An antistar would burn in the same way, giving rise to antinuclei.

4 The peripheral stars of the galaxy M63 rotate around the center so fast that they would fly away without the presence of additional mass. This is indirect evidence for the presence of dark matter. The dark matter problem is one of the most important and intriguing questions confronting modern particle astrophysics and cosmology. The root of the problem is that there seems to be more gravitationally interacting matter than what is visible.there has been wide spread speculation about what might constitute the dark matter. One possible form of dark matter could be weakly interacting massive particles (WIMPs).The most promising candidate for WIMP is the lightest supersymmetric particle that, in the minimal supersymmetric extension of the Standard Model, is the neutralino. Pairs of neutralinos could annihilate in the Galactic Halo, producing, among other particles, proton/antiproton and electron/positron pairs - all of which can be detected by PAMELA. the dark matter search solar events A solar flare on the surface of the Sun, as seen by the TRACE instrument. Elemental abundances in the solar corona can be measured by the detection of high energy particles accelerated in Solar Energetic Particle (SEP) events. The acceleration is driven by solar flares or Coronal Mass Ejections. PAMELA will measure the high energy part of the proton, electron and helium spectrum during SEPs, and especially will carry out for the first time measurements of the positron emission associated with solar events. These observations are crucial for understanding the mechanisms of production and acceleration taking place in the solar regions.

5 The PAMELA Flight Model The PAMELA Flight Model integrated into the satellite Resurs-DK1 The PAMELA experiment represents the most important step of the extensive research program of the international collaboration WiZard-RIM (Russian Italian Mission), dedicated to the detection of antimatter and dark matter signals in space. As part of this research program, several balloon-borne experiments (MASS89, MASS91, TS93, CAPRICE94, CAPRICE98), three experiments onboard the space station MIR (MARYA-2, SilEye-1 and SilEye-2), and two satellite missions (NINA and NINA-2) have already been performed between 1989 and the activity of the WiZard-RIM collaboration mission details The Resurs-DK1 characteristics are: Mass: 6.7 tons Orbit: elliptic Altitude: km Inclination: 70.0 Lifetime: > 3 years PAMELA, installed onboard the Russian Resurs-DK1 spacecraft, was placed into orbit by a Soyuz rocket. The launch took place on the 15 th June 2006 from the cosmodrome of Baikonur, in Kazakhstan. PAMELA on board has characteristics: Global Dimensions: 70 x 70 x 120 cm 3 Mass: 470 kg Power Budget: 360 W The TsSKB-Progress Soyuz rocket

6 Magne Silicon Tracker T Anticoincidence System Time Of Flight System Imaging Calorimeter Magnet Neutron Detector Bottom Scintillator the PAMELA instrument th observational capabilities PAMELA will provide results over an unexplored range of energies, with very high statistics. During its three years of planned operation, the apparatus will: measure the proton flux in the energy interval 80 MeV GeV; measure the electron flux in the energy interval 50 MeV GeV; measure the antiproton flux from 80 MeV to 190 GeV; measure the positron flux from 50 MeV to 270 GeV; identify the electron and proton components up to 10 TeV; search for light antinuclei with a sensitivity of the order of 10-8 in the antihe/he ratio up to 30 GeV/n; measure the light nuclei flux (up to oxygen) from 100 MeV/n to 600 GeV/n; study the time and energy distributions of the energetic particles emitted in solar flares and Coronal Mass Ejections; investigate the fluxes of high energy particles in the Earth magnetosphere.

7 ime Of Flight system The Time Of Flight System measures the velocity of the particles crossing the apparatus, and gives the trigger signal for the data acquisition. It comprises 6 layers of scintillator, two above the CARD, two above the tracker and two above the calorimeter. The time resolution is of the order of 80 ps for nuclei over a distance of 0.8 m. The Anticoincidence System is composed by two sets of scintillators.the primary AC system consists of four plastic scintillators (CAS) surrounding the sides of the magnet and one covering the top (CAT). A secondary AC system consists of four plastic scintillators (CARD) that surround the volume between the first two time-of-flight planes.the scintillators allow particles entering the tracking system from outside the geometrical acceptance to be identified. tic Spectrometer Anticoincidence System The Magnetic Spectrometer measures the momentum of the incident particle, and determines also the sign and the absolute value of the electric charge. Its core is a Nd-Fe-B permanent magnet divided into five modules which are interleaved with six frames holding silicon sensors. The Silicon Tracker is composed of 18 ladders of double-sided microstrip detectors arranged on 6 planes.the measured spatial resolution in the bending view is 4 µm and 15 µm in the non-bending view. The combined characteristics of the magnet and of the tracker allow a Maximum Detectable Rigidity (MDR) of about 1200 GV/c to be reached. sub detectors Bottom Scintillator The Imaging Calorimeter is able to identify protons and electrons with an efficiency greater than 90% and a rejection power of 10-4, thank to its capability to reconstruct the topological and energetic characteristics of the showers which develop inside its volume. It is composed of 44 silicon layers interleaved with tungsten planes, each 2.6 mm thick, for a total of 0.6 interaction lengths and 16.3 radiation lengths. Imaging Calorimeter The Bottom Scintillator is located beneath the calorimeter and is used for triggering the neutron detector in order to record particles of the highest energy. The Neutron Detector, placed at the bottom of the apparatus, expands the energy range of the recorded protons and electrons up to 10 TeV. The signal from this device is used for the selection of electrons over the proton background, making use of the different neutron yield coming from hadronic or electromagnetic showers. It consists of 36 3 He counters enveloped by a polyethylene moderator. Neutron Detector

8 The mission PAMELA is realized by an international collaboration of research institutes, under the responsibility of the Principal Investigators Prof. P. Picozza (University and INFN, Rome Tor Vergata, Italy) and Prof. A. Galper (Moscow State Engineering and Physics Institute, Russia). International Program Committee: Professors P. Carlson (Sweden), A. Galper (Russia), P. Picozza (Italy), M. Simon (Germany) Scientific Coordinator: Prof. P. Spillantini (Italy) Technical Coordinator: Prof. G. Castellini (Italy) Art Director: Orfeo Pagnani Realized by: om grafica - roma the WiZard-RIM collaboration University and INFN, Bari (Italy) University and INFN, Florence (Italy) University and INFN, Naples (Italy) University and INFN, Rome Tor Vergata, Rome (Italy) University and INFN, Trieste (Italy) Laboratori Nazionali di Frascati INFN, Frascati (Italy) Istituto di Fisica Applicata Nello Carrara, Consiglio Nazionale delle Ricerche, Florence (Italy) Moscow State Engineering and Physics Institute, Moscow (Russia) Lebedev Physical Institute, Moscow (Russia) Ioffe Physical Technical Institute, St. Petersburg (Russia) Royal Institute of Technology, Stockholm (Sweden) University of Siegen, Siegen (Germany) NASA Goddard Space Flight Center, Greenbelt (Usa) Particle Astrophysics Laboratory, New Mexico State University, Las Cruces (Usa) PAMELA is a mission sponsored by: INFN, RSA, ASI, DLR, RAS, KTH/SNSB. Edited by Roberta Sparvoli and Vincenzo Buttaro for the WiZard-RIM collaboration. Figures taken with the courtesy of NASA, ESO, the Stanford-Lockheed ISR, TsSKB-Progress. Special thanks to Cecilia Migali and Nora Capozio from INFN Communication Office. For more information about PAMELA and the activities of the WiZard-RIM collaboration, visit the web site: