a Payload for Antimatter Matter Exploration

and L ight–nuclei Astrophysics

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.

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 composi-

tion 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.

origin and propagation of cosmic rays

A supernova remnant,

the Crab nebula, as

observed by the Very

Large Telescope.

The triple ring

system

surrounding

Supernova

1987A, as

detected by

the Hubble

Space

Telescope.

A pictorial view

of a supernova

explosion and a

conical section

of the

expanding cloud

of ejected

material.

Matter-Antimatter asymmetryis 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.

During itsmission,

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.

antimatter in the Universe

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.

Nucleosynthesis in

ordinary stars,

producing heavy

elements. An antistar

would burn in the same

way, giving rise to

antinuclei.

The dark matterproblem 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.

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.

the dark matter searchsolar events

without the presence of

additional mass. This is

indirect evidence for the

presence of dark matter.

The peripheral stars of

the galaxy M63 rotate

around the center so fast

that they would fly away

A solar flare

on the surface

of the Sun,

as seen by the

TRACE

instrument.

the activity of theWiZard-RIM

collaboration

PAMELA, installed onboard the Russian

Resurs-DK1 spacecraft, was placed into orbit by

a Soyuz rocket.

The launch took place on the 15th June

2006 from the cosmodrome of

Baikonur, in Kazakhstan.

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 2000.

The PAMELA

Flight Model

integrated into

the satellite

Resurs-DK1

mission details

The TsSKB-Progress

Soyuz rocket

The Resurs-DK1 characteristics are:

Mass: 6.7 tons

Orbit: elliptic

Altitude: 300 - 600 km

Inclination: 70.0°

Lifetime: > 3 years

PAMELA on board has characteristics:

Global Dimensions: 70 x 70 x 120 cm3

Mass: 470 kg

Power Budget: 360 W

The PAMELA

Flight Model

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 - 700 GeV;

• measure the electron flux in the energy interval 50 MeV - 400 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.

the PAMELA instrument

observational capabilities

th

Silicon Tracker

Time Of Flight System

Neutron Detector

Imaging Calorimeter

Bottom Scintillator

Magnet

Anticoincidence

System

Magne

T

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.

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.

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.

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 3He counters

enveloped by a polyethylene moderator.

e sub–detectors

etic Spectrometer

Imaging Calorimeter

Neutron Detector

Bottom Scintillator

AnticoincidenceSystem

Time Of Flight system

• 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)

the WiZard-RIM collaboration

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).

Art D

irect

or: O

rfeo

Pag

nani

• R

ealiz

ed b

y: o

mgr

afic

a -

rom

a

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)

• 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)

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: http://wizard.roma2.infn.it.

PAMELA is a mission sponsored by: INFN, RSA, ASI, DLR, RAS, KTH/SNSB.