The PAMELA Experiment: Preliminary Results after Two Years of Data Taking Emiliano Mocchiutti - INFN...

The PAMELA Experiment: Preliminary Results after

Two Years of Data Taking

Emiliano Mocchiutti - INFN Triesteon behalf of the PAMELA Collaboration

Emiliano Mocchiutti - INFN Trieste - 21st European Cosmic Ray Symposium, Košice 10th September 2008

Moscow St. Petersburg

Russia:

Sweden:KTH, Stockholm

Germany:Siegen

Italy:Bari Florence Frascati TriesteNaples Rome CNR, Florence

The PAMELA Collaboration

Overview

PAMELA physics

PAMELA apparatus

Preliminary PAMELA results

More about PAMELA at ECRS08:

A. N. Kvashnin “Measurements of cosmic ray particles in the energy range of 1011” (Wednesday, 16:35)

P. Hofverberg “Measurements of low energy antiparticles with the PAMELA experiment” (Wednesday, 18:05)

V. Mikhailov “Trapped charged particles measurements in radiation belts by PAMELA instrument” (Thursday, 12:20)

L. Grishanteva “Secondary electron and positron fluxes in the Earth magnetosphere near the geomagnetic equator” (Thursday, 12:35)

V. Malvezzi “Performance of the PAMELA space telescope in the identification of the light nuclei cosmic rays component” (P5.01)

L. Marcelli “PAMELA mission: preliminary results about nuclei analysis” (P5.02) V. Malakhov “Methods of reconstruction of pitch angle distribution” (P2.08)


PAMELA as a Space Observatory at 1AUSearch for dark matter annihilation

Search for antihelium (primordial antimatter)

Search for new Matter in the Universe (Strangelets?)

Study of cosmic-ray propagation

Study of solar physics and solar modulation

Study of terrestrial magnetosphere

Study of high energy electron spectrum (local sources?)


PAMELA apparatus

GF: 21.5 cm2 sr Mass: 470 kgSize: 130x70x70 cm3

Power Budget: 360W

Spectrometer microstrip silicon tracking system + permanent magnet- Magnetic rigidity R = pc/Ze- Charge sign- Charge value from dE/dx

Time-Of-Flight (ToF)plastic scintillators + PMT:- Trigger- Albedo rejection;- Charge identification from dE/dX.Anti-Coincidenceplastic scintillators + PMT:- rejection of particles out of acceptanceElectromagnetic calorimeterW/Si sampling (16.3 X0, 0.6 λI) - Discrimination e+ / p, anti-p / e- (shower topology)- Direct E measurement for e-

Neutron detectorHe3 counters + polyetilene:- High-energy e/h discrimination

+_


energy range Antiprotons 80 MeV - 190 GeV

Positrons 50 MeV – 270 GeV

Electrons up to 400 GeV

Protons up to 700 GeV

Electrons+positrons up to 2 TeV (from calorimeter)

Light Nuclei up to 200 GeV/n He/Be/C: AntiNuclei search sensitivity of 3x10-8 in He/He

Simultaneous measurement of many cosmic-ray species New energy range Unprecedented statistics

Design Performance


Mass: 6.7 tonnesHeight: 7.4 mSolar array area: 36 m2

Main task: multi-spectral remote sensing of earth’s surface Built by TsSKB Progress in Samara, Russia

Lifetime >3 years Data transmitted to ground via high-speed radio downlink

PAMELA mounted inside a pressurized container

Resurs-DK1 Satellite


Resurs-DK1 Resurs-DK1 LaunchLaunch

1515thth June 2006 June 2006

16 Gigabytes trasmitted daily 16 Gigabytes trasmitted daily to Ground Stationto Ground Station

(NTsOMZ) in Moscow(NTsOMZ) in Moscow

Till ~now PAMELA has Till ~now PAMELA has collected collected

~11 TB of data, corresponding ~11 TB of data, corresponding to to

>10>1099 triggers triggers


• Low-earth elliptical orbit

• 350 – 610 km

• Quasi-polar (70o inclination)

PAMELA Orbit

Download @orbit 3754 – 15/02/2007 07:35:00 MWT

S1 S2 S3

orbit 3752 orbit 3753orbit 3751

Inner radiation belt

(SAA)

Outer radiation belt

NP SP

EQ EQ

95 min

S1

S2

S3

Low energy particles stops inside the apparatus Counting rates: S1>S2>S3

SAA

RatemetersIndependent from trigger


Preliminary

Proton and Helium spectra

Very high statistics over a wide energy range Precise measurement of spectral shape Possibility to study time variations and transient phenomena

A. N. Kvashnin (Wednesday, 16:35)


Proton spectra and solar modulationInterstellar spectrum

July 2006August 2007 February 2008

Decre

asin

g

sola

r activ

ity

Incre

asin

g

GC

R fl

ux

Preliminary


Preliminary

Primary and Albedo (sub-cutoff) measurements

0.4 to 0.51.0 to 1.51.5 to 2.02 to 4

> 1410 to 147 to 104 to 7

Geomagnetic cutoff (GV/c)

Secondary reentrant-albedo protons

Magnetic equator

•Up-ward going albedo excluded•SAA excluded


Black B > 0.3 GRed 0.22 G < B < 0.23 GBlue 0.21 G < B < 0.22 GGreen 0.20 G < B < 0.21 GPink 0.19 G < B < 0.20 GTurquoise 0.19 G > B

P/(

cm^

2 sr

GeV

s) Trapped

Galactic

Trapped proton flux in the Inner Van Allen Belt (Shout Atlantic Anomaly)

V. Mikhailov (Thursday, 12:20)L. Grishanteva (Thursday, 12:35)

Emiliano Mocchiutti - INFN Trieste - 21st European Cosmic Ray Symposium, Košice 10th September 2008Prelim

inary!

December 13th 2006 event

Solar quiet spectrum

SEPs


Preliminary

Preliminary Results B/C

V. Malvezzi (P5.01)L. Marcelli (P5.02)


More than 10More than 1077 p and ~1000 p have been p and ~1000 p have been identified between 1 and 100 GeVidentified between 1 and 100 GeV

~300 p over 10 GeV~300 p over 10 GeV

PAMELA anti-protons


Anti-proton to proton ratio: PAMELAPreliminary

P. Hofverberg (Wednesday, 18:05)


Anti-proton to proton ratioPreliminary

P. Hofverberg (Wednesday, 18:05)


Till March 2Till March 2ndnd 2008 2008 ~2x10~2x1055 e e-- and ~ and ~ 2x10 2x1044 e e++ from 200 MeV up to 10 GeV have been from 200 MeV up to 10 GeV have been identifiedidentified

About 15000 positrons over 1 GeVAbout 15000 positrons over 1 GeV

PAMELA positrons


ee--

Fraction of charge released along the calorimeter track (left, hit, right)

pp ee++

+ Energy-momentum match Starting point of shower

Preliminary

Positron: p background evaluation

““pre- sampler” ppre- sampler” p


Positron fraction: Preliminary


PAMELA has been in orbit and studying cosmic rays for ~25PAMELA has been in orbit and studying cosmic rays for ~25

months. >10months. >1099 triggers registered, and ~11 TB of data has been triggers registered, and ~11 TB of data has been

down-linked.down-linked.

Antiproton to proton flux ratio (~100 MeV - ~100 GeV) shows noAntiproton to proton flux ratio (~100 MeV - ~100 GeV) shows no

significant deviations from secondary expectations. More highsignificant deviations from secondary expectations. More high

energy data to come (up to ~150 GeV).energy data to come (up to ~150 GeV).

Positron fraction (~400 MeV - ~10 GeV) indicates chargePositron fraction (~400 MeV - ~10 GeV) indicates charge

dependent modulation effects. More data to come at lower anddependent modulation effects. More data to come at lower and

higher energies (up to ~200 GeV).higher energies (up to ~200 GeV).

PAMELA is studying elemental spectra up to Z=8, and low massPAMELA is studying elemental spectra up to Z=8, and low mass

isotopes.isotopes.

PAMELA also measures the high energy tail of solar particle PAMELA also measures the high energy tail of solar particle

events.events.

http://pamela.roma2.infn.ithttp://pamela.roma2.infn.it

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