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XCIV Congresso Nazionale Societ à Italiana di Fisica Genova 22-27 Settembre, 2008. La missione PAMELA: primi risultati scientifici. Paolo Papini INFN – Firenze a nome della collaborazione PAMELA. Italy :. CNR, Florence. Bari. Florence. Frascati. Naples. Rome. Trieste. Russia :.

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La missione pamela primi risultati scientifici

XCIV Congresso Nazionale

Società Italiana di Fisica

Genova 22-27 Settembre, 2008

La missione PAMELA:primi risultati scientifici

Paolo Papini

INFN – Firenze

a nome della collaborazione PAMELA


La missione pamela primi risultati scientifici

Italy:

CNR, Florence

Bari

Florence

Frascati

Naples

Rome

Trieste

Russia:

Moscow

St. Petersburg

Germany:

Sweden:

Siegen

KTH, Stockholm

Tha PAMELA collaboration


La missione pamela primi risultati scientifici

PAMELA as a Space Observatory at 1 AUPayload forAntimatterMatterExploration and Light Nuclei Astrophysics

  • Search 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 prehistory
PAMELA prehistory

Astromag/WiZard project (PAMELA precursor) on board of the Space Station FreedomCANCELED

Balloon-borne experiments: MASS-89,91 TS-93 CAPRICE-94,97,98

Space experiments*: NINA-1,2 SILEYE-1,2,3 ALTEA

(*study of low energy nuclei and space radiation environment)

C 98

C 94

C 97

M 91

M 89

TS 93

NINA-2

NINA-1

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

- - - - X

SILEYE-3

SILEYE-1

SILEYE-2

ASTROMAG

ALTEA


Pamela history
PAMELA history

1996: PAMELA proposal

22.12.1998: agreement between RSA (Russian Space Agency) and INFN to build and launch PAMELA.

Three models required by the RSA:

Mass-Dimensional and Thermal Model (MDTM)

Technological Model (TM)

Flight Model (FM)

 Starts PAMELA construction

2001: change of the satellite complete redefinition of mechanics

2006: flight!!!

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007


Pamela nominal capabilities
PAMELA nominal capabilities

Energy range

Antiprotons 80 MeV - 150 GeV

Positrons50 MeV – 270 GeV

Electronsup to 400 GeV

Protons up to 700 GeV

Electrons+positronsup to 2 TeV (from calorimeter)

Light Nuclei up to 200 GeV/n He/Be/C

AntiNuclei search

  • Simultaneous measurement of many cosmic-ray species

  • New energy range

  • Unprecedented statistics


Pamela detectors
PAMELA detectors

Main requirements  high-sensitivity antiparticle identification and precise momentum measure

+ -

Time-Of-Flight

plastic scintillators + PMT:

  • Trigger

  • Albedo rejection;

  • Mass identification up to 1 GeV;

    - Charge identification from dE/dX.

    Electromagnetic calorimeter

    W/Si sampling (16.3 X0, 0.6 λI)

  • Discrimination e+ / p, anti-p / e-

    (shower topology)

  • Direct E measurement for e-

    Neutron detector

    plastic scintillators + PMT:

  • High-energy e/h discrimination

GF: 21.5 cm2 sr Mass: 470 kg

Size: 130x70x70 cm3

Power Budget: 360W

Spectrometer

microstrip silicon tracking system+ permanent magnet

It provides:

- Magnetic rigidity R = pc/Ze

  • Charge sign

  • Charge value from dE/dx


La missione pamela primi risultati scientifici

PAMELA milestones

  • Launch from Baikonur: June 15th 2006, 0800 UTC.

  • Power On: June 21st 2006, 0300 UTC.

  • Detectors operated as expected after launch

  • PAMELA in continuous data-taking mode since commissioning phase ended on July 11th 2006

  • As of ~ now:

    • more than 2 years of data taking (~73% live-time)

    • ~10 TByte of raw data downlinked

    • >109 triggers recorded and under analysis


Resurs dk1 satellite orbit
Resurs-DK1 satellite + orbit

  • Resurs-DK1: multi-spectral imaging of earth’s surface

  • PAMELA mounted inside a pressurized container

  • Lifetime >3 years (assisted)

  • Data transmitted to NTsOMZ, Moscow via high-speed radio downlink. ~16 GB per day

  • Quasi-polar and elliptical orbit (70.0°, 350 km - 600 km)

  • Traverses the South Atlantic Anomaly

  • Crosses the outer (electron) Van Allen belt at south pole

PAMELA

Resurs-DK1

Mass: 6.7 tonnes

Height: 7.4 m

Solar array area: 36 m2

350 km

70o

SAA

610 km

~90 mins


La missione pamela primi risultati scientifici

Analysis of a PAMELA orbit

S1

S2

S3

SAA

NP SP

EQ EQ

orbit 3752

orbit 3753

95 min

orbit 3751

Low energy particles stops inside the apparatus

 Counting rates: S1>S2>S3

Outer radiation belt

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

S1

S2

S3

Inner radiation belt

(SAA)

Ratemeters

Independent from trigger


Principle of operation
Principle of operation

Track reconstruction

  • Measured @ground with protons of known momentum

    •  MDR~1TV

  • Cross-check in flight with protons (alignment) and electrons (energy from calorimeter)

Iterative c2 minimization as a function of track state-vector components a

Magnetic deflection

|η| = 1/R

R = pc/Ze magnetic rigidity

sR/R = sh/h

Maximum Detectable Rigidity (MDR)

def: @ R=MDR sR/R=1

MDR = 1/sh


Principle of operation1
Principle of operation

track average

4He

B,C

3He

Be

d

(saturation)

p

Li

1st plane

Z measurement

Bethe Bloch

ionization energy-loss of heavy (M>>me) charged particles


Principle of operation2
Principle of operation

Velocity measurement

  • Particle identification @ low energy

  • Identify albedo (up-ward going particles b < 0 )

  •  NB! They mimic antimatter!


Principle of operation3
Principle of operation

Electron/hadron separation

  • Interaction topology

  • e/h separation

  • Energy measurement of electrons and positrons

  • (~full shower containment)

hadron (19GV)

electron (17GV)

+ NEUTRONS!!


La missione pamela primi risultati scientifici

Flight data:

0.171 GV positron

Flight data:

0.169 GV electron


La missione pamela primi risultati scientifici

32.3 GV

positron


La missione pamela primi risultati scientifici

36 GeV/c

interacting proton


La missione pamela primi risultati scientifici

Flight data: 0.632 GeV/c

antiproton annihilation


La missione pamela primi risultati scientifici

Flight data: 0.763 GeV/c

antiproton annihilation



La missione pamela primi risultati scientifici

NB! still large discrepancies among different primary flux measurements

Galactic H spectra

Preliminary!!

Very high statistics over a wide energy range

 Precise measurement of spectral shape

 Possibility to study time variations and transient phenomena

(statistical errors only)

Power-law fit: ~ E-g

g~ 2.76 for Z=1

  • Proton of primary origin

  • Diffusive shock-wave acceleration in SNRs

  • Local spectrum:

  • injection spectrum  galactic propagation

  • Local primary spectral shape:

  • study of particle acceleration mechanism

LBM ->


La missione pamela primi risultati scientifici

Geomagnetic

cutoff (GV/c)

0.4 to 0.5

1.0 to 1.5

1.5 to 2.0

2 to 4

4 to 7

7 to 10

10 to 14

> 14

Geomagnetic cutoff

Preliminary!!

(statistical errors only)

Magnetic poles

( galactic protons)

Secondary reentrant-albedo protons

Magnetic equator

  • Up-ward going albedo excluded

  • SAA excluded


La missione pamela primi risultati scientifici

Preliminary Results B/C

Preliminary

Calorimeter based charge identification!


La missione pamela primi risultati scientifici

Solar modulation

Interstellar spectrum

PAMELA

Ground neutron monitor

sun-spot number

Preliminary!!

(statistical errors only)

Increasing

GCR flux

July 2006

August 2007

February 2008

Decreasing

solar activity



La missione pamela primi risultati scientifici

S1

CARD

CAT

S2

.

TOF

TRK

CAS

S3

CAL

S4

ND

High-energy antiproton analysis

Basic requirements:

  • Clean pattern inside the apparatus

    • single track inside TRK

    • no multiple hits in S1+S2

    • no activity in CARD+CAT

  • Minimal track requirements

    • energy-dependent cut on track c2 (~95% efficiency)

    • consistency among TRK, TOF and CAL spatial information

  • Galactic particle

    • measured rigidity above geomagnetic cutoff

    • down-ward going particle (no albedo)


La missione pamela primi risultati scientifici

electron (17GV)

Antiproton (19GV)

1 GV

5 GV

Antiproton identification

  • dE/dx vs R (S1,S2,TRK) and b vs R proton-concistency cuts

  • electron-rejection cuts based on calorimeter-pattern topology

-1  Z  +1

p (+ e+)

p

e-(+ p-bar)

“spillover” p

p-bar


La missione pamela primi risultati scientifici

Proton spillover background

Minimal track requirements

MDR > 850 GV

  • Strong track requirements:

  • strict constraints on c2 (~75% efficiency)

  • rejected tracks with low-resolution clusters along the trajectory

    • - faulty strips (high noise)

    • - d-rays (high signal and multiplicity)


La missione pamela primi risultati scientifici

10 GV

50 GV

High-energy antiproton selection

p

p-bar


La missione pamela primi risultati scientifici

10 GV

50 GV

High-energy antiproton selection

p

p-bar

R < MDR/10



La missione pamela primi risultati scientifici

Positron selection with calorimeter

p (non-int)

p (int)

  • The main difficulty for the positron measurement is the interacting-proton background:

  • fluctuations in hadronic shower development p0 ggmight mimic pure e.m. showers

  • proton spectrum harder than positron  p/e+ increase for increasing energy

e-

p (non-int)

e+

p (int)

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

Rigidity: 20-30 GV


La missione pamela primi risultati scientifici

Positron identification

Energy-rigidity match

e-

( e+ )

Energy measured in Calo/

Deflection in Tracker (MIP/GV)

 ‘electrons’

 ‘hadrons’

p-bar

p


La missione pamela primi risultati scientifici

Positron selection with calorimeter

Rigidity: 20-30 GV

e-

e+

p

Preliminary

+

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

  • Energy-momentum match

  • Starting point of shower


La missione pamela primi risultati scientifici

Positron selection with calorimeter

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

Flight data:

rigidity: 20-30 GV

Test beam data

Momentum: 50GeV/c

e-

e-

e-

p

e+

e+

p

  • Energy-momentum match

  • Starting point of shower


Positron selection
Positron selection

Rigidity: 20-30 GV

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

Neutrons detected by ND

e-

e-

p

e+

e+

p

  • Energy-momentum match

  • Starting point of shower


La missione pamela primi risultati scientifici

Positron selection

Energy loss in silicon tracker detectors:

  • Top: positive (mostly p) and negative events (mostly e-)

  • Bottom: positive events identified as p and e+ by trasversal profile method

p

e-

p

e-

p

e+

p

e+

Rigidity: 10-15 GV

Rigidity: 15-20 GV


La missione pamela primi risultati scientifici

Proton background evaluation

Preliminary!!

Rigidity: 6-8 GV

e-

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

+

Constraints on:

e+

Energy-momentum match

p

Shower starting-point

p


La missione pamela primi risultati scientifici

Positron to Electron Fraction

Charge sign dependent solar modulation

End 2007:

~20 000 positrons total


La missione pamela primi risultati scientifici

Electron to positron ratio

Preliminary

e-/e+

Rigidity (GV)

U.W. Langner, M.S. Potgieter, Advances in Space Research 34 (2004)



La missione pamela primi risultati scientifici

Increase of low energy component

December 13th 2006 event

from 2006-12-1 to 2006-12-4


La missione pamela primi risultati scientifici

Increase of low energy component

December 13th 2006 event

from 2006-12-1 to 2006-12-4

from 2006-12-13 00:23:02 to 2006-12-13 02:57:46


La missione pamela primi risultati scientifici

Increase of low energy component

December 13th 2006 event

from 2006-12-1 to 2006-12-4

from 2006-12-13 00:23:02 to 2006-12-13 02:57:46

from 2006-12-13 02:57:46 to 2006-12-13 03:49:09


La missione pamela primi risultati scientifici

Decrease of high energy component

Increase of low energy component

Increase of low energy component

December 13th 2006 event

from 2006-12-1 to 2006-12-4

from 2006-12-13 00:23:02 to 2006-12-13 02:57:46

from 2006-12-13 02:57:46 to 2006-12-13 03:49:09

from 2006-12-13 03:49:09 to 2006-12-13 04:32:56


La missione pamela primi risultati scientifici

Increase of low energy component

December 13th 2006 event

from 2006-12-1 to 2006-12-4

from 2006-12-13 00:23:02 to 2006-12-13 02:57:46

from 2006-12-13 02:57:46 to 2006-12-13 03:49:09

from 2006-12-13 03:49:09 to 2006-12-13 04:32:56

from 2006-12-13 04:32:56 to 2006-12-13 04:59:16


La missione pamela primi risultati scientifici

Increase of low energy component

December 13th 2006 event

from 2006-12-1 to 2006-12-4

from 2006-12-13 00:23:02 to 2006-12-13 02:57:46

from 2006-12-13 02:57:46 to 2006-12-13 03:49:09

from 2006-12-13 03:49:09 to 2006-12-13 04:32:56

from 2006-12-13 04:32:56 to 2006-12-13 04:59:16

from 2006-12-13 08:17:54 to 2006-12-13 09:17:34


La missione pamela primi risultati scientifici

Modulation of galactic cosmic ray intensity

~5% Decrease at mid-latitude

GLE

Jungfraujoch Neutron Monitor (Rc~4.5 GV)‏

The 14th December 2006 Forbush Decrease

Erwin O. Flückiger


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

Preliminary


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

from 2006-12-14 08:58:42 to 2006-12-14 11:59:57

Preliminary

(red - black) / black


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

from 2006-12-14 12:00:01 to 2006-12-14 23:59:59

(red - black) / black


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

from 2006-12-15 00:00:01 a 2006-12-15 23:59:54

Preliminary

(red - black) / black


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

from 2006-12-16 00:00:04 a 2006-12-16 23:59:59

Preliminary

(red - black) / black


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

from 2006-12-17 00:00:04 a 2006-12-17 23:59:59

Preliminary

(red - black) / black


La missione pamela primi risultati scientifici

The 14th December 2006 Forbush Decrease

from 2006-12-1 to 2006-12-4

from 2006-12-17 00:00:04 a 2006-12-17 23:59:59

Preliminary

(red - black) / black



La missione pamela primi risultati scientifici

SAA morphology

Latitude

Altitude

Altitude

Neutron rate

(background)

Longitude

South-Atlantic Anomaly (SAA)

SAA


La missione pamela primi risultati scientifici

Fluxes in SAA

B > 0.30 G

0.22 G ≤ B < 0.23 G

0.21 G ≤ B < 0.22 G

0.20 G ≤ B < 0.21 G

0.19 G ≤ B < 0.20 G

B < 0.19 G

Always: 10 GV < cutoff < 11

Preliminary


La missione pamela primi risultati scientifici

Conclusions

  • PAMELA is continously taking data since July 2006

  • Presented preliminary results from ~600 days of data:

    • Antiproton charge ratio (~1 GeV ÷100 GeV)

      • no evident deviations from secondary expectations

      • more data to come at lower and higher energies (up to ~150 GeV)

    • Positron charge ratio (~400 MeV ÷10 GeV)

      • indicates charge dependent modulation effects

      • more data to come at lower and higher energies (up to ~200 GeV)

    • Galactic primary proton spectra

      • primary spectra up to Z=8 to come

    • Galactic secondary-to-primary ratio (B/C)

      • abundance of other secondary elements (Li,Be) and isotopes (d,3He) to come

    • High energy tail of proton SEP events

      • spectra of other components (electrons, isotopes,…) to come

    • Radiation belts

      • morphology

      • spectrum

  • PAMELA is already providing significant experimental results, which will help in understanding CR origin and propagation

  • More exciting results will come in the next future!


La missione pamela primi risultati scientifici

A calorimeter self-triggering showering event. Note the high energy release in the core of the shower and the high number (26) neutrons detected.

CALO SELF TRIGGER EVENT: 167*103 MIP RELEASED

279 MIP in S4

26 Neutrons in ND