La missione PAMELA: primi risultati scientifici Paolo Papini INFN – Firenze a nome della collaborazione PAMELA XCIV Congresso Nazionale Società Italiana di Fisica Genova Settembre, 2008

Moscow St. Petersburg Russia: Sweden: KTH, Stockholm Germany: Siegen Italy: BariFlorenceFrascatiTriesteNaple s Rome CNR, Florence Tha PAMELA collaboration

Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics PAMELA as a Space Observatory at 1 AU Payload for Antimatter Matter Exploration 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 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) X ASTROMAG C 94 C 97C 98 TS 93 M 89 M 91 NINA-1 NINA-2 SILEYE-1SILEYE-2 SILEYE-3 ALTEA

PAMELA history 1996: PAMELA proposal : 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!!!

PAMELA nominal capabilities Energy range Antiprotons 80 MeV 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  Simultaneous measurement of many cosmic-ray species  New energy range  Unprecedented statistics

PAMELA detectors GF: 21.5 cm 2 sr Mass: 470 kg Size: 130x70x70 cm 3 Power Budget: 360W Spectrometer microstrip silicon tracking system + permanent magnet It provides: - Magnetic rigidity  R = pc/Ze - Charge sign - Charge value from dE/dx 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 Main requirements  high-sensitivity antiparticle identification and precise momentum measure + -

PAMELA milestones Launch from Baikonur: June 15 th 2006, 0800 UTC. Power On: June 21 st 2006, 0300 UTC. Detectors operated as expected after launch PAMELA in continuous data-taking mode since commissioning phase ended on July 11 th 2006 As of ~ now: more than 2 years of data taking (~73% live-time) ~10 TByte of raw data downlinked >10 9 triggers recorded and under analysis

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 km) Traverses the South Atlantic Anomaly Crosses the outer (electron) Van Allen belt at south pole Resurs-DK1 Mass: 6.7 tonnes Height: 7.4 m Solar array area: 36 m km 610 km 70 o PAMELA SAA ~90 mins Resurs-DK1 satellite + orbit

– 15/02/ :35:00 MWT S1 S2 S3 orbit 3752 orbit 3753 orbit 3751 NP SP EQ EQ 95 min Outer radiation belt Inner radiation belt (SSA)‏

– 15/02/ :35:00 MWT S1 S2 S3 orbit 3752 orbit 3753 orbit 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 Analysis of a PAMELA orbit SAA Ratemeters Independent from trigger

Principle of operation with protons of known momentum  MDR~1TV Cross-check in flight with protons (alignment) and electrons (energy from calorimeter) Iterative  2 minimization as a function of track state- vector components  Magnetic deflection |η| = 1/R R = pc/Ze  magnetic rigidity  R /R =    Maximum Detectable Rigidity (MDR) R=MDR   R /R=1 MDR = 1/   Track reconstruction

Principle of operation Z measurement Bethe Bloch ionization energy-loss of heavy (M>>me) charged particles 1 st plane p d 3 He 4 He Li Be B,C track average e±e± (  saturation)

Principle of operation Particle low energy Identify albedo (up-ward going particles  < 0 )  NB! They mimic antimatter! Velocity measurement

Principle of operation Interaction topology e/h separation Energy measurement of electrons and positrons (~full shower containment) electron (17GV) hadron (19GV) Electron/hadron separation + NEUTRONS!!

Flight data: GV electron Flight data: GV positron

32.3 GV positron

36 GeV/c interacting proton

Flight data: GeV/c antiproton annihilation

Flight data: GeV/c antiproton annihilation

Nuclei

Galactic H and He spectra 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 -   ~ 2.76 for Z=1  ~ 2.71 for Z=2

Galactic H spectra 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 -   ~ 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 -> NB! still large discrepancies among different primary flux measurements

Proton flux * E 2.75 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 Power-law fit: ~ E -   ~ 2.76 NB! still large discrepancies among different primary flux measurements LBM -> (statistical errors only)

Geomagnetic cutoff 0.4 to to to to 4 > to 14 7 to 10 4 to 7 Geomagnetic cutoff (GV/c) Secondary reentrant-albedo protons Magnetic equator Magnetic poles (  galactic protons) Up-ward going albedo excluded SAA excluded (statistical errors only)

Preliminary Results B/C Preliminary Calorimeter based charge identification!

Interstellar spectrum July 2006 August 2007 February 2008 Decreasing solar activity Increasing GCR flux Solar modulation sun-spot number Ground neutron monitor PAMELA (statistical errors only)

Antiprotoni

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  2 (~95% efficiency) –consistency among TRK, TOF and CAL spatial information Galactic particle –measured rigidity above geomagnetic cutoff –down-ward going particle (no albedo) S1 S2 CAL S4 CARD CAS CAT TOF ND TRK. S3

Antiproton identification dE/dx vs R (S1,S2,TRK) and  vs R proton-concistency cuts electron-rejection cuts based on calorimeter-pattern topology e - (+ p-bar) p-bar p -1  Z  +1 “spillover” p p (+ e + ) electron (17GV) Antiproton (19GV) 1 GV5 GV

Proton spillover background MDR > 850 GV Minimal track requirements Strong track requirements: strict constraints on  2 (~75% efficiency) rejected tracks with low-resolution clusters along the trajectory - faulty strips (high noise) -  -rays (high signal and multiplicity)

High-energy antiproton selection p-bar p 10 GV50 GV

High-energy antiproton selection R < MDR/10 p-bar p 10 GV50 GV

Positroni

Positron selection with calorimeter p (non-int) e-e-e-e- e+e+e+e+ Fraction of charge released along the calorimeter track (left, hit, right) p (int) Rigidity: GV The main difficulty for the positron measurement is the interacting- proton background: fluctuations in hadronic shower development     might mimic pure e.m. showers proton spectrum harder than positron  p/e + increase for increasing energy

Positron identification e-e- ( e + ) pp-bar Energy-rigidity match  ‘electrons’  ‘hadrons’ Energy measured in Calo/ Deflection in Tracker (MIP/GV)

Positron selection with calorimeter e-e-e-e- Fraction of charge released along the calorimeter track (left, hit, right) p e+e+e+e+ + Energy-momentum match Starting point of shower Rigidity: GV Preliminary

Positron selection with calorimeter p e-e-e-e- e+e+e+e+ p Flight data: rigidity: GV Fraction of charge released along the calorimeter track (left, hit, right) Test beam data Momentum: 50GeV/c e-e-e-e- e-e-e-e- e+e+e+e+ Energy-momentum match Starting point of shower

Positron selection e-e-e-e- p e-e-e-e- e+e+e+e+ p Neutrons detected by ND Rigidity: GV Fraction of charge released along the calorimeter track (left, hit, right) e+e+e+e+ Energy-momentum match Starting point of shower

Positron selection Rigidity: GVRigidity: GV e-e-e-e- e-e-e-e- e+e+e+e+ e+e+e+e+p p p p 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

Rigidity: 6-8 GV Proton background evaluation Fraction of charge released along the calorimeter track (left, hit, right) + Constraints on: Energy-momentum match Shower starting-point e+e+ p e-e- p

Positron to Electron Fraction End 2007: ~ positrons total Charge sign dependent solar modulation

e - /e + Rigidity (GV) Electron to positron ratio U.W. Langner, M.S. Potgieter, Advances in Space Research 34 (2004) Preliminary

Fisica solare

Increase of low energy component December 13th 2006 event from to

Increase of low energy component December 13th 2006 event from to from :23:02 to :57:46

Increase of low energy component December 13th 2006 event from to from :23:02 to :57:46 from :57:46 to :49:09

Increase of low energy component December 13th 2006 event from to from :23:02 to :57:46 from :57:46 to :49:09 from :49:09 to :32:56 Increase of low energy component Decrease of high energy component

Increase of low energy component December 13th 2006 event from to from :23:02 to :57:46 from :57:46 to :49:09 from :49:09 to :32:56 from :32:56 to :59:16

Increase of low energy component December 13th 2006 event from to from :23:02 to :57:46 from :57:46 to :49:09 from :49:09 to :32:56 from :32:56 to :59:16 from :17:54 to :17:34

The 14th December 2006 Forbush Decrease Modulation of galactic cosmic ray intensity ~5% Decrease at mid-latitude Jungfraujoch Neutron Monitor (R c ~4.5 GV)‏ GLE Erwin O. Flückiger

The 14th December 2006 Forbush Decrease from to Preliminary

The 14th December 2006 Forbush Decrease from to from :58:42 to :59:57 (red - black) / black Preliminary

The 14th December 2006 Forbush Decrease from to from :00:01 to :59:59 (red - black) / black

The 14th December 2006 Forbush Decrease from to from :00:01 a :59:54 (red - black) / black Preliminary

The 14th December 2006 Forbush Decrease from to from :00:04 a :59:59 (red - black) / black Preliminary

The 14th December 2006 Forbush Decrease from to from :00:04 a :59:59 (red - black) / black Preliminary

The 14th December 2006 Forbush Decrease from to from :00:04 a :59:59 (red - black) / black Preliminary

Fasce di radiazione

South-Atlantic Anomaly (SAA) SAA SAA morphology Latitude Altitude Longitude Neutron rate (background)

B < 0.19 G 0.19 G ≤ B < 0.20 G 0.20 G ≤ B < 0.21 G B > 0.30 G 0.22 G ≤ B < 0.23 G 0.21 G ≤ B < 0.22 G Always: 10 GV < cutoff < 11 Fluxes in SAA Preliminary

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, 3 He) 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!

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*10 3 MIP RELEASED 279 MIP in S4 26 Neutrons in ND