The electron/positron puzzle in the Fermi and PAMELA era Aldo Morselli INFN Roma Tor Vergata May 18 2010 GGI Conference The Dark Matter connection: Theory & Experiment 1 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Neutralino WIMPs Assume χ present in the galactic halo • χ is its own antiparticle => can annihilate in galactic halo producing gamma-rays, antiprotons, positrons…. • Antimatter not produced in large quantities through standard processes (secondary production through p + p --> anti p + X) • So, any extra contribution from exotic sources ( χ χ annihilation) is an interesting signature • ie: χ χ --> anti p + X • Produced from (e. g.) χ χ --> q / g / gauge boson / Higgs boson and subsequent decay and/ or hadronisation. 2 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Antiproton/proton ratio 1997 Caprice coll. Astrophysics Journal, 487, 415, 1997 3 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
MASS Matter Antimatter Space Spectrometer 4 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
the MASS89 Calorimeter 5 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
MASS 89 the calorimeter 6 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
MASS 89 the calorimeter 7 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
from Las Cruces to Prince Albert 8 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
9 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
10 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
11 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
12 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
MASS 89 flight 13 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
MASS 89 flight 14 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
MASS 89 15 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
PAMELA P ayload for A ntimatter M atter E xploration and L ight Nuclei A strophysics In orbit on June 15, 2006, on board of the DK1 satellite by a Soyuz rocket from the Bajkonour launch site. First switch-on on June 21 2006 From July 11 Pamela is in continuous data taking mode 16 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Pamela Separating p from e - 17 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
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 λ I) - 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 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 18 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
• ~ 4 years from PAMELA launch • Launched in orbit on June 15, 2006, on board of the DK1 satellite by a Soyuz rocket from the Bajkonour cosmodrom. 19 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Antiproton-Proton Ratio The conventional GALPROP model with γ 0 = 2.54 ( δ = 0.33 ) Diffuse and Convention gives a satisfactory Propagation Model Upper and lower bounds description of those data A.Lionetto, A.Morselli, V.Zdravkovic JCAP09 (2005) 010 [astro-ph/0502406] • PAMELA data: Phys. Rev. Lett. 102, 051101-1 (2009) arxiv:0810.4994 20 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Antiproton flux p r e l i m i n a r y 21 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Positron ratio Positron ratio conventional GALPROP model γ 0 = 2.54 ( δ = 0.33 ) Secondary positrons only ! E< 10 Gev, probably solar modulation effect Nature 458, 607 2009 [arxiv:0810.4995] e + /(e + + e - ) ∝ E - γ p + γ 0 - δ γ p: proton source power-index It improves only adopting very soft electron spectra (high γ 0 ) 22 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Positron ratio Positron ratio Pamela Nature paper July06-February08 Pamela new data (~ 30% more) July06-December08 and new analysis Nature 458,607, 2009 [arxiv:0810.4995] arXiv:1001.3522 Secondary production 23 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Pamela Electron Spectrum ( e - ) y r a n i m i l e r p 24 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Pamela Electron Spectrum ( e - ) y r a n i m i l e r p 25 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Proton Spectrum y r a n i m i l e r p 26 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
PAMELA Helium 27 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Carbon 28 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Boron 29 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
B/C preliminary preliminary preliminary Li/C Be/C The HEAO-3 sharp peak at ~1 GeV/nucleon seem to be confirmed by PAMELA 30 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
The CAPRICE 94 flight 31 31 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
The TS93 and CAPRICE silicon-tungsten imaging calorimeter. 48 cm 48 cm 32 32 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
High Energy Gamma Experiments Experiments ~1993 33 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
34 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Elements of a pair-conversion telescope • photons materialize into matter-antimatter pairs: E γ --> m e + c 2 + m e - c 2 • electron and positron carry information about the direction, energy and polarization of the γ -ray (energy measurement) 35 35 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Anti-Coincidence Dome Spark Chamber Trigger Telescope Cos-B Cerenkov Counter SAS-2 8/1975-4/1982 Energy Calorimeter 11/1972-7/1973 The gamma-ray missions EGRET 4/1991-1999 36 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
GILDA 37 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
New Detector Technology • Silicon strip detector Strip-shaped PN diode 300-500micron thick 50-500micron wide VLSI amplifier Stable particle tracker that allows micron-level tracking of gamma-rays Well known technology in Particle Physics experiments. Used by our collaboration in balloon experiments (MASS, TS93, CAPRICE), on MIR Space Station ( SilEye) and on satellite (NINA) 38 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
GILDA GLAST 39 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
Fermi launch 11 June 2008 40 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
1451 sources First Fermi LAT Catalogs k l a t s u o i v e r Fermi Large Area p a i g Telescope First Source r u M Catalog arXiv:1002.2280, a n o m 2010 ApJS accepted. i S (1FGL)contains 1451 sources detected and characterized in the 100 MeV to 100 GeV, first 11 months data. The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope arXiv: 1002.0150, includes 671 gamma-ray sources at high Galactic latitudes (|b| > 10 deg), with TS> 25 and associated statistically with AGNs. The First Fermi Large Area Telescope Catalog of Gamma-ray Pulsars 2010ApJS..187..460A . Contains 46 high- confidence pulsed detections using the first six months of data 41 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
How Fermi LAT detects gamma rays Incoming γ Incoming 4 x 4 array of identical towers with: • Precision Si-strip tracker (TKR) Conversion Conversion – With W converter foils ( γ i in e + /e /e - ) in W foils in W foils • Hodoscopic CsI calorimeter (CAL) • DAQ and Power supply box γ Incoming direction Incoming direction reconstruction by reconstruction by tracking the tracking the charged particles charged particles e + e - Energy Energy m measurement with e.m. with e.m. calorimeter calorimeter An anticoincidence detector around the telescope distinguishes gamma- rays from charged particles 42 Florence GGI, May 3 2010 Aldo Morselli, INFN Roma Tor Vergata
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