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Search for Dark Matter in the Sky

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Search for Dark Matter in the Sky Search for Dark Matter in the Sky Aldo Morselli INFN Roma Tor Vergata 14 Jun 2012 Dark Side of the Univers Aldo2012 Morselli, INFN Buzios Roma Tor Vergata 10-15 June 1 Aldo Morselli, INFN Roma Tor Vergata 2 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. Aldo Morselli, INFN Roma Tor Vergata 3 They Play Together! Aldo Morselli, INFN Roma Tor Vergata 4 Differential yield for each annihilation channel WIMP mass=200GeV A.Cesarini, F.Fucito, A.Lionetto, A.Morselli, P.Ullio, Aldo Astroparticle Morselli, INFN Physics, Roma Tor Vergata 21, 267, 2004 [astro-ph/0305075] 5 Differential yield for b bar neutralino mass A.Cesarini, F.Fucito, A.Lionetto, A.Morselli, Aldo P.Ullio, Morselli, Astroparticle INFN Roma Tor Vergata Physics, 21, 267-285, 2004 [astro-ph/0305075] 6 Happy 4th Birthday Fermi !! 11 June 2008 Aldo Morselli, INFN Roma Tor Vergata 7 Fermi Symposium Roma, May 9-12 1011 Aldo Morselli, INFN Roma Tor Vergata 8 4 years in orbit • over 1.37 billion Fermi LAT events to the FSSC • the LAT Collaboration has published 199 papers (Cat I and Cat II). Collectively these papers have been cited nearly 10,000 times. • Fermi satellite, the GBM has triggered on 1949 transients (and at 939 GRBs are creeping ever closer to the 1000 mark). The observatory has performed 77 autonomous repoints and the mission overall has produced over 800 refereed papers with new Fermi results or using/interpreting Fermi results and issued over 30 press/web releases. Aldo Morselli, INFN Roma Tor Vergata 9 The Fermi LAT gamma-ray sky 3-year all-sky map, E > 1 GeV Aldo Morselli, INFN Roma Tor Vergata 10 The Fermi LAT 2FGL Source Catalog http://fermi.gsfc.nasa.gov/ssc/data/access/lat/2yr_catalog/ August 4, 2008, to July 31, 2010 100 MeV to 100 GeV energy range 1873 sources 1095 AGN’s 589 unidentified Fermi Coll. ApJS (2012) 199, 31 arXiv:1108.1435 Aldo Morselli, INFN Roma Tor Vergata 11 Third EGRET Catalog 1991-2000, 270 sources , 1.5 M γ’s Aldo Morselli, INFN Roma Tor Vergata 12 • Towards the Second Fermi LAT Catalog 2FGL: 1095 589 13 Aldo Morselli, INFN Roma Tor Vergata 13 Fermi Gamma-Ray Large Area Space Telescope Tracker 1.68 m 84 cm Grid Silicon Tracker tower ACD Thermal 18 planes of X Y silicon detectors + converters Anticoincidence Blanket 12 planes with 3% R.L. of W , 4 planes with 18% R.L 2 planes without converters Shield total 1.5 R.L. DAQDAQ Electronics Electronics Calorimeter ( 8.6 Rad.Length) Aldo Morselli, INFN Roma Tor Vergata 14 How Fermi LAT detects gamma rays Incoming γ 4 x 4 array of identical towers with: • Precision Si-strip tracker (TKR) Conversion – With W converter foils (γ in e+/e-) in W foils • Hodoscopic CsI calorimeter (CAL) • DAQ and Power supply box γ Incoming direction reconstruction by tracking the charged particles e+ e- Energy measurement with e.m. calorimeter An anticoincidence detector around the telescope distinguishes gamma- rays from charged particles Aldo Morselli, INFN Roma Tor Vergata 15 Aldo Morselli, INFN Roma Tor Vergata 16 6 5 0.15Xo(deg) 0.07Xo(deg) Multiple 4 0.05Xo(deg) 3 Scattering 2 10 1 projected angular distribution ( degrees) 0 0.1 1 10 0.15Xo(deg) 1 0.07Xo(deg) E(GeV) 0.05Xo(deg) 0.1 projected angular distribution ( degrees) 0.01 0.1 1 E(GeV) 10 E(GeV) Aldo Morselli, INFN Roma Tor Vergata 17 Fermi Instrument Response Function http://www.slac.stanford.edu/exp/glast/groups/canda/lat_Performance.htm Aldo Morselli, INFN Roma Tor Vergata 18 Fermi Instrument Response Function http://www.slac.stanford.edu/exp/glast/groups/canda/lat_Performance.htm Aldo Morselli, INFN Roma Tor Vergata 19 How Fermi LAT detects electrons Trigger and downlink • LAT triggers on (almost) Incoming Electron every particle that crosses the LAT ACD identifies – ~ 2.2 kHz trigger rate charged particle • On board processing removes many charged particles events Main track – But keeps events with more pointing to the that 20 GeV of deposited hit ACD tile energy in the CAL – ~ 400 Hz downlink rate • Only ~1 Hz are good γ-rays Same tracking and Electron identification energy • The challenge is identifying reconstruction algorithms used the good electrons among for γ-rays the proton background – Rejection power of 103 – 104 required – Can not separate electrons from positrons Aldo Morselli, INFN Roma Tor Vergata 20 Event topology A candidate electron A candidate hadron (recon energy 844 GeV) (raw energy > 800 GeV) • TKR: clean main track with extra-clusters • TKR: small number of extra very close to the track clusters around main track • CAL: clean EM shower profile, not fully contained • CAL: large and asymmetric shower • ACD: few hits in conjunction with the track profile • ACD: large energy deposit per tile Aldo Morselli, INFN Roma Tor Vergata 21 Fermi Electron + Positron spectrum Extended Energy Range (7 GeV - 1 TeV) One year statistics (8M evts) Fermi LAT Coll. Physical Review D, Aldo 82 Morselli, 092004 INFN (2010) Roma Tor[arXiv:1008.3999] Vergata 22 Geomagnetic field + Earth shadow = directions from which only electrons or only positrons are allowed events arriving from West: e+ allowed, e- blocked events arriving from East: e- allowed, e+ blocked • For some direcons, e- or e+ forbidden • Pure e+ region looking West and pure e- region looking East • Regions vary with parcle energy and spacecra posion • To determine regions, use code by Don Smart and Peggy Shea (numerically traces trajectory in geomagnec field) • Using Internaonal Geomagnec Reference Field for the 2010 epoch Aldo Morselli, INFN Roma Tor Vergata 23 Positron Fraction The Fermi-LAT has measured the cosmic-ray positron and electron spectra separately, between 20 and 130 GeV, using the Earth's magnetic field as a charge discriminator •Two independent methods of background subtraction produce consistent results •The observed positron fraction is consistent with the one measured by PAMELA Differences between different experiments below few GeV’s probably due to charge-sign-dependent modulation but still under study Fermi Coll., PRL, 108 (2012) 011103 arXiv:1109.0521 Aldo Morselli, INFN Roma Tor Vergata 24 Positron to Electron Fraction • Positron Ratio do not behave as expected Aldo Morselli, INFN Roma Tor Vergata 25 Antiproton-Proton Ratio • PAMELA ( preliminary) A.Lionetto, et.al JCAP09 (2005) 010 [astro-ph/0502406] Diffuse and Convention Propagation Model Upper and lower bounds A.Lionetto, A.Morselli, V.Zdravkovic JCAP09 (2005) 010 [astro-ph/0502406] antiprotons compatible with standard production Aldo Morselli, INFN Roma Tor Vergata 26 Lepto- philic Models here we assume a democratic dark matter pair- annihilation branching ratio into each charged lepton species: 1/3 into e+e-, 1/3 into µ+ µ- and 1/3 into τ+ τ- Here too antiprotons are not produced in dark matter pair annihilation. Astrp Phys.32 (2009) 140 [arXiv:0905.0636] Aldo Morselli, INFN Roma Tor Vergata 27 Lepto- philic Models here we assume a democratic dark matter pair- annihilation branching ratio into each charged Pamela + Fermi positrons lepton species: 1/3 into e+e-, 1/3 into µ+ µ- and 1/3 into τ+ τ- Here too antiprotons are not produced in dark matter pair annihilation. Astrp Phys.32 (2009) 140 [arXiv:0905.0636] Aldo Morselli, INFN Roma Tor Vergata 28 Pulsars 1. On purely energetic grounds they work (relatively large efficiency) 2. On the basis of the spectrum, it is not clear 1. The spectra of PWN show relatively flat spectra of pairs at Low energies but we do not understand what it is 2. The general spectra (acceleration at the termination shock) are too steep The biggest problem is that of escape of particles from the pulsar 1. Even if acceleration works, pairs have to survive losses 2. And in order to escape they have to cross other two shocks Extensive discussion two week ago @ GGI ( Serpico, Blasi .. ) New Fermi data on pulsars will help to constrain the pulsar models Aldo Morselli, INFN Roma Tor Vergata 29 What if we randomly vary the pulsar parameters relevant for e+e- production? (injection spectrum, e+e- production efficiency, PWN “trapping” time) Under reasonable assumptions, electron/positron emission from pulsars offers a viable interpretation of Fermi CRE data which is also consistent with the HESS and Pamela results. D.Grasso et al. Astropart. Phys. 32 (2009), pp.140 [arXiv:0905.0636] Aldo Morselli, INFN Roma Tor Vergata 30 Cosmic Ray Electrons Anisotropy the levels of anisotropy expected for Geminga-like No-anisotropy map and Monogem-like sources (i.e. sources with similar distances and ages) seem to be higher than the scale of anisotropies excluded by the results However, it is worth to point out that the model results are affected by large uncertainties related to the choice of the free parameters Flight data sky map Distribuon of significance, fied by a Gaussian Fermi Coll. Physical Review D 82, Significance map 092003 (2010) [arXiv:1008.5119] Aldo Morselli, INFN Roma Tor Vergata 31 electron + positron expected anisotropy in the directions of Monogem and Vela Fermi/LAT ULs Vela GALPROP spectrum Monogem Fermi Coll. Physical Review D 82, 092003 (2010) [arXiv:1008.5119] Aldo Morselli, INFN Roma Tor Vergata 32 other Astrophysical solution • Positrons created as secondary products of hadronic interactions inside the sources • Secondary production takes place in the same region where cosmic rays are being accelerated -> Therefore secondary positron have a very flat spectrum, which is responsible, after propagation in the Galaxy, for the observed positron excess Blasi, arXiv:0903.2794 Aldo Morselli, INFN Roma Tor Vergata 33 B/C Ratio CREAM 2008 Astr.Phys.
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