Dark Matter Searches with AMS02. AMS: Alpha Magnetic Spectrometer


 Myrtle Sims
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1 Dark Matter Searches with AMS02 AMS: Alpha Magnetic Spectrometer 2007/2008 Wim de Boer on behalf of the AMS collaboration University of Karlsruhe July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 1
2 Outline Physics Motivations Detector requirements Prospects for Indirect Dark Matter searches Conclusions July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 2
3 AMS Physics motivations Search for cosmic anti matter Search for Dark Matter Precision measurement on cosmic rays AMS will collect ~10 10 Cosmic Rays (e ±, γ, p ±,3,4He,B,C, 9,10 Be, elements Z<25 in NearEarth Orbit from few GV to few TV Gamma ray astrophysics Region of antimatter July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 3
4 WIMP Annihilation Final States χ χ ~ f f f χ χ f f χ χ f f χ χ χ W χ ± χ 0 W χ Z Z Dominant Diagram for WMAP cross section: χ + χ A b bbar quark pair Bfragmentation well studied at LEP! Yield and spectra of positrons, gammas and antiprotons well known! July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 4
5 Model of our galaxy July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 5
6 Diffusion equation Particle density: Source function: Diffusion coefficient: GALPROP program by Moskalenko and Strong provides numerical solution to this diffusion eq. for equilibrium taking into account particle densities of ALL nuclei. Convection velocity: Diffusive reacceleration: Momentum loss rate: Radioactive decay: Fragmentation: Source fct??? July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 6
7 Propagation in GALPROP compared with DarkSusy: LARGE DIFFERENCE Antiprotons Positrons Spectrum after propagation of injection of 13 GeV source with NFW profile in DarkSusy (analytical solution of diffusion equation l) and GalProp (numerical solution of diffusion equation including more physical effects, like reacceleration July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 7
8 Problems: Any unidentified background produces a WIMP signal For every antiproton at some energy there are 10, ,000 protons For every positron at some energy there are ~10,000 protons which have same charge sign Secondary particles (long and short lived) are locally produced Single scatters change apparent particle charge sign in simple trackers July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 8
9 AMS02 Particle Identification July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 9
10 Superconducting Magnet Flux Return Coils B Dipole Coils B He Vessel 2500 Liters Superfluid He Analyzing power BL 2 = 0.8 Tm 2 July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 10
11 TRD detector to separate e + from protons : 3 300GeV e+/p rejection in GeV with ECAL e+/p rejection >10 6 July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 11
12 TRD detector 20 layers,328 chambers,5248 tubes Mechanical Accuracy <100µm Assembly in progress CERN beamtest with TRD prototype: proton rejection > 100 up to 250 GeV at electron efficiency 90% reached Single tube spectra for p+/e separation. July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 12
13 Silicon Tracker Rigidity ( R/R 2% for 1 GeV Protons) with Magnet Signed Charge (de/dx) 8 Planes, ~6m 2 Pitch (Bending): 110 µm (coord. res. 10 µm ) Pitch (NonBending): 208µm (coord. res. 30 µm ) Charge measurent up Z ~ 26 July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 13
14 Ring Imaging Cerenkov Counter Accurate Velocity Aerogel Radiator(n=1.03, 3cm) NaF radiator (n=1.33, 0.5cm) Cerenkov Cone β/β = (0.67±0.01)*103% (test beam) Isotopic Separation. Mirror Q measurements up Z~ 30 Photomultipliers 8.5 x 8.5 mm 2 spatial pixel granularity July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 14
15 Charge measurements ToF, Tracker, RICH performance verified at heavy ion test beam (CERN,GSI) Fe Ca P Ne B July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 15
16 Electromagnetic Calorimeter 3D sampling calorimeter 9 superlayers of 10 fiber/lead planes each alternate in x and y scintillating fibers viewed by PMT 16.4 X 0 radiation length Measure energy (few % resolution) and angle (10.5 angular resolution) of γ, e +,e  p ± e ± 103 p ± Rejection at 95% e ± Efficiency Via Shower Profile 1 GeV  1 TeV July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 16
17 AMS02 capabilities Beryllium Boron Helium 1 year 1 year 6 months 1 day 6 months 1 day 10 Be (t 1/2 =1.5Myr) / 9 Be will allow to estimate the propagation time and size of the ISM B is secondary produced in nuclear interaction, C is primary produced in stars. B/C is sensitive to the diffusion constant 3 He/ 4 He ratio is sensitive to the density of the ISM July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 17
18 AMS02 : detector performance Acceptances defined by selection cuts during reconstruction Preliminary Antiprotons: A(<16 GeV) 1200cm 2 sr >16GeV 330 cm 2 Rejection e p 10 6 Positrons: Acceptance 550 cm 2 sr Rejection e p 10 5 Gamma (ECAL mode): Acceptance ~ 600 cm 2 sr Rejection e+  ~ 10 4 p ~ 10 5 Gamma (Conversion mode): Acceptance ~ 550 cm 2 sr July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 18
19 Expected statistics after one year of AMS02 operations Antiprotons Gamma rays Positrons July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 19
20 Summary AMS is a High Energy Physics detector in space foreseen to operate on the ISS for 3 years Asked by NASA to be Ready For Flight in September 2007 The cosmic rays, including gamma rays, will be measured with a high accuracy from the GeV to the TeV range Unique opportunity to perform Dark Matter searches July, COSPAR, Paris, W. de Boer, Univ. Karlsruhe 20