SpadaPlanck07 ThePhysicsAMS 02

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Published on October 29, 2007

Author: Yuan

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The Physics of AMS-02:  The Physics of AMS-02 Francesca Spada – INFN Rome on behalf of the AMS-02 Collaboration Plank07 - Warsaw Slide2:  Precision Cosmology WMAP CMB spectrum SSDS 3D matter spectrum HUBBLE SuperNova Ia redshift Slide3:  Several models provide CDM candidates (WIMPS) R-parity conserving Supersymmetric models Lightest SUSY particle: neutralino χ Extra-dimensional models Lightest Kaluza-Klein particle: n=1 mode of U(1) gauge boson B(1) May be discovered at LCH? Difficult to correlate with CDM Part of the parameter space not accessible Astrophysical WIMP detection is needed Slide4:  Indirect search of CDM = detection of WIMP annihilation products cc annihilations can produce: Neutrinos direct production W decay Heavy Quarks decay charged Pions decay e+ direct production (strongly suppressed): Ee = mX W decay Heavy Quarks decay Leptons and charged Pions decay Photons direct Production : Eg = mX decay of neutral Pions p No direct production Hadronization : Eh << mX Channels accessible to AMS Slide5:  Precursor flight 10 days on Space Shuttle Discovery limit on He/He ratio < 1.1·10-6 very nice measurements of primary and secondary p, p, e-, e+, He, and D spectra from ~1 to 200 GeV (Phys. Rept. vol. 366/6 (2002) 331) 3 years on the ISS Superconducting magnet New detectors for multichannel approach ANTIMATTER SEARCH: He/He ratio < 10-9 COSMIC RAY FLUXES up to Z=26 DARK MATTER SEARCH (*) ready for launch date The AMS-02 detector:  The AMS-02 detector TRD e/p separation TOF b, Z CRYOMAGNET and TRACKER Z, R RICH b, Z Electromagnetic CALorimeter e/p separation, E Electronics crates Transition Radiation Detector (TRD):  Fleece radiator + straw tubes (Xe:CO2) e/p separation > 102 up to 300 GeV 3D tracking Transition Radiation Detector (TRD) Time of Flight (TOF):  2+2 layers of scintillators, Dt ~160 ps Main Trigger Z separation b with few % precision Time of Flight (TOF) Superconducting Magnet:  Coils cooled to 1.8 K by 2.5 m3 of superfluid He Contained dipolar field of 0.85 Tm2 First Superconducting Magnet ever operating in Space! Superconducting Magnet Silicon Tracker:  8 layers double sided silicon microstrip detector Z separation R up to 2-3 TeV sR < 2% for R < 10 GeV Silicon Tracker Ring Imaging Cherenkov (RICH):  2 Radiators: NaF (center), Aerogel (elsewhere) Z and isotopes separation smass = 2% below 10 GeV/n b with 0.1% precision Ring Imaging Cherenkov (RICH) Electromagnetic Calorimeter:  9 superlayers of Lead + Scint. Fibers Standalone Trigger e,  detection sE <3% for E > 10 GeV e/p separation > 103 3D imaging Electromagnetic Calorimeter AMS-02 Fluxes from Cosmic Rays:  AMS-02 Fluxes from Cosmic Rays AMS ~1 s AMS ~1 hour AMS ~1 day AMS ~1 year Particle Energy range p 0.1 up to TeV p 0.5 to 300 GeV e- 0.1 up to TeV e+ 0.1 to 300 GeV He 1 up to TeV anti – He, …, C 1 up to TeV Light Isotopes 1 to 10 GeV/nucleon  1 to TeV Expected ratios e+/p ~ 5·10-4 @ 10 GeV e+/e- ~ 10-1 @ 10 GeV g (galactic center)/p ~ 10-4 @ 10 GeV g (galactic center)/e- ~ 10-2 @ 10 GeV p/p ~ 10-4 @ 10 GeV p/e- ~ 10-2 @ 10 GeV Positrons:  Positrons An excess in the 10 GeV region has been reported by HEAT based on a ~102 positrons sample AMS will collect about 105 positrons in the 10 < E < 50 GeV region, in 3 years Main background sources: rel. abundance rejection factor protons ~ 104 102 -103 [TRD] x 103 [ECAL] ³ 105 electrons ~ 10 104 [TOF+Tracker] e+ p P.Maestro, PhD thesis, 2003 Positrons:  Possible neutralino scenarios Example of neutralino annihiliation signals observed by AMS with the boost factors* that fit the HEAT data and motivated with a inhomogenous dark matter density (clumpiness) gaugino dominated mc= 340 GeV, boost factor=95 e+ primarily from hadronization gaugino dominated mc= 238 GeV, boost factor=116.7 hard e+ from direct gauge boson decay Positrons Positrons:  More neutralino scenarios: boost factors The mimimal boost factor to see the LSP annihilation at 95% C.L. in the positron channel in 3 years is reduced if the gauginos mass universality condition in mSugra is relaxed* mSugra : Mi (GUT) = m1/2 i=1,…,3 tan b = 10 Relaxing gaugino mass universality : Gluino Mass : M3 = 50% m1/2 J. Pochon, PhD thesis, 2005 Positrons Positrons:  Kaluza-Klein scenarios No suppression of the direct annihilation into e+e- because the lightest KK is a boson Characteristic steep spectra from the hard direct production very different from the broad neutralino ones Positrons Antiprotons:  Main background sources: rel. abundance rejection factor protons ~ 104 106 [ToF, RICH, …] electrons ~ 102 103 – 104 [TRD+Ecal] Antiproton acceptance : 1-16 GeV : 0.160 m2·sr 16-300 GeV : 0.033 m2·sr Antiprotons Antiprotons:  Antiprotons AMS-02 Conventional p flux Statistical errors (3 years) Neutralino scenarios Large errors at low momentum – sensitive to details of CR propagation, C/B ratio Low energy Spectrum is well explained by secondary production. Expected signal at high energy (10 – 300 GeV)* *P. Ullio (astro-ph/9904086) Possible distorsions due to WIMPs (large boost factor needed) Antiprotons:  Antiprotons Neutralino scenarios AMS-02 measured antiproton/proton ratio, some regions are not accessible to LHC AMS-02 with Mχ = 206 GeV* AMS-02 expected AMS-02 with Mχ = 840 GeV* AMS-02 expected Not accessible to LHC Photons:  The center of the galaxy can be a very intense point-like source of g from dark matter annihilations Unlike positrons, photons travel long distances and point to their source The annihilation signal could be enhanced by a cuspy profile of the DM density at the galaxy center (super-massive black holes, adiabatic compression, ...) Photons Photons:  Two g detection modes in AMS-02 Photon conversion direction from Tracker, energy from Tracker+Ecal Single photon direction and angle from Ecal Main bg: d rays Rejection factor: >105(p), 4·104(e) [TRD veto, invariant mass] Main bg: secondaries (p0) from p interactions Rejection power: 5·106 [veto on hits, g direction] Photons Photons:  Expected performance – Resolutions and acceptance Photons Photons:  *A. Jacholkowska et al., Phys. Rev. D74, 023518 (2006) Kaluza-Klein & SuSy Models scan for different halo profiles* Galactic center treated as point source NFW halo profiles (Navarro, Frenk & White, ApJ 490 (1997) 493) Photons Conclusions:  Conclusions The AMS experiment, during its 3 year mission, will be able to measure simultaneously and with unprecedented precision the rates and spectra of positrons, photons and antiprotons in the GeV-TeV range, looking for a Dark Matter annihilation signal. confirm or disprove with high accuracy the excess in HEAT positron data in the few GeV region a  signal from the galactic center will be visible in AMS in the case of cuspy halo profile or extra enhancements very accurate measurement of the high energy tail of the antiproton spectrum The AMS simultaneous measurements of other fundamental quantities (p and e- spectra, B/C ratio) will help to disentangle purely astrophysical effects from true dark matter signals. Several models for Dark Matter candidates can be constrained by the new AMS data. End of 2008, AMS-02 will be ready at NASA KSC for the launch to the ISS Photons:  Conversion mode (sel. acc.) GC : ~ 40 days Single photon mode (geom. acc.) GC : ~ 15 days AMS-02 exposure to the galactic center Photons

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