Measurement of anisotropies in cosmic ray arrival directions with the Alpha Magnetic Spectrometer on the ISS July 13, 2017 ICRC 2017, Busan, Korea Iris Gebauer for the AMS collaboration INSTITUT FÜR EXPERIMENTELLE KERNPHYSIK KIT – Universität des Landes Baden-Württemberg und Software-Entwurf und -Qualität 9/22/12 1 www.kit.edu nationales Forschungszentrum in der Helmholtz-Gemeinschaft Institut für Programmstrukturen und Datenorganisation
WHY ANISOTROPY SEARCHES? AMS has observed a number of unexpected structures in the spectra of positrons, protons, helium and other nuclei. These structures may be connected to new phenomena which could induce some degree of anisotropy in their arrival directions. Preliminary data. PRL 110, 141102 (2013) Please refer to the AMS forthcoming publication in PRL. mainly primary protons Expectation Expectation Secondary lithium P + gas → e + + X Expectation Cosmic ray arrival directions are therefore directly related to the understanding of the spectral features observed by AMS. July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 2 Institut für Experimentelle Kernphysik
WHAT DOES AN ISOTROPIC SKY LOOK LIKE? AMS-02 does not scan the galactic sky uniformly. AMS-02 galactic pointing direction 2.5 years ISS global position 1 day ( Galactic coordinates ) r o t a North u q e pole s h t r a South E pole On top of that we have: ● Geomagnetic cutoff → high rate of low energy particles at poles → trigger busy ● Position dependent efficiencies July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 3 Institut für Experimentelle Kernphysik
WHAT DOES AN ISOTROPIC SKY LOOK LIKE? AMS-02 does not scan the galactic sky uniformly. AMS-02 proton sky ISS global position 1 day (>40 GV, Galactic coordinates ) Lots of exposure North pole South pole Opening angle: ~ 40 degs for protons On top of that we have: ~ 25 deg for electrons ● Geomagnetic cutoff → high rate of low energy particles at poles → trigger busy ● Position dependent efficiencies July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 4 Institut für Experimentelle Kernphysik
REFERENCE MAPS FOR ANISOTROPY SEARCHES Reference maps: best guess for an image of an isotropic sky measured by AMS-02 in the respective data taking period. Any deviation from this reference map might be detected as a signal. July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 5 Institut für Experimentelle Kernphysik
REFERENCE MAPS FOR ANISOTROPY SEARCHES Reference maps: best guess for an image of an isotropic sky measured by AMS-02 in the respective data taking period. Any deviation from this reference map might be detected as a signal. Choices for reference maps: I) other cosmic ray species (e.g. protons used for positrons) / = positrons protons Ratio (positrons/protons) 25-350 GeV 25-350 GV July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 6 Institut für Experimentelle Kernphysik
THE SEARCH FOR ANISOTROPIES WITH AMS-02 A likelihood fit procedure is used to expand the normalized ratio of data and reference map into a dipole. ∞ ∑ l f (θ , ϕ)= ∑ m (θ , ϕ) a lm Y l l = 0 m =− l Ratio (data/reference) North-South: Forward-Backward: East-West: Dipole amplitude: Analysis is performed for any coordinate system of interest. July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 7 Institut für Experimentelle Kernphysik
POSITRONS OVER ELECTRONS – GALACTIC COORDINATES Data: 5 years, Mar11 – Mar16 16-350 40-350 100-350 65-350 25-350 E max =350 GeV Analysis is based on 70,000 positrons and 1 mio. electrons between 16 and 350 GeV. All dipole components are compatible with statistical fluctuations within 1σ. July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 8 Institut für Experimentelle Kernphysik
POSITRONS OVER ELECTRONS – LIMIT ON DIPOLE STRENGHT ● Isotropic expectation: calculated from MC using isotropic signal and reference maps → 68.3% CL of δ distribution is quoted. ● 95% C.L. limit: calculated from MC using simulated dipoles Preliminary and isotropic reference data. Please refer maps to the AMS → 95% CL is bayesian , forthcoming publication computed from the in PRL . distribution of true dipole strengths for the dipole strength measured on data July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 9 Institut für Experimentelle Kernphysik
ISOTROPY OF POSITRON ARRIVAL DIRECTIONS A search for a possible dipole signal in the the arrival directions of positrons was performed, using electrons and protons as a reference for isotropy. No significant deviation from isotropy is found. No significant time dependence was observed. Upper limits at ISS orbit 5yrs: Preliminary data. Please refer to the δ e+/e- (>16 GeV) < 2 % at 95% C.L. Galactic AMS forthcoming coordinates publication in δ e+/p (>16 GeV) < 2% at 95% C.L. PRL . Each analysis was performed by 3 independent groups within AMS. All analyses are in excellent agreement. July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 10 Institut für Experimentelle Kernphysik
REFERENCE MAPS FOR ANISOTROPY SEARCHES Reference maps: best guess for an image of an isotropic sky measured by AMS-02 in the respective data taking period. Any deviation from this reference map might be detected as a signal. Choices for reference maps: I) other cosmic ray species (e.g. protons used for positrons) II) same cosmic ray species (at different energy) July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 11 Institut für Experimentelle Kernphysik
RELATIVE PROTON ANISOTROPIES AMS-02, PRL 114 Use low energy protons to normalize for exposure and efficiencies → Reference map. Stay well above geomagnetic cutoff. Fullspan protons only (same geometry for all rigidities). Reference Signal 40 – 80 GV 300 – 1800 GV Protons with energy>300 GV Protons with 40 GV<E<80GV in galactic coordinates in galactic coordinates Signal map Reference map July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 12 Institut für Experimentelle Kernphysik
RELATIVE PROTON ANISOTROPIES – GALACTIC COORDINATES Data: 5 years, Mar11 - Mar16 R max =1.8 TV Dipole amplitude: Preliminary data. Please refer to the AMS forthcoming publication in Analysis is based on 1.3 10 7 protons above 40 GV PRL . July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 13 Institut für Experimentelle Kernphysik
REFERENCE MAPS FOR ANISOTROPY SEARCHES Reference maps: best guess for an image of an isotropic sky measured by AMS-02 in the respective data taking period. Any deviation from this reference map might be detected as a signal. Choices for reference maps: I) other cosmic ray species (e.g. protons used for positrons) II) same cosmic ray species (at different energy) III) simulation of an isotropic sky from data / = 40 GV-1.8 TV protons 40 GV-1.8 TV IsoSky Ratio (proton/IsoSky) July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 14 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Idea: Project detector's field of view on the galactic sky for the respective measurement time and weight with detector livetime and efficiencies. Method: IG, PoS(ICRC2015)408 α α See poster by MA Velasco, today 15h room F, CRD052, board #028 July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 15 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 17:33:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 16 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 17:53:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 17 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 18:13:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 18 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 18:33:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 19 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 18:53:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 20 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 19:13:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 21 Institut für Experimentelle Kernphysik
SIMULATION OF AN ISOTROPIC SKY Fri, 13 Jul 2012 19:33:24 GMT Position Of ISS High Low Number of expected particles July 13th, Anisotropy searches with AMS-02 (contribution CRD-071) Iris Gebauer 22 Institut für Experimentelle Kernphysik
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