AMS-02 and more: Direct Measurements of Cosmic Rays Andreas Obermeier, AMS Collaboration I. Physics Institute B, RWTH Aachen University, Aachen (Germany) Astroteilchenphysik in Deutschland Status und Perspektiven Karlsruhe, September 30th, 2014
A. Obermeier, RWTH Aachen Direct Measurements of CR Ø Conducted above the atmosphere Ø Balloon or Space Experiments Ø Limited: Size, Time, Weight, Power Ø But: good Energy resolution, elemental or even isotopic detail
A. Obermeier, RWTH Aachen 3 /22 Astroteilchenphysik in D., September 30th 2014
A. Obermeier, RWTH Aachen 4 /22 Achievable Exposure Ø Record circumpolar flight time (LDB): 52 days (Super-TIGER) Ø Total Exposure: ~ 350 m 2 sr days Ø ULDB Flights might double that Ø Expected Exposure for AMS-02 ( years of operation time): 200 m 2 sr days Ø To reach 50 TeV/nucleon in energy spectra one needs about 4000 m 2 sr days
A. Obermeier, RWTH Aachen 5 /22 The recent History: Energy Spectra Ø Energy spectra of individual CR elements from H to Fe Ø Up to a total energy of 5 GeV Oxygen: 6 TeV/nucleon Iron: 4 TeV/nucleon Ø Energy measurement with ECAL, TRD, magnetic Spectrometers, Cherenkov, direct Cherenkov (ICTs) P. Boyle & D. Müller, Particle Data Book (2011)
A. Obermeier, RWTH Aachen 6 /22 The recent History: TIGER/ACE-CRIS: OB origins Ø Measured the relative abundance of CR elements/isotopes compared to the Solar System Ø Abundances arrange themselves nicely when 20% admixture of heavy star ejecta is assumed Ø Possible preferred origin of CR in OB associations GCRS/(80% SS + 20% MSP) (Fe = 1) 1-1 Refractory (Grains) Volatile (Gas) Mixed N O Ne Mg Si Al S P Ar Ca Atomic Mass (A) Fe Cu Co Ni Ga Zn Sr Ge Se Refractory Fit Volatile Fit 2 B. Rauch et al., ApJ (2009) and W. Binns et al., Space Science Reviews (2007)
A. Obermeier, RWTH Aachen 7 /22 The recent History: TRACER: Galactic Propagation Ø B/C ratio drops not to zero B/C ratio Ø Residual path length or nested propagation models are preferred Ø Impact on shape of source spectra -1-2 TRACER HEAO CRN AMS-01 ATIC CREAM =0.64, 2 =0.69 g/cm 0 =0.6, =0.38 g/cm 0 =0.6, =0.0 g/cm 0-1 2 3 1 kinetic Energy [GeV/amu] 2 2 4 ] -1 sr s GeV/amu) 2 (m 2.65 [(GeV/amu) 2.65 Flux E 2 TRACER 2003 TRACER 2006 2.37 2.71 Oxygen 2.56 2 3 kinetic Energy [GeV/amu] 4 A. Obermeier et al., ApJ (2011) and (2012)
A. Obermeier, RWTH Aachen 8 /22 The recent History: CREAM: Discrepant Hardening Ø Different spectral indices for p and He at high energies Ø Break in spectra of heavy nuclei at ~200 GeV/nucleon Ø Hints at complex acceleration process at various sources H. Ahn et al., ApJ Letters (20)
A. Obermeier, RWTH Aachen 9 /22 The recent History: PAMELA: The Positron Fraction Ø The Positron Fraction rises with energy Ø Hinted at by previous experiments (e.g. HEAT), but first conclusive measurement by PAMELA Ø Very difficult to explain by secondary production Ø Possible primary sources: Pulsars or Dark Matter Ø Sparked over 00 citations! Ø German contribution to PAMELA from Siegen University O. Adriani et al., Nature (2009)
AMS-02 and the Positron Fraction Ø For its first publication AMS-02 determined the positron fraction Ø Now, 3 years of data are analyzed Ø Results include: Ø the Positron Fraction up to 500 GeV, Ø the positron flux, Ø the electron flux Ø the combined flux of positrons and electrons Ø German contribution to AMS from RWTH Aachen and KIT Karlsruhe A. Obermeier, RWTH Aachen /22 Astroteilchenphysik in D., September 30th 2014
A. Obermeier, RWTH Aachen 11 /22 The AMS Collaboration USA MIT - CAMBRIDGE NASA GODDARD SPACE FLIGHT CENTER NASA JOHNSON SPACE CENTER UNIV. OF HAWAII UNIV. OF MARYLAND - DEPT OF PHYSICS YALE UNIVERSITY - NEW HAVEN MEXICO UNAM NETHERLANDS ESA-ESTEC NIKHEF FRANCE LUPM MONTPELLIER LAPP ANNECY LPSC GRENOBLE PORTUGAL LAB. OF INSTRUM. LISBON SPAIN CIEMAT - MADRID I.A.C. CANARIAS. ITALY FINLAND UNIV. OF TURKU SWITZERLAND ETH-ZURICH UNIV. OF GENEVA GERMANY RWTH-I. KIT - KARLSRUHE TURKEY METU, ANKARA ASI IROE FLORENCE INFN & UNIV. OF BOLOGNA INFN & UNIV. OF MILANO-BICOCCA INFN & UNIV. OF PERUGIA INFN & UNIV. OF PISA INFN & UNIV. OF ROMA INFN & UNIV. OF TRENTO RUSSIA ITEP KURCHATOV INST. KOREA EWHA KYUNGPOOK NAT.UNIV. CHINA CALT (Beijing) IEE (Beijing) IHEP (Beijing) NLAA (Beijing) SJTU (Shanghai) SEU (Nanjing) SYSU (Guangzhou) SDU (Jinan) TAIWAN ACAD. SINICA (Taipei) CSIST (Taipei) NCU (Chung Li)
A. Obermeier, RWTH Aachen 12 /22 40 th COSPAR, Moscow, August 3 rd 2014 The AMS-02 Detector Tracker L1 TRD upper ToF Inner Tracker lower ToF RICH Tracker L9 ECAL Ø ToF Ø Trigger, Velocity, Charge Ø TRD Ø Heavy/light separation Ø Tracker Ø precision Tracking, Charge, Charge-sign, Rigidity Ø RICH Ø Velocity, Charge Ø ECAL Ø Energy, heavy/light separation
A. Obermeier, RWTH Aachen 13 /22 Proton Rejection of AMS-02 ECAL TRD Ø At 90% electron efficiency Ø Combined: Above 6 up to 500 GeV
A. Obermeier, RWTH Aachen 14 /22 Most important systematic: Charge Confusion Ø Only the tracker determines the charge sign Ø Electrons incorrectly identified as positrons Ø Due to: Ø Elastic or inelastic scattering Ø Tracker resolution Charge Confusion 1-1 -2-3 AMS data MC predictions Ø Largest systematic uncertainty at high energies -4 2 Energy [GeV]
Analysis based on Template Fits Ø 2D Template Fits in ECAL Estimator and TRD Estimator space Ø Projection onto TRD Estimator is shown Ø Charge Confusion fixed Events Ø Efficient and background free determination of the number of positrons/ electrons positrons protons TRD Estimator (173 206 GeV) A. Obermeier, RWTH Aachen 15 /22 15
A. Obermeier, RWTH Aachen 16 /22 The Positron Fraction Ø Positron Fraction measured up to 500 GeV Ø Increase confirmed Ø Hint at an end to the increase M. Aguilar et al., PRL (2013) with already more than 200 citations; And L. Accardo et al., PRL (2014)
A. Obermeier, RWTH Aachen 17 /22 The Electron and Positron Flux Ø Individual Fluxes measured up to 200 GeV Ø Smooth development with energy Ø Different shape for electrons and positrons M. Aguilar et al., PRL (2014)
A. Obermeier, RWTH Aachen 18 /22 The Electron + Positron Flux ) -1 sr sec ] 2 [ m 2 (GeV 3 E 400 AMS-02 ATIC 350 BETS 97&98 PPB-BETS 04 Fermi-LAT 300 HEAT H.E.S.S. H.E.S.S. (LE) 250 200 150 0 50 0 1 2 Energy (GeV) 3 Ø Combined Flux measured up to 1 TeV with more than million events! Ø No small scale features M. Aguilar et al., PRL (2014), submitted
A. Obermeier, RWTH Aachen 19 /22 Fitting a minimal Model to Positron Fraction and Combined Flux Diffuse Flux Source Flux e + +e - Courtesy of A. Kounine
A. Obermeier, RWTH Aachen 20 /22 The Fit Result in the individual Fluxes e - e + Courtesy of A. Kounine
A. Obermeier, RWTH Aachen 21 /22 Outlook Future AMS-02 Science Program Ø Energy spectra of protons and helium Ø Spectra of heavy nuclei Other Experiments: Active and Planned Ø Super-TIGER: Balloon-borne, 52 day Antarctic flight; Measurement of ultra-heavy CR Ø B/C ratio Ø Anti-protons, anti-helium Ø Isotopes at low-energies Ø Anisotropies, time dependent fluxes Ø Strange unexpected things Ø ISS-Cream: Planned for installation on ISS for 3 years; Measurement of elemental spectra Ø Calet: Designed for ISS to explore highest energies electrons Ø GAPS: Balloon-borne, will be flown to search for anti-deuterons
A. Obermeier, RWTH Aachen 22 /22 Conclusion Ø Direct measurement of cosmic radiation is a vital component of cosmic ray research. Ø It provides elemental information and can even resolve isotopes. This has led to important insights in the past and will continue to do so. Ø The challenge to reach higher exposure factors needs new ideas. This is exciting! Ø In Germany only few institutes take part in direct measurements, although the cost of ballooning is small and it is a great opportunity to train young scientists. Ø Future Experiments will need to focus on areas not covered by AMS-02. E.g. Isotopes and beyond 1 TeV/nucleon Ø Vernon Jones at COSPAR 2014: There is enough ballooning capacity for more and new astropyhsics payloads.