AMS Results B.Bertucci University & INFN Perugia Moscow, Aug.26, 2015 1 @Reid Wiseman/NASA/REX
Outline ① AMS in a nutshell ② Results: ü Positron and electrons ü Status of anti-protons ü Nuclear fluxes ③ Conclusions 2 @Reid Wiseman/NASA/REX
In the international year of light the Universe has never been so dark! - Dark energy & Dark matter dominate the universe Complementary approaches, different messengers (and new ideas?) are needed to probe the nature of our universe: - Light : from radio to ultra TeV γ rays - Particles: Cosmic Rays: in space, on ground, under water and in ice / Particle accelerators - Gravitational waves : finally?..and to learn something more of our surroundings 3
In the international year of light the Universe has never been so dark! - Dark energy & Dark matter dominate the universe Complementary approaches, different messengers (and new ideas?) are needed to probe the nature of our universe: - Light : from radio to ultra TeV γ rays - Particles: Cosmic Rays: in space, on ground, under water and in ice / Particle accelerators - Gravitational waves : finally?..and to learn something more of our surroundings 4
AMS is a precision, multipurpose magnetic spectrometer operating on the ISS since 2011 to perform accurate measurements of charged cosmic rays in the GeV-TeV energy range: Its main objectives: - Searching for the ultimate nature of matter and physics beyond the Standard Model : anti-matter, dark matter, strange matter - Understanding the origin of cosmic rays and their propagation into the galaxy 5
The quest for Dark Matter Sca1ering Annihila-on χ + χ p, p, e, e+, γ χ p, p, e, e+, γ χ p, p, e, e+, γ χ +χ p+ p χ Produc-on Sun e-, p,γ e+,"p, γ χ 6
The Cosmic Background: Origin, propagation and production of CRs and their secondaries SNR χ e-, p,γ e+,"p, γ Sun π± à µ± à e±" p+pà p+p Boron-to-Carbon Ratio p, He,C..,e- 0.4 0.3 0.2 χ AMS-02 PAMELA (2014) TRACER (2006) CREAM-I (2004) ATIC-02 (2003) AMS-01 (1998) Buckley et al. (1991) CRN-Spacelab2 (1985) Webber et al. (1981) HEAO3-C2 (1980) Simon et al. (1974-1976) Dwyer & Meyer (1973-1975) Orth et al. (1972) 0.1 0.05 0.04 0.03 0.02 1 10 10 2 10 3 Kinetic Energy (GeV/n) 7
THE EXPERIMENTAL CHALLENGE DESIGN : state of the art detectors providing redundant measurements of particle properties TEST: test and calibration on ground MONITORING on ISS : calibration on flight EXPOSURE : Acceptance & Time p, He,C..,e- SNR χ e-, p,γ e+,"p, γ Sun π± à µ± à e±" p+pà p+p χ 8
FINLAND UNIV. OF TURKU 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. BRASIL IFSC SÃO CARLOS INSTITUTE OF PHYSICS SWITZERLAND ETH-ZURICH UNIV. OF GENEVA ITALY 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) NCKU (Tainan) AMS: a large Interna-onal collabora-on 60 ins-tutes / 600 people / 20 years 9
(part of ) the Collaboration after the 1 st event on orbit 10
AMS: A TeV precision, multipurpose spectrometer TRD Identify e +, e - Par-cles and nuclei are defined by their charge (Z) and energy (E ~ P) TOF Z, E Silicon Tracker Z, P 1 TRD" TOF" 2 3-4 5-6 7-8 Tracker" Magnet ±Z ECAL E of e +, e - TOF" RICH" 9 ECAL" RICH Z, E Z and P ~ E are measured independently by the Tracker, RICH, TOF and ECAL 11
6 5m x 4m x 3m 7.5 tons Acceptance & Exposure time à Statistics!
Extensive tests and calibration at CERN AMS 27 km 7 km p, e +, e -, π 20 400 GeV 2000 positions θ Z 19 January 2010 Φ X 13
Full coverage of anti-matter & CR physics e P He,Li, Be,..Fe γ e + P He,C 600 GeV electron" TRD TOF Tracker +Magnet RICH ECAL Physics example Cosmic Ray Physics Dark matter Anti matter 14
In 4 years on ISS, AMS has collected >68 billion cosmic rays. To match the statistics, systematic error studies have become important.
The Search for the Origin of Dark Matter Collisions of Dark Matter (neutralinos, χ) will produce a signal of e+, p, above the background from the collisions of ordinary cosmic rays e + /(e + + e - ) Positrons: χ + χ e + + Antiprotons: χ + χ p + Collision of Cosmic Rays mχ=800 GeV mχ=400 GeV Collision of Cosmic Rays mχ= 1 TeV I. Cholis et al., JCAP 0912 (2009) 007 Donato et al., PRL 102, 071301 (2009) e ± energy [GeV] 16
Physics of 11 million e +, e - events Measuring electrons and positrons TRD iden-fy e ± Probability electron proton ISS data:83-100 GeV TRD estimator TRACKER measures P ECAL measures E e ± : E=P proton: E<P Normalized entities proton electron ISS data:83-100 GeV ECAL measures E and shower shape to separate e ± from protons Fraction of events E/P ISS data:83-100 GeV Boosted Decision Tree, BDT: proton electron ε e =90% ECAL BDT 17
10.9 million e+ and e- events Unprecedented accuracy and energy range allowed a detailed study of the positron fraction behaviour with energy 18
10.9 million e+ and e- events Unprecedented accuracy and energy range allowed a detailed study of the positron fraction behaviour with energy 19
Positron fraction : ü No sharp structures ü Steady increase of the positron content up to 275 GeV ü Well described by an empirical model with a common source term for e + /e -
Electron/Positron fluxes: No sharp structures
Electron/Positron fluxes: For the first time a detailed study of the spectral index variation with energy : Hardening of the positron spectrum is at the origin of the positron fraction increase
Electron + Positron flux: Charge insensitive measurement à higher energy, directly comparable wi previous experiments No sharp structures A single power low describes the spectrum after 30 GeV ) -1 sr sec ] 2 [ m 2 Φ (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) 250 200 150 100 50 0 1 10 10 2 10 Energy (GeV) 3
What is AMS observing? Something different with respect conventional models of e + production by collisions of CR hadrons with the interstellar matter (ISM): Astrophysical Sources?: - Local sources as pulsars (slow fall at high energies, anysotropy..) - Interactions of CR hadrons in old SNR (but this should affect also other secondary species as anti-protons, B/C) Dark matter?: - The mass of the DM particle gives a sharp cutoff with energy - Isotropic distribution - Effects also on anti-p Cholis arxiv: astro- ph/1304.1840 AMS PAMELA Astrophysical objects? See. P. Salati talk at this conference Kopp hep- ph/1304.1184 Dark Matter?
AMS p/p status report 290,000 p events 25
AMS p/p status report The accuracy of the AMS measurement challenges current knowledge of cosmic background! Giesen et al, 2015 Fornengo, Maccione, Vittino, JCAP 2014 26
The Search for the Origin of Dark Matter To identify the Dark Matter signal we need to measure the e +, e and p signal accurately until 2024. e + /(e + + e - ) Positrons: χ + χ e + + Collision of Cosmic Rays mχ=800 GeV mχ=400 GeV Antiprotons: χ + χ p + mχ= 1 TeV Collision of Cosmic Rays e ± energy [GeV] To understand background, we need precise knowledge of: 1. The cosmic ray fluxes (p, He, C, ) 2. Propagation and Acceleration (Li, B/C, ) 27
AMS: Mul-ple Measurements of Nuclear Charge TRD" Tracker" TOF" RICH" 1 2 3-4 5-6 7-8 9 ECAL" Charge Resolu-on (Z=6) Tracker Plane 1 0.30 TRD 0.33 Upper TOF 0.16 Inner Tracker 2-8 0.12 Lower TOF 0.16 RICH 0.32 Tracker Plane 9 0.30 28
Full Control of fragmentation in the detector Carbon Fragmentation to Boron R = 10.6 GV front view Z TRK_L1 =6.1 Z TRD =6.0 Z 0 =9.9 Z 1 =5.3 Z TRK_IN =4.8 B Contamina-on < 3% Selec-on efficiency > 96% ß C ß N ß O Z TOF_LOW =5.2 Z RICH =5.1 29 29
Full control of effects from detector material : Measurement of nuclear cross sections when AMS is flying in horizontal attitude L2 - - - L8 L9 First, we use the seven inner tracker layers, L2- L8, to define beams of nuclei: He, Li, Be, B, L1 L2 - - - L8 Second, we use lel- to- right parncles to measure the nuclear interacnons in the lower part of the detector. Third, we use right- to- lel parncles to measure the nuclear interacnons in the upper part of detector. 30
AMS Measurement of He+C Cross Section 600 [mb] InEl He + C 4 550 500 450 400 AMS Measured Cross Section Ableev 1977 Jaros 1985 Tanihata 1985 Abdrahmanov 1980 Propane Chamber Aksinenko 1980 Streamer Chamber Bokova 1975 Emulsion Technique 350 10 2 10 He Rigidity [GV] 3 10 31
The isotropic proton flux Φ i for the i th rigidity bin (R i, R i +ΔR i ) is: To match the statistics of 300 million events, extensive systematic errors studies have been made. 1) σ trig. :trigger efficiency 2) σ acc. : a. the acceptance and event selec-on b. background contamina-on c. geomagne-c cutoff 3) σ unf. a. unfolding b. the rigidity resolu-on func-on 4) σ scale. : the absolute rigidity scale 32
AMS H and He fluxes Change of the spectral index is observed in H and He fluxes AMS-02 H flux measurement: 300 million events AMS-02 He flux measurement: 50 million events 300 million events 33
AMS H and He fluxes Change of the spectral index is observed in H and He fluxes AMS-02 H flux measurement: 300 million events ] GV sec sr [m 3.5 3 2.5 2 1.5 3 10 AMS-02 He flux measurement: 50 million events AMS-02 a) Flux R 1 0.5 Rigidity (R ~ ) [GV] 10 2 10 3 10 34
AMS H and He fluxes Two power laws R γ,r γ+1 with a characteristic transition rigidity R 0 and a smoothness parameter s well describe H, He measured spectra: =C R 45GV " R 1+ R 0 /s # s Δγ = 0 35
Model Independent Spectral Indices Comparison γ = d log (Φ)/ d log (R) Spectral Index He p Rigidity (R) [GV] 36
AMS p/he flux ratio 8 7.5 7 Φ p /Φ He = C R γ 6.5 6 p/he 5.5 5 4.5 4 3.5 3 10 Rigidity (R) (R ~ ) [GV] 2 10 3 10 37
AMS p/he flux ratio 8 7.5 7 6.5 AMS-02 Single power law fit (R>45 GV) Traditional Models Φ p /Φ He = C R γ 6 p/he 5.5 5 4.5 4 3.5 3 10 Change of slope at ~45 GV Rigidity (R ~ ) [GV] 2 10 3 10 38
More nuclear fluxes are coming.. Primaries: e.g. C 1.4 M events 39
More nuclear fluxes are coming.. Secondaries: Boron-to-Carbon Ratio 0.4 0.3 0.2 0.1 0.05 0.04 0.03 AMS-02 PAMELA (2014) TRACER (2006) CREAM-I (2004) ATIC-02 (2003) AMS-01 (1998) Buckley et al. (1991) CRN-Spacelab2 (1985) Webber et al. (1981) HEAO3-C2 (1980) Simon et al. (1974-1976) Dwyer & Meyer (1973-1975) Orth et al. (1972) B/C 7 M Carbon events 2 M Boron events 0.02 1 10 10 2 10 Kinetic Energy (GeV/n) 3 Li 1.5 M events AMS Orth et al (1978) Juliusson et al (1974) 40
Conclusions o In AMS is providing simultanenous measurements of different cosmic ray species with O(% ) accuracy in an extended energy range o new phenomena are being highligted by these measurements whose nature will be futher clarified as more data will be collected by the experiment. 41
Conclusions AMS will match the lifetime of the Space Station ü Continue the study of Dark Matter ü Search for the Existence of Antimatter ü Search for New Phenomena, ü Time dependent effects of low energy CR 42
THANKS FOR YOUR ATTENTION! Спасибо за внимание! 43
Measuring the interacnons of nuclei within AMS requires horizontal parncles, which are detected when the ISS flies with AMS horizontal AMS horizontal: 2 days in 4 years during dockings & undockings 44
20 layers: fleece radiator and proportional tubes Transition Radiation Detector p e ± One of 20 layers radiator p e ± Normalized Probabilities TRD estimator = -ln(p e /(P e +P p )) TRD likelihood = -Log 10 (P e ) TRD classifier = -Log 10 (P e )-2
One of 20 layers 20 layers: fleece radiator and proportional tubes p Transition Radiation Detector radiator e ± Proton rejection at 90% e + efficiency Typically, 1 in 1,000 protons may be misidentified as a positron ISS Data p e ± Rigidity (GV) Normalized Probabilities TRD estimator = -ln(p e /(P e +P p )) TRD likelihood = -Log 10 (P e ) TRD classifier = -Log 10 (P e )-2
Time of Flight System Measures Velocity and Charge of particles Z = 6 σ = 48ps Events Velocity [Rigidity>20GV] 47
2 1 Tracker 9 planes, 200,000 channels The coordinate resolution is 10 µm. 3 4 5 6 Laser rays 7 8 9 Inner tracker alignment stability monitored with IR Lasers. The Outer Tracker is continuously aligned with cosmic rays in a 2 minute window 48 48
Ring Imaging CHerenkov (RICH) Par-cle Measurement of Nuclear Charge (Z 2 ) and its Velocity to 1/1000 Aerogel NaF Θ V 10,880 photosensors Intensity Z 2 Aerogel Fe NaF Fe p = 633 GeV/c p = 203 GeV/c 49 49
Electromagnetic Calorimeter provides a precision, 17 X 0, TeV, 3-dimensional measurement of the directions and energies of electrons and positrons Lead foil (1mm) p ± e ± 50,000 fibers, φ = 1 mm distributed uniformly Inside 600 kg of lead Fibers (φ1mm) 2% energy resolution at high energies 17X 0
Electromagnetic Calorimeter provides a precision, 17 X 0, TeV, 3-dimensional measurement of the directions and energies of electrons and positrons Lead foil (1mm) p ± e ± 50,000 fibers, φ = 1 mm distributed uniformly Inside 600 kg of lead Fibers (φ1mm) Proton rejection at 90% e + efficiency ISS data: 83 100 GeV 17X 0 Typically, 1 in 10,000 protons may be misidentified as a positron Momentum (GeV/c)
Positron fraction behaviour with energy ü No sharp structures ü Steadily increasing at energies above 8 GeV ü Maximum at 275 GeV?
e + and e - fluxes before AMS 53
e + and e - fluxes after AMS AMS: 0.6 10 6 e + AMS: 9.2 10 6 e - 54
e + + e - flux measurements before AMS ) -1 sr sec ] 2 [ m 2 Φ (GeV 3 E 400 AMS-02 (2011-2013) ATIC01&02 (2001 & 2003) 350 300 250 200 150 100 50 BETS04 (2004) BETS9798 (1997 & 1998) CAPRICE94 (1994) Fermi-LAT (2009) HEAT94 (1994) HEAT9495 (1994 & 1995) HEAT95 (1994 & 1995) H.E.S.S. (2004-2007) H.E.S.S. (LE) (2004 & 2005) 0 2 3 1 10 10 10 55 Energy (GeV)
) -1 sr sec ] 2 [ m 2 Φ (GeV 3 E e + + e - flux measurements after AMS 400 AMS-02 (2011-2013) ATIC01&02 (2001 & 2003) 350 300 250 200 150 100 50 Energy Range: 0.5 GeV to 1 TeV Event Sample: ~ 10.6 million e ± events BETS04 (2004) BETS9798 (1997 & 1998) CAPRICE94 (1994) Fermi-LAT (2009) HEAT94 (1994) HEAT9495 (1994 & 1995) HEAT95 (1994 & 1995) H.E.S.S. (2004-2007) H.E.S.S. (LE) (2004 & 2005) 0 2 3 1 10 10 10 56 Energy (GeV)
Detailed study of e +,e - spectral index behaviour spectral index = d log (Φ)/ d log (E) 1. The electron flux and the positron flux are different in their magnitude and energy dependence. 2. Both spectra cannot be described by single power laws. 3. The spectral indices of electrons and positrons are different. 4. Both change their behavior at ~30GeV. 5. The rise in the positron frac-on from 20 GeV is due to an excess of positrons, not the loss of electrons (the positron flux is harder). 57
Spectral Indices of electrons, positrons, and (electrons + positrons) -2.2-2.4-2.6-2.8-3 -3.2-3.4-3.6 Φ(e + +e ) = C E γ 10 10 2 γ= 3.170 ± 0.008 (stat + syst.) ± 0.008 (energy scale) E > 30 GeV Energy (GeV) 58