First AMS Results. Institut für Experimentelle Kernphysik.

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1 First AMS Results Karen Andeen, Wim de Boer, Iris Gebauer, Melanie Heil, Stefan Kunz, Nikolay Nikonov, Valerio Vagellii, Markus Weber, Stefan Zeissler. Previous: Florian Hauler, Andreas Sabellek, Mike Schmanau + many diploma students Institut für Experimentelle Kernphysik KIT University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

2 Nobel Prizes, (1) Pulsar, (2) Microwave, (3) Microwave (4) Binary Pulsars, (5) Solar neutrino X Ray sources The purpose of the AMS experiment is to perform accurate, high statistics, long duration measurements in space of energetic (0.1 GV - TV) charged CR including particle identification energetic gamma rays. 2

3 l Experiment auf der ISS Forscher finden Hinweise auf Dunkle Materie Ein Wissenschaftlerteam am Forschungszentrum CERN in Genf hat erstmals Hinweise auf die Existenz der Dunklen Materie gefunden. "Das wäre so, als würde ein neuer Kontinent entdeckt", erklärte die CERN-Forscherin Pauline Gagnon gegenüber Reuters die Bedeutung der Entdeckung. "Es würde das Tor in eine neue Welt öffnen." Unfortunately, there are other explanations. and One swallow does not make a summer 3

4 PAMELA Positron excess Pamela, arxiv: v1 4

5 What is known about Dark Matter? 95% of the energy of the Universe is non-baryonic 23% in the form of Cold Dark Matter From CMB + SN1a + surveys Dark Matter enhanced in Galaxies, but DM widely distributed in halo-> DM must consist of weakly interacting and massive particles -> WIMP s Annihilation with <σv>= cm 3 /s, if thermal relic If it is not dark It does not matter DM halo profile of galaxy cluster from weak lensing 5

6 Jungmann,Kamionkowski, Griest, PR 1995 Comoving number density THERMAL HISTORY OF WIMPS Thermal equilibrium abundance Actual abundance T>>M: f+f->m+m; M+M->f+f T<M: M+M->f+f T=M/22: M decoupled, stable density (whe n annihilation rate expansion rate, i.e. =< v>n (x fr ) H(x fr )!) WMAP -> h 2 = > < v>= cm 3 /s DM increases in Galaxies: 1 WIMP/coffee cup 10 5 <ρ>. DMA ( ρ 2 ) restarts. T=M/22 Annihilation in lighter particles and antiparticles, like positrons and gammas! x=m/t Only assumption: WIMP = thermal relict, d.h. produced in hot early universe 6

7 Indirect Dark Matter Searches Annihilation products from dark matter annihilation: Gamma rays (EGRET, FERMI, AMS-02) Positrons (PAMELA, AMS-02) Antiprotons (PAMELA, AMS-02) e+ + e- (ATIC, FERMI, HESS, PAMELA, AMS-02) Neutrinos (Icecube, no results yet) e-, p drown in cosmic rays? 7

8 International commitments to AMS USA A&M FLORIDA UNIV. JOHNS HOPKINS UNIV. MIT - CAMBRIDGE NASA GODDARD SPACE FLIGHT CENTER NASA JOHNSON SPACE CENTER UNIV. OF MARYLAND-DEPRT OF PHYSICS UNIV. OF MARYLAND-E.W.S. S.CENTER YALE UNIV. - NEW HAVEN MEXICO UNAM NETHERLANDS ESA-ESTEC NIKHEF NLR FRANCE GAM MONTPELLIER LAPP ANNECY LPSC GRENOBLE SPAIN CIEMAT - MADRID I.A.C. CANARIAS. PORTUGAL LAB. OF INSTRUM. LISBON DENMARK UNIV. OF AARHUS FINLAND HELSINKI UNIV. UNIV. OF TURKU GERMANY RWTH-III MAX-PLANK INST. KIT, KARLSRUHE ROMANIA ISS UNIV. OF BUCHAREST SWITZERLAND ETH-ZURICH UNIV. OF GENEVA ITALY ASI CARSO TRIESTE IROE FLORENCE INFN & UNIV. OF BOLOGNA INFN & UNIV. OF MILANO INFN & UNIV. OF PERUGIA INFN & UNIV. OF PISA INFN & UNIV. OF ROMA INFN & UNIV. OF SIENA RUSSIA I.K.I. ITEP KURCHATOV INST. MOSCOW STATE UNIV. CHINA BISEE (Beijing) IEE (Beijing) IHEP (Beijing) SJTU (Shanghai) SEU (Nanjing) SYSU (Guangzhou) SDU (Jinan) KOREA EWHA KYUNGPOOK NAT.UNIV. TAIWAN ACAD. SINICA (Taiwan) CSIST (Taiwan) NCU (Chung Li) NCKU (Tainan) NCTU (Hsinchu) NSPO (Hsinchu) 8

9 Alpha Magnetic Spectrometer AMS-02 9

10 Tracker Superconducting Magnet 2500 L SF Helium TRD Identify e+, e- Particles are defined by their mass (m), charge (Q) and energy (E = P) TOF m, Q, E Matter Antimatter Silicon Tracker m, Q, E Magnet ± Q ECAL E of e+, e- RICH m, Q, E 10 10

11 3x3x3m, 7 t G.F cm 2 sr Exposure: 17 yrs dp/p 2 ~ TV, h/e = 10-6 (ECAL +TRD); Δx=10µm; Δt=100ps 11

12 ACC MAGNET Alpha Magnetic Spectrometer AMS-02 VACUUM CASE TRACKER MATTER PLANE 1NS RICH ECAL LTOF ANTIMATTER TRACKER PLANE 1N TRD UTOF TRACKER PLANE 6 Weight 7500 kg Volume 64 cubic meters Power 2500 watts Data downlink 2 Mbps (average) Magnetic field intensity 0,125 Tesla or 1250 Gauss (4000 times stronger than the Earth magnetic field) Magnetic material Neodymium alloy (Nd 2 Fe 14 B), weighting 1200 kg Subsystems 15 among particle detectors and supporting subsystems Launch 16th May 2011, 08:56 am EDT Mission duration through the lifetime of the ISS, until 2028 (it will not return back to Earth) Construction Cost $1.5 billion (estimated) 12

13 TRD electronics Experts 13

14 Lifting off the loader to place the AMS/PSS on the flatbed truck Left side. Wim de Boer 14 14

15 AMS arriving at Cape Canaveral 15

16 BNN report 16

17 Launch, at 8:56 am (European time) 17

18 Launch, at 8:56 am (European time) 18

19 Launch, at 8:56 am (European time) 19

20 Pictures from NASA aircraft 20

21 POCC at CERN in control of AMS since 19 June

22 AMS POCC in continuous communication with MFSC and ISS Mission Control Center, JSC 22

23 PARTICLE IDENTIFICATION = THE NAME OF THE GAME 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 (->MOST important background) 23

24 Contraints for a Space Experiment Thermal Environment (day/night: T~100 o C, every 90 min) Vibration (6.8 g RMS) and G-Forces (17g) Limitation : Weight ( lb) and Power (2000 W) Vacuum: < Torr Reliable for more 17 years Redundancy Radiation: Ionizing Flux ~1000 cm -2 s -1 Orbital Debris and Micrometeorites Must operate without services and human Intervention 24

25 Calorimetry in space due to limitations in weight, space experiments have an ECAL section, normally with limited thickness Standard measurement for thickness is the radiation length (X 0 ) which is related to the development of the energy deposition a detector with high X 0 has a good energy and angular resolution and it is capable of measuring particles in the energy range 10GeV-1TeV with good accuracy (<5%) AGILE : 1.5X 0 GLAST 10X 0 AMS-02 : 16.1 X 0 AMS: 3D sampling calorimeter: measure energy (few % resolution) and angle (1-0.5 angular resolution) 10-3 p rejection at 95% e efficiency via shower profile 1 GeV - 1 TeV 25

26 CHARGE MEASUREMENTS Z determination by Tracker and Rich ToF, Tracker, RICH performance verified at heavy ion test beam (CERN,GSI) Fe Ca P Ne B 26

27 Nuclei separation Charge measurement: TOF, Tracker and RICH He Li He Be Test Results from Tracker detector C O C N Si Verified by heavy ion beam tests at CERN & GSI. TOF 27

28 POSITRON EVENT Bending plane Transition Detector Radiation TRD Identifies e+/e- (Xrays) Time Of Flight TOF Trigger / Charge Q / Flight direction Magnet + Silicon Tracker TRK Measure momentum / sign(q) / Charge Q Electromagnetic Calorimeter ECAL Measure energy / Identifies e+/e- (shower shape) Most particle properties are measured redundantly 320 GeV positron 28

29 POSITRON EVENT Bending plane Transition Detector Radiation TRD Identifies e+/e- (Xrays) Time Of Flight TOF Trigger / Charge Q / Flight direction Magnet + Silicon Tracker TRK Measure momentum / sign(q) / Charge Q Electromagnetic Calorimeter ECAL Measure energy / Identifies e+/e- (shower shape) Most particle properties are measured redundantly 320 GeV positron 29

30 POSITRON EVENT Bending plane Transition Detector Radiation TRD Identifies e+/e- (Xrays) Time Of Flight TOF Trigger / Charge Q / Flight direction Magnet + Silicon Tracker TRK Measure momentum / sign(q) / Charge Q Electromagnetic Calorimeter ECAL Measure energy / Identifies e+/e- (shower shape) Most particle properties are measured redundantly 320 GeV positron 30

31 POSITRON EVENT Bending plane Transition Detector Radiation TRD Identifies e+/e- (Xrays) Time Of Flight TOF Trigger / Charge Q / Flight direction Magnet + Silicon Tracker TRK Measure momentum / sign(q) / Charge Q Electromagnetic Calorimeter ECAL Measure energy / Identifies e+/e- (shower shape) Most particle properties are measured redundantly 320 GeV positron 31

32 TRD TRANSITION RADIATION DETECTOR Transition Radiation Ionization 20 layer of radiator (fleece) and straw tubes for Xrays (~KeV) detection TRD proton rejection ( analysis selection cut ) 32

33 ECAL ELECTROMAGNETIC CALORIMETER Sampling calorimeter Lead (58%), scintillating fibers (33%), optic glue (9%) 658x658x167 mm, 18 Layers (17 X0, 0.6 λnuc ) 1296 readout cells Accurate 3D sampling of shower development Maximize hadron rejection Hadr shower EM shower ECAL shower topology MVA ECAL only ~ % eff 33

34 SILICON TRACKER Silicon layer Particle trajectory sampled 9 times 2264 double-sided Si micro strip sensors 6.75m 2 active area Single point resolution 10 μm (bend plane) 30 μm (not-bend plane) Sensitive to Charge Confusion background. Electron MC Maximum Detectable Rigidity ~ 2 TV Measured as positrons Analysis of the noise in the tracker Measured as electrons Discrimination between good sign reconstruction and wrong sign recontruction 34

35 FIRST DATA FROM AMS Over the first eighteen months of operations in space, AMS has collected over 25 billion events. 6.8 million are electrons or positrons. 35

36 All of the analysis of AMS data is being performed by two independent groups Group A: RWTH-Aachen, Karlsruhe; Bologna, Milan, Perugia, Pisa, Rome; MET-Ankara; Lisbon; Group α: MIT, Yale, Hawaii; LAPP-Annecy, Grenoble; Academia Sinica, NCU; IHEP-Beijing; Geneva; CIEMAT-Madrid; 36

37 Effect of TRD and ECAL on background reduction 37

38 Events Example of Positron Selection: The TRD Estimator shows clear separation between protons and positrons with a small charge confusion background positrons protons TRD Estimator ( GeV) 38

39 TEMPLATE ANALYSIS (V. VAGELLI) Selected data Fit as sum of Positrons Protons (bkg) CC electrons (bkg) DATA DRIVEN ANALYSIS Get background and signal contributions from DATA by fitting shapes (templates) of background and data to E/P distribution 39

40 TEMPLATE ANALYSIS RESULTS 40

41 SYSTEMATICS The result depends on the cuts applied ( template shapes, fit procedure, ) Sistematics evaluation: Perform the same analysis varying cut efficiency Look at the spread of the distribution σ(syst) = sqrt( σ 2 (tot) σ 2 (stat) ) 41

42 TEMPLATE ANALYSIS RESULTS KIT E/P template analysis AMS-02 official analysis Signal purity and background contributions known in each energy bin 42

43 Comparison with previous results 43

44 Positron fraction AMS-02 (6.8 million e +, e events) e ± energy [GeV] 44

45 Positron fraction No structure in the spectrum AMS-02 e ± energy [GeV] 45

46 AMS will be on ISS for 20 years. The data to ~1 TeV will be presented when there are sufficient events. AMS-02 data on ISS 8% of total Data to

47 ON THE ORIGIN OF EXCESS POSITRONS If the excess has a particle physics origin, there should be no anisotropy. 47

48 Anisotropy 48

49 Limits on the amplitude of a dipole anisotropy in any axis in galactic coordinates on the positron to electron ratio δ at the 95% confidence level 49

50 An Example: Comparing AMS data with a minimal model. In this model the e + and e - fluxes, F e+ and F e-, are parameterized as the sum of individual diffuse power law spectra and the contribution of a single common source of e ± : F e + = C e + E e+ + C s E s e -E/E s Eq(1) F e - = C e - E e- + C s E s e -E/E s (E in GeV) Eq(2) Coefficients C e+ and C e- correspond to relative weights of diffuse spectra for positrons and electrons. C s is the weight of the source spectrum. e+, e- and s are the corresponding spectral indexes. E s is a characteristic cutoff energy for the source spectrum. With this parametrization the positron fraction depends on 5 parameters. 50

51 A fit to the data in the energy range 1 to 350 GeV yields a 2 /d.f. = 28.5/57 and: e- e+ = 0.63 ± 0.03, i.e., the diffuse positron spectrum is less energetic than the diffuse electron spectrum; e- S = 0.66±0.05, i.e., the source spectrum is more energetic than the diffuse electron spectrum; C e+ /C e- = ± 0.001, i.e., the weight of the diffuse positron flux amounts to 10% of that of the diffuse electron flux; C S /C e- = ± , i.e., the weight of the common source constitutes only 1% of that of the diffuse electron flux; 1/E s = ± GeV 1, corresponding to a cutoff energy of GeV

52 Positron fraction Simple Model FIt Data Fit to Data with Model 2 /d.f. = 28.5/57 e ± energy [GeV] The agreement between the data and the model shows that the positron fraction spectrum is consistent with e ± fluxes each of which is the sum of its diffuse spectrum and a single common power law source. 52

53 Positron fraction Expectation for DM signal M. Turner and F. Wilczek, Phys. Rev. D42 (1990) 1001; J. Ellis, 26th ICRC Salt Lake City (1999) astro-ph/ ; H. Cheng, J. Feng and K. Matchev, Phys. Rev. Lett. 89 (2002) ; S. Profumo and P. Ullio, J. Cosmology Astroparticle Phys. JCAP07 (2004) 006; D. Hooper and J. Silk, Phys. Rev. D 71 (2005) ; E. Ponton and L. Randall, JHEP 0904 (2009) 080; G. Kane, R. Lu and S. Watson, Phys. Lett. B681 (2009) 151; D. Hooper, P. Blasi and P. D. Serpico, JCAP (2009) ; B2 Y Z. Fan et al., Int. J. Mod. Phys. D19 (2010) 2011; M. Pato, M. Lattanzi and G. Bertone, JCAP 1012 (2010) e + +. m =800 GeV e + /(e + + e - ) 0.1 m =400 GeV Dark Matter model based on I. Cholis et al., arxiv: e ± energy [GeV] 53

54 Pulsars can do it too? (Gebauer, Kunz) 54

55 CONCLUSIONS AMS-02 detector has collected ~7 millions of cosmic electrons and positrons in 18 months of data taking, in the energy range GeV to TeV. The matter/antimatter separation capabilities allow AMS-02 to produce high precision data on positron fraction measurement. The redundancy in particle identification tools allows to perform a data based background counting method, reducing systematics in the final measurement. The positron fraction spectrum increases steadily up to ~250 GeV and shows no fine structure. 55