Towards Direction Dependent Fluxes With AMS-02

Transcription

1 Towards Direction Dependent Fluxes With AMS-02 Stefan Zeissler, Karen Andeen, Wim de Boer, Iris Gebauer, Carmen Merx, Nikolay Nikonov, Valerio Vagelli DPG Conference 2015, Wuppertal Institut für Experimentelle Kernphysik KIT University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

2 Minimal Model e-: primary particles accelerated by SRN simple power law e+: secondary produced by interaction of nucleons with the ISM simple power law Secondary e+ contribution Such models do not describe the rise in the positron fraction. Additional production of primary e+/- is needed in a minimal model this can be parametrized as a power law with a cutoff energy EC primary e- from SNR secondary e+ from ISM interactions primary e+/- common source See V. Vagelli T

3 Minimal Model primary e- from SNR secondary e+ from ISM interactions primary e+/- common source Minimal model combined fit to e++e- and positron fraction data Positron fraction Primary e- from SNR Primary e+/- from common source (DM activity? Astrop. source?) Secondary e+ P so rim ur ary ce e +/ fro m co m m on (e++e-) Secondary e+ contribution A common source for e+/- dominates over the diffuse e+ starting at ~ 15 GeV The common source exhibits an expected cutoff at ~ 1 TeV 3 See V. Vagelli T 73.5

4 Candidates For Additional Sources Astrophysical origin Particle physics origin Pulsars: Fast rotating neutron stars with strong magnetic fields e+/- Dark Matter: Annihilating dark matter might produce standard model particles e+/- e+/- X X e+/- e+/e+/- e+/e+/- Both models can be tuned to explain the data! Pulsars are point sources anisotropy expected Dark matter is everywhere low anisotropy expected 4 Details: S. Kunz T 92.2

5 Search For Anisotropies - Exposure AMS-02 does not scan the galactic sky uniformly. uat o Ear th North pole r AMS-02 galactic pointing direction 2.5 years s eq ISS global position 1 day South pole On top of that we have: High rate of low energy particles at poles Trigger busy Geomagnetic field 5

6 Search For Anisotropies Electrons with Emin = 30 GeV in Galactic Coordinates Low exposure at earths equator High exposure at pole regions 4.00 Electron counts 1.3e+03 Data maps are dominated by detector- and geomagnetic field effects for which we need to correct A map of the isotropic sky as seen by the detector is needed! 6

7 Reference Map Standard way: Proton map to re ffe c ts ca nc e lo ut! Protons are expected to be isotropic on a very high level Protons are very abundant (~90% of all CR) Easy to select D et ec Few particles at the pole fluctuations 0.80 Side effects: Electrons Protons 1.20 Details: C. Merx T 73.4 Particle dependent acceptances and selection efficiencies Different sign of charge Different geomagnetic field effects 7

8 Map Of the Isotropic Sky 1) Idea: Pair up live time and acceptance in galactic sky. Galactic Sky (isotropic) 1) Get particle incoming direction in detector coordinates for every position in galactic sky 2) 2) Get acceptance for incoming direction Theta 3) Weight acceptance with detector live time Repeat 1-3 for every Pixel and every second of measuring time (detector movement). Phi 3) T exp Fill Map 8

9 Simulated Isotropic Sky Fri, 13 Jul :33:24 GMT Position Of ISS High Low Expected Particle Rate 9

10 Simulated Isotropic Sky Fri, 13 Jul :53:24 GMT Position Of ISS High Low Expected Particle Rate 10

11 Simulated Isotropic Sky Fri, 13 Jul :13:24 GMT Position Of ISS High Low Expected Particle Rate 11

12 Simulated Isotropic Sky Fri, 13 Jul :33:24 GMT Position Of ISS High Low Expected Particle Rate 12

13 Simulated Isotropic Sky Fri, 13 Jul :53:24 GMT Position Of ISS High Low Expected Particle Rate 13

14 Simulated Isotropic Sky Fri, 13 Jul :13:24 GMT Position Of ISS High Low Expected Particle Rate 14

15 Simulated Isotropic Sky Fri, 13 Jul :33:24 GMT Position Of ISS High Low Expected Particle Rate 15

16 Simulated Isotropic Sky Fri, 13 Jul :53:24 GMT Position Of ISS High Low Expected Particle Rate 16

17 Simulated Isotropic Sky Fri, 13 Jul :13:24 GMT Position Of ISS High Low Expected Particle Rate 17

18 Simulated Isotropic Sky Fri, 13 Jul :33:24 GMT Position Of ISS High Low Expected Particle Rate 18

19 Simulated Isotropic Sky Fri, 13 Jul :53:24 GMT Position Of ISS High Low Expected Particle Rate 19

20 Simulated Isotropic Sky Fri, 13 Jul :13:24 GMT Position Of ISS High Low Expected Particle Rate 20

21 Simulated Isotropic Sky Fri, 13 Jul :33:24 GMT Position Of ISS High Low Expected Particle Rate 21

22 Simulated Isotropic Sky Fri, 13 Jul :53:24 GMT Position Of ISS High Low Expected Particle Rate 22

23 Applications of IsoSky Map We get a simulated map of the isotropic sky as AMS-02 would see it Sum over 2.5 years of data taking Emin = 30 GeV Use as a reference map for Anisotropy Studies (see C. Merx T 73.4) 23 Get time and position dependent exposure information Time and direction dependent fluxes

24 Direction Dependent Flux N (E, φ, θ) Φ (E, φ, θ)= Acc (E)ε Sel T exp (E, φ, θ)δ E Assumed to be constant in earth bound coordinates 24 IsoSky Map

25 Direction Dependent Flux Cut based analysis N (E, φ, θ) Φ (E, φ, θ)= Acc (E)ε Sel T exp (E, φ, θ)δ E Idea: Keep the single particle informations (incoming direction, time) by doing a cut based analysis. BDT> GeV Select leptons with high purity using a cut on ECAL and TRD. Control background an selection efficiencies with TRD template fits Keep background small << 1% 25

26 Integrated Flux Result of the integrated cut based all electron analysis compared to the official AMS-02 result. Integrated lepton flux Under investigation Why direction dependent flux? Search for sources Anisotropies 26 Why time dependent flux? Solar Physics

27 Conclusion And Outlook The isotropic sky as seen by AMS-02 using MC simulations combined with real time trigger informations has been presented. We get particle counts, keeping single particle informations, using a cut based analysis controlled by template fits. These two methods combined can provide a measurement of the flux in direction and time bins. 27

28 Backup 28

29 Known Pulsars Galactic center Galactic disc 29

30 Electromagnetic Calorimeter (ECAL) Calorimeter of lead (58%), scintillating fibers (33%) and optical glue (9%) 16.7 cm 17 X0 m = 496 kg 64.8 cm 64.8 cm Shower 3D reconstruction e/p rejection Multivariate analysis (Boosted Decision Tree - BDT) 30

31 Transition Radiation Detector (TRD) High energy particle crossing interface of two media with different permittivity ² and has the probability to emit X-rays (~KeV) with 2 Intensity =E / mc Gamma factor e/p-rejection Electrons 20 Layers Protons Energy/ADC 31

32 Cut Based Analysis Idea: Select leptons with high purity using ECAL and TRD Control selection efficiencies with TRD template fits 1.) Appy efficient cut on EcalBDT and evaluate signal over background ratio with TRD template fits BDT> GeV ~95% eff S/B ~ 10 32

33 Cut Based Analysis Idea: Select leptons with high purity using ECAL and TRD Control selection efficiencies with TRD template fits 2.) Apply TRD cut and get S/B from Templates Fix TRD cut in a way that S/N>>100 (less than 1% Background) BDT> GeV

34 Lepton Counts Here I want to plot the lepton counts compared to Valerios to show how much we loose due to the cut based approach and point out that we loose particles BUT keep the particles informations (time, incoming direction). Why direction dependent flux? Search for sources Anisotropies 34 Why time dependent flux? Solar Physics