Fluxes of Galactic Cosmic Rays

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2 Fluxes of Galactic Cosmic Rays sr s m - GeV Flux solar Modulation: Φ = 550 MV proton helium positron electron antiproton photon galdef 50080/60080 (γ) Status of Cosmic Ray Measurements: good agreement between cosmic ray propagation/production model and data in background fluxes (Ô,, «, other heavy nuclei) general model works! AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons AMS-0 protons AMS-0 helium kinetic Energy [GeV] ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº¾»½

3 Fluxes of Galactic Cosmic Rays sr s m - GeV Flux solar Modulation: Φ = 550 MV AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons AMS-0 protons AMS-0 helium proton helium positron electron antiproton photon kinetic Energy [GeV] galdef 50080/60080 (γ) Status of Cosmic Ray Measurements: good agreement between cosmic ray propagation/production model and data in background fluxes (Ô,, «, other heavy nuclei) general model works!, Ô, are sensitive to dark matter signals (annihilation) and fluxes/fractions show some unexplained features need precise measurement of fluxes up to high energies! ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº¾»½

4 Fluxes of Galactic Cosmic Rays sr s m - GeV Flux solar Modulation: Φ = 550 MV AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons AMS-0 protons AMS-0 helium proton helium positron electron antiproton photon kinetic Energy [GeV] galdef 50080/60080 (γ) Status of Cosmic Ray Measurements: good agreement between cosmic ray propagation/production model and data in background fluxes (Ô,, «, other heavy nuclei) general model works!, Ô, are sensitive to dark matter signals (annihilation) and fluxes/fractions show some unexplained features need precise measurement of fluxes up to high energies! µ Balloon Experiment: Investigate influence of atmosphere on flux measurements! ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº¾»½

5 Requirements for positron flux measurements total rejection is made up of the single rejections of the different subdetectors ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½ ÈÐÔ

6 Air shower in Earth s atmosphere ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

7 Please notice following analysis is preliminary! Any suggestions and comments are very welcome! ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

8 PLANETOCOSMICS Simulation of the Earth s atmosphere and magnetic field with PLANETOCOSMICS (developed by L. Desorgher, Uni. Bern laurent/planetocosmics) general properties: based on GEANT atmospheric model: NRLMSISE¼¼ magnetic field: IGRF ¾¼¼ magnetosphere: Tsyganenko ¾¼¼½ ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

9 PLANETOCOSMICS Simulation of the Earth s atmosphere and magnetic field with PLANETOCOSMICS (developed by L. Desorgher, Uni. Bern laurent/planetocosmics) general properties: based on GEANT atmospheric model: NRLMSISE¼¼ magnetic field: IGRF ¾¼¼ magnetosphere: Tsyganenko ¾¼¼½ properties of this simulation: input spectra are the fluxes of the conventional Galprop model (galdef astro-ph/0065) detection plane ¼ in km altitude particle gun ¼¼ in km height over the geographic South Pole starting positions randomly distributed in cone over detector (¼ radius m), (¼ height m) (dimensions of PEBS) only primaries that can hit the detector are started but all particles in ¼ the km shell around the earth are detected to compensate for scattered particles from cosmic rays outside of the starting cone ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

10 Properties of Earth s Atmosphere (NRLMSISE¼¼) kinetic energy/temperature of atmosphere (ideal gas) ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

11 Properties of Earth s Atmosphere (NRLMSISE¼¼) Mass [%] N He O H Ar Altitude [km] density of atmosphere composition of atmosphere ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

12 Properties of Earth s Atmosphere (NRLMSISE¼¼) Mass [%] N He O H Ar Altitude [km] density of atmosphere composition of atmosphere ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

13 Distribution of particle starting positions 90+latitude [deg] longitude [deg] 0 geographic distribution of starting positions starting position is decribed by angles and an altitude ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

14 Distribution of particle starting positions entries [#] zenith [deg] zenith angle entries [#] azimuth [deg] starting position is decribed by angles and an altitude azimuth angle ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

15 Verification of atmospheric physics model (counts for ¼ days with acceptance ¼½ m ¾ sr and without detector effiencies) sr s m - ] Flux [GeV µ +, 0 km µ -, 0 km π +, 0 km π -, 0 km Energy [GeV] ] Counts [GeV ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

16 Verification of atmospheric physics model (counts for ¼ days with acceptance ¼½ m ¾ sr and without detector effiencies) sr s m - ] Flux [GeV µ +, 0 km µ -, 0 km π +, 0 km π -, 0 km Energy [GeV] ] Counts [GeV atmosphere for a final verification µ... to be done! looks promising, but need comparison with measured - and -fluxes in ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº»½

17 Influence of altitude to particle flux (mean values from ½ - ¼¼ GeV) (mean values from ½ - ¼¼ GeV) cosmic rays starting from ¼ km altitude! Positrons have major contributions by secondaries from other primary galactic Protons don t have such an additional source. Atmosphere is electromagnetically more effective than hadronically. ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¼»½

18 Influence of altitude to particle flux (mean values from ½ - ¼¼ GeV) (mean values from ½ - ¼¼ GeV) cosmic rays starting from ¼ km altitude! Positrons have major contributions by secondaries from other primary galactic Protons don t have such an additional source. Atmosphere is electromagnetically more effective than hadronically. Maximum height for a balloon is ¼ km. µ Seems to be ok! ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¼»½ ÈÐÔ

19 Positron fluxes in ¼ km sr s m - ] Flux [GeV primary e + total e, 0 km + sec. e, 0 km Energy [GeV] ] Counts [GeV primaries scaled to input fluxes counts ¼ for days with ¼½ acceptance m sr, but without detector effiencies ¾ ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½½»½

20 Positron fluxes in ¼ km sr s m - ] Flux [GeV primary e + total e, 0 km + sec. e, 0 km Energy [GeV] ] Counts [GeV Ratio total primary + e, 0 km primary on alt. primary + e, 0 km Energy [GeV] primaries scaled to input fluxes counts ¼ for days with ¼½ acceptance m sr, but without detector effiencies ¾ just a few percentage loss of primaries to lower energies and also just a few additional percentage of secondaries from other cosmic rays ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½½»½

21 Positron fluxes in ¼ km corrections PEBS prim Æ Æ PEBS atmo sec PEBS Ætot Ô Æ Ê Ô (all quantities are energy dependent) Æ tot PEBS number of particles (GalProp, PLANETOCOSMICS): PEBS, prim, sec Æ Æ, tot Æ Æ, tot Æ Ô detection efficiency (detector simulation): PEBS ¼ ½¼ GeV, with TRD inside (lower acceptance) ½¼ GeV meaning of quantities: proton Rejection (detector simulation): ½¼ for all energies ¼ loss of particles in atmosphere (PLANETOCOSMICS): atmo energy dependent tracker misidentification (detector simulation): Ê Ô PEBS energy dependent ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¾»½

22 Positron fluxes in ¼ km corrections PEBS prim Æ Æ PEBS atmo sec PEBS Ætot Ô Æ Ê Ô (all quantities are energy dependent) Æ tot PEBS number of particles (GalProp, PLANETOCOSMICS): PEBS, prim, sec Æ Æ, tot Æ Æ, tot Æ Ô detection efficiency (detector simulation): PEBS ¼ ½¼ GeV, with TRD inside (lower acceptance) ½¼ GeV meaning of quantities: proton Rejection (detector simulation): ½¼ for all energies ¼ loss of particles in atmosphere (PLANETOCOSMICS): atmo energy dependent tracker misidentification (detector simulation): Ê Ô error estimates: PEBS energy dependent statistical errors: Æ systematic errors for atmospheric physics: % systematic errors for detector properties: % ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¾»½

23 Positron fluxes in ¼ km corrections PEBS prim Æ Æ PEBS Rejections: ToF atmo sec PEBS Ætot Ô Æ Ê Ô (all quantities are energy dependent) Æ tot PEBS Proton rejections of ToF with Ø ½¼¼ ps resolution (important for low energy range Ô-spectrum) ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¾»½

24 Positron fluxes in ¼ km corrections PEBS prim Æ Æ PEBS atmo sec PEBS Ætot Ô Æ Ê Ô (all quantities are energy dependent) Æ tot PEBS Rejections: ToF TRD Proton Rejection Factor 50% e-efficiency 70% e-efficiency 90% e-efficiency E Beam / GeV Proton rejections of ToF with Ø ½¼¼ ps resolution (important for low energy range Ô-spectrum) Proton rejections of AMS0 TRD for 8 layers radiator and straw tubes with test beam data (important for low energy range) ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¾»½

25 Positron fluxes in ¼ km corrections PEBS prim Æ Æ PEBS atmo sec PEBS Ætot Ô Æ Ê Ô (all quantities are energy dependent) Æ tot PEBS Rejections: ToF TRD Tracker Proton Rejection Factor 50% e-efficiency 70% e-efficiency 90% e-efficiency Proton rejections of ToF with Ø ½¼¼ ps resolution (important for low energy range Ô-spectrum) E Beam / GeV Proton rejections of AMS0 TRD for 8 layers radiator and straw tubes with test beam data (important for low energy range) misidentification prob. of tracker for with the resolution: Ô ¼ ± GeV ½¼ ± Ô ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¾»½

26 Positron fluxes in ¼ km corrections PEBS prim Æ Æ PEBS atmo sec PEBS Ætot Ô Æ Ê Ô (all quantities are energy dependent) Æ tot PEBS [ Æ tot Ê Ætot Ê ] Rejections: Proton rejections of ECal and Tracker presentation H. Gast not yet: consider -/-efficiencies of detector (should be a small effect) general: use energy dependent rejections (to be done... ) ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½¾»½

27 Total counts of - and -fluxes (Æ PEBS ) ] [Gev PEBS N total e, PEBS, 0 days - total e, PEBS, 0 days Energy [GeV] counts with detector efficiencies and atmospheric loss! days PEBS with acceptance ¼½ m sr ¾ ¼ ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

28 Electron and Positron fluxes with ¼ days PEBS sr s m - ] Flux [GeV + e, PEBS, 0 days - e, PEBS, 0 days AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons -7 Energy [GeV] uncertanties in atmospheric correction all corrections applied large error bars mainly from µ room for improvement! ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

29 Electron and Positron fluxes with ¼ days PEBS sr s m - ] Flux [GeV - + e, PEBS, 0 days - e, PEBS, 0 days - e + e + +e Positron Fraction PEBS, 0 days HEAT AMS0 conv. Galprop AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons - -7 Energy [GeV] Energy [GeV] uncertanties in atmospheric correction all corrections applied large error bars mainly from µ room for improvement! assumptions for and : same behaviour in atmosphere same rejection same tracker resolution smaller errors (atmo cancels in fraction) µ ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

30 Electron and Positron fluxes with ¼ days PEBS sr s m - ] Flux [GeV - + e, PEBS, 0 days - e, PEBS, 0 days - e + e + +e Positron Fraction PEBS, 0 days HEAT AMS0 conv. Galprop AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons - -7 Energy [GeV] Energy [GeV] uncertanties in atmospheric correction all corrections applied large error bars mainly from µ room for improvement! discrepancy at lower energies due to different solar modulations PEBS errors are dominated by statistics at higher energies this PEBS has ¾ statistics of HEAT ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

31 Electron and Positron fluxes with ¼ days PEBS sr s m - ] Flux [GeV - + e, PEBS, 0 days - e, PEBS, 0 days - e + e + +e Positron Fraction m / = 500 GeV, m = 00 GeV 0 tanβ= 5, µ>0, A = 0 0 DM signal boost factor: 50.0 PEBS, 0 days HEAT AMS0 Galprop + DM DM, DarkSUSY conv. Galprop AMS-0 electrons AMS-0 positrons HEAT 9/5 positrons - -7 Energy [GeV] Energy [GeV] uncertanties in atmospheric correction all corrections applied large error bars mainly from µ room for improvement! this dark matter signal is distinguishable with ¼ a days PEBS flight in ¼ km altitude! ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

32 Antiproton and Photon fluxes in ¼ km (counts for ¼ days with acceptance ¼½ m ¾ sr and without detector effiencies) sr s m - ] Flux [GeV primary p total p, 0 km sec. p, 0 km Energy [GeV] ] Counts [GeV in the same order as for positrons! Ô MC statistics for secondaries are low, but influence of atmosphere seems to be ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

33 Antiproton and Photon fluxes in ¼ km (counts for ¼ days with acceptance ¼½ m ¾ sr and without detector effiencies) sr s m - ] Flux [GeV primary p total p, 0 km sec. p, 0 km Energy [GeV] ] Counts [GeV good Ecal and time let s see... acceptance is lower than BESS s, but can maybe compensated with ToF, ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

34 Antiproton and Photon fluxes in ¼ km (counts for ¼ days with acceptance ¼½ m ¾ sr and without detector effiencies) sr s m - ] Flux [GeV primary p total p, 0 km sec. p, 0 km Energy [GeV] ] Counts [GeV sr s m - ] Flux [GeV primary γ total γ, 0 km sec. γ, 0 km Energy [GeV] ] Counts [GeV good Ecal and time let s see... acceptance is lower than BESS s, but can maybe compensated with ToF, diffuse s, averaged over all directions in the galaxy ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

35 Antiproton and Photon fluxes in ¼ km (counts for ¼ days with acceptance ¼½ m ¾ sr and without detector effiencies) sr s m - ] Flux [GeV primary p total p, 0 km sec. p, 0 km Energy [GeV] ] Counts [GeV good Ecal and time let s see... acceptance is lower than BESS s, but can maybe compensated with ToF, diffuse s, averaged over all directions in the galaxy too many secondaries, flux measurement not possible! ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

36 Total particle rates Total Particle Rate [Hz] - Minimum Energy [GeV] threshold within ½µs PEBS ¼ in km with ¼½ acceptance m sr minimum energy from ToF as trigger ¾ allows particle rates of Ç ½¼¼µ khz ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

37 Total particle rates Total Particle Rate [Hz] Are there more particles? but maybe atmosphere works as shield low energetic electrons ( Ç ½¼¼µ khz) reason for AMS LEPS (few % ¼ ) solar protons (low energies, but many) particles from the radiation belts - Minimum Energy [GeV] anomalous cosmic rays photons from point sources needs more investigation! µ PEBS trigger has to be fitted to the µ estimated count rate! threshold within ½µs PEBS ¼ in km with ¼½ acceptance m sr minimum energy from ToF as trigger ¾ allows particle rates of Ç ½¼¼µ khz ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

38 Summary & Outlook What have been done: Pole in ¼ km altitude with PEBS simulation of the positron fraction measurement on the South (ca. ½¼ ¾ statistics of HEAT) error estimation including the correction of the main uncertainties good measurement of positron fraction possible ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½

39 Summary & Outlook What have been done: Pole in ¼ km altitude with PEBS simulation of the positron fraction measurement on the South (ca. ½¼ ¾ statistics of HEAT) error estimation including the correction of the main uncertainties good measurement of positron fraction possible What should be done: use more precise properties of PEBS detector produce more Monte Carlos higher statistics investigate detectability of Ô dark matter signal better comparisons with atmospheric fluxes ÈÐÔ ÚÓÒ ÓØÒÑ ÈË ÏÓÖ ÓÔ ÅÝ ¾¼¼ ß Ó Ñ ÊÝ Ò Ø ØÑÓ ÔÖ ¾»»¾¼¼ ß Ôº½»½