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High energy cosmic rays

High energy cosmic rays. Roberta Sparvoli Rome “ Tor Vergata ” University and INFN, ITALY. Nijmegen 2012. Lecture # 2 : outline. SATELLITE and ISS EXPERIMENTS FUTURE activities. Satellite flights. PAMELA Payload for Matter/antimatter Exploration and Light-nuclei Astrophysics.

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High energy cosmic rays

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  1. High energycosmic rays Roberta Sparvoli Rome “Tor Vergata”University and INFN, ITALY Nijmegen 2012

  2. Lecture # 2 :outline SATELLITE and ISS EXPERIMENTS FUTURE activities

  3. Satellite flights

  4. PAMELAPayload for Matter/antimatter Exploration and Light-nuclei Astrophysics • Direct detection of CRs in space • Main focus on antiparticles(antiprotons and positrons) • PAMELA on board of Russian satellite Resurs DK1 • Orbital parameters: • inclination ~70o ( low energy) • altitude ~ 360-600 km (elliptical) • active life >6 years ( high statistics)  Launched on 15th June 2006  PAMELA in continuous data-taking mode since then! Launch from Baykonur

  5. + - PAMELA detectors • Time-Of-Flight • plastic scintillators + PMT: • Trigger • Albedo rejection; • Mass identification up to 1 GeV; • - Charge identification from dE/dX. • Electromagnetic calorimeter • W/Si sampling (16.3 X0, 0.6 λI) • Discrimination e+ / p, anti-p / e- • (shower topology) • Direct E measurement for e- • Neutron detector • 36 He3 counters : • High-energy e/h discrimination Main requirements: - high-sensitivity antiparticle identification - precise momentum measurement • Spectrometer • microstrip silicon tracking system+ permanent magnet • It provides: • - Magnetic rigidity R = pc/Ze • Charge sign • Charge value from dE/dx GF: 21.5 cm2 sr Mass: 470 kg Size: 130x70x70 cm3 Power Budget: 360W

  6. Flight data: 0.171 GV positron Flight data: 0.169 GV electron

  7. Antiparticles SECONDARY ORIGIN, COMING FROM INTERACTION OF PRIMARy CR WITH THE INTERSTELLAR MEDIUM

  8. Antiproton/proton identification: • Negative/positive curvature in the spectrometer  p-bar/p separation • Rejection of EM-like interaction patterns in the calorimeter  p-bar/e- (and p/e+ ) separation Main issue: • Proton “spillover” background: wrong assignment of charge-sign @ high energy due to finite spectrometer resolution • Strong tracking requirements • Spatial resolution < 4mm • R < MDR/10 • Residual background subtraction • Evaluated with simulation (tuned with in-flight data) • ~30% above 100GeV Antiprotons

  9. (Donato et al. 2001) • Diffusion model with convection and reacceleration • Uncertainties on propagation param . and c.s. • Solar modulation: spherical model ( f=500MV ) Antiproton flux Largest energy range covered hiterto Overall agreement with pure secondary calculation Experimental uncertainty (statsys) smaller than spread in theoretical curves  constraints on propagation parameters Adriani et al. - PRL 105 (2010) 121101 • (Ptuskin et al. 2006) GALPROP code • Plain diffusion model • Solar modulation: spherical model ( f=550MV )

  10. Antiproton-to-proton ratio Adriani et al. - PRL 105 (2010) 121101 Overall agreement with pure secondary calculation Very stringent constraints to exotic production mechanisms!

  11. New antiproton/proton ratio Preliminary Using all data till 2010 and multivariate classification algorithms 20-50% increase in respect to published analysis

  12. New positron fraction data Preliminary Using all data till 2010 and multivariate classification algorithms about factor 2-3 increase in respect to published analysis

  13. S1 CARD CAT S2 TOF SPE CAS S3 CALO S4 ND Positron/electron identification: • Positive/negative curvature in the spectrometer  e-/e+ separation • EM-like interaction pattern in the calorimeter  e+/p (and e-/p-bar) separation Main issue: • Interacting proton background: • fluctuations in hadronic shower development:p0 ggmimic pure e.m. showers • p/e+: ~103 @1GV ~104 @100GV • Robust e+ identification • Shower topology + energy-rigidity match • Residual background evaluation • Done with flight data • No dependency on simulation Positrons

  14. 32.3 GV positron

  15. Adriani et al. , Nature 458 (2009) 607 Adriani et al., AP 34 (2010) 1 (new results) Positron fraction Low energy  charge-dependent solar modulation High energy  (quite robust) evidence of positron excess above 10 GeV • (Moskalenko & Strong 1998) • GALPROP code • Plain diffusion model • Interstellar spectra

  16. Adriani et al. , Nature 458 (2009) 607 Adriani et al., AP 34 (2010) 1 (new results) Positron fraction Low energy  charge-dependent solar modulation (see tomorrow) High energy  (quite robust) evidence of positron excess above 10 GeV • (Moskalenko & Strong 1998) • GALPROP code • Plain diffusion model • Interstellar spectra

  17. New positron fraction data Preliminary Using all data till 2010 and multivariate classification algorithms about factor 2-3 increase in respect to published analysis

  18. Positron Flux

  19. A challenging puzzle for CR physicists Antiprotons  Consistent with pure secondary production Positrons  Evidence for an excess

  20. (Cholis et al. 2009) Contribution from DM annihilation. Positron-excess interpretations Dark matter boost factor required lepton vs hadron yield must be consistent with p-bar observation Astrophysical processes known processes large uncertainties on environmental parameters (Blasi 2009) e+ (and e-) produced as secondaries in the CR acceleration sites (e.g. SNR) (Hooper, Blasi and Serpico, 2009) contribution from diffuse mature & nearby young pulsars.

  21. Interpretation: DM M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3 Which DM spectra can fit the data? DM with and dominant annihilation channel (possible candidate: Wino)‏ positrons antiprotons No! Yes!

  22. Interpretation: DM M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3 Which DM spectra can fit the data? DM with and dominant annihilation channel (no “natural” SUSY candidate)‏ But B≈104 positrons antiprotons Yes! Yes!

  23. Interpretation: DM M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3 DM with and dominant annihilation channel positrons antiprotons Yes! Yes! Yes!

  24. Interpretation: DM I. Cholis et al.Phys. Rev. D 80 (2009) 123518; arXiv:0811.3641v1

  25. Astrophysical Explanation: SNR Positrons (and electrons) produced as secondaries in the sources (e.g. SNR) where CRs are accelerated. But also other secondaries are produced: significant increase expected in the p/p and B/C ratios. P.Blasi et al., PRL 103 (2009) 051104 arXiv:0903.2794

  26. Astrophysical Explanation: Pulsars Are there “standard” astrophysical explanations of the high energy positron data? Young, nearby pulsars Geminga pulsar Not a new idea: Boulares, ApJ 342 (1989), Atoyan et al (1995)‏

  27. Mechanism: the spinning B of the pulsar strips e- that accelerated at the polar cap or at the outer gap emit γ that make production of e± that are trapped in the cloud, further accelerated and later released at τ ~ 105 years. Young (T < 105 years) and nearby (< 1kpc) If not: too much diffusion, low energy, too low flux. Geminga: 157 parsecs from Earth and 370,000 years old B0656+14: 290 parsecs from Earth and 110,000 years old. Diffuse mature pulsars Astrophysical Explanation:Pulsars

  28. Astrophysical Explanation: Pulsars H. Yüksak et al., arXiv:0810.2784v2 Contributions of e- & e+ from Geminga assuming different distance, age and energetic of the pulsar diffuse mature &nearby young pulsars Hooper, Blasi, and Serpico arXiv:0810.1527 Mirko Boezio, Innsbruck, 2012/05/29

  29. Howtoclarify the matter? Courtesyof J. Edsjo

  30. (Strong & Moskalenko 1998) GALPROP code • + • (Kane et al. 2009) • Annihilation of 180 GeV wino-like neutralino • consistent with PAMELA positron data Positronsvs antiprotons Large uncertainties on propagation parameters allows to accommodate an additional component A p-bar rise above 200GeV is not excluded Adriani et al. - PRL 105 (2010) 121101 • (Blasi & Serpico 2009) • p-bar produced as secondaries in the CR acceleration sites (e.g. SNR) • consistent with PAMELA positron data • (Donato et al. 2009) • Diffusion model with convection and reacceleration

  31. Theoretical uncertainties on “standard” positron fraction γ = 3.54 γ = 3.34 Flux=A • E- T. Delahaye et al.,Astron.Astrophys. 501 (2009) 821; arXiv: 0809.5268v3

  32. Absolute fluxes of primary GCRs Needed for: identify sources and acceleration propagation mechanisms of cosmic rays; estimate the production of secondary particles, such as positrons and antiprotons, in order to disentangle the secondary particle component from possible exotic sources; estimate the particle flux in the geomagnetic field and in Earth's atmosphere to derive the atmospheric muon and neutrino flux.

  33. Adriani et al. , Science 332 (2011) 6025 H & He absolute fluxes First high-statistics and high-precision measurement over three decades in energy Dominated by systematics (~4% below 300 GV) Low energy  minimum solar activity (f = 450÷550 GV) High-energy  a complex structure of the spectra emerges…

  34. P & He absolute fluxes@ high energy Spectral index Deviations from single power law (SPL): Spectra gradually soften in the range 30÷230GV Abrupt spectral hardening @ ~235 GV Eg: statistical analysis for protons SPL hp in the range 30÷230 GV rejected @ >95% CL SPL hpabove 80 GV rejected @ >95% CL 2.85 2.77 2.48 2.67 232 GV 243 GV ? ? Solar modulation Solar modulation Standard scenario of SN blast waves expanding in the ISM needs additional features

  35. H/He ratio vs R Instrumental p.o.v. Systematic uncertainties partly cancel out (livetime, spectrometer reconstruction, …) Theoretical p.o.v. Solar modulation negligible  information about IS spectra down to GV region Propagation effects (diffusion and fragmentation) negligible above ~100GV  information about source spectra (Putze et al. 2010)

  36. P/He ratio vs R First clear evidence of different H and He slopes above ~10GV Ratio described by a single power law (in spite of the evident structures in the individual spectra) aHe-ap = 0.078 ±0.008 c2~1.3

  37. 2H and 1H flux2H/1H Preliminary

  38. 3He and 4He flux3He/4He Preliminary

  39. 2H/4He

  40. Boron and Carbon nuclei spectra Carbon Boron

  41. Anisotropy studies (p up to 1 TeV)

  42. Electrons Needed for: Recalculathe the expected positron fraction with better accuracy Closeby sources?

  43. Results from ATIC

  44. FERMI All-Electron Spectrum Theoreticaluncertainties on “standard” positronfraction FERMI e+ + e- flux (2009) A. Abdo et al., Phys.Rev.Lett. 102 (2009) 181101 M. Ackermann et al., Phys. Rev. D 82, 092004 (2010)

  45. Electrons measured with H.E.S.S.

  46. Adriani et al. , PRL 106, 201101 (2011) Electron energy measurements spectrometer Two independent ways to determine electron energy: Spectrometer Most precise Non-negligible energy losses (bremsstrahlung) above the spectrometer  unfolding Calorimeter Gaussian resolution No energy-loss correction required Strong containment requirements  smaller statistical sample calorimeter • Electron identification: • Negative curvature in the spectrometer • EM-like interaction pattern in the calorimeter

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