1. ROBERTA SPARVOLI UNIVERSITY OF ROME “TOR VERGATA” AND INFN MORIOND 2013: VERY HIGH ENERGY PHENOMENA IN THE UNIVERSE Electron/positron ratio & antiproton/proton ratio in PAMELA and Fermi

2. Dark Matter searches Evidence for the existence of an unseen, “dark”, component in the energy density of the Universe comes from several independent observations at different length scales: Rotation curves of galaxies Lensing Large Scale StructureCMB Galaxy clusters SN Ia Bertone, Hooper & Silk, hep-ph/0404175, Bergstrom, hep-ph/0002126, Jungman et al, hep-ph/9506380

3. The “Concordance Model” of cosmology  tot = 1.003  0.010  m ~ 0.22 [  b =0.04]   ~ 0.74 Most of matter of non-baryonic nature and therefore “dark” ! The “concordance model” of big bang cosmology attempts to explain cosmic microwave background observations, as well as large scale structure observations and supernovae observations of the accelerating expansion of the universe.

4. Different data: WD supernovae CMB Matter surveys all agree at one point

5. Kaluza-Klein DM in UED Kaluza-Klein DM in RS Axion Axino Gravitino Photino SM Neutrino Sterile Neutrino Sneutrino Light DM Little Higgs DM Wimpzillas Q-balls Mirror Matter Champs (charged DM) D-matter Cryptons Self-interacting Superweakly interacting Braneworld DM Heavy neutrino NEUTRALINO Messenger States in GMSB Branons Chaplygin Gas Split SUSY Primordial Black Holes L. Roszkowski Dark matter candidates

6. DM candidates: WIMP’s ! SUSY particles ?

7. Neutralino as the CDM candidate Stable (if R-parity is conserved) Mass: m  ~ 10-1000 GeV Non-relativistic at decoupling  CDM Neutral & colourless Weakly interacting (WIMP) Good relic density   Linear combination of the neutral gauge bosons B and W 3 and the neutral higgsinos H 1 and H 2. The neutralino is a good candidate because:

8. SIGNALS from RELIC WIMPs Direct searches: elastic scattering of a WIMP off detector nuclei Measure of the recoil energy Indirect detection: in cosmic radiation  signals due to annihilation of accumulated  in the centre of celestial bodies (Earth and Sun)  neutrino flux  signals due to  annihilation in the galactic halo  neutrinos  gamma-rays  antiprotons, positrons, antideuterons For a review, see i.e. Bergstrom hep-ph/0002126 and  keep directionality can be detected only if emitted from high  density regions Charged particles diffuse in the galactic halo antimatter searched as rare components in cosmic rays PAMELA FERMI, AMS

9. Neutralino annihilation Production takes place everywhere in the halo!! The presence of neutralino annihilation will destort the positron, antiproton and gamma energy spectrum from purely secondary production

10. Spectrum deformation

11. LIGHTEST KALUZA-KLEIN PARTICLE (LKP): B (1) ‏ Another possible scenario: KK Dark Matter Bosonic Dark Matter: fermionic final states no longer helicity suppressed. e+e - final states directly produced. As in the neutralino case there are 1-loop processes that produces monoenergetic γ γ in the final state.

12. Kaluza-Klein Dark Matter in e + e - Direct annihilation of the Lightest Kaluza-Klein particle (LKP) into electron-positron pair in the Galactic halo (Baltz and Hooper, JCAP 7, 2007, and references therein) e - + e + yield is estimated to be ~20% per annihilation Could be a unique opportunity to observe a sharp feature in the electron spectrum (predicted in some models)

13. First hint of something new: results from ATIC (Nature, 2008)

14. PAMELA positron fraction (Nature 2009)

15. FERMI e + + e - flux (2009) FERMI All-Electron Spectrum (PRL 2009)

16. Electrons measured with H.E.S.S.(2009)

17. PAMELA

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

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

20. New positron fraction data Using all data till 2010 and multivariate classification algorithms about factor 2 increase in positron statistics respect to published analysis

21. New positron flux

22. Antiproton flux Largest energy range covered so far ! Adriani et al. - PRL 105 (2010) 121101

23. Antiproton-to- proton ratio Adriani et al. - PRL 105 (2010) 121101 Largest energy range covered so far !

24. New antiproton flux –> 400 GeV Using all data till 2010 and multivariate classification algorithms 40% increase in antip respect to published analysis (Donato et al. 2009) Diffusion model with convection and reacceleration Plain Diffusion Model (Ptuskin 2006)

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

26. 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. (Cholis et al. 2009) Contribution from DM annihilation.

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

28. Interpretation: DM Which DM spectra can fit the data? DM with and dominant annihilation channel (no “natural” SUSY candidate)‏ Yes! But B≈10 4 M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3 positrons antiprotons

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

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

31. Astrophysical Explanation: secondaries in SNR P.Blasi et al., PRL 103 (2009) 051104 arXiv:0903.2794 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.

32. New antiproton/pr oton ratio  400 GeV Overall agreement with models of pure secondary calculations for solar minimum (constraints at low and high energy for DM models!) The solid line shows a calculation for secondary antiprotons including an additional antiproton component produced and accelerated at cosmic-ray sources.

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

34. Astrophysical Explanation: Pulsars 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 ~ 10 5 years. Young (T < 10 5 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

35. 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

36. How to clarify the matter? Courtesy of J. Edsjo

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

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

39. Electron energy measurements Two independent ways to determine electron energy: 1. Spectrometer Most precise Non-negligible energy losses (bremsstrahlung) above the spectrometer  unfolding 2. Calorimeter Gaussian resolution No energy-loss correction required Strong containment requirements  smaller statistical sample spectrometer calorimeter Adriani et al., PRL 106, 201101 (2011) Electron identification: Negative curvature in the spectrometer EM-like interaction pattern in the calorimeter

40. Electron absolute flux  Largest energy range covered in any experiment hitherto with no atmospheric overburden  Low energy minimum solar activity (  450÷550 GV)  High energy  No significant disagreement with recent ATIC and Fermi data  Softer spectrum consistent with both systematics and growing positron component Spectrometric measurement Adriani et al., PRL 106, 201101 (2011) e + +e - Calorimetric measurements e-e- Flux=A E -   = 3.18 ± 0.04

41. PAMELA Electron & Positron Spectra Flux=A E -   = 3.18 ±0.04 Flux=A E -   = 2.70 ±0.15 Preliminary

42. 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 (  450÷550 GV) High-energy  a complex structure of the spectra emerges… Adriani et al., Science 332 (2011) 6025

43. P & He absolute fluxes @ high energy 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 hp above 80 GV rejected @ >95% CL Solar modulation 2.85 2.67 232 GV Spectral index 2.77 2.48 243 GV Standard scenario of SN blast waves expanding in the ISM needs additional features

44. 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)

45. 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)  He -  p = 0.078 ±0.008  2 ~1.3

46. FERMI OBSERVATORY

56. PAMELA & FERMI Same trend for positrons (increasing with energy) Compatible spectral indexes for electrons and positrons : PAMELA :FERMI:  = 3.18 ± 0.04 for electrons  = 3.19 ± 0.07 for electrons  = 2.70 ± 0.15 for positrons  = 2.77 ± 0.14 for positrons

57. Conclusions Electron/Positron data have opened new physics in Cosmic Rays in the last 5 years; ATIC, FERMI, PAMELA measurements all pointed towards an excess. Evident excess in the electron and positron (and therefore in the all-electron) spectra revealed the presence of a leptonic new source; The contemporary absence of a hadronic new source, as shown by the PAMELA antiproton data, seems to point towards a astrophysical source rather than to dark matter. BUT ….

58. Conclusions Recent rumors by AMS – not yet supported by an official paper - make us guess that the DM interpretation might play a role again. “Big news in the search for dark matter may be coming in about two weeks”, Ting said at the annual meeting of the American Association for the Advancement of Science. “That's when the first paper of results from AMS will be submitted to a journal”. “It will not be a minor paper" Ting said, hinting that the findings were important enough that the scientists rewrote the paper 30 times before they were satisfied with it …

59. Conclusions Apart from AMS data, the new CALET mission (Japan-Italy-US) will perform high statistics measurements of electrons up to 10 TeV; Built around a 30 r.l. calomiter, it will be mounted on the ISS in 2o14; With its good geometrical factor, it will improve significantly the systematic uncertainties of previous calorimetric measurements.