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Indirect detection of Dark Matter …. from an experimental point of view ….

Jan Conrad conrad.at.fysik.su.se. Indirect detection of Dark Matter …. from an experimental point of view …. A Decade of New Experiments XXXVII SLAC Summer Institute, August 3-14, 2009. The reason why I am not at SLAC. Me. Ellen, 14 month.

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Indirect detection of Dark Matter …. from an experimental point of view ….

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  1. Jan Conrad conrad.at.fysik.su.se Indirect detection of Dark Matter…. from an experimental point of view …. A Decade of New Experiments XXXVIISLAC Summer Institute, August 3-14, 2009.

  2. / The reason why I am not at SLAC Me Ellen, 14 month Thanks for suggesting this solution to Greg Madejski and JoAnne Hewett (we’ll see if it works).

  3. Jan Conrad, Stockholm Universitet • Questions can be adressed to me by mail: conrad@physto.se (there are no stupid questions!) • During lectures I usually try to read the audience, which will not be possible  positive and negative feedback would be very useful (via mail).

  4. Jan Conrad, Stockholm Universitet Goal for the lectures. • You should understand the experimental approaches to indirect detection of dark matter and what we can expect in the next decade. • You should understand that DM indirect detection is challenging and what the challenges are • I hope I can give you some additional insight in what to make of the presented results. • I hope I will be able to convey the message that revolutions are on the horizon.

  5. Jan Conrad, Stockholm Universitet Contents and non-contents • Not in this lecture(s): • Why DM ?  Tegmark,Weiner • DM candidates  Weiner • Results will be presented mainly if they illustrate a special point  for newest results: see talks by Moskalenko, Pearce, Burnett, Egberts • Lecture I • Preliminaries (minimal theoretical background) • The set up • Charged cosmic rays, • Signatures • Astrophysics and backgrounds • A detour cosmic ray diffusion in the Galaxy • Instrumental background • Experimental approaches • PAMELA, ATIC, FERMI results on charged cosmic rays. • GAPS Also important for gamma-rays --- lecture II

  6. Jan Conrad, Stockholm Universitet • Lecture II • Gamma-rays • Signatures • Astrophysics and backgrounds • Experimental approach and experiments • Source confusion • Selected Results • Neutrinos • Signature • backgrounds • Experimental approach and experiments • Selected results • Impact of Astrophysics • Interplay between different indirect experiments • Indirect indirect detection (multi-wavelength) Some additional slides contain more detailed information …

  7. Jan Conrad, Stockholm Universitet The set-up c • Prime DM candidate: Weakly Interacting Massive Particle (WIMP), denoted by • Mass: ~ 10 GeV - ~ 10 TeV • ”Weakly” interacting • Experimental signatures (roughly) applicable to a variety of candidates: • Supersymmetric neutralino • Kaluza Klein • Axino, Gravitino, SuperWIMPs • ….etc. etc. • Other CDM candidates: • axions ( discussed if time) For motivation and theory: see Neil Weiners talk

  8. Jan Conrad, Stockholm Universitet The set-up: WIMP annihilation or decay g W-/Z/q c p0 g nm c nmne W+/Z /q p m e± Anti-p, anti-d Indirect detection rate = (particle physics part) × (astrophysical part) PPP APP

  9. Jan Conrad, Stockholm Universitet Signal: general considerations orders of magnitude parameter space (x-sections) • Particle physics part • DM particle’s spin mass, annihilation cross section, branching fraction into final states and yield for a given final state (given by underlying theory (KK,MSSM, IDM etc).  For experimentalist: Analysis optimized for given signature • Astrophysical part • (Density of DM particles)2, diffusion, absorption (where applicable) • For experimentalists: Where to look for the signal? > Order of magnitude uncertainties More details in respective section. Note there is virtually no experiment dedicated solely (or even mainly) to IDMD !!! (one exception: GAPS …. will be discussed.)

  10. Jan Conrad, Stockholm Universitet Cosmic rays Dark Matter on Galactic scales Dark Matter on Galactic scales c e+ W-/Z/q _ p W+/Z /q e± e- m m c Anti-p, anti- d

  11. Jan Conrad, Stockholm Universitet Cosmic rays: signatures Positron fraction and spectrum Antiproton fraction and spectrum Anti-deuteron spectrum

  12. Jan Conrad, Stockholm Universitet APP: cosmic ray propagation in the Galaxy: why we need to talk about it: • Cosmic rays produced in secondary processes provide a formidable background to DM searches with anti-particles. • Photon-production by Galactic cosmic rays provide a formidable background to DM searches with gamma-rays • Any potential signal in CR will need to be interpreted with effects of the propagation in mind Strong et al, ApJ 537, 736, 2000 Strong et al, ApJ 613, 962, 2004 Diffuse gamma-ray prediction 1 Diffuse gamma-ray prediction 2

  13. Jan Conrad, Stockholm Universitet APP: cosmic ray propagatioin in the galaxy To some: To us: Diffusion reacceleration convection energy loss spallation decay IC synch Radiation field brems B-field B-field CNO Gas e p  π± e± Gas  π0  γγ  π0  γγ DM p-bar,  Li, B   π± e±

  14. Jan Conrad, Stockholm Universitet Many other experiments will be important for indirect detection: • By standard, quantitatively described by diffusion equation (see additional slides) with a number of assumptions (e.g. GALPROP code) • Constrained through CR and gamma-ray observations • Diffusion coefficient  Primary/secondary nuclei ratio (HEAO-3, ACE,PAMELA,CREAM,TRACER) • Interstellar radiation field:  optical,FIR,CMB (DIRBE, FIRAS) • Interstellar gas (H1,HII) 21cm, CO surveys (Bonn,Parkes) • B-field  radio surveys (Jodrell Bank, Parkes ,WMAP, Planck) • Spallation, pion production cross-sections accelerators For a more detailed account: Moskalenko, SSI 2008

  15. Jan Conrad, Stockholm Universitet Cosmic ray anti-matter: detection principle Scintillator (TOF) PID (TRD,Cherenkov) magnet Anti-coincidence (scintillator) Scintillator (TOF) PID (TRD,Cherenkov) Calorimeter

  16. Jan Conrad, Stockholm Universitet Examples: PAMELA and AMS-02, spectrometer 1.2 m, 450 kg 1.5 m, ~6000 kg

  17. Jan Conrad, Stockholm Universitet Examples for ”calorimeters”: ATIC/FERMI/HESS  e– e+ 1500 kg, h=1.2m

  18. Jan Conrad, Stockholm Universitet Example: PAMELA and ATIC • Launched: June 15, 2006 from Baikonur, • Quasi-polar orbit • Expected livetime: > 3 years • Three flights (2001,2003 and 2008) • Total livetime: 50 days

  19. Jan Conrad, Stockholm Universitet Instrumental backgrounds for e+,e-,γ Hadronic background is dominant. Necessary rejection factors: ATIC, Fermi electrons ~ 103-4 PAMELA, AMS ~ 104-5 Fermi γ ~ 105-6

  20. Jan Conrad, Stockholm Universitet Hadron/electron discrimination • Main idea: • Veto detectors (Anti-coincidence) • difference in shower shape for em/hadronic showers in calorimeter • Background rejection gets harder with rising energy • Full analyses apply combined information of several detectors in multivariate classification (Neural networks …)

  21. Jan Conrad, Stockholm Universitet Example: Fermi electron analysis.

  22. Jan Conrad, Stockholm Universitet Anti-proton/proton ratio 500 days of data, 109 triggers, ca. 1000 anti-protons, ca. 107 protons, background < 3 % 6 anti-protons ca 600 > 5 GeV Compatible with secondary production O. Adriani et al. Phys.Rev. Lett. 102:051101,2009

  23. Jan Conrad, Stockholm Universitet Positron fraction: the PAMELA anomaly 500 days of data, 150 k electrons, 10k positrons Errors include background removal uncertainty Very soft electron spectrum (index: -3.54) at odds with Fermi (see later) Conventional production: Delahaye et. al arXiv:0809.5268  Conventional production: GALPROP Strong & MoskalenkoAstrophys.J.509:212-228,1998 O. Adriani et al. Nature 458:607-609,2009

  24. Jan Conrad, Stockholm Universitet Possible sources M. Schubnell, arXiv:0905.044 B. Katz et al., arXiv:0907.1686 • No extra source: • Experimental • Non standard diffusion • Extra source • Dark matter • Conventional sources • Pulsars • Supernovae L. Bergström et al., Phys.Rev.D78:103520,2008 D. Malyshev et al. 0903.1310 P. Biermann et al., arXiv:0903.4048

  25. Jan Conrad, Stockholm Universitet Pulsars invoked already 20 years ago ….

  26. Jan Conrad, Stockholm Universitet e++e- spectrum: the ATIC anomaly Based on ATIC 1 + ATIC2 ATIC collab. Nature 456, 362-365(2008) Statistical errors only, background subtracted HEAT BETS PPB-BETS x Emulsion chambers background GALPROP Sol. Mod.

  27. Jan Conrad, Stockholm Universitet Fermi-LAT as an electron detector ATIC background Fermi-LAT effective geometric Factor Energy resolution: ~ 20 %@ 1 TeV (cf. ATIC ~ 2 % @ 150 GeV cf. PAMELA ~ 6 % @ 200 GeV ) Residual hadron contamination < 20 % Cf: ATIC effective geometric factor (less for PAMELA)

  28. Jan Conrad, Stockholm Universitet e++e- spectrum A. Abdo (Fermi-LAT) Phys.Rev.Lett.102:181101,2009 6 month of data • ATIC is gone?? • Data is compatible with power-law (- 3.04). • Is there a deviation from power-law? 3.8 σ 5.1 σ , Isbert (ATIC, TANGO in Paris 2009) One slide on possible explanations in appendix Also see Eun-Suk Seo’s topical talk ATIC: 1724 events > 100 GeV Fermi: 171431 events> 100 GeV F. Aharonian (HESS), arXiv:0905.0105 ± 15 % reject KK model that fits ATIC at 99% (including E resolution).

  29. Jan Conrad, Stockholm Universitet …and explanations …. • No extra source: • Experimental (for ATIC) • Non standard diffusion • Extra source • Dark matter • Conventional sources • Pulsars • Supernovae D. Grasso et al., arXiv:0907.0373 P. Biermann et al., arXiv:0903.4048 Bergström et al. 0905.0333

  30. Jan Conrad, Stockholm Universitet A remark on boost-factors • The annihilation cross-section is set by DM abundance in Big bang freeze out  not sufficient to explain observed alleged signal. • ”Boost” of rate has been invoked: DM substructure ~ 10?? e.g. Sommerfeld factor ~ 0-1000? (requires modifications to model) L. Bergström, arXiv 0903.4849

  31. Jan Conrad, Stockholm Universitet If it is DM, what would it mean? • Data prefers models with mostly leptonic annihilation channels (in fact, muons) • Most models predict rather large masses (> 1 TeV). • This is hard to accomodate within MSSM considering the anti-proton (gamma) constraint. • Most models need an additional enhancement of annihilation cross-section (”boost”). • Most models make predictions which are testable with soon existing data (gamma-rays). One can ask how much sense it makes to do this considerations at this point of time ….. some groups even publish theoretical analysis on preliminary data …. which I think is not very useful (unless you go with Carlo Rubbia (alleged): ”Better wrong than late” )

  32. Jan Conrad, Stockholm Universitet Cosmic ray detectors of relevance to DM TRACER PEBS VERITAS AMS Fermi PAMELA HESS future exp. spectrometers ”calorimeters” auxiliary BESS-polar CREAM PPB-Bets CALET ATIC GAPS

  33. Jan Conrad, Stockholm Universitet Cosmic ray experiments: comparison

  34. Jan Conrad, Stockholm Universitet GAPS detection principle Atomic Transitions no,lo n=nK~15 n=6 g n=5 g n=4 g n=3 n=2 p+ n=1 p+ p- p- po Slide stolen from Jason Koglin, Columbia U. _ D p* Plastic Scintillator TOF Si(Li) Target/Detector Auger e- Refilling e- p* 44 keV LadderDeexcitations Dn=1, Dl=1 p* 30 keV p* A time of flight (TOF) system tags candidate events and records velocity Nuclear Annihilation The antiparticle slows down & stops in a target material, forming an excited exotic atom with near unity probability Deexcitation X-rays provide signature Pions from annihilation provide added background suppression

  35. Jan Conrad, Stockholm Universitet GAPS sensitivity 2011 prototype 2014 flight GAPS white paper

  36. Jan Conrad, Stockholm Universitet Summary (cosmic rays): • General: • CR probe DM on Galactic scales • Cosmic ray propagation in the Galaxy is important for gamma-rays and cosmic rays  needs imput from a variety of experiments. • Instrumental and astrophysical backgrounds are challenging. • Anti-deuterons provide a potential smoking gun signal • Status: • PAMELA let the genie out of the bottle • Signatures detected which could be the first sign of DM. • The experimental situation is confusing with different (apparently) not consistent results (ATIC vs. Fermi !, PAMELA vs. Fermi ?). • Outlook: • Future experiments (AMS-02,PEBS) and additional data will be crucial: • For constraining backgrounds for e.g. gamma-rays and cosmic rays. • For distinguishing signal hypothesis.

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