1. Indirect Dark Matter Search with AMS-02 Stefano Di Falco INFN & Universita’ di Pisa for the AMS collaboration

2. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 2 Indirect search for Dark Matter AMS a multichannel approach pp, (dd) No direct production Hadronization : E h << m X Direct production Decay of W Decay of Heavy Quark Decay of Charged Pions e + e - Direct production: E e = m X Decay of W, Decay of Heavy Quark Decay of Leptons and Charged Pions Photons Direct Production : E  = m X Decay of Neutral Pions e + HEAT excess?  EGRET excess? p excess?

3. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 3 The AMS ( Alpha Magnetic Spectrometer ) experiment AMS-01AMS-02 1998 10 days on Space Shuttle Discovery - He/He < 1.1·10 -6 - very nice measurements of primary and secondary p, p, e -, e +, He, and D spectra from ~ 1 to 200 GeV ( (Phys. Rept. vol. 366/6 (2002) 331) 2008*-…  3 years on ISS - Superconducting magnet - New detectors - ANTIMATTER SEARCH: He/He < 10 -9 - COSMIC RAY FLUXES up to Z=26 - DARK MATTER SEARCH *ready for launch date

4. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 4 The AMS detector TRD (Transition Radiation Detector): 20 layers of Foam + Straw Drift Tubes (Xe/CO 2 ) 3D tracks, e/h separation>10 2 rej. up to 300 GeV 1 m ~2 m AMS Weight: 7 Tons 1 out of 328 Straw tube Modules

5. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 5 The AMS detector TOF (Time of Flight): 2+2 layers of scintillators,  t =~160ps Trigger, Z separation,  with few % precision 1 m ~2 m 2 out of 4 layers

6. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 6 The AMS detector Superconducting Magnet: 12 racetrack coils & 2 dipole coils cooled to 1.8° K by 2.5 m 3 of superfluid He Contained dipolar field: BL 2 = 0.85 Tm 2 1 m ~2 m Technological challenge: first superconducting magnet operating in space B

7. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 7 The AMS detector Tracker: 8 layers double sided silicon microstrip detector  R(igidity) <2% for R<10 GV, R up to 2-3 TV, Z separ. 1 m ~2 m

8. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 8 The AMS detector RICH (Ring Imaging CHerenkov): 2 Radiators: NaF (center), Aerogel(elsewhere),  with 0.1% precision, Z and isotopes separation, (2% precision on mass below 10 GeV/n) 1 m ~2 m reflector PMT plane radiator

9. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 9 The AMS detector ECAL (Electromagnetic Calorimeter): Sampling: 9 superlayers of Lead+Scint. Fibers trigger, e ,  detection:  E(nergy) 10 GeV, 3D imaging: e/h separation>10 3 rej 1 m ~2 m

10. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 10 Expected particle fluxes e + /p ~ 5·10 -4 @ 10 GeV e + /e - ~ 10 -1 @ 10 GeV p and He from AMS-01 e +, e - and  from Moskalenko & Strong* *ApJ 493 (1998) 694  galactic center /p ~ 10 -4 @ 10 GeV  galactic center /e - ~ 10 -2 @ 10 GeV Very high particle identification needed

11. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 11 AMS response to positrons and protons PositronPositron ProtonProton TRD signal X rays from transition radiation No signal if  <10 3 (E<300 GeV) Rejection factor 10 2 -10 3 up to 300 GeV

12. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 12 AMS response to positrons and protons PositronPositron ProtonProton t~4ns,  t~160ps  TOF ~ 1, |Z|=1, Reject upgoing particles Reject p up to 1.5 GeV (kinetic energy) Reject He (|Z|=2)  TOF ~ 0.92±0.04@1.5GeV, |Z|=1 TOF signal

13. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 13 AMS response to positrons and protons PositronPositron ProtonProton Tracker signal Positive curvature (with TOF): Z= +1 Charge determination: reject e - and He ++ Rigidity measurement (E/p matching): Rigidity (GV) Resolution in Rigidity (%) Positive curvature (with TOF): Z= +1

14. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 14 AMS response to positrons and protons PositronPositron ProtonProton RICH signal  RICH ~ 1, |Z|=1,  ~17° (41° at center),  ~0.2° N p.e. ~ 7 (4 at center) Reject p up to 10 GeV (kinetic energy) Reject He (|Z|=2)  RICH ~ 0.996±0.001@10GeV, |Z|=1

15. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 15 AMS response to positrons and protons PositronPositron ProtonProton ECAL signal Electromagnetic shower: prompt known longitudinal profile recoverable leakage narrow strongly collimated Hadronic shower: not prompt wrong longitudinal profile unrecoverable leakage wide weakly collimated Rejection factor ~10 3 ~ 16X 0 ~ 1 I

16. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 16 AMS response to positrons and protons PositronPositron ProtonProton ECAL+Tracker: E/p matching E/P > 1-(  Tracker  ECAL )/E  Tracker (E)/E = 0.05%·E(GeV)  3% (E>50GeV)  ECAL (E)/E = 12%/sqrt(E(GeV))  2% Radiative tail

17. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 17 Positron and background acceptance Kinetic energy (GeV) Results from a montecarlo study using discriminant analysis* * P. Maestro, PhD Thesis, 2003 Acceptance for e + : ~ 0.045 sr m 2 from 3 to 300 GeV Rejection factor for p : ~ 10 5 ** Rejection factor for e - : ~ 10 4 ** Including a ~7 flux factor improvement because ~E kin /2 )

18. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 18 Reconstructed energy (GeV) Number of Positrons in 3 years In 3 years AMS will collect O(10 5 ) e + with 10<E< 50 GeV [ O(10 2 ) for HEAT ] Total contamination: ~ 4% Good sensitivity up to 300 GeV

19. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 19 Positron fraction: statistical error in 3 years Parametrization of the standard prediction for positron flux* (without Dark Matter) Errors are statistical only The positron fraction e + /(e + +e - ) is preferred to the e + flux because is less sensitive to uncertainties on cosmic-ray propagation and solar modulation *Baltz et al., Phys. Rev. D 59, 023511

20. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 20 Possible scenarios from neutralino annihiliation Example of neutralino annihiliation signal observed by AMS with the boost factors found by Baltz et al.* to fit the HEAT data and motivated with a inhomogenous dark matter density (clumpiness) *Baltz et al.; Ph.Rev D65, 063511  gaugino dominated m  = 340 GeV, boost factor=95 e + primarily from hadronization  gaugino dominated m  = 238 GeV, boost factor=116.7 hard e + from direct gauge boson decay

21. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 21 More neutralino scenarios: needed boost factors The mimimal boost factor to see the LSP annihilation at 95% C.L. in the positron channel in 3 years is reduced if the gaugino mass universality condition in mSugra is relaxed* mSugra : m 1/2 = M 1 = M 2 = M 3 tan  = 10 Relaxing gaugino mass universality : Gluino Mass : M 3 = 50% m 1/2 *J. Pochon, PhD Thesis, 2005

22. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 22 Possible positron signals from Kaluza-Klein model Kaluza-Klein model are interesting because allow for direct production of e + e - pairs in the annihilations of the LKP (B 1 ) — Background ( no DM)  AMS 3 years Signal with Boost adjusted on HEAT data + Bg ∆ AMS (3 years) Signal with Boost at visibility limit + Bg Positron fraction e + /(e + +e - ) much steeper raises can fit HEAT data* *J.Feng,Nucl.Phys.Proc.Suppl.134 (2004) 95 **J Pochon & P Salati Boost factors needed:** ~O(10 2 ) to fit HEAT data ~1  10 for discovery

23. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 23 Dark Matter annihilation into photons ● The center of the galaxy can be a very intense point-like source of gammas from dark matter annihilations. ● Unlike positrons, gammas travel long distances and point to the source ● The annihilation signal could be enhanced by a cuspy profile of the DM density at the galaxy center (super- massive black hole (SMBH), adiabatic compression,...)

24. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 24 Photon detection in AMS Photon conversion: Direction (angle): from Tracker Energy: from Tracker (and ECAL) Single Photon (direct measurement) Direction (angle): from ECAL Energy: from ECAL

25. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 25 Gamma energy and angular resolution 3% 6% 0.02 o ~1o~1o Energy resolution Angular resolution

26. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 26 Main backgrounds to Photons Conversion mode  rays Rejection factor: >10 5 (p), 4·10 4 (e) Using: TRD veto, invariant mass Single Photon mode Secondaries (  0 ) from p interactions Rejection power: 5·10 6 Using: veto on hits,  direction

27. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 27 Gamma acceptance and effective area Acceptance (m 2.sr) Max Acceptance: Conversion mode: 0.06 m 2 ·sr Single photon mode: 0.097 m 2 ·sr GeV Field of view: Conversion mode: ~ 43° Single photon mode: ~ 23°

28. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 28 AMS-02 Exposure to  from galactic center 51º latitude Revolution : 90’ Conversion mode (sel. acc.) GC : ~ 15 days Single photon mode (geom. acc.) GC : ~ 40 days

29. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 29 Statistical significance (single photon mode) * F. Pilo, PhD Thesis, 2004 E (GeV) 68% C.L. 95% C.L. Statistical error on photon spectrum from galactic center (AMS 3 years):* Good sensitivity between 3 and 300 GeV

30. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 30 Gamma sensitivity to neutralino annihilation Example*: m  = 208 GeV ( AMS 1 year) — Background — Signal — Background + Signal E 2 Flux (GeV/cm 2 s) * L. Girard. PhD Thesis,2004 Egret E (GeV) — Background — Signal — Background + Signal

31. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 31 Gamma sensitivity for different halo profiles *A. Jacholkowska et al., astro-ph/0508349 Kaluza-Klein & SuSy Models Scan for different halo profiles*: **Navarro, Frenk & White, ApJ 490 (1997) 493

32. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 32 Antiproton detection in AMS Antiproton signal: -Single track in TRD + Tracker - Z = -1 Rejection : p : > 10 6 (ToF, Rich …) e- : > 10 3 -10 4 TRD /Ecal Acceptance : 1-16 GeV : 0.160 m 2 ·sr 16-300 GeV : 0.033 m 2 ·sr Main Backgrounds: Protons: charge confusion, interactions with the detector and misreconstructed tracks. Electrons: beta measurement, e/h rejection

33. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 33 Antiproton flux measurement with AMS Conventional p flux with Statistical Errors (3 years) Range 0.1 to ~ 500 GeV AMS-02 * Current Measurements: large errors below 35 GeV, *V. Choutko (2001)

34. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 34 Possible DM signal in Antiproton spectrum However models require a boost factor. 1)M  =964 GeV (x4200) 2)M  =777 GeV (x1200) * P. Ullio (1999) Low Energy Spectrum well explained by secondary production. There is room for a signal at high energy (10 – 300 GeV):*

35. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 35 Conclusions The AMS experiment, during its 3 year mission, will be able to measure simultaneously and with unprecedented precision the rates and spectra of positrons, gammas and antiprotons in the GeV-TeV range, looking for an excess of events that could hint for a dark matter annihilation signal. Several models for dark matter candidates can be constrained by the new AMS data. The AMS simultaneous measurements of other fundamental quantities (p and e spectra, B/C ratio,…) will help to refine the astrophysical predictions enhancing the compelling evidence for a dark matter signal.

36. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 36 Backup

37. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 37 Background flux calculations Gas (HI,H 2,HII…) distribution CR source distribution and spectrum (index, abundances) Diffusion model (reacceleration, diffusion) and parameters (D,size h, cross-sections…) Physical background: Antimatter channels: secondary products from cosmic ray spallation in the interstellar medium; Gamma ray channel: diffuse Galactic emission from cosmic ray interaction with gas (π 0 production, inverse Compton, bremsstrahlung) Local Background Flux determined by propagation of CR yield per unit volume through simulation (GALPROP)  (m -2 s -1 sr -1 GeV -1 ) = φ bg + φ signal

38. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 38 Signal flux calculations  (m -2 s -1 sr -1 GeV -1 ) = φ bg + φ signal CR yield per unit volume (r,z,E) ≡ g ann (E). * *(ρ χ (r,z) /m χ ) 2 WMAP (+…) constraints on   h 2 ≡ coannihilation cross- section Rotational velocity measurements ρ χ (r,z) ≡ density distribution DM density profile shape (+ “boost factors * ”) Accelerator constraints Boost factors: clumpiness,cuspiness, baryon interaction, massive central black hole… g ann (E) ≡ particle production rate per annihilation SUSY parameter space (5+…) Local Flux determined by propagation of CR yield per unit volume through simulation (GALPROP) COSMOLOGY m χ ≡ neutralino mass ASTROPHYSICS HEP (propagation model and parameters …)

39. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 39 Indirect Search: neutralino annihilation

40. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 40 Indirect Search: neutralino annihilation Particle Physics models:  anni, annihilation channels and m X should be compatible with DM Relic Density Propagation G diffusion model earth vicinity Cosmology Nominal Local density of Dark Matter: 0.3 GeV/cm 3 Distribution: Clumps = Boost 2 Halo shape (Galactic Centre) Charged: Gamma:

41. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 41 Antideuterons

42. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 42 Antideuterons 1 /GeV/year ● Antideuterons have never been measured in CR ● could be an alternative channel to look for dark matter signals. Claim: almost background-free channel at low energies DM signal Spallation spectrum

43. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 43 Antideuterons Spallation spectrum Estimate of AMS potential under study: focused on low momenta, antiproton flux is the main background – need 10 5 discrimination - mass resolution is crucial! tertiary component TOA flux prediction is even less optimistic

44. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 44 Some favourites Dark Matter candidates Models of Supersymmetry : mSugra – 5 parameters: m 0 : scalar mass m 1/2 : gaugino mass A 0 : sleptons and squarks coupling tan  : ratio of VED of the Higgs doublets sign(  ) : Higgs mass parameter –R-parity conservation Ligthest Susy Particle stable : Neutralino Extensions  à la Kaluza-Klein: 2 working models with Extra Dimensions –Universal Extra Dimensions (UED) all SM particles propagates in X-dimensions Lightest First Excitation Level is stable : B (1) ( ~  (1) ) –Warped Grand Unified Theories Z3 symmetry to ensure proton stability Lightest Z3 charged particle is stable ( R (1) )

45. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 45 Positron fraction after 3 years: AMS and PAMELA AMS PAMELA

46. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 46 Antiproton expected flux (without DM) Low Energy Spectrum well explained by secondary production. The prediction are very sensitive to the physics details of cosmic ray propagation, particularly at low momentum. This is controlled by secondary/primary ratios, like B/C. AMS will measure the B/C ratio with high precision Uncertainty mainly due to present determination of B/C

47. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 47 B/C measurement in AMS Charged nuclei Charge(Z): from TOF, Tracker and RICH Rigidity(R): from Tracker and Magnet Velocity(  ): from TOF and RICH  Mass and Charge

48. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 48 Gamma detectors in space

49. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 49 AMS response to positrons and protons PositronPositron ProtonProton TRD signal X rays from transition radiation No signal if  <10 3 (E<300 GeV) Rejection factor 10 2 -10 3 up to 300 GeV t~4ns,  t~160ps  TOF ~ 1, |Z|=1, Reject upgoing particles Reject p up to 1.5 GeV (kinetic energy) Reject He (|Z|=2)  TOF ~ 0.92±0.04@1.5GeV, |Z|=1 TOF signalTracker signal Positive curvature (with TOF): Z= +1 Charge determination: reject e - and He ++ Rigidity measurement (E/p matching): Rigidity (GV) Resolution in Rigidity (%) Positive curvature (with TOF): Z= +1 RICH signal  RICH ~ 1, |Z|=1,  ~17° (41° at center),  ~0.2° N p.e. ~ 7 (4 at center) Reject p up to 10 GeV (kinetic energy) Reject He (|Z|=2)  RICH ~ 0.996±0.001@10GeV, |Z|=1 ECAL signalECAL+Tracker: E/p matching E/P > 1-(  Tracker  ECAL )/E  Tracker (E)/E = 0.05%·E(GeV)  3% (E>50GeV)  ECAL (E)/E = 12%/sqrt(E(GeV))  2% Radiative tail Electromagnetic shower: prompt known longitudinal profile recoverable leakage narrow strongly collimated Hadronic shower: not prompt wrong longitudinal profile unrecoverable leakage wide weakly collimated Rejection factor ~10 3 ~ 16X 0 ~ 1 I

50. La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 50 The AMS detector ECAL (Electromagnetic Calorimeter): Sampling calorimeter: Lead+Scint. Fibers trigger, e ,  detection:  E(nergy) 10 GeV, 3D imaging: e/h separation>10 3 rej TRD (Transition Radiation Detector): 20 layers of Foam + Straw Drift Tubes (Xe/CO 2 ) 3D tracks, e/h separation>10 2 rej. up to 300 GeV TOF (Time of Flight): 2+2 layers of scintillators,  t =~160ps Trigger, Z separation,  with few % precision Superconducting Magnet: Nb-Ti coils in superfluid He(1.8  K). Contained dipolar field: BL 2 = 0.85 Tm 2 Tracker: 8 layers double sided silicon microstrip detector  R(igidity) <2% for R<10 GV, R up to 2-3 TV, Z separ. RICH (Ring Imaging CHerenkov): 2 Radiators: NaF (center), Aerogel(elsewhere),  with 0.1% precision, Z and isotopes separation, (2% precision on mass below 10 GeV/n) 1 m ~2 m