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Indirect Dark Matter Search with AMS-02

Indirect Dark Matter Search with AMS-02. Stefano Di Falco INFN & Universita’ di Pisa for the AMS collaboration. Indirect search for Dark Matter. nn Direct production Decay of W Decay of Heavy Quark Decay of Charged Pions. g EGRET excess?. e + HEAT excess?. p excess?. Photons

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Indirect Dark Matter Search with AMS-02

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

  2. Indirect search for Dark Matter nn Direct production Decay of W Decay of Heavy Quark Decay of Charged Pions g EGRET excess? e+ HEAT excess? p excess? Photons Direct Production : Eg = mX Decay of Neutral Pions AMS a multichannel approach e+e- Direct production: Ee = mX Decay of W, Decay of Heavy Quark Decay of Leptons and Charged Pions pp, (dd) No direct production Hadronization : Eh << mX S. Di Falco, Indirect dark matter search with AMS-02

  3. The AMS (Alpha Magnetic Spectrometer) experiment AMS-01 AMS-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 yearsonISS - Superconducting magnet • New detectors • ANTIMATTER SEARCH: He/He < 10-9 • COSMIC RAY FLUXES up to Z=26 • DARK MATTER SEARCH *ready for launch date S. Di Falco, Indirect dark matter search with AMS-02

  4. The AMS detector 1 out of 328 Straw tube Modules TRD (Transition Radiation Detector): 20 layers of Foam + Straw Drift Tubes (Xe/CO2 ) 3D tracks, e/h separation>102 rej. up to 300 GeV 1 m ~2 m AMS Weight: 7 Tons S. Di Falco, Indirect dark matter search with AMS-02

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

  6. The AMS detector B Superconducting Magnet: 12 racetrack coils & 2 dipole coils cooled to 1.8° K by 2.5 m3 of superfluid He Contained dipolar field:BL2 = 0.85 Tm2 1 m Technological challenge: first superconducting magnet operating in space ~2 m S. Di Falco, Indirect dark matter search with AMS-02

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

  8. The AMS detector radiator reflector PMT plane RICH (Ring Imaging CHerenkov): 2 Radiators: NaF (center), Aerogel(elsewhere), b with 0.1% precision, Z and isotopes separation, (2% precision on mass below 10 GeV/n) 1 m ~2 m 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: sE(nergy) <3% for E>10 GeV, 3D imaging: e/h separation>103 rej 1 m ~2 m S. Di Falco, Indirect dark matter search with AMS-02

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

  11. AMS response to positrons and protons X rays from transition radiation No signal if g<103 (E<300 GeV) Rejection factor 102-103 up to 300 GeV TRD signal Positron Proton S. Di Falco, Indirect dark matter search with AMS-02

  12. AMS response to positrons and protons t~4ns, Dt~160ps bTOF~ 1, |Z|=1, • Reject upgoing particles • Reject p up to 1.5 GeV • (kinetic energy) • Reject He (|Z|=2) bTOF~ 0.92±0.04@1.5GeV, |Z|=1 TOF signal Positron Proton S. Di Falco, Indirect dark matter search with AMS-02

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

  14. AMS response to positrons and protons • q~17° (41° at center), Dq~0.2° • Np.e.~7 (4 at center) • Reject p up to 10 GeV • (kinetic energy) • Reject He (|Z|=2) bRICH~ 1, |Z|=1, bRICH~0.996±0.001@10GeV, |Z|=1 RICH signal Positron Proton S. Di Falco, Indirect dark matter search with AMS-02

  15. AMS response to positrons and protons • Electromagnetic shower: • prompt • known longitudinal profile • recoverable leakage • narrow • strongly collimated ~16X0 • Hadronic shower: • not prompt • wrong longitudinal profile • unrecoverable leakage • wide • weakly collimated Rejection factor ~103 ~1lI ECAL signal Positron Proton S. Di Falco, Indirect dark matter search with AMS-02

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

  17. Positron and background acceptance Results from a montecarlo study using discriminant analysis* Kinetic energy (GeV) Kinetic energy (GeV) Acceptance for e+: ~0.045 sr m2 from 3 to 300 GeV Rejection factor for p : ~105 ** Rejection factor for e-: ~104 * P. Maestro, PhD Thesis, 2003 ** Including a ~7 flux factor improvement because <Edep>~Ekin/2 ) S. Di Falco, Indirect dark matter search with AMS-02

  18. Number of Positrons in 3 years In 3 years AMS will collect O(105) e+ with 10<E< 50 GeV [ O(102) for HEAT ] Total contamination: ~4% Reconstructed energy (GeV) Good sensitivity up to 300 GeV S. Di Falco, Indirect dark matter search with AMS-02

  19. Positron fraction: statistical error in 3 years 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 Parametrization of the standard prediction for positron flux* (without Dark Matter) Errors are statistical only *Baltz et al., Phys. Rev. D 59, 023511 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) • gaugino dominated mc= 340 GeV, boost factor=95 e+ primarily from hadronization • gaugino dominated mc= 238 GeV, boost factor=116.7 hard e+ from direct gauge boson decay *Baltz et al.; Ph.Rev D65, 063511 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* • Relaxing gaugino mass universality : • Gluino Mass : M3 = 50% m1/2 • mSugra : • m1/2 = M1 = M2 = M3 • tan b = 10 *J. Pochon, PhD Thesis, 2005 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 (B1) Boost factors needed:** ~O(102) to fit HEAT data ~110 for discovery much steeper raises can fit HEAT data* • 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-) • Background ( no DM) **J Pochon & P Salati *J.Feng,Nucl.Phys.Proc.Suppl.134 (2004) 95 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,...) S. Di Falco, Indirect dark matter search with AMS-02

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

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

  26. Main backgrounds to Photons Conversion mode Single Photon mode d rays Rejection factor: >105(p), 4·104(e) Using: TRD veto, invariant mass Secondaries (p0) from p interactions Rejection power: 5·106 Using: veto on hits, g direction S. Di Falco, Indirect dark matter search with AMS-02

  27. Gamma acceptance and effective area Acceptance (m2.sr) GeV Max Acceptance: Conversion mode: 0.06 m2·sr Single photon mode: 0.097 m2·sr Field of view: Conversion mode: ~43° Single photon mode: ~23° S. Di Falco, Indirect dark matter search with AMS-02

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

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

  30. Gamma sensitivity to neutralino annihilation Example*: m = 208 GeV (AMS 1 year) Egret E2Flux (GeV/cm2s) • Background • Signal • Background + Signal • Background • Signal • Background + Signal E (GeV) * L. Girard. PhD Thesis,2004 S. Di Falco, Indirect dark matter search with AMS-02

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

  32. Antiproton detection in AMS Main Backgrounds: • Protons: charge confusion, interactions with the detector and misreconstructed tracks. • Electrons: beta measurement, e/h rejection Rejection : p : > 106 (ToF, Rich …) e- : > 103-104 TRD /Ecal Acceptance : 1-16 GeV : 0.160 m2·sr 16-300 GeV : 0.033 m2·sr Antiproton signal: -Single track in TRD + Tracker - Z = -1 S. Di Falco, Indirect dark matter search with AMS-02

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

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

  36. Backup S. Di Falco, Indirect dark matter search with AMS-02

  37. Background flux calculations F(m-2 s-1 sr-1 GeV-1) = φbg + φsignal Local Background Flux determined by propagation of CR yield per unit volume through simulation (GALPROP) Gas (HI,H2,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 (π0 production, inverse Compton, bremsstrahlung) S. Di Falco, Indirect dark matter search with AMS-02

  38. Signal flux calculations F(m-2 s-1 sr-1 GeV-1) = φbg + φsignal Local Flux determined by propagation of CR yield per unit volume through simulation (GALPROP) (propagation model and parameters …) CR yield per unit volume (r,z,E) ≡ gann(E).*<σv>*(ρχ(r,z) /mχ)2 gann(E) ≡ particle production rate per annihilation COSMOLOGY ASTROPHYSICS Rotational velocity measurements WMAP (+…) constraints on h2 mχ ≡ neutralino mass HEP <σv> ≡ coannihilation cross-section DM density profile shape (+ “boost factors*”) Accelerator constraints ρχ(r,z) ≡density distribution SUSY parameter space (5+…) Boost factors: clumpiness,cuspiness, baryon interaction, massive central black hole… S. Di Falco, Indirect dark matter search with AMS-02

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

  40. Indirect Search: neutralino annihilation Charged: • Propagation G • diffusion model • earth vicinity • Cosmology • Nominal Local density of Dark Matter: 0.3 GeV/cm3 • Distribution: • Clumps <2 > = Boost <>2 • Halo shape (Galactic Centre) • Particle Physics • models: anni , annihilation channels and mX • should be compatible with DM Relic Density Gamma: S. Di Falco, Indirect dark matter search with AMS-02

  41. Antideuterons 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 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 105 discrimination - mass resolution is crucial! tertiary component TOA flux prediction is even less optimistic S. Di Falco, Indirect dark matter search with AMS-02

  44. Some favourites Dark Matter candidates • Models of Supersymmetry : mSugra • 5 parameters: • m0 : scalar mass • m1/2 : gaugino mass • A0 : 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) ) S. Di Falco, Indirect dark matter search with AMS-02

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

  46. Antiproton expected flux (without DM) Uncertainty mainly due to present determination of B/C 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 S. Di Falco, Indirect dark matter search with AMS-02

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

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

  49. AMS response to positrons and protons E/P > 1-(sTrackersECAL)/E • q~17° (41° at center), Dq~0.2° • Np.e.~7 (4 at center) • Reject p up to 10 GeV • (kinetic energy) • Reject He (|Z|=2) X rays from transition radiation • Charge determination: • reject e- and He++ • Rigidity measurement • (E/p matching): sTracker(E)/E = 0.05%·E(GeV)  3% (E>50GeV) sECAL(E)/E = 12%/sqrt(E(GeV))  2% t~4ns, Dt~160ps bTOF~ 1, |Z|=1, Positive curvature (with TOF): Z= +1 bRICH~ 1, |Z|=1, • Reject upgoing particles • Reject p up to 1.5 GeV • (kinetic energy) • Reject He (|Z|=2) • Electromagnetic shower: • prompt • known longitudinal profile • recoverable leakage • narrow • strongly collimated Radiative tail No signal if g<103 (E<300 GeV) Resolution in Rigidity (%) Positive curvature (with TOF): Z= +1 Rejection factor 102-103 up to 300 GeV bTOF~ 0.92±0.04@1.5GeV, |Z|=1 bRICH~0.996±0.001@10GeV, |Z|=1 ~16X0 Rigidity (GV) • Hadronic shower: • not prompt • wrong longitudinal profile • unrecoverable leakage • wide • weakly collimated Rejection factor ~103 ~1lI ECAL+Tracker: E/p matching ECAL signal RICH signal Tracker signal TOF signal TRD signal Positron Proton S. Di Falco, Indirect dark matter search with AMS-02

  50. The AMS detector TRD (Transition Radiation Detector): 20 layers of Foam + Straw Drift Tubes (Xe/CO2 ) 3D tracks, e/h separation>102 rej. up to 300 GeV TOF (Time of Flight): 2+2 layers of scintillators, Dt =~160ps Trigger, Z separation, b with few % precision Superconducting Magnet: Nb-Ti coils in superfluid He(1.8 K). Contained dipolar field:BL2 = 0.85 Tm2 1 m Tracker: 8 layers double sided silicon microstrip detector sR(igidity)<2% for R<10 GV, R up to 2-3 TV, Z separ. RICH (Ring Imaging CHerenkov): 2 Radiators: NaF (center), Aerogel(elsewhere), b with 0.1% precision, Z and isotopes separation, (2% precision on mass below 10 GeV/n) ECAL (Electromagnetic Calorimeter): Sampling calorimeter: Lead+Scint. Fibers trigger, e,  detection: sE(nergy) <3% for E>10 GeV, 3D imaging: e/h separation>103 rej ~2 m S. Di Falco, Indirect dark matter search with AMS-02

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