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Indirect Dark Matter Search
with AMS-02
Stefano Di FalcoINFN & Universita’ di Pisafor the AMS collaboration
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 2
Indirect search for Dark Matter
AMSa multichannel approach
pp, (dd)No direct productionHadronization : Eh <<
mX
Direct productionDecay of W Decay of Heavy QuarkDecay of Charged Pions
e+e- Direct production: Ee = mX Decay of W, Decay of Heavy Quark Decay of Leptons and Charged Pions
PhotonsDirect Production : E = mX Decay of Neutral Pions
e+ HEATexcess?
EGRET excess?
p excess?
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 3
The AMS (Alpha Magnetic Spectrometer) experimentAMS-01 AMS-02
1998 10 days on Space Shuttle Discovery
- He/He < 1.1- He/He < 1.1··1010-6 -6
- very nice measurements of primary very nice measurements of primary and secondary p, p, eand secondary p, p, e--, e, e++, He, and D , He, and D spectra from spectra from ~~1 to 200 GeV1 to 200 GeV
((Phys. Rept. vol. 366/6 (2002) 331)
2008*-…3 years on ISS
- Superconducting magnet- Superconducting magnet- New detectorsNew detectors- ANTIMATTER SEARCH: He/He < ANTIMATTER SEARCH: He/He < 1010-9-9 - COSMIC RAY FLUXES up to COSMIC RAY FLUXES up to Z=26 Z=26 - DARK MATTER SEARCH
*ready for launch date
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/CO2 )3D tracks, e/h separation>102 rej. up to 300 GeV
1 m
~2 m
AMS Weight: 7 Tons
1 out of 328 Straw tube Modules
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 =~160psTrigger, Z separation, with few % precision
1 m
~2 m2 out of 4 layers
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 m3 of superfluid HeContained dipolar field: BL2 = 0.85 Tm2
1 m
~2 m Technological challenge:first superconducting magnet operating in space
B
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 detectorR(igidity)<2% for R<10 GV, R up to 2-3 TV, Z separ.
1 m
~2 m
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
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. Fiberstrigger, e, detection: E(nergy) <3% for E>10 GeV, 3D imaging: e/h separation>103 rej
1 m
~2 m
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-01e+, 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
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 11
AMS response to positrons and protons
Positron
Proton
TRD signal
X rays from transition radiation
No signal if <103 (E<300 GeV)
Rejection factor 102-103
up to 300 GeV
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 12
AMS response to positrons and protons
Positron
Proton
t~4ns, t~160psTOF ~ 1, |Z|=1,
•Reject upgoing particles
•Reject p up to 1.5 GeV
(kinetic energy)
•Reject He (|Z|=2)
TOF ~ 0.92±[email protected], |Z|=1
TOF signal
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 13
AMS response to positrons and protons
Positron
Proton
Tracker signal
Positive curvature(with TOF): Z= +1
•Charge
determination:
reject e- and He++
•Rigidity
measurement
(E/p matching):
Rigidity (GV)R
eso
luti
on in R
igid
ity (
%)
Positive curvature(with TOF): Z= +1
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 14
AMS response to positrons and protons
Positron
Proton
RICH signal
RICH ~ 1, |Z|=1,
~17° (41° at center), ~0.2°
Np.e. ~7 (4 at center)
•Reject p up to 10 GeV
(kinetic energy)
•Reject He (|Z|=2)
RICH~0.996±0.001@10Ge
V, |Z|=1
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 15
AMS response to positrons and protons
Positron
Proton
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 ~103
~16X0
~1I
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 16
AMS response to positrons and protons
Positron
Proton
ECAL+Tracker: E/p matching
E/P > 1-(TrackerECAL)/E
Tracker(E)/E = 0.05%·E(GeV) 3% (E>50GeV)
ECAL(E)/E = 12%/sqrt(E(GeV)) 2%
Radiative tail
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 17
Positron and background acceptance
Kinetic energy (GeV) Kinetic energy (GeV)
Results from a montecarlo study using discriminant analysis*
* P. Maestro, PhD Thesis, 2003
Acceptance for e+: ~0.045 sr m2 from 3 to 300 GeVRejection factor for p : ~105 **
Rejection factor for e-: ~104
** Including a ~7 flux factor improvement because <Edep>~Ekin/2 )
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(105) e+ with 10<E< 50 GeV
[ O(102) for HEAT ]
Total contamination: ~4%
Good sensitivity up to 300 GeV
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 19
Positron fraction: statistical error in 3 years
Parametrization of thestandard 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
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 20
Possible scenarios from neutralino annihiliationExample 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
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 21
More neutralino scenarios: needed boost factorsThe 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 :
• m1/2 = M1 = M2 = M3
• tan = 10
Relaxing gaugino mass universality :
•Gluino Mass : M3 = 50% m1/2
*J. Pochon, PhD Thesis, 2005
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 (B1)
— Background ( no DM)
AMS 3 years Signal with Boost adjusted on HEAT data + Bg
∆ AMS (3 years) Signal with Boost at visibility limit + Bg
Posit
ron
fra
cti
on
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(102) to fit HEAT data ~110 for discovery
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,...)
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 24
Photon detection in AMS
Photon conversion:
Direction (angle): from TrackerEnergy: from Tracker (and ECAL)
Single Photon (direct measurement)
Direction (angle): from ECALEnergy: from ECAL
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 25
Gamma energy and angular resolution
3%
6%
0.02o
~1o
Energy resolution
Angular resolution
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 26
Main backgrounds to Photons
Conversion mode
raysRejection factor: >105(p), 4·104(e)Using: TRD veto, invariant mass
Single Photon mode
Secondaries (0) from p interactionsRejection power: 5·106
Using: veto on hits, direction
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 27
Gamma acceptance and effective areaA
ccep
tan
ce
(m2.s
r)
Max Acceptance:
Conversion mode: 0.06 m2·sr
Single photon mode: 0.097 m2·sr
GeV
Field of view:
Conversion mode: ~43°
Single photon mode: ~23°
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 28
AMS-02 Exposure to from galactic center
51º latitudeRevolution : 90’
Conversion mode (sel. acc.) GC : ~ 15 days
Single photon mode (geom. acc.)GC : ~ 40 days
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
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
E2Flu
x (
GeV
/cm
2s)
* L. Girard. PhD Thesis,2004
Egret
E (GeV)
— Background— Signal— Background + Signal
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
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 : > 106 (ToF, Rich …) e- : > 103-104 TRD /Ecal Acceptance :1-16 GeV : 0.160 m2·sr16-300 GeV : 0.033 m2·sr
Main Backgrounds:
• Protons: charge confusion, interactions with the detector and misreconstructed tracks.
• Electrons: beta measurement, e/h rejection
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)
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):*
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.
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 36
Backup
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 37
Background flux calculations
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)
Local Background Flux determined by propagation of CR yield per unit volume through simulation
(GALPROP)
(m-2 s-1 sr-1 GeV-1) = φbg + φsignal
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) = φbg + φsignal
CR yield per unit volume (r,z,E) ≡ gann(E).*<σv>*(ρχ(r,z) /mχ)2
WMAP (+…) constraints on h2
<σv> ≡ coannihilation cross-section
Rotational velocity measurements
ρχ(r,z) ≡ density distribution
DM density profile shape
(+ “boost factors*”)Accelerator constraints
Boost factors: clumpiness,cuspiness, baryon interaction, massive central black hole…
gann(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
mχ ≡ neutralino mass
ASTROPHYSICS
HEP
(propagation model and parameters …)
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 39
Indirect Search: neutralino annihilation
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 mX
•should be compatible with DM Relic Density
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)
Charged:
Gamma:
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 41
Antideuterons
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
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 105 discrimination - mass resolution is crucial!
tertiary component
TOA flux prediction is even less optimistic
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:
• 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) )
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 45
Positron fraction after 3 years: AMS and PAMELA
AMSPAMELA
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
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 RICHRigidity(R): from Tracker and MagnetVelocity(): from TOF and RICH
Mass and Charge
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 48
Gamma detectors in space
La Thuile, March 2006 S. Di Falco, Indirect dark matter search with AMS-02 49
AMS response to positrons and protons
Positron
Proton
TRD signal
X rays from transition radiation
No signal if <103 (E<300 GeV)
Rejection factor 102-103
up to 300 GeV
t~4ns, t~160psTOF ~ 1, |Z|=1,
•Reject upgoing particles
•Reject p up to 1.5 GeV
(kinetic energy)
•Reject He (|Z|=2)
TOF ~ 0.92±[email protected], |Z|=1
TOF signal Tracker signal
Positive curvature(with TOF): Z= +1
•Charge
determination:
reject e- and He++
•Rigidity
measurement
(E/p matching):
Rigidity (GV)R
eso
luti
on in R
igid
ity (
%)
Positive curvature(with TOF): Z= +1
RICH signal
RICH ~ 1, |Z|=1,
~17° (41° at center), ~0.2°
Np.e. ~7 (4 at center)
•Reject p up to 10 GeV
(kinetic energy)
•Reject He (|Z|=2)
RICH~0.996±0.001@10Ge
V, |Z|=1
ECAL signal ECAL+Tracker: E/p matching
E/P > 1-(TrackerECAL)/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 ~103
~16X0
~1I
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. Fiberstrigger, e, detection: E(nergy) <3% for E>10 GeV, 3D imaging: e/h separation>103 rej
TRD (Transition Radiation Detector):20 layers of Foam + Straw Drift Tubes (Xe/CO2 )3D tracks, e/h separation>102 rej. up to 300 GeVTOF (Time of Flight): 2+2 layers of scintillators, t =~160psTrigger, Z separation, with few % precisionSuperconducting Magnet: Nb-Ti coils in superfluid He(1.8 K). Contained dipolar field: BL2 = 0.85 Tm2
Tracker:8 layers double sided silicon microstrip detectorR(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