indirect dark matter search with ams-02

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?


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


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


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


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


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


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


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


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


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



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



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 (

%)




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)


RICH~0.996±0.001@10Ge

V, |Z|=1



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



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


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 )


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


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


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


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


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


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,...)


Photon detection in AMS

Photon conversion:

Direction (angle): from TrackerEnergy: from Tracker (and ECAL)

Single Photon (direct measurement)

Direction (angle): from ECALEnergy: from ECAL


Gamma energy and angular resolution

3%

6%

0.02o

~1o

Energy resolution

Angular resolution


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


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°


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


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


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


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


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


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)


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):*


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.


Backup


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


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 …)


Indirect Search: neutralino annihilation


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:


Antideuterons


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


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


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) )


Positron fraction after 3 years: AMS and PAMELA

AMSPAMELA


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


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


Gamma detectors in space



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)


TOF ~ 0.92±[email protected], |Z|=1

TOF signal Tracker signal


•Charge

determination:

reject e- and He++

•Rigidity

measurement

(E/p matching):

Rigidity (GV)R

eso

luti

on in R

igid

ity (

%)


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)


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


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

indirect dark matter search with ams-02

Documents

years ams

e flux

collecto105 e

geve e

spacethe ams detectortracker

indirect dark matter

inhomogenous dark matter

dark mattererrors