astroparticle physics with ams-02deboer/html/talks/paris_short.pdf · july, 20. 2004 cospar, paris,...

July, 20. 2004 COSPAR, Paris, W. de Boer, Univ. Karlsruhe 1

Astroparticle Physics with AMS-02

AMS: Alpha Magnetic Spectrometer

2007/2008

Wim de Boer

on behalf of the AMS collaboration

University of Karlsruhe


Outline

• Physics Motivations

• Detector requirements

• Prospects for Indirect Dark Matter searches

• Conclusions


AMS Physics motivations

• Search for cosmic anti matter

• Search for Dark Matter

• Precision measurement on cosmic rays

• Gamma ray astrophysics

AMS will collect ~10AMS will collect ~101010 Cosmic Rays Cosmic Rays ((e±, γ , p±,3,4He,B,C, 9,10Be, elements Z<25 in Nearin Near--Earth Orbit from Earth Orbit from few GV to few TVfew GV to few TV

Reg

ion

of

antim

atte

r


AMS-02 Particle Identification


WMAP determines WIMP annihilation x-section

Neutralino annihilation is a strong source of antiprotons, positrons and gammas by annihilation into quarks.

Thermal equilibrium abundance

Actual abundance

T=M/25

Com

ovin

g nu

mbe

r den

sity

x=m/T

T>>M: f+f->W+W; W+W->f+fT<M: W+W->f+fT=M/25: W decoupled, stable density(wenn annihilation rate < expansion rate, i.e. Γ=<σv>nχ < H !)

Jung

man

n,K

amio

nkow

ski,

Grie

st, P

R 1

995

Boltzmann equation:H-Term takes care of decrease in density byexpansion. Right-hand side:Annihilation and Production.

Present number density requires <σv>=2.10-26 cm3/s


Neutralino Annihilation Final States

B-fragmentation well studied at LEP!Yield and spectra of positrons,gammas and antiprotons well known!

BDominant Diagram for WMAPcross section:χ + χ ⇒ A ⇒ b bbar quark pair


Excess of Diffuse Gamma Rays above 1 GeV

Prel.A B C

D E F

Stro

ng, M

oska

lenk

o, R

eim

er, t

o be

pub

lishe

d

A: inner Galaxy (l=±300, |b|<50)B: Galactic plane avoiding AC: Outer Galaxy

D: low latitude (10-200)

E: intermediate lat. (20-600)F: Galactic poles (60-900)


Local electron and proton spectradetermine shape of gamma background

Solar modulation by solar winds important below few GeV


Excess of Diffuse Gamma Rays same in all directionsand compatible with neutralino mass of 50-100 GeV

Important: if experiment measures gamma rays down to 0.1 GeV, then normalizations of DM annihihilation and background can both left free, so one is not sensitive to absolute background estimates, BUT ONLY TO THE SHAPE, which is much better known.


Diffuse Gamma Rays for different sky regions

A B C

D E F


Longitude and latitude profiles

NFW profile

Isothermal Profile +disc enhancement

NFW profile excluded, isothermal profile perfect as expected often from rotation curves,see e.g. Jimenez, Verde and Oh, astro-ph/0201352. Asymmetry determines halo ellipticity.


Halo profile

x

z

y

ab

c

(α,β,γ) − define the slope ρ0 - local density 0.3-0.7 GeV/cm3

a -scale parameter (depends on ρ0) Isothermal profile: α,β,γ,a = 2,2,0,4

Ellips: x2/a2 +y2/b2 + z2/c2 = c

Isothermal core

NFW cusp

W. de Boer et al., to be published


EGRET excess interpreted as DM consistent withWMAP, Supergravity and electroweak constraints

0

WMAP

EGRET

Stau coannihilation

mAresonance MSUGRA can fulfill

all constraints from WMAP,LEP, b->sγ, g-2 and EGRET simultaneously, if DM is neutralino with massin range 50-100 GeV and squarks and sleptons are O(1-2 TeV)


Positron fraction and antiprotons from DM annihilation

SAME Halo and MSSM parameters as for GAMMA RAYSbut signal strong function of propagation model!

Positrons AntiprotonsAntiprotonsPositrons


Propagation in GALPROP compared with DarkSusy:LARGE DIFFERENCE

Spectrum after propagation of injection of 1-3 GeV source with NFW profilein DarkSusy (analytical solution of diffusion equation l) and GalProp (numericalsolution of diffusion equation including all physical effects, like reacceleration)

Antiprotons Positrons


Propagation models

Propagation model:- describes propagation (diffusion, convection, reacceleration) of cosmic

ray particles in galaxies- calculates nuclear interaction of primary produced particles with interstellar medium (ISM) Predicts abundances of element. Estimates backgrounds.

- considers local modulation effects, solar modulation.


Diffusion equation

Particle density:

Source function: with

Diffusion coefficient:

Convection velocity:Diffusive reacceleration:Momentum loss rate:Radioactive decay:Fragmentation:

GALPROP program by Moskalenko and Strong provides numerical solution to this diffusion eq. for equilibrium taking into account particle densities of ALL nuclei.


AMS-02 capabilities

BoronBeryllium Helium

1 year 1 day6 months1 year 6 months 1 day

10Be (t1/2=1.5Myr) / 9Bewill allow to estimate thepropagation time andsize of the ISM

B is secondary produced in nuclear interaction, C is primary produced in stars. B/C is sensitive tothe diffusion constant

3He/4He ratio is sensitive to the density of the ISM


AMS02 : detector performanceAMS02 : detector performance

Acceptancesdefined by selection cuts during reconstruction Antiprotons:

A(<16 GeV) ∼ 1200cm 2sr>16GeV ∼ 330 cm 2

Rejection e- ∼ 10 4p ∼ 10 6

Preliminary

Positrons:

Acceptance ∼ 550 cm 2 srRejection e- ∼ 10 3

p ∼ 10 5

Gamma (ECAL mode):Acceptance ~ 600 cm 2 srRejection e+ - ~ 10 4

p ~ 10 5

Gamma (Conversion mode):Acceptance ~ 550 cm 2 sr


Expected statistics after oneyear of AMS-02 operations


Summary

AMS is a High Energy Physics detector in space foreseen to operate on the ISS for 3 years

Complete detector in 2006

The cosmic rays, including gamma rays, will be measured with a high accuracy from the GeV to the TeVrange

Unique opportunity to perform Dark Matter searches

astroparticle physics with ams-02deboer/html/talks/paris_short.pdf · july, 20. 2004 cospar, paris,...

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