Antimatter in the Universe constraints from gamma-ray ... · PDF filethe invention of antimatter ! 1930 : Paul Dirac predicts the "antielectron"!! "Quantum Theory of the Electron"

Antimatter ?!!

Positron Astrophysics!!- direct detection : in-situ measurements!!- indirect detection : e-e+ annihilation radiation!

Nuclear Antimatter and the Baryon Asymmetry !!- the "matter trail" from us to clusters of galaxies !!- antimatter in a high redshift Universe!

What's next in Antimatter Astronomy ?!!- a mission concept for a CGB telescope!

!

!

Peter von Ballmoos, IRAP Toulouse!

Antimatter in the Universe!constraints from gamma-ray astronomy !

star trek!the invention of antimatter ?!

the invention of antimatter !

1930 : Paul Dirac predicts the "antielectron"!!"Quantum Theory of the Electron" !

basic notion in a nutshell!total energy : E !impulse : P= pc!mass : M=mc2!

special relativity : E2 = P2 + M2 !!!

=> two solutions E = ± !

€

P2 +M 2E!

Antimatter ?!

two solutions E = ± ! P2 +M 2

energy levels of the electrons!

moc2!

-moc2!

0!

energy!

Dira

c se

a!

e-!

Antimatter ?!

two solutions E = ± ! P2 +M 2


moc2!

-moc2!

0!

energy!

Dira

c se

a!

vacuum!

Antimatter ?!

e+e pair production!


energy!

Dira

c se

a!

moc2!

-moc2!

0!

e+!

e-!

e+ : hole in the Dirac sea!

in quantum electrodynamics (QED, Feynman)!!!!!!!!!!!!!e+e- pair production !! !e+e- annihilation!

e+ : e- moving backwards in time!

Antimatter ?!

the discovery of antimatter!

p!

p!

high energy e+!

low energy e+!

direct detection! indirect detection!

Positron Astrophysics!

Positron Astrophysics!

Ee+ > 1 GeV!- direct / indirect detection!- e+ fraction over the years ...!- "PAMELA anomaly"!- scenarios for the e+ anomaly!

AMS-02!

direct detection! indirect detection!

Ee+ < 1 MeV!- legend of the "great annihilator"!- todays annihilation sky!- e+ sources, transport,annihilation!- experimental perspectives !

Pamela! Compton-GRO! INTEGRAL!

direct positron detection : the typical e+ and e- instrument!!need of a magnet spectrometer for e+ and e- separation!

Magnet Spectrometer !

Transition Radiation Detector (TRD) or Gas Cherenkov!

Time of Flight (ToF)!

EM Calorimeter!

direction & charge!

e / hadron discrimination !

rigidity / charge sign !

energy & !shower shape!

adapted !from M. Schubnell !

U. Michigan!

need for efficient proton rejection : !the flux of CR protons in the energy range 1 – 50 GeV !exceeds that of positrons by a factor of >104!!!

direct positron detection : the e+ fraction !!High energy positrons (Ee+ > 1 GeV) are observed in cosmic rays!

expected at this level from decays following p+p collisions, but ...!

x 10! electrons!

positrons!

1960 !

1970 !

1965 !

Positron fraction : early balloon experiments!e+

e− + e+

0.01

0.1

1

0.1 1 10 100

De Shong (1964)Fanselow (1969)Agrinier (1969)

pois

itron

frac

tion

E [GeV]

positron fraction ≈ 0.1!!consistent with expectations !assuming production in interstellar space by cosmic rays encountering !4 g/cm2 of material! De Shong, Hildeband, Meyer, !

Phys. Rev. Let. 12 (1964)!

1970 !

1980 !

1975 !0.01

0.1

1

0.1 1 10 100

De Shong (1964)Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)

pois

itron

frac

tion

E [GeV]

Positron fraction : early balloon experiments!e+

e− + e+

! !

challenges :!- proton contamination!- low statistics (small Aeff, short flights)!- atmospheric positrons!- inter-comparisons (at low E) difficult because of!

!- cutoff rigidity! !- solar modulation/activity!

!!!!!!!!!!!!

Buffington, Orth, Smoot, 1974!

!!!!!!!!!!!!MASS!

0.01

0.1

1

0.1 1 10 100

De Shong (1964)Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)

pois

itron

frac

tion

E [GeV]

1980 !

1990 !

1985 !

Positron fraction : an increase > 10 GeV ?!e+

e− + e+

Müller and Tang (1987) : "This increase appears to suggest that either a primary component of positrons becomes significant above 10 GeV or that the spectrum of primary negatrons decreases above 10 GeV more sharply than that of secondary positrons."!

model for CR induced !secondary e+ !(Moskalenko & Strong 98) !

0.01

0.1

1

0.1 1 10 100

De Shong 1964Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)

pois

itron

frac

tion

E [GeV]

1990 !

2000!

1995 !


e− + e+


proton contamination ?!

HEAT particle ID !

(redundancy)

0.01

0.1

1

0.1 1 10 100

De Shong 1964Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)HEAT2000 - Beatty (2004)AESOP 2000,02,06 Clem & Evanson

pois

itron

frac

tion

E [GeV]

2000!

2010!

2005!


e− + e+

MASS (Golden 1996) : ... measurements do not show any compelling evidence for an increase in this ratio with energy, and our results are consistent with a constant fraction of 0.078 ± 0.016 over the entire energy region."!HEAT (Beatty 2004) : "... a primary contribution to the !positron intensity above a few GeV can still not be ruled out."!


2000!

2010!

2005!0.01

0.1

1

0.1 1 10 100

De Shong 1964Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)HEAT2000 - Beatty (2004)AESOP 2000,02,06 Clem & Evanson PAMELA 2006-08 Adriani(2009)

pois

itron

frac

tion

E [GeV]

Positron fraction : + PAMELA!e+

e− + e+

1.6.105 e-and e+ detected!151672 e-and 9,430 e+ identified!

=> flood of articles attributing the e+ excess! !to the decay or annihilation of DM!!=> excess of papers denying the !

!need for an explanation in terms of DM!!

0.01

0.1

1

0.1 1 10 100

De Shong 1964Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)HEAT2000 - Beatty (2004)AESOP 2000,02,06 Clem & Evanson PAMELA 2006-08 Adriani(2009)FERMI 2008-11 Ackermann(2012)

pois

itron

frac

tion

E [GeV]

2005!

2015!

2010!

Positron fraction : + FERMI!e+

e− + e+

confirmation of the "PAMELA excess"!!(FERMI LAT is a !γ-ray telescope!without a magnet !on-board …!it identifies e+/e- !

using the earth B !)!!!

0.01

0.1

1

0.1 1 10 100

De Shong 1964Fanselow (1969)Agrinier (1996)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)HEAT2000 - Beatty (2004)AESOP 2000,02,06 Clem & Evanson PAMELA 2006-08 Adriani(2009)FERMI 2008-11 Ackermann(2012)

pois

itron

frac

tion

E [GeV]

2005!

2015!

2010!0.01

0.1

1

0.1 1 10 100

De Shong (1964)Fanselow (1969)Agrinier (1969)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)HEAT2000 - Beatty (2004)AESOP 2000,02,06 Clem & Evanson PAMELA 2006-08 Adriani(2009)FERMI 2008-11 Ackermann(2012)AMS02 2011-12 Aguilar(2013)

pois

itron

frac

tion

E [GeV]

Positron fraction : + AMS02!e+

e− + e+

6.8.106 positrons and electrons detected!


Aguilar 2013 : "... positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena."!

0.01

0.1

1

0.1 1 10 100

De Shong (1964)Fanselow (1969)Agrinier (1969)Buffington (1975)Daugherty (1975)Golden (1987)Muller and Tang (1987)MASS89 - Golden (1994)AESOP 94, 97, 98, 99 Clem & Evenson MASS91 - Grimani (2002)TS93 - Golden (1996)CAPRICE94 - Boezio(2000)CAPRICE98 Boezio(2001)HEAT94-95 - Barwick (1997)AMS01_98 Aguilar(2007)HEAT2000 - Beatty (2004)AESOP 2000,02,06 Clem & Evanson PAMELA 2006-08 Adriani(2009)FERMI 2008-11 Ackermann(2012)AMS02 2011-12 Aguilar(2013)

pois

itron

frac

tion

E [GeV]

2005!

2015!

2010!

Positron fraction : the state of the art!e+

e− + e+

AMS-02!

Fermi!Aeff : ~ 1 m2 !2789 kg!2.3 m3!

Aeff : 6.5 m2!

8500 kg!64 m3!

Pamela!Aeff : 21.5 cm2 sr !470 kg!0.64 m3 !


"anomaly" ?!with respect to what ?!!=> models for CR induced ! secondary positrons !

secondary positrons from interactions in the Interstellar Medium!

e!+!-!

Sources:!SNRs, Shocks,!Superbubbles!

Particle acceleration!Photon emission! P!

He!CNO!

X,γ!

gas!

gas!

B!

ISRF!

π!

e!+!-!

+!-!

P!_!

LiBeB!

ISM!

π!0!

synchrotron!

IC!

bremss!

Newton!Chandra!

FERMI!

ACE!BESS!

Halo!

disk!

escape!

He!CNO!solar!

modulation!

AMS!

diffusion! fragmentation ! energy losses ! reacceleration! convection!

INTEGRAL!

adapted from Moskalenko, 2004 !

P,e+!

A local origin for the "excess" positrons ?!

anisotropy expected from a local source!If the excess has a particle physics origin, it should be isotropic!

AMS-02!Fermi!Pamela!

Drlica-Wagner, 2011!Giaccari, 2012! AMS collaboration, !ICRC 7/2013!

no significant anisotropy found in either data !!

Andromeda (GALEX)!- γ-rays converting into e-e+ pairs in the vicinity of the magnetic poles of pulsars !- decay of radioisotopes within a cosmic accelerator (supernova remnant)!- dark matter particles annihilating in the galactic halo ...!!

- or a revisited model for the production/propagation of secondary e+ ...!!

Scenarios for the e+ "anomaly"!

illustration by Coutu 2013!

indirect positron measurements!

Low energy positrons (Ee+ < 1 MeV) observed through the !gamma-rays they produce when they annihilate!!

!- the legend of the "great annihilator"!!- todays annihilation sky!!- imaging, spectroscopy!!- candidate positron sources!!- positron transport and annihilation!!- experimental perspectives !

1960 !

1970 !

1965 !

the galactic e+ are already in the data …!

511

keV!

Observation of Hard Radiation from the Region of the Galactic Center !Haymes, Ellis, Fishman, Glenn, Kurfess, ApJ. 157, 1969!

the early years : balloon astronomy!

1970 !

1980 !

1975 !

balloone borne Ge detectors solve the puzzle :!!

a narrow annihilation line !at 510.7±0.3 keV and an orthopositronium continuum!!

Johnson et al, 1972!!

473 keV feature a!radioactive isotope ?!

Leventhal, !MacCallum!& Stang, 1978 !

variability ?!

SMM !

1980 !

1990 !

1985 !

HEAO

3 !

b) SPRING 1980!a) FALL1979!

SMM 1980-1989!no variability needed!!Flux511 ~ FOV!=> 2 component model!diffuse disk+compact GC!!

Lingenfelter & Ramaty, 1989!Share et al.,1988 & 1990 !von Ballmoos, 1991!!

SMM 1980-85!

Figaro 88!

variability !!

1990 !

2000!

1995 !

the great annihilator is back !!SIGMA observes an outbreak of the galactic center source 1E 1740.7-2942!broad, redshifted annihilation line!

no variability!!=> no need for !a "great annihilator"!Purcell et al 1997!!

SIGMA!

OSSE`!

a first e+e- skymap … !and an "annihilation fountain"!

CGRO-OSSE!

2000!

2010!

2005!

INTEGRAL SPI!!

the first 511 keV all-sky map!first year of INTEGRAL data, !!

Bulge : 2D Gaussian ~ 8o x 7o FWHM!Bulge/Disk = 1-3!!

no point sources!no fountain!no other sources!!!!!!!!!!!Knödlseder et al. 2005!!!

2003!

2013!

2008!

status (in a nutshell) : total flux ~ 2 . 10-3 γ/s/cm-2 !

morphology ! !!!!!!!!!!

!!!!narrow bulge, wide bulge, disk bulge / disk = 1-3!slight asymmetry !!

no point sources, !no fountain, !no other source regions!!!

spectroscopy!!!!!!!!!!

!positrons annihilate!in warm phases!

!!!=> we need to explain!2.1043 annihilations s-1!

at the Galactic Center!!!

!!

Skinner et al. 2011!

warm neutral!

warm ionized!

Jean et al. 2005!

The origin of the galactic e+ : two grand families!

Cosmic accelerators !production of e-e+ pairs !!!

Accretion on compact objects !

Rotating neutron stars!

Explosions and shocks!

Binaries!Micro-quasars!

!

gamma-ray bursts!supernova remnants!

Interaction CR/ISM!

Pulsars!Magnetars!

!

gravitationnal collaps!SN type II (Core-collapse)!

gamma-ray burst!

thermonuclear exlosions!SN de type Ia!

Thermonuclear runaways!Novae

X-ray bursters!

Cosmic Explosions!radioactive decays!!

!

+ "light" dark matter ...!

Gerry Skinner, 2010!

1)  Cosmic Ray models only predict 1-2 x1042 e+ s-1 while a flux of 10-3 photons of 511 keV s-1 cm-2 implies an annihilation rate of 1-2 x1043 low energy e+ s-1 !

2)  High energy positrons are likely to escape from the Galaxy before slowing!

3) !HE positrons can annihilate in flight (IA), producing a gamma-ray continuum in the 1-10 MeV range. However, gamma-ray observations (i.e. COMPTEL) constrain the maximum energy of the injected e+ to < 4-10 MeV. (e.g. Beacom and Yüksel (2006) and Sizun et al (2006) !

4) !Most of all : there are more than enough ways in which positrons injected at MeV can explain the observed 511 keV flux …!

!

Are "our" directly detected e+ at the origin !of the 511 keV annihilation radiation ? probably not :!

What are the positron sources ?!

Production!

Annihilation!

Escape from the galaxy ?!

Slowing!

down!

Annihilation in flight ?!Escape local !environment!

We are NOT observing e+ sources ! !

supposed!"real world"!

observed!511 keV !skymap!

e+ source!

optimal!annihilation!conditions!

e+ slowing time! ∞!0!

How far do the positrons travel before they annihilate ?!


supposed!"real world"!


e+ source!



How far do the positrons travel before they annihilate ?!


How far do the positrons travel before they annihilate ?!supposed!"real world"!


e+ source!




Candidate sources and Constraints ! (Prantzos et al 2011)!

44!

What we need ?!

What part of the sky has to be observed ? all the sky / the GC region!!Which angular resolution do we need ? 0.1-0.5° / 2-3° !!Which energy resolution do we need ? 0.5 % / a few % is enough!!What sensitivity ? 2.10-6 s-1.cm-2 / 10-5 s-1.cm-2!!!

!!!!

not better !!

sens

itivity

[ph/

cm2 s

1 ]!

!

?!!

total galactic 511 keV flux!

the evolution of detector sensitivity in the 511 keV line!

Des mondes d'antimatière ?!

E = mc2

in the Big Bang equal quantites of matter and antimatter are created in case of symmetry between particles and antiparticles, (almost) all this this matter and antimatter should have annihilated ...

Nuclear Antimatter and Baryon Asymmetry!

predicted Big Bang freeze out density for antinucleons !

T ≥ 1 GeV !!!!at T < 20 MeV < 1 GeV !!!!at T < 20 MeV !annihilation rate < expansion rate of universe!=> antinucleons “freeze out” of thermal equilibrium !!

the expected relic baryon to photon density ratio η is!

η ≡nBnγ

≈nBnγ

≈10−18

nγ ≈ nq ≈ nq ~ T3_

nγ ~ T3nN ≈ nN ≈ (Tm)

3/2e−m/T_

Sakharov (1967)!

Baryon Number Violation! !!

!obvious : B=0 (T >> 1 MeV) ! B≠0 (T ~ 3.10-4 eV)!

!Violation of C and CP! !!

!K°L physics (~ 10-3 effect)!!Departure from thermal equilibrium! !!

!Universe expands and cools off with time !!this is a departure from thermal equilibrium.!

!

In the hot primordial Universe (kT >> mnc2), fermions and radiation were in equilibrium; the number densities of baryons, antibarions and photons was .!!

After feeeze-out (T < 1 GeV), the !baryon density to photon number !density ratio η becomes!!!!the cosmic expansion lets this ratio invariant!(nB ~ T3, nγ ~ T3) and since !

η ≡nB − nBnγ

η ≡nB − nBnγ

≈nBnγ

Temperature of CMB ! nγ,0 ≈ 410 cm-3!!

!nb,0 ≈ 0.25.10-6 cm-3!

nB ≅ nB ~ nγ

nB ≅ 0

≈0.25 ⋅10−6

412≈ 6 ⋅10−10 nbvis,0 ≈ 0.03.10-6 cm-3!

~0.5 % of Ωcrit!

fit of CMB powerspectrum!

~ 4% of Ωcrit!

observed Baryon Asymmetry!

mater-antimatter asymmetry !

1,000,000,003 1,000,000,000

€

q

€

q

matter + antimatter " hν#Big-Bang : hν " matter + antimatter!

3! . (us)

baryon / anti-baryon asymmetry : nB << nB << nγ!_

(slide by A. Cohen, 1999)!

Baryon Asymmetry – an initial condition ?!

Is there antimatter in the Universe ?!

probe the presence of antimatter through!ordinary matter with the resulting !annihilation gamma-rays providing indirect evidence.!!e+e- annihilation provides a clear feature, but as most common !and easily produced form of antimatter, e+ are too ubiquituous => p!!on what scale ?!!!! !!=> gamma-ray astronomy !!!how much baryonic antimatter do gamma-ray observations allow ?!!

- antimatter fraction or filling factor allowed!- possible structure or anisotropies!!!!!

-!

spontaneous magnetization of ferromagnetic material!

When cooled below the Curie temperature, the magnetization of a piece of ferromagnetic material spontaneously divides into magnetic domains, each of which has its own randomly determined direction of!magnetization. !The original symmetry is reflected by the fact that there is no overall preferred direction of magnetization.!

gamma rays from nucleon-antinucleon annihilation !

typical rest-frame spectrum produced by p-p annihilation !with π° decay!!maximum intensity at !mπc2/2 ~ 70 MeV!

N − N→π 0 → γ +γ

π±→ µ± +νµ (νµ )

π±→ e± +νe(νµ )+νµ (νµ )

1/2 of 2mNc2 ! ν's !!

1/6 of 2mNc2 ! e-, e+ (100 MeV) ! !

!

1/3 of 2mNc2 200 MeV γ's!→

→

→

3-year differential sensitivity for an isolated point source! !minimum flux above 100 MeV to obtain a 5σ detection in 3 years (assuming a power law spectrum α=-2)!

x 10-9 ph cm-2 s-1!

the components of the diffuse high-energy spectrum and the Isotropic Diffuse Gamma-Ray Emission!!gamma rays (100 MeV) do not provide a unique signature for AM annihilation.!!=> upper limits to the annihilation rate !

FERMI : point sources sensitivity and diffuse background!

a "matter trail" from the solar system to clusters of galaxies!

solar system!micro-meteorites and solar wind particles are continuously bombarding the earth without causing annihilation radiation. Aproximating the a solar wind flux with! , one can roughly estimat the annihilation radiation from an anti-planet :!!

! ! ! ! !r,d : radius, distance of anti-planet!!

example : !Jupiter (r= 7.107 m, d=7.1011m) : Fγ≈1 ph cm-2 s-1!! !FERMI features ~10-8 ph cm-2 s-1 sensitivites!

!

!stars!In the Fermi-LAT point-source catalog (2FGL) about a third, i.e. 576 sources are lacking reliable association with sources detected in other wavelength bands. Bondi Hoyle accretion of galactic gas onto an anti-star would produce detectable 100 MeV fluxes out to at least 150 pc (FERMI) corresponding to ~ 2.106 stars!=> antimatter fraction fAM ≤ 4.10-5!

!!!!

Fγ (100MeV ) ≈108(r / d)2 ph cm−2 s−1

nv ≈ 2 ⋅108(d /1AU)−2 cm−2 s−1

a "matter trail" from the solar system to clusters of galaxies!!galactic gas!!the observed diffuse galactic gamma ray flux (well exlained by CR interaction) limits the antimatter fraction fAM ≤ 10-15 !!!!!!!!!!!the argument can obviously be extended as long as a sufficiently dense matter trail extends out to the next bigger structure ... !!!!

galaxy cluster Abell 2029 !

X-rays (Chandra)! optical (DSS/Palomar)!

f = nB / nB

Fγ ∝fTGas

nB2dV4πR2∫

FX ∝ TGasnB2dV4πR2∫

In galaxy clusters the majority of the baryons are in the hot intracluster gas.!=> we detect the X-rays produced through thermal bremsstrahlung!!

For antibaryons mixed with baryons at a ratio!!

!=> high energy γ-rays from pp annihilation ! !occuring in the same!two-body collisions that produce x-rays!!!see e.g. Steigman 1976!


hot intracluster gas - constraints from HE gamma-rays!

f ≤ const ⋅TGasFγFx

GeV γ-ray flux upper limits :!!EGRET!Reimer et al, 2003 !!!!!!!!Steigman 2008 !

FERMI!Ackerman et al, 2010!extrapolated down to 100 MeV!!!!

!

adapted from!



Bullet Cluster (dist 1.14 Gpc) !X-ray : Chandra !optical : Magellan and HST!lensing : Magellan / ESO!

1 Mpc!

dynamical state of the system => clusters were initially separated by ~ 20 Mpc!!

=> matter/antimatter domains ≥ tens of Mpc!

colliding clusters of galaxies (relative speed ≈ 4700 km/s)!

f ≤ const ⋅TGasFγFx

= const ⋅14keV 5.3⋅10−9 ph cm−2s−1

4.7 ⋅10−12erg cm−2s−1≅ 5 ⋅10−7

Fermi !!



Annihilation radiation from the boundaries of matter-antimatter regions, emitted in the early Universe before - and/or - after recombination.!!Stecker et al. (1971) solved the cosmological photon transport equation accounting for pair production and Compton scattering at high z.!!!!Cohen, De Rújula, and Glashow (1998) propose to combine gamma-ray constraints with the fact that CMB is highly uniform!!

=> redshifted gamma-ray "bump" above ~ 1 MeV!!!

antimatter at high redshifts!

...!

D!!!!!what domain-size D is compatible with the observed MeV gamma-ray sky ? !

Cohen, De Rújula, and Glashow (CDG,1998) propose to!combine gamma-ray constraints with the fact that CMB is highly uniform!

antimatter domains and the diffuse gamma-ray background !

Cohen, De Rújula, and Glashow (CDG,1998) propose to combine gamma-ray constraints with the fact that CMB is highly uniform.!CMB density fluctuations <10−4 at scales larger than 15 Mpc imply that – if existing - matter and antimatter domains must have been in close contact :!!t=3.8.105 y !recombination!z≈1100 !n and n must have been uniform!!

! ! !=> !annihilation at domain boundaries is inavoidable!! !=> !drop in pressure in the annihilation region!! !=> !matter and antimatter flow into this region!! !=> !annihilation due to flow of n and n into combustion zone !

!t=3 Gy !Structure formation!z ≈ 20 !n and n separate !

! !=> !further annihilation uncertain (-> ignored)!! !=> !the spectrum of photons continues to evolve dur to the!! ! !expansion of the universe as well as subsequent scattering!

!t=13.8 Gy !today ! ! ! ! !!z=0 ! !=> calculated γ-ray spectrum shifted from 100 MeV -> 1 MeV!!

antimatter domains and the diffuse gamma-ray background !

Cosmic diffuse X- and Gamma-Ray Background!

!COMPTEL (Weidenspointner and Varendorff 2001)!!- no MeV bump!!- transition from a softer to a harder component at ~ 5 MeV!!- no deviation from isotropy within statistics!!!

COMPTEL !

Cohen, De Rújula, and Glashow (1998) !

it's only a model!

Sy1!

Sy2!

FSRQ !

superposition of spectra from various classes of unresolved point sources!=> no need for antimatter domains with sizes D ≈ the observable Universe !

3C273!

FSRQ : Flat Spectrum Radio Quasar !

MeV background and unresolved AGN's!

3C273!

Cen-A!

a dedicated MeV background satellite detector ... !

"In the present search for cosmological antimatter, !absence of evidence is not necessarily evidence of absence. !A dedicated MeV background satellite detector experiment designed to be as clean from radiation induced intrinsic contamination as possible would help to clarify the situation."!!

"The satellite should be light-weight and contain only the MeV detector and no other experiments in order to minimize the mass in which cosmic rays can induce intrinsic MeV photon production. It should be also flown in a region far from the Earth’s radiation belts, since such radiation induces intrinsic MeV photon production within the satellite and detector." !! Stecker 2003!!

... a dedicated MeV background satellite detector !!

modeling of the instrumental background!! !facilitated by the minimal passive matter, low stable and stable BG !!

subtract foreground emission!! !this is the signal for galactic / extragalactic HE astronomers !!

multipole analysis of the Cosmic Diffuse Gamma Ray background!! !search for domain boundaries !! !and/or constrain antimatter fraction contained in the early Universe!! !

!concept!equivalent to the !

early CMB multipole analysis!

which telescope for the MeV (antimatter) astronomy !

grazing!incidence!!

mirror!telescopes!

UV!sub-mm/IR!

Cherenkov!

water !

air !

radio!

coded apertures!! pair production!

tracking!total external reflection!

x-rays!

MeV!astronomy!

g a m m a - r a y s !

Compton!scattering!

Instrument concepts in gamma-ray astronomy!

The instrumental categories in nuclear astrophysics reflect our current perception of light itself.!!

geometric optics!absorption!

quantum optics!incoherent scattering!

wave optics!coherent scattering!

dete

ctor

a

pertu

re!

ex. !coded masks!! !"on-off" collimators!

ex. !Compton telescopes!! !tracking chambers!

ex. !Laue lenses!! !Fresnel lenses!

e.g. first 26Al all-sky map !

Compton Telescopes ! ! ! GRO/ COMPTEL!

The Catch 22 of Compton Telescopes!

MEGA (2002/05)!DLR study!#

Aeff ≈ 100 cm2!

!!

ACT(96-05)!NASA studies!!Aeff ≈ 1000 cm2!

!!!Sensitivity aim : 1.2.10-6 cm-2s-1 !

(broad lines in 106 sec)!main science driver : SN1a!!Mission mass / cost : 4 T / 760 M$!Feasibility of 1m3 of solid state det.!!

… little or no success in the last decade in moving ACT forward as a real mission, despite all the hard work on the ACT concept study …# !!

+#

�#

Mission mass / cost : 1 T / < 200 M$!science drivers : radioactivities, blazars,!GRB, polarization …!!

Sensitivity : 4.10-6 cm-2s-1 !(broad lines in 106 sec)!!

Prototype demonstrated feasibility - !despite very good survey sensitivity, !falls short of detecting the capital SN1a# #!! !!

ACT class – tons, complicated, expensive !

MEGA class – lacks sensitivity!

!all sky Compton imager

- design considerations for Compton Telescopes!- the asCi choice - detector and mission concept!- performance estimates!!!

Time of Flight coincidence - COMPTEL data!

<- upward downward ->!COMPTEL calibration data!!channel width : 0.25 ns!distance D1-D2 : 1.5 m ≈> 5 ns)!

<- upward downward ->!COMPTEL flight data!!channel width : 0.25 ns!�upward BG� from spacecraft and the Earth!

ground Neuherberg! in orbit!

Background reduction : TOF option!

! TOF ?!!

TOF!

low earth orbit!

ground Neuherberg!

Background reduction : shield option!

low earth orbit!

ground Neuherberg!

Background reduction : solid angle option!

S/C!

low earth orbit!

go to L2 !

detector !on boom!

ground Neuherberg!

trans-Earth coast!!!

detector : !NaI - 7 cm, 7 cm Ø !!

plastic veto!!

inboard : on spacecraft (Wsc = 2π)!extended position (boom, 7.6 m) !!!!!!!solid angle ratio Wsc/Wb!s/c seen in extended position (Wb~0.28 sr) !!

=> Wsc/Wb ≈ 20!!

onboard BG (bsc + br)/5 = (bsc/20) + br !!!

=> ! br/bsc ≈ 0.2 !!!!

Apollo 15 background spectrum!

!

aNCT!

Compton camera ! !!!

characteristics!- Ge strip detectors, !- 54 cm2 x 1.5 cm, 0.2 cm pitch !!

expected performance!- effective area : 5-18 cm2!- ΔE/E : 0.2 - 1 %!- FoV : 40°×60° FWHM!- ang. res. : 2-3° HPHW!- narr. line sens. : (1-2)×10-5 γ cm-2 s-1!- 100% Polari Sens. 37 mCrab (0.2-0.5)!!

status!balloon flights in 2009 (Crab), 2010 crash!financed NASA & CNES project !NCT 2.0 flight in 2014!later ULDB balloon flights!!

collaboration!SSL, UCB detector, electronics, gondola !IRAP – ACshield & electronics!!

Lowell, A. et al. 2012!

: all sky Compton imager (option 3x3)!

!!

asCi! NCT!

!

effective aera at 1 MeV!

MEGALIB (3x3 asCi)!A. Zoglauer 12/2011 !

mast!

focal distance 10.14 m!

mass per optic 37.5 kg!

NuStar mast (ATK)!total launch mass ~360 kg (Pegasus), SMEX cost envelope!

for asCi : no metrology / fine pointing required from P/L!no issues with stiffness, thermal control, metrology!

!

solid angle – background considerations!

from a 10 m mast, a protheus is seen under 7.10± steradian!i.e. 0.06 % of the sky!!!!!!!!!!!

mars odyssee!obstructed in low earth orbit!

payload mass and accomodation!

The launcher performances open the possibility to perform a dual launch with a co-passenger that require a L2 position as well. !

Item Mass [kg]

Service Module mass 441 Payload Module mass (mature) ASIC (112), Mast (40)

152

Satellite dry mass 593 20% system margin 119 Hydrazine 50 asCi mass at launch (with contigency)

762

Soyuz-Fregate capability 2100 Adapter mass 121 Mass reserve (available for Co-passenger)

1217

orbit!

The L2 position selection associated with the asCi satellite mass and dimensions imply the use of a Soyuz Fregate-2B launch!

!

narrow line sensitivity!

Antimatter astronomy is MeV astronomy!

It is noteworthy that the questions about antimatter in the Universe, both the origin the Galactic positrons and the baryon asymmetry, await investigation through low energy gamma-ray astronomy, at 0.5 MeV and a few MeV, respectively .. !!MeV Astronomy is the key to Antimatter in the Universe ! !!!

" !test baryon symmetric Univers to cosmological distances!!

" !annihilation of the lightest charged leptons that should be at !the endpoint of any annihilation process.!

+ !spectroscopy and polarization of gamma-ray bursts, !radioactivities, pulsars, magnetars, BH, binaries, AGN's !

!

Galactic Radioactivities!26Al, 60Fe, 44Ti, activation lines!

e-e+ Annihilation Radiation!sensitive all sky spectro-imaging!

Compact Sources!XRBs, µ-quasars, magnetars, AGN …!!!Gamma-ray bursts !localization, spectroscopy, polarisation ! !

Cosmic gamma background!multipole analysis, search/constrain AM!! !!!

science summary!

Documents

Antimatter in the Universe constraints from gamma-ray ... · PDF filethe invention of antimatter ! 1930 : Paul Dirac predicts the "antielectron"!! "Quantum Theory of the Electron"