1. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Search for exotic process with space experiments Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata Rencontres de Moriond, Very High Energy Phenomena in the Universe Les Arc, January 2001
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

2. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
GLAST
14 layers of 2.5% X0 converter (Pb)+4 layers of 2.5% X0
18 layers of X Y silicon strips
Exploded view:
One of the 16 towers
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

3. Elements of a pair-conversion telescope
• photons materialize
into matter-antimatter pairs:
Eg --> me+c2 + me-c2
• electron and positron
carry information about
the direction, energy and
polarization of the g-ray
(energy measurement)
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

4. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
GLAST Performance
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

5. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
One year All-Sky Survey Simulation,
Eg > 100 MeV
All-sky intensity map based on five years EGRET data.
All-sky intensity map from a GLAST one year survey,
based on the extrapolation of the number of sources
versus sensitivity of EGRET
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

6. Uncover the nature of Dark Matter
Probing the era of Galaxy Formation
Uncover the nature of Dark Matter
Roll- offs in the g -ray spectra
from AGN at large z probe the extra-galactic background light (EBL) over cosmological distances.
A dominant factor in EBL models is the era of galaxy formation:
AGN roll- offs may help distinguish
models of galaxy formation, e. g.,
Cold Dark Matter vs. Hot Dark
Matter-- 5 eV neutrino
contributions, etc.
See for example
Macminn, D., and J. R. Primack,
1995, astro- ph/
Counts / bin
Energy (GeV)
(* assumes no intrinsic source cutoff)
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

7. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Dark matter problem
Experimentally in spiral galaxies the ratio between the matter density and the
Critical density W is :
W lum ≤ 0.01
but from rotation curves must exist a galactic dark halo of mass at least:
W halo ≥ 0.03 ÷ 0.1
from gravitational behavior of the galaxies in clusters the
Universal mass density is :
W 0.1 ÷ 0.3
from structure formation theories:
W halo ≥ 0. 3
but from big bang nucleosinthesis the Barionic matter cannot be more then:
W B ≤ 0. 1
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

8. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Candidates for Galactic Dark Matter
• Massive Compact Halo Objects (MACHOs)
• Low (sub- solar) mass stars. Standard baryonic composition.
• Use gravity microlensing to study.
• Could possibly account for 25% to 50% of Galactic Dark Matter.
• Neutrinos
• Small contribution if atmospheric neutrino results are correct, since mn< 1eV.
• Large scale galactic structure hard to reconcile with neutrino dominated dark matter
• Weakly Interacting Massive Particles ( WIMPs)
• Non- Standard Model particles, ie: supersymmetric neutralinos
• Heavy (> 10GeV) neutrinos from extended gauge theories.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

9. Microwave and infrared background Earth
Flux absorption due to the interaction with the infrared and microwave background
g ray source
Microwave and infrared
background
Earth
if the center of mass energy is: g e+ e-
E=w1 J
photons interactions produce electron positron pairs
E=w2
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

10. (2a)
Flux absorption due to the interaction with the infrared and microwave background
The cross section of the process gg -> e+e- is:
where re is the classical radius of the electron and:
E=w1 g e+ e-
E=w2 J
w1 and w1 are respectively the energies of the low and the high energies
gamma ray and J is their angle of incidence.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

11. (3a)
Flux absorption due to the interaction with the infrared and microwave background
the ratio between the flux I(L) at a distance L from the source
and the initial flux I can be written as:
I(L)/Io=exp(-kg L)
where kg is the absorption coefficient:
that contains the cross section and the low energy photon distribution.
For the microwave spectrum: g e+ e-
E=w1
E=w2 J
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

12. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Ratio between surviving flux and initial flux versus photon energies
for two different distances due to the sum of the infrared and black-body background
A.Morselli , INFN/AE-94/22
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

13. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Energy density of the extragalactic diffuse background radiation
Characteristic absorbed g ray energy (TeV):
103
102 10 1
0.1
Eg (TeV)
12.5
1.25
0.125
125
1250
12500
l (mm)
Hegra
, astro/ph/
E2 n(E) (ev/cm3)
Near Infrared
Far Infrared
Average models
Dust
Starlight
Energy (ev)
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

14. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Comulative Extragalactic Background light as a function of redshift z
Cold Dark Matter Model
CHDM
Cold Dark Matter Model
WCDM=0.9 , Wb=0.1
early era of galaxy formation ( 1< zf < 3 )
CHDM = Cold + Hot Dark Matter Model
WCDM=0.6 , Wn=0.3 , Wb=0.1
late era of galaxy formation ( 0.2 < zf < 1 )
Macminn & Primac astro-ph
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

15. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Why Supersymmetry ?
The standard electroweak model is very successful but nevertheless has some problems:
• the unitarity of electroweak interaction breaks down at energy Scales < 1 TeV in the
absence of a mechanism to account for electroweak symmetry breaking
• it leaves many fundamental parameters unexplained (like sin2 JW )
• moreover the gauge structure in the standard model suggest the existence of a Grand Unified theory of electroweak and strong interaction at an energy around GeV
• … and at energies around the Plank mass GeV there is the need of a theory that
includes the Gravitational force because the quantum gravitational effects cannot be neglected.
The Supersymmetry seems to be the most promising field of research to solve
these problems. If Supersymmetry is true there is the prediction of the existence of a
whole class of new particles that are the supersymmetric partners of the known particles.
In particular the Lightest Supersymmetric Particle (LSP) must be stable by R-parity conservation and can escape detection due to its weakly interacting nature.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

16. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Neutralino WIMPs
Assume c present in the galactic halo
• c is its own antiparticle => can annihilate in galactic halo
producing gamma-rays, antiprotons, positrons….
• Antimatter not produced in large quantities through standard processes
(secondary production through p + p --> p + X)
• So, any extra contribution from exotic sources (c c annihilation) is an
interesting signature
• ie: c c --> p + X
• Produced from (e. g.) c c --> q / g / gauge boson / Higgs boson and
subsequent decay and/ or hadronisation.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

17. Supersymmetry introduces free parameters:
In the MSSM, with Grand Unification assumptions the masses and couplings of the SUSY particles as well as their production cross sections, are entirely described once five parameters are fixed:
• M2 the mass parameter of supersymmetric partners of gauge fields (gauginos)
• the higgs mixing parameters m that appears in the neutralino and chargino mass matrices
• m0, the common mass for scalar fermions at the GUT scale
• A, the trilinear coupling in the Higgs sector
• the ratio between the two vacuum expectation values of the Higgs fields defined as:
tang b = v2 / v1 = <H2> / <H1>
Experimental lower limit on the mass of the lightest neutralino assuming MSSM
(Minimal Standard Supersymmetric Model)
Lep , s = 189 GeV
UHM : universal soft supersymmetry-breaking scalar masses for Higgs
nUHM: non-universal
1999 : available LEP data
2000 : assessment of the likely sensitivity of data to be taken in 2000.
( the m<0 plot is similar)
hep-ph/
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

18. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
In the minimal supersymmetric extension of the Standard Model
four neutral spin-1/2 Majorana particles are introduced:
• the partners of the neutral gauge bosons B, W
• the neutral CP-even higgsinos H01, H02.
Diagonalizing the corresponding mass matrix, four mass eigenstates are
obtained.
The lightest of these, c , is commonly referred as the neutralino.
It is useful to introduce the gaugino fraction Zg defined as:
Zg= |N1|2 + |N2|2
and classify the neutralino as higgsino-like when Zg <0.01, mixed
when 0.01 < Zg < 0.99 and gaugino like if Zg >0.99.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

19. SuperSymmetric Dark Matter
Possible signature:
Gamma Ray
from Neutralino Annihilation
Annihilation at rest:
bump around Neutralino mass fg
10 GeV
100 GeV
Diffuse
background
A=pseudoscalar
c±=chargino
c0 =neutralino
H=Higgs boson
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

20. Signal rate from Supersymmetry
The signal rate is :
where:
rc0.4 is the local halo neutralino density in units of 0.4 GeV/cm3
fhalo is a factor that can vary between 0.3 and 2 due to the uncertainty in modeling the galactic halo.
Sensitivity of GLAST up to 300 GeV ~ cm-2 s-1
with fhalo ~1, rc0.4 ~ 3 , fb = ( 100 MeV / E(MeV) ) photon cm-2 s-1 sr-1
In two years, full eff. DE/E ~5% fmin ≥ ph cm-2 s-1 sr-1
DE/E ~10% fmin ≥ ph cm-2 s-1 sr-1
GLAST has the possibility to explore a good portion of the possible values of this parameters space
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

21. Signal rate from Supersymmetry (2)
(5bS)
Signal rate from Supersymmetry (2)
But in more general form we have:
where:
y is the angle between the line of sight and the Galactic center,
r(y) is the distance along that line of sight
I(y) is the angular dependence of the gamma-ray flux.
The galactic dark matter density distribution can have the form
r(r) ~ r-a with a ~ 1.8 and the predicted photon flux can be
104 brighter from certain directions!
(the sources can appear nearly point-like)
I(y)
R ~ 8.5 kpc y
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

22. Total photon spectrum from the galactic center from cc ann.
g lines
50 GeV
300 GeV
• Two-year scanning mode
Infinite energy resolution
With finite energy resolution
Bergstrom et al.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

23. GLAST Performance : Energy resolution for lateral photons
sE/E =1.5%
q > 560
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

24. (7S)
Number of photons expected in GLAST for cc -> gg from a 1-sr cone near the galactic center
gaugino-like
higgsino-like neutralino
Two-year scanning mode exposure.
Each point is a different set of Minimal SuperSymmetric Standard Model parameters
The galaxy dark matter halo profile giving the maximal flux has been assumed.
The solid line shows the number of events needed to obtain a five-sigma detection over
the galactic diffuse gamma-ray background as estimated from EGRET data.
Bergstrom et al. astro-ph/
g or Z c g
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

25. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Energy versus time For X and Gamma ray detectors
Aldo Morselli 10/00
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

26. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Sensitivity of g-ray detectors in 2002
All sensitivities are at 5s.
Cerenkov telescopes
sensitivities
(Veritas, MAGIC,
Whipple, Hess, Celeste, Stacee, Hegra)
are for 50 hours of observations.
Large field of view
detectors sensitivities
(AGILE, GLAST,
Milagro,ARGO
are for 1 year of observation.
MAGIC sensitivity based on the availability
of high efficiency PMT’s
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

27. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Distortion of the secondary antiproton flux induced by a signal from a heavy Higgsino-like neutralino.
•Background from normal
secondary production
•Signal from very heavy (~ 1 TeV)
neutralino annihilations
( astro-ph )
Mass91 data from
XXVI ICRC, OG , 1999 •
Caprice94 data from
ApJ , 487, 415, 1997
Particles and photons are sensitive to
different neutralinos.
Gaugino-like particles are more likely to
produce an observable flux of antiprotons
whereas Higgsino-like annihilations are
more likely to produce an observable
gamma-ray signature
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

28. • •Background from normal secondary production •Signal from ~ 300 GeV
Distortion of the secondary positron fraction induced by a signal from a heavy neutralino.
•Background from normal
secondary production
(ApJ 493, 694, 1998)
•Signal from ~ 300 GeV
neutralino annihilations
(Phys.Rev. D59 (1999) astro-ph ) •
Caprice98 data from
XXVI ICRC, OG , 1999
Caprice94 data from
ApJ , 532, 653, 2000
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

29. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Distortion of the secondary positron fraction induced by a signal from a heavy neutralino.
Mc=336 GeV
Ks=11.7
C2/7=1.53
Mc=2313 GeV
Ks=1 104
C2/7=1.08
BR(e+e-)
Mc=106 GeV
Ks=19
C2/7=2.24
Mc=130 GeV
Ks=54
C2/7=1.35
Baltz & Edsjö
Phys.Rev. D59 (1999)
astro-ph
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

30. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Distortion of the secondary positron fraction
induced by a signal from a heavy neutralino.
Distortion of the secondary antiproton flux
induced by a signal from a heavy Higgsino-like neutralino.
Antiproton flux, m-2 s-1 sr-1 GeV-1
Energy of antiproton (GeV)
Expected data from Pamela for one year of operation are shown in red.
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

31. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

32. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
antiproton
positron
Pamela
Separating p from e-
Magnet
Silicon
Calorimeter
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

33. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

34. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

35. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
10 GeV e-
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

36. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
10 GeV p
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

37. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Cosmic Ray Physics with charged particles: - Study of the origin and propagation of cosmic rays using sample of galactic and extragalactic material. - Test of cosmological models - Search for dark matter and supersymmetry Cosmic Ray Physics with photons: - Study of the origin of cosmic rays by looking one by one the sources of cosmic rays - Test of cosmological models - Test of galaxies formation models - Search for dark matter and supersymmetry - Complementary with gravitational waves detectors
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

38. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
Summary and 1st Conclusions
• Neutralinos are a promising candidate for WIMP dark matter
• Neutralinos can annihilate in the galactic halo ...
• … this could give rise to high energy (> 10GeV) antiproton signature
and/or gamma-ray signature.
Pamela experiment is designed to measure antiproton spectrum from
80MeV to 190GeV.
• >3 year mission large event samples
• Combination of TRD + Si tracker + imaging Si- W calo + TOF (trigger)
and anticoincidence can isolate a pure sample of antiprotons.
• Engineering model currently under construction.
• Flight model due ~ June 2002.
• Launch: beginning 2003.
In 2005 GLAST will search for gamma-ray signature
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata

39. Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata
2nd Conclusions
GLAST will explore a good portion
of the supersymetric parameter space
GLAST will explore the Cold and Hot
Dark Matter contribution through
the IR absorption of g-ray from
extragalactic sources
… and these are only additional items for GLAST !
Aldo Morselli INFN, Sezione di Roma 2 & Università di Roma Tor Vergata