Transcript Diapositiva 1 - Istituto Nazionale di Fisica Nucleare

DARK MATTER
Fisica delle Astroparticelle
Piergiorgio Picozza
a.a. 2003-2004
What is the Universe made of ?
We know that there is
dark matter, which is
needed to explain the
dynamics of stars in
Galaxies and of galaxies
in clusters. This dark
matter does not
interact with light, and
we do not know witch
particles is made of.
•
The peripheral stars of the galaxy M63 rotate around the center so fast
that they would fly away in space without the presence of additional mass
inside the galaxy. This is indirect evidence for the presence of dark matter
HALO SUBSTRUCTURE
Milky Way
A.Font and J.Navarro,
astro- ph/ 0106268
600 kpc
Dark matter problem
Experimentally in spiral galaxies the ratio between the matter density and the Critical
density
Wc is :
W lum ≤ 0.01
but from rotation curves must exist a galactic dark halo of mass at least:
W halo ≥ 0.1
from gravitational behavior of the galaxies in clusters the Universal
mass density is :
W halo @ 0.2 ÷ 0.3
from structure formation theories and analyses of the CMB:
W halo ≥ 0. 3
but from big bang nucleosinthesis and analyses of the CMB the Barionic matter cannot be
more than:
0. 03 ≤ W B ≤ 0. 05
Supersymmetry
Particle
Sparticle
For unbroken supersymmetry they should be degenerate in mass
Sparticle have not be found at accelerators so far
Supersymmetry is broken
Supersymmetry breaking schemes:
1) gravity-mediated scenarios
2) Gauge mediated scenarios
3) Anomaly mediated scenarios
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
fixed:
5 parameters are
• M1/2 the mass parameter of supersymmetric partners of gauge fields
(gauginos)
•m
the higgs mixing parameters that appears in the neutralino and chargino mass
• m0
the common mass for scalar fermions at the GUT scale
•A
the trilinear coupling in the Higgs sector
matrices
• tang b = v2 / v1 = <H2> / <H1> the ratio between the two vacuum expectation values
of the
Higgs fields
(3S)
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.
Limits on Supersymmetry already established
LEP
Experimental
lower limit on
the mass of the
lightest
neutralino
assuming
MSSM
(Minimal Standard
Supersymmetric
Model)
Mc > 50 GeV
hep-ph/0004169
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.
SuperSymmetric Dark Matter
Possible signature:
Gamma Ray
from Neutralino
Annihilation
Annihilation at rest:
bump around Neutralino mass
fg
Diffuse
A=pseudoscalar
c=chargino
c0 =neutralino
H=Higgs boson
background
10 GeV
100 GeV
(4S)
Gamma- Z0 Annihilation c c -> g Z0: E'= Mc ( 1mz2/4Mc2 )
Total photon spectrum from the galactic center from
cc ann.
• Two-year scanning mode
Infinite energy resolution
With finite energy resolution
g lines
50 GeV
300 GeV
Bergstrom et al.
(6S)
a)
b)
CDM neutralinos annihilation in
the Galactic halo in minimal SUSY
In R-parity- violating SUSY
Antiproton fluxes
A
range of minimal (R-parity-conserving) SUSY predictions of
Galactic antiprotons spectrum, with neutralino masses = 45-700 GeV
PAMELA
ANTIPROTONS
expectation
Secondary
production
(upper and
lower limits)
Simon et al.
Primary
production from
c c annihilation
Secondary
production
(m(c) = 964 GeV)
Primary
production
PAMELA
POSITRONS
expectation
for 3 years of operation
Secondary
production
Secondary
production
‘Leaky box model’
Secondary
production
‘Moskalenko +
Strong model’
without
reacceleration
Primary
production from
c c annihilation
(m(c) = 336 GeV)
Total
Primary production
Distortion of the secondary antiproton flux induced by a signal from a heavy Higgsinolike neutralino.
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
Caprice94 data from
ApJ, 487, 415, 1997
Mass91 data from
XXVI ICRC, OG.1.1.21 , 1999
Caprice98 data from
ApJ, 561, (2001), 787.
astro-ph/0103513
∆ BESS data from
Phys.Rev.Lett, 2000, 84, 1078
AMS data : preliminary
Background from normal
secondary production
Signal from 964 GeV
neutralino annihilations
( astro-ph 9904086)
AMS
Antiproton Lifetime
•
•
•
•
LEAR Collaboration > 0.08 years
Penning trap
> 0.28 years
APEX Collaboration > 300 kyr
Cosmic rays
> 0.8 Myr
• A p lifetime < 13 Myr (CR Galactic storage time)
would indicate CPT violation
It would appear as a distortion in the energy
spectrum
POSITRONS
• Cosmic ray positrons are produced from decaying
mesons in p-A inelastic scattering.
• WIMPs could contribute to monochromatic positrons
from direct annihilation in e+ e-, and to continous
positrons from other annihilation channels.
• Excess or bump beginning at a few GeV and
extending upward in energy depending on the WIMP
mass.
• Some indication in the present data at high energy:
residual unremoved proton background?
Positron Ratio
•Background from normal
secondary production
(ApJ 493, 694, 1998)
•Signal from ~ 300 GeV
neutralino annihilations
(Phys.Rev. D59 (1999) astro-ph 98008243)
•
Caprice98 data from
XXVI ICRC, OG.1.1.21, 1999
Caprice94 data from
ApJ , 532, 653, 2000
Distortion of the secondary positron fraction induced by a signal from a
heavy neutralino.
Baltz & Edsjö
Phys.Rev. D59 (1999)
astro-ph 9808243
Positron with HEAT
ICRC 01
p.1867
Positron with HEAT
(2)
hep- ph/ 0108138
Positron with HEAT
(3)
hep- ph/ 0202156