Download Astroparticle physics A.M. van den Berg () O. Scholten

Astroparticle physics
Donald Perkins
SUMMARY slides
www.rug.nl/kvi/research/astroparticlephysics/students/index
www.kvi.nl/~scholten
A.M. van den Berg ([email protected])
O. Scholten ([email protected])
Summary
Summary
1
2
1
Cosmological principle
•
On large scales the Universe is isotropic and homogeneous
•
physical distance can be scaled: r(t) = R(t) ro where R(t) is the scale
parameter, which is the same everywhere!
•
Hubble’s law: dR/dt = H R(t)
•
Value of Hubble’s constant is: H = 71 +/- 4 km/s/Mpc
•
Friedmann equation derived from Newtonian mechanics
Summary
3
Friedmann equations
1st
2
 R  8 G  m   r     kc 2
H    
 2
3
R
R
2
(5.11)
expansion rate
of the Universe
1 
 R 
 P  c 2
2 
 Rc 
  3
2nd


(5.19)
   4 GR    3P  (5.20)
R
c2 
 3 
Summary
kc 2
H 2R2
conservation of energy
or
fluid equation
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2
Curvature of the Universe
•
Closed: k > 0;  > 1
•
Open: k < 0;  < 1
•
Flat: k = 0;  = 1
  1
Summary
kc 2
H 2R2
5
Energy density and scale parameters
Summary
Dominant
regime
Equation of
State
Radiation
1
P  c 2
3
Matter
P
Vacuum
P   c 2
Energy
density
Scale
parameter
  R 4  t 2
Rt
2 2  v  2   R 3  t 2
c  
3
c
Rt
  constant
1
2
2
3
R  expt 
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3
Energy density and scale parameters
Energy density
Scale parameter
matter
 t⅔
matter
 R-3
vacuum
 constant
log R
log 
radiation
 R-4
radiation
 t½
log R
vacuum
 exp(t)
log t
Summary
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Energy densities at this moment
•  + k = r + m +  + k
•
•
•
•
Radiation (CMB):
Total matter (galactic rotation, LSS):
– Luminous baryonic matter (stars, gas, dust):
– Total baryon density (visible or invisible, BBN):
– Total dark matter:
Vacuum energy density (SN Hubble plot, CMB):
Curvature (CMB):
r  5x10-5
m  0.24
lum  0.01
b  0.04
b  0.20
  0.76
k  0.00
• c c2 = [ 3/(8 G) ]H02= 5.4 GeV m-3
• r c2 = 0.26 MeV m-3 (400 106 photons m-3)
• m c2 = 1.2 GeV m-3 (~1 proton m-3)
Summary
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4
Age and size of the Universe
•
2
 R  8 G  m   r     kc 2
H    
 2
3
R
R
2
Friedmann equation

H (t ) 2  H 02  m (0)(1  z )3   r (0)(1  z ) 4    (0)   k (0)(1  z ) 2

• R(t) = R0/(1+z) thus dR/dt = -(1+z) -2 dz/dt
• dt = -dz / [(1+z) H(t)]
•
Integrate from z=0 to z=∞ provides t0; analytical possible for a few
cases; t0 = 14 Gyr
•
Flat static universe size is D = ct0 = 4 Gpc
Summary
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Evolution of the Universe
End of
1019Ge 1015Ge
100GeV 100 MeV 1 MeV
V
V
0.05
MeV
4000 K
10-43 s
10-34 s
10-10 s
300 s
3x105
yr
Inflation
era
ElectroWeak
Quarkgluon
10-5 s
1s
10 K
3K
3x109 yr 15x109 yr
Nucleo Recombi Galaxy/star
Anti-matter Neutrinos
na-tion
Electrons synthesi
formation
s
era
Present
era
T (K)
1010
BBN (nuclei)
103
1 mn
Recombination (atom)
3.105 y
Time t
T(K) ~ 1010 / t(s)
Summary
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10
5
End of EW
unification
Quark-hadron
transition
1 GeV
Big-Bang
nucleosynthesis
1 MeV
1 keV
1010
104
1 eV
decoupling of
matter & radiation
10-10 10-6
Summary
1013
107
neutrino
decoupling
1 meV
Summary
1016
1
106
t (s)
101
Temperature (K)
Energy / particle
radiation
dominated
kT  t -½
1 TeV
matter
dominated
kT  t -⅔
1012 3x1017
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12
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Big-Bang Nucleosynthesis
- Universe is hot, expanding plasma of radiation & relativistic particles
- roughly equal # electrons, positrons, (anti)neutrinos, and photons
- nucleons outnumbered by more than a billion to one
- no composite nuclei
Reactions, e.g.:
annihilation/creation: e + e+   + 
_
charge transfer: e + p  e+ + n
and: e + n  e + p
neutron decay: n  p + e + e
Nn / Np = exp(-Q/kT)
Q = mn-mp = 1.3 MeV
Summary
Nn/Np  0 as T  0, but: freeze-out!
neutrons are captured together with protons
to make Deuterium and then Helium
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Big-Bang Nucleosynthesis
•
•
Bottlenecks at mass 5 and 8 (not stable)
After 20 minutes the BBN stops, because the energy of particles
(temperature) is too low to cross the Coulomb barrier (this will only start
again under gravitational forces).
0.14 n/p
0.20 n/p
0.25 4He/p
Burless, Nollett
& Turner 1999
Summary
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Summary
15
The WMAP results
position of 1st maximum is related to curvature (total density)
amplitude of 1st maximum is related to nB / n;
the stronger / higher the amplitude, the more baryons
Baryon-to-photon ratio
η = 6.1 × 10−10
+0.3 × 10−10
-0.2 × 10−10
 + m ≈ 1
Summary
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8
Horizon and flatness problem
FLATNESS PROBLEM: why is  = 1
If (t=0) > 1 the Universe would have recollapsed at once
If (t=0) < 1 the Universe would have cooled very quickly
HORIZON PROBLEM
Regions on the CMB sky separated by more than 1o had no
time to interact, yet their temperature is the same to 100 ppm
What is needed
An initial condition of the Universe with a temperature
between 1 MeV and 1014 GeV, which is almost
homogenous and has  = 1 to a very high precision
Summary
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distance →
in thermal
equilibrium
time →
Summary
Thus 2 different regions can connect and
thermal equilibrium can be obtained in the
whole physical region.
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9
Summary
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Old and new inflation
Summary
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10
Summary
m = matter density
 = vacuum density
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m = 0.30 +/- 0.05
 ≈ 2 m
 = 0.70 +/- 0.05
m +  = 1.02 +/- 0.05
Summary
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Baryon asymmetry
•
Number of baryons >>> Number of
anti-baryons
•
Detection based on detectors in
satellites (BESS, PAMELA)
•
Moon shadow technique,
absorption + magnetic deflection
(MILAGRO)
•
Limit at 10-4 consistent with
production of anti-particles in the
interstellar matter by high-energy
collisions of normal matter particles
Summary
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Matter-antimatter asymmetry: NB/NantiB > 104
1. Baryon number violating interactions
• Kind of obvious, because we see more matter than anti-matter
• However, no experimental proof
2. Non-equilibrium situation
• In thermal equilibrium, the particle densities depend only on the
mass of the particles and on the temperature. Because particles
and anti-particles have identical masses, no asymmetry could
develop; thus we need non-equilibrium!
3. CP and C violation
• Also kind of obvious, the make an asymmetry we should be able to
distinguish matter from anti-matter
• Experimental proof of C violation (weak interaction) and CP
violation (neutral kaon system; see 3.15)
Summary
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Andrei Sakharov
Summary
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Dark Matter
•
•
Astronomical DM searches
– Evidence:
• Galaxy rotation curves and clusters of galaxies
• Weak lensing of clusters of galaxies
• Filaments of the cosmological web
– Hints: planets and MACHO’s (not enough?)
Physics searches
– WIMPs: Underground laboratories: no conclusive evidence (only
DAMA), still many efforts (cryo, scintillation)
– Neutrino mass
• Mass difference measured by oscillation !
Summary
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13
NGC 2403
inside hub:
M(<r) ~ r3  v ~ r
Summary
outside hub:
M(<r) ~ r0  v ~ r-1/2
mass to light ratio
mass(r) =  light(r)
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DM Direct detection techniques
•
•
•
•
•
WIMP + nucleus 
WIMP + nucleus + recoil energy
Measure the nuclear recoil energy
Recoil nuclei: Ekinetic ~few keV
Backgrounds from nuclear
processes: neutrons!
However, look for oscillations,
annually or daily
220 km/s orbital velocity of Sun
Summary
30 km/s orbital velocity of Earth
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14
Detection of Cosmic Rays and Neutrinos
•
•
Cosmic ray detection
– Direct (balloon, satellites, also for anti-particles!)
– Indirect (air showers; Pierre Auger Observatory)
• Light emission from sky
– Cherenkov and Fluorescence
• Light emission from particles in the shower
– Cherenkov and scintillators
• Radio detection
High-energy neutrino detection
– Muon track for high-energy muon neutrinos (Cherenkov)
– Radio detection in dielectric solids (Cherenkov)
– Large detectors under design (KM3NeT) and operation (ICECUBE
and Mediterranean projects)
Summary
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Summary
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15
Sources of Cosmic Rays and Neutrinos
•
•
•
•
•
•
•
Power-law spectrum for cosmic rays (Fermi acceleration)
Sources
– Galactic (supernova’s)
– Extragalactic
– New physics ???
Interactions with photons
– GZK mechanism (CMB + proton leads to neutrinos + …)
All experiments have registered particles with E > 1020 eV (super GZK)
First sources identified ???
No cosmic neutrino events (except for SN1978A and the sun)
Large detectors under design (KM3NeT) and operation (ICECUBE and
Mediterranean projects)
Summary
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HESS / VERITAS
HESS telescopes in Namibia
VERITAS telescopes at Kitt Peak Arizona
Gamma
ray
not to scale
~ 10 km
~ 1o
Ch
er
en
ko
v
lig
ht
Particle
shower
~ 250 m
Summary
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16
HESS picture of Galactic Center
High intensity
High intensity
High intensity subtracted
Summary
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Summary
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17
Star formation
•
•
•
•
•
•
Stars are formed from gas clouds under
gravitational contraction
Virial theorem: <P>V = -(1/3) Egrav
(hydrostatic equilibrium)
Ignition of hydrogen fusion starts in the
core at kT ~ 1 keV; need tunneling
through coulomb barrier!
Gamow peak
pp cycles and CNO cycle
neutrino’s as probe for interior
Quiescent burning can last long
(Hertzsprung-Russell diagram)
Maxwell-Boltzmann
distribution
 exp(-E/kT)
relative probability
•
Summary
tunnelling through
Coulomb barrier
 exp(- EG / E )
Gamow peak
E0
kT
energy
E0
35
Star death
•
•
•
•
•
•
After exhausting of hydrogen fuel, further contraction, leading to fusion
of helium, red Giant
For light stars, end is white dwarf with degenerate electron gas
If core > 1.4 M catastrophic collapse; type II SN, neutron star;
degenerate neutron gas
If core > 4-6 M same but ends as black hole
For heavy stars, fusion goes on until iron
Explosive hydrogen burning in binary systems (material from normal
star falls onto white dwarf (type Ia novae)
Summary
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Summary
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