Submitted By: Sandeep Kaur
Msc 2
WHAT IS DARK MATTER?
 Dark matter is a kind of matter hypothesized in
astronomy and cosmology to account for gravitational
effects that appear to be the result of invisible mass.
 Dark matter cannot be seen directly with telescopes;
evidently it neither emits nor absorbs light or other
electromagnetic radiation at any significant level.
If we can't see it,How do we know it exists??
 The existence and properties of dark matter are inferred
from its gravitational effects on visible matter.
OBSERVATIONAL EVIDENCE :
SOMETHING IS NOT RIGHT WITH…..
 Galactic Rotation Curves
 Galactic Clusters
 Appearance of far away Galaxies
 Cosmic Microwave Background

What's the solution?Lets find out.
GALAXIES ROTATE
Galaxies are collections of
billions of stars. Most of the
light from a galaxy comes
from its center. This
indicated that most of the
galaxies stars and most of its
mass is concentrated at its
center. Under this scenario,
we should expect the stars in
the outer part of the galaxy to
rotate about the center, and
this is just what we observe.
GALAXY ROTATION CURVES
o In the late 1960s and early 1970s, Vera
Rubin at the Department of
Terrestrial Magnetism at the Carnegie
Institution of Washington was the first
to both make robust measurements
indicating the existence of dark matter
and attribute them to dark matter.
o Rubin worked with a new sensitive
spectrograph that could measure the
velocity curve of edge-on spiral galaxies
to a greater degree of accuracy .
o
Rubin's observations and calculations
showed that most galaxies must contain
about six times as much “dark” mass
as can be accounted for by the visible
stars.
GALAXY CLUSTERS
 Galaxies have been
called the atoms of
the universe. Nearly
all the visible matter
in the universe is
found in galaxies
which are distributed
throughout space.
Galaxies are often
found in groups called
clusters.
GALAXY CLUSTERS
 Radio astronomers have found hot gas
in the space between galaxies in a
cluster. This gas produces a pressure
that pushes the galaxies apart.
 The galaxies’ mutual gravitational
attraction causes them to cling
together. The heavier the galaxies,
the stronger the gravitational
attraction.
So, are galaxies massive enough to
hang together??
 From X-rays emitted by very hot gas
within the clusters. The temperature
and density of the gas can be
estimated from the energy and flux of
the X-rays, hence the gas pressure;
assuming pressure and gravity
balance, this enables the mass profile
of the cluster to be derived.
 Chandra X-ray Observatory use this
technique to independently determine
the mass of clusters.

“It turns out that galaxies do
not have enough visible
mass to stay grouped in
clusters. The extra mass
they need must come
from dark matter.”
WHO SQUASHED THE
GALAXIES?
 In 1995, the Hubble
Space Telescope
focused its attention on
a very small patch of
sky. It was able to see
farther away than any
other optical telescope
in history. It saw
thousands of new
galaxies. Many
appeared squashed or
stretched out.
 A gravitational lens is
formed when the light
from a more distant
source is "bent"
around a massive
object (such as a
cluster of galaxies)
between the source
object and the
observer. The
process is known as
Gravitational
Lensing.
 The observed distortion of background
galaxies into arcs when the light passes
through a gravitational lens, has been
observed around Abell 1689 By measuring
the distortion geometry, the mass of the
cluster causing the phenomena can be
obtained.
 Weak gravitational Lensing looks at
minute distortions of galaxies observed in
vast galaxy surveys due to foreground
objects through statistical analyses. By
examining the apparent shear deformation of
the adjacent background galaxies,
astrophysicists can characterize the mean
distribution of dark matter by statistical
means.
BULLET CLUSTER
X-ray observations show that
much of the baryonic matter in
the system is concentrated in
the center of the system.
Weak Gravitational Lensing
observations of the same
system show that much of the
mass resides outside of the
central region of baryonic gas.
COSMIC MICROWAVE
BACKGROUND:
 The cosmic microwave background (CMB) is
the thermal radiation assumed to be left over
from the "Big Bang" of cosmology.
 In older literature, the CMB is also variously
known as cosmic microwave background
radiation (CMBR) or "relic radiation."
 The CMB is a cosmic background radiation
that is fundamental to observational
cosmology because it is the oldest light in the
universe, dating to the epoch of
recombination.
BIG BANG
• The night sky presents the viewer with a picture of a
calm and unchanging Universe. So the 1929 discovery
by Edwin Hubble that the Universe is in fact expanding
at enormous speed was revolutionary.
• Hubble noted that galaxies outside our own Milky Way
were all moving away from us, each at a speed
proportional to its distance from us.
• He quickly realized what this meant that there must
have been an instant in time when the entire Universe
was contained in a single point in space. The Universe
must have been born in this single violent event which
came to be known as the "Big Bang."
BACKGROUND RADIATION
 According to the theories of physics, if we were to
look at the Universe one second after the Big
Bang, what we would see is a 10-billion degree
sea of neutrons, protons, electrons, anti-electrons
(positrons), photons, and neutrinos.
 Then, as time went on, we would see the
Universe cool, the neutrons either decaying into
protons and electrons or combining with protons to
make deuterium (an isotope of hydrogen).
 As it continued to cool, it would eventually reach
the temperature where electrons combined with
nuclei to form neutral atoms.
BACKGROUND RADIATION
• Before this "recombination" occurred, the
Universe would have been opaque because
the free electrons would have caused light
(photons) to scatter the way sunlight scatters
from the water droplets in clouds.
• But when the free electrons were absorbed to
form neutral atoms, the Universe suddenly
became transparent.
• Those same photons - the afterglow of the
Big Bang known as cosmic background
radiation -can be observed today.
ANISOTROPIES IN CMB:
 The anisotropies in the CMB are explained as
acoustic oscillations in the photon-baryon
plasma (prior to the emission of the CMB
after the photons decouple from the baryons
at 379,000 years after the Big Bang) whose
restoring force is gravity.
 Ordinary matter interacts strongly with
radiation whereas, by definition, dark matter
does not. Both affect the oscillations by their
gravity, so the two forms of matter will have
different effects.
CANDIDATES OF DARK MATTER:
• There is no shortage of ideas as to what
the dark matter could be. Serious
candidates have been proposed with
masses ranging from 9 x 10^-72 M☉
(axions) up to 104M☉ (black holes). That's
a range of masses of over 75 orders of
magnitude! It should be clear that no one
search technique could be used for all
dark matter candidates
CATEGORIZATION (A)
BARYONIC MATTER
NON BARYONIC MATTER
 Massive Compact Halo Object
(Macho) . These include brown
dwarf stars and black holes.
 Brown dwarfs are spheres of H
and He with masses below
0.08 , so they never begin
nuclear fusion of hydrogen.
 Black holes could be the
remnants of an early
generation of stars which were
massive enough so that not
many heavy elements were
dispersed .
 The Axion is mentioned as
a possible solution to the
strong CP problem and is
non baryonic candidate of
dark matter.
 The largest class is the
Weakly Interacting Massive
Particle (Wimp)which
consists of literally hundreds
of suggested particles. The
most popular of these
Wimps is the neutralino
from supersymmetry.
CATEGORIZATION (B)
HOT DARK MATTER
• A dark matter candidate
is called ``hot" if it was
moving at relativistic
speeds at the time when
galaxies could just start to
form.Light neutrinos
come under this category.
COLD DARK MATTER
• A dark matter candidate
is called ``cold" if it was
moving non-relativistically
at the time when galaxies
could just start to form.
WIMPS
Its name comes from the fact that obtaining
the correct abundance of dark matter today
by thermal production require a self
annihilation cross section of 10^-26 cm cube
per sec which is roughly what is expected for
a new particle in 100Gev mass range that
interacts via electroweak force.This class of
natural dark matter candidates is generally
called weakly interacting massive particles
(WIMPs).
SUPERSYMMETRIC WIMP
NEUTRALINO
 An extension of the standard model,
called Supersymmetry (SUSY)
offers a promising framework for the
type of particle species that could fit
the observed properties of dark
matter.
 The most promising candidate
particle is the lightest
supersymmetric particle (LSP). This
is a supersymmetric particle that all
other supersymmetric particles
would decay into, itself being stable.
This particle is called the neutralino.
 In order to be consistent with an
early universe annihilation rate,
leaving proper relic abundances,
such a particle should have a small
o The relic density provides a target
but measurable interaction crossannihilation cross section
section with ordinary matter.
Specifically a cross-section for
s ~ 3 x 10-26 cm3/s
interaction between a neutralino and
a nucleon in ordinary matter is of
the order of the electroweak scale .
AXIONS
•
Axions arise from attempts to explain why the strong
interaction seems to obey a certain symmetry called "CP
symmetry". Among other things, CP symmetry would prevent
the neutron from having a large electric dipole moment without it, it's very hard to understand why such a dipole
moment has not yet been detected. The best explanation for
this is called "Peccei-Quinn symmetry", and predicts a new
light neutral particle called the axion.
• The axion is stable in many theories, and can also be
produced in the early universe. Though axions are far lighter
than WIMPs (often 1 eV or much less), they can be created in
the right amount by a non-thermal process which also
naturally leaves them slow-moving.
LIST OF DARK MATTER
EXPERIMENTS
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Advanced Thin Ionization Calorimeter
Alpha Magnetic Spectrometer
ANAIS
ArDM
Axion Dark Matter Experiment(ADMX)
CERN Axion Solar Telescope
Cryogenic Dark Matter Search(CDMS)
Cryogenic Rare Event Search with
Superconducting Thermometers
DAMA/LIBRA
DAMA/NaI
Dark Matter Time Projection Chamber
DarkSide
DEAP
Directional Recoil Identification from
Tracks
EDELWEISS
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European Underground Rare Event
Calorimeter Array
Korea Invisible Mass Search
Large Underground Xenon
experiment(LUX)
Microlensing Observations in
Astrophysics
MultiDark
Optical Gravitational Lensing Experiment
PAMELA detector
PandaX
PICASSO
PVLAS
SIMPLE (dark matter experiment)
SNOLAB
UK Dark Matter Collaboration
WIMP Argon Programme
XENON
ZEPLIN-III
SCDMS
•
Utilizing state-of-the-art cryogenic germanium
detectors, the SuperCDMS (SCDMS) collaboration is
searching for WIMPs
• SuperCDMS is the successor to the CDMS II
experiment, which was located deep underground in
the Soudan mine in Minnesota, USA.
• After a brief testing period located at Soudan, SCDMS
plans to be located at SNOLAB (Vale Inco Mine,
Sudbury, Canada).
• The use of underground facilities provide shielding
from cosmogenic events and as a result reduce
interference of known background particles.
PROCEDURE

SuperCDMS detectors are designed with the primary function of detecting the minute
phonon signals generated within the detector crystal by elastic collisions between detector
nuclei and WIMPs. The energy deposited in a detector by an interacting WIMP may be as
low as a few tens of keV. Event detection at such energy levels requires a sensitive
experimental apparatus. The foremost requirement is that the detector maintained at a
very low temperature to distinguish the deposited energy from the thermal energy of the
detectors nuclei. The SCDMS project and associated test facilities employ He-3/He-4
dilution refrigerators which, with the appropriate cryostat apparatus are able to achieve
detector base temperatures as low as 10mK.
 An incident particle collides with a nucleus in the detector, which sets off vibrations
throughout the crystal lattice. These vibrations, which are called phonons, propagate
through the crystal and some reach the surface. Once there, they are absorbed by the
aluminum fins. In the aluminum fins, the phonons transfer their energy to quasi-particle
Cooper pair electrons. The incident phonon energy breaks these Cooper pairs and gives
the energy to the electrons. These quasi-particle electrons diffuse to the tiny strips of
tungsten that are attached to aluminium fins. The change in the TES resitance causes a
small change in the current flowing through them
CDMS PARAMETER SPACE
ADMX
 The goal of the Axion Dark-Matter eXperiment (ADMX) Gen 2
project is to discover axions that would constitute the dark
matter in our Milky Way halo.
 ADMX consists of a large microwave cavity resonator located
inside a high-field solenoid magnet. Halo dark-matter axions
which enter the cavity have a small but finite probability to
convert into microwave photons.
 This exceedingly weak microwave signal is then detected by a
receiver which is capable of near quantum-limited noise
performance. This ADMX configuration is currently in
operation and taking data over plausible axion masses and
couplings.
 The Gen 2 configuration of ADMX adds a dilution refrigerator
to reduce the temperature of the cavity and receiver front end.
RECENT DATA
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Researchers at Leicester University
spotted the curious signal in 15 years
of measurements taken by the
European Space Agency.They noticed
that the intensity of x-rays recorded by
the spacecraft rose by about 10%
whenever it observed the boundary of
Earth’s magnetic field that faces
towards the sun.
Similar signal had been detected by
Nasa’s Chandra X-ray Observatory.
Dark matter axions, or axion-like
particles, could be responsible for this
as they can convert to photons in the
magnetic field of the Earth.
DARK ENERGY
 INTRODUCTION
In the early 1990's, one thing was fairly certain
about the expansion of the Universe The Universe is
full of matter and the attractive force of gravity pulls all
matter together. So theoretically,universe had to
slow.Then came 1998 and the Hubble Space
Telescope (HST) observations of very distant
supernovae that showed that, a long time ago, the
Universe was actually expanding more slowly than it is
today. So the expansion of the Universe has not been
slowing due to gravity, as everyone thought, it has
been accelerating. No one expected this, no one knew
how to explain it. But something was causing it.
WHAT IS DARK ENERGY?
 One explanation for dark energy is that it is a property of space.
Albert Einstein was the first person to realize that empty space is not
nothing. Space has amazing properties, many of which are just
beginning to be understood.
 The first property that Einstein discovered is that it is possible for
more space to come into existence.
 Then one version of Einstein's gravity theory, the version that
contains a cosmological constant, makes a second prediction:
"empty space" can possess its own energy. Because this energy is
a property of space itself, it would not be diluted as space expands.
As more space comes into existence, more of this energy-of-space
would appear. As a result, this form of energy would cause the
Universe to expand faster and faster.
 Unfortunately, no one understands why the cosmological constant
should even be there, much less why it would have exactly the right
value to cause the observed acceleration of the Universe.
 Another explanation for how space acquires
energy comes from the quantum theory of
matter. In this theory, "empty space" is
actually full of temporary ("virtual") particles
that continually form and then disappear. But
when physicists tried to calculate how much
energy this would give empty space, the
answer came out wrong - wrong by a lot. The
number came out 10120 times too big. That's
a 1 with 120 zeros after it. It's hard to get an
answer that bad. So the mystery continues.
 Another explanation for dark energy is that it
is a new kind of dynamical energy fluid or
field, something that fills all of space but
something whose effect on the expansion of
the Universe is the opposite of that of matter
and normal energy. Some theorists have
named this "quintessence" . But, if
quintessence is the answer, we still don't
know what it is like, what it interacts with, or
why it exists. So the mystery continues.
 A last possibility is that Einstein's theory of gravity is
not correct. That would not only affect the expansion
of the Universe, but it would also affect the way that
normal matter in galaxies and clusters of galaxies
behaved.
 But if it does turn out that a new theory of gravity is
needed, what kind of theory would it be?
 How could it correctly describe the motion of the
bodies in the Solar System, as Einstein's theory is
known to do, and still give us the different prediction
for the Universe that we need?
“ So the mystery continues”
SURVEY
According to the
Planck mission team,
and based on the
standard model of
cosmology, the total
mass–energy of the
known universe
contains 4% ordinary
matter, 21% dark
matter and 75% dark
energy.

Chart of the matter of the universe. In a
way, this chart is an embarrassment for
scientists. We are only able to account for
4% of the matter in the universe.
THANK YOU