COVID 19 Respect the GoI Order - CUSB

Venktesh Singh

Central University of South Bihar

Gaya – 824 236, Bihar (India)

COVID – 19 “Respect the GoI Order”

Venktesh Singh

Central University of South Bihar

Gaya – 824 236, Bihar (India)

Introduction

Experiments

Results

Summary (April 04, 2020) @ GLA University, Mathura through Zoom

COVID – 19 “Respect the GoI Order”

• In 1933，Prof. Zwicky at Caltech checked out

the Coma Cluster. Studied the kinetic energy of

the Coma cluster, he found that the kinetic

energy is far bigger than the potential energy

created by luminous mass. The galaxies were

flying around too fast (as measured by the

Doppler effect) for their visible mass to keep

them together, so he proposed the concept of “dark matter”

Origin of Dark Matter Concept: Father of DM

Virial theorem :：In the stationary gravitational system, the potential

energy is twice the kinetic energy !

According to his calculation, the mass of the dark matter must be as

much as 300 times of the ordinary matter.

COVID-19 "Respect the GOI order" 3

• A few decades later in 1970’s, Vera Rubin

found that the rotation curves of spiral

galaxies are FLAT !

Origin of Dark Matter Concept: Mother of DM

Dark Matter rediscovered


Flat Rotation Curves – so what ?


We can measure how fast stars rotate around galactic centre by looking at the

frequency shift of known spectral lines originating in the stars due to the Doppler

effect.

Star’s motion towards you,

relative to the galactic centre

alters wavelength of light

Rotation of Stars around Galactic Centre

Wavelength shifts are about a part in

106. These are hard measurements.COVID-19 "Respect the GOI order" 6

Use the fact that massive objects, even if they emit no light, exert

gravitational forces on other objects.

Study the motions (dynamics) of visible objects like stars in galaxies, and

look for the effects that are not understandable by the mass of the other

light emitting or absorbing objects around them.

m1

m2

r12

Evidence for Dark Matter


Dark Matter dominates in galaxies e.g. in NGC3198

We are going to concentrate on the DM in the Dark Halo of our own galaxy

Origin of Dark Matter Concept: Mother of DM

v

(r)Disk Radius

This is what we expect.... ….…..but here is a typical result……...


Spiral Galaxies Rotation Curve Gravitational Mass >> Luminous Mass

Evidence for Dark Matter


In Ursa Major Constellation.

Distance is 30 million light years.

For comparison, distance from Earth to the galactic centre is a factor of

~1000 less, ~ 30 thousand light years

33 thousand light years

A Spiral Galaxy – NGC319


Gravitationally bounded in Galactic Halo

Velocity distribution being Maxwellian

Dark Matter Current WisdomSimulated dark matter halo from

a cosmological N-body simulation


Milky Way’s Dark Halo


Measuring a Galaxy’s Rotation Velocity

One of the most famous

method is measurement ofHydrogen-alpha (or Hα) line,

which lies at precisely

656.28 nano-meters (for a

non-moving source).

To measure the rotational

speed of a galaxy, we mapout a line like Hα across

the galaxy and compare it to

the value from a source at

rest.


Measuring a Galaxy’s Rotation Velocity


Measuring a Galaxy’s Rotational Velocity

The hydrogen line, 21-centimeter line or H I (roman one) line refers to

the EM radiation spectral line that is created by a change in the energy

state of neutral Hydrogen atoms. The observation of the 21cm line of

hydrogen marked the birth of spectral-line radio astronomy.

It is commonly observed in astronomical settings such as hydrogen

clouds in our galaxy and others.

Owing to its long lifetime, the line has an extremely small natural

width, so most broadening is due to Doppler shifts caused by bulk

motion or nonzero temperature of the emitting regions.


This electromagnetic radiation is at the

precise of 1420405751.7667±0.0009 Hz,

which is equivalent to the vacuum

of 21.1061140542 cm in free space.

The line come from the atomic transition of

an electron between the two hyperfine

levels of the hydrogen 1s ground state that

have an energy difference of ≈ 5.87433 μeV.

Schematic illustration of fine and hyperfine

structure in a neutral hydrogen atom.



It is called the spin-flip transition.

This logic fails here because the wave functions of the e and the p overlap; that is,

the electron is not spatially displaced from the proton, but encompasses it.

Measuring a Galaxy’s Rotational VelocityThe ground state of neutral hydrogen consists of an electron bound to a proton.

Both have intrinsic magnetic dipole moments due to their spin, whose interaction

results in a slight increase in energy (less tightly bound) when the spins are

parallel, and a decrease when anti-parallel.

When the spins are parallel, the

magnetic dipole moments are anti-

parallel because the electron and

proton have opposite charge, thus

one would expect this configuration

to actually have lower energy just as

two magnets will align so that the

north pole of one is closest to the

south pole of the other.


A spontaneous occurrence of the transition is

unlikely to be seen in a laboratory on Earth, but

it can be artificially induced using a hydrogen

maser.


This transition is highly forbidden with an

extremely small transition rate of 2.9×10−15 s−1,

and a mean lifetime of the excited state of

around 10 million years.

The magnetic dipole moments are therefore best thought of as tiny current loops.

As parallel currents attract, the parallel magnetic dipole moments (i.e., anti-

parallel spins) have lower energy.



cmm 106.2121106.0

186

15

109979.2.107433.5101357.4..1

ms

eV

eVsc

E

hc

The frequency, ν, of the quanta that are emitted by this transition

between two different energy levels is given by the Planck–Einstein relation E = hν.

According to that relation, the photon energy of a 1,420,405,751.7667 Hz photon is ≈ 5.87433 μeV. The constant of

proportionality, h, is known as the Planck constant.


Maybe there is more matter in galaxies that we have not observed.WHAT? Faint stars? Planets? Rocks? Gas? Dust? Exotic Particles ?

Maybe Newton’s law of gravitation is wrong for very large distances OR

very small accelerations.

Many alternative theories have been seriously proposed,

cannot yet rule this out

Possible Interpretations

Need about 10 times as much dark matter as visible matter to explain the rotation curve discrepancy !

Astronomers have argued that dark matter can explain the strange motions ofgalaxies in clusters and stars in galaxies, but that it can’t be normal stuff

“MoND” = Modified Newtonian Dynamics


Maybe there is more matter in galaxies that we have not observed.WHAT? Faint stars? Planets? Rocks? Gas? Dust? Exotic Particles ?

Maybe Newton’s law of gravitation is wrong for very large distances OR

very small accelerations.

Many alternative theories have been seriously proposed,

cannot yet rule this out

Possible Interpretations

Need about 10 times as much dark matter as visible matter to explain the rotation curve discrepancy !

Astronomers have argued that dark matter can explain the strange motions ofgalaxies in clusters and stars in galaxies, but that it can’t be normal stuff

“MoND” = Modified Newtonian Dynamics

Viable alternative, until 2006…Need to look more into the phenomenon of gravitational lensing on larger scales COVID-19 "Respect the GOI order" 21

Bending of light in gravitational fields can make lenses out

of massive objects

LENSING OBJECT

USSOURCE

NO

LENS

LENS

Strong or close lens, expect a ring of light, or a ring of

images in the presence of the lens.

When not resolved, expect increased intensity.

Gravitational Lensing of Light


Gravitational Lensing of Light

1.4 million light years


Light from a quasar behind a galaxy cluster is bent by the mass

in the cluster.

Use to probe the distribution of matter in the cluster.

Light from a distant quasar is bent around a foreground galaxy

Two images of the same quasar !

Probing DM with Distant Quasars:

Gravitational Lensing


Coma Cluster of Galaxies (From Horizons by Seeds)

Visible light X- rays

Space between galaxies is not empty, but filled with hot gas

(observable in X rays)

That this gas remains gravitationally bound,

provides further evidence for dark matter.

Hot Gas in Clusters of Galaxies


• Given what we know about gravitational lensing (tracing the

total mass in blue), hot X-ray gas in (the dominant baryonic

mass, red).

• We can show that dark matter exists in at least one system:

Images from Clowe et al. 2006 and the Chandra press release

The Bullet Cluster


• Lensing of background galaxies

seen in the optical images lets

the mass distribution be

mapped.

• The X-rays trace the hot gas,

the dominant source of baryons

in this cluster merger.

• They don’t line up! Why? Dark

Matter seems to not interact

with itself the way diffuse gas

does during a cluster collision.

The Bullet Cluster


• Dark matter has already been

discovered through • Galaxy clusters• Galactic rotation curves• Weak lensing• Strong lensing• Hot gas in clusters• Bullet Cluster• Supernovae• CMB

• We have entered in the regime of

dark matter identification

Astrophysical Evidences

1. Galaxy Structure

1. Rotational curve，

2. Gravitational lensing

2. Clusters of Galaxy


2. Velocity distribution

3. Hot gas (X-ray)

3. Cosmic Microwave Background

4. Large Scale Structure of the Universe.







1. Galaxy Structure






3. Hot gas (X-ray)









1. Galaxy Structure






3. Hot gas (X-ray)









1. Galaxy Structure






3. Hot gas (X-ray)




http://esamultimedia.esa.int/images/Science/1e0657_H1.jpg

http://esamultimedia.esa.int/images/Science/1e0657_H1.jpg






1. Galaxy Structure






3. Hot gas (X-ray)




CMB Fluctuation• Dark matter has already been





1. Galaxy Structure






3. Hot gas (X-ray)




CMB Fluctuation• Dark matter has already been





1. Galaxy Structure






3. Hot gas (X-ray)




[Tyson et al., Ap. J. 498 L107-110, 1998]

Reconstructed Matter Distribution in

CL0024-1654


Need about 10 times as much dark matter in the overall cluster as

observable in the individual galaxies to explain the observed

lensing.

Galaxies and Galaxy clusters are made up of about 10% visible

matter and 90% dark matter, whose nature is currently not

understood and which means that on a galaxy and cluster scale,

only a few %, perhaps lower, of the matter is solidly understood.

...OR you could consider modifying Newton’s law of gravitation, but

the modifications proposed to explain both rotation curves and

cluster lensing are so complicated that nobody except the propose-

author claims to understand them !

How much Dark Matter in Clusters ?


Galaxy clusters would not have formed

Hot gas surrounding most galaxy clusters would haveescaped

Galaxy collisions would look different

Most stars would have escaped from galaxies There would be much less structure in the universe!

Unless Newton’s Gravitation Law is wrong!21/ for large ?F r r

If there were no dark matter:

IT MEANS DARK MATTER IS PRESENT.

Evidences for Dark Matter


Is the mass in the universe all observable through emission or absorbsion

of electromagnetic radiation ?

Dark Matter

...is matter that does not shine or absorb light, and has

therefore escaped direct detection by electromagnetic

transducers like telescopes, radio antennas, x-ray satellites...

It turns out that there is strong experimental evidence that there is

more than 4 times as much dark matter as luminous matter in the

observable universe.

Question ?


Visual Matter


Dark Energy: “We know

less than nothing”

Standard Model

Matter Well

Understood

Dark Matter: “We

know nothing !

But perhaps have

better guesses”

Dark Matter: Obeys known Laws of Gravitation.

Universe Energy Budget


All we know is that dark matter reacts to gravitation but not to

electromagnetism since it does not emit any light i.e. electric

charge =0 and colourless

It should be massive

Very long lived or absolutely Stable

(Protected by a conserved quantum number)

Very Weak in nature

Hot or warm or cold, prefer COLD Dark Matter (Mass>>>KE)

Mass, spin NOT known

Relic abundance compatible to observation

Motivated by theory (Vs. “ad-hoc” ) May be it interacts with ordinary matter through the weak

nuclear force, the one responsible for radioactive decays.

Dark matter would then be made of weakly interacting particles.

What we know about Dark Matter ? Know something !


If so, then its mass would mostly

come from protons and neutrons =

baryons

The density of baryons right after

the big bang leaves a unique

imprint in the abundances of

deuterium and lithium.

Density of baryonic matter is only ~

4 % of critical density, total is 30%.

Most dark matter must be non-baryonic !

The Nature of Dark Matter


Can dark matter be composed of normal

matter?

• Baryonic dark matter:

Ordinary matter formed from protons, neutrons, electrons,etc. e.g., planets, brown dwarfs, dark nebulae, black holes.

• Non-baryonic dark matter:

Neutrinos, axions, super-symmetric partners (neutralinos,photinos etc.) and Weakly Interacting Massive Particle(WIMP – Strong DM candidate)

Dark Matter could be .......


– Just trying to explain flat rotation curves with things like black

holes, brown dwarfs, etc.

– These are “Baryonic,” made from conventional stuff on the

periodic table (like people, planets, etc.)

– Can be probed via gravitational lensing

Rocks

From pebbles to giant planets like Jupiter. If there are enough of

them, they could make up the dark matter.

Jupiter-size and above planets are a serious contender, and are called

MACHOs by the community – MAssive Compact Halo Objects.



Dense filamentary structures that some theorists think could thread

the universe, giving rise to its present-day lumpiness.

Currently disfavored by cosmological data, but may come back into

vogue sometime.

Dark Matter could be .......Neutrinos

Light, neutral particles of which at least some have a small mass.

Produced in enormous numbers in stars and possibly at the big bang.

If there are enough of them, they could (maybe) be the dark matter.

Don’t emit significant amounts of light, can be very massive.

Would need lots of them.


Black Holes

Cosmic Strings

Particles having mass roughly that of an atomic nucleus, could be as

light as carbon or as heavy as 7 nuclei of xenon.

Need a few per liter to constitute dark matter. Unlike nucleus, only

interact WEAKLY with other matter, through the same mechanism

that is responsible for nuclear beta-decay.


Very light particles, mass around 1/1,000,000,000,000 of an electron.

Needed for building most realistic models of the neutron from

standard model particle physics. Not detected.

To be the dark matter, there should be around 10,000,000,000,000 per

cubic centimeter here on Earth.


Axions

WIMPs

Weakly interactive massive particle

– Neutrinos?

• Seem to have mass, but too small.

– Axions?

• Axion is a hypothetical elementary particle postulated by Peccei-Quinn theory in 1977 to resolve the strong-CP problem inquantum chromo-dynamics (QCD).”

• As yet, not detected (axions are predicted to change to and fromphotons in the presence of strong magnetic fields, and thisproperty is used for creating experiments to detect axions).

WIMPs could be a Dark Matter candidate


WIMP

List of CDM Candidates (incomplete)

COVID-19 "Respect the GOI order"

Current Wisdom (?) :Most of the Experimental Programs focus on the Search of WIMPs

Key Variables: Mass and Cross – Sections 48

Fig. from L.Baudis; Klypin, Zhao and Somerville 2002

1010 (GeV/m) WIMP’s passing through us per cm2 per second !

Cold dark matter is present

at all scales including

galactic halos (rotation

curves), including ours

(revolution speed of

Magellanic Clouds, etc.)

Milky Way.

If dark matter particles do

not have weak interaction,

no hope to detect them,

if they do are called WIMPs

Not necessarily only one type

Milky Way’s Dark Halo


Non-WIMP Dark Matter Candidates


Dark Matter Detection








• Direct detection:– WIMP scattering off nuclei

• Indirect detection:– Detection of WIMP

annihilation products

– SuperK, ANTARES, AMANDA…(Mediterranean)

Detection of WIMP


Indirect Detection of WIMP


Searches of Dark Matter Candidates


WIMP Direct Detection


• Nuclear vs electronic recoil– (discrimination almost required now)

• Recoil energy spectrum shape– (exponential, rather similar to background…)

• Annual flux modulation– (tricky, most events close to threshold, small effect)

• Diurnal direction modulation– (nice signature, but requires low pressure gaseous target)

• No multiple interactions– (removes limited fraction of background)

• Consistency between targets of different nuclei– (essential once first signal is clearly identified)

Possible WIMP Signatures


Direct Detection


Rate = 5.1 x 10 – 9 kg – 1 day – 1

Rate = 1 event kg – 1 10 day – 1Direct Detection


Challenges for WIMP Detection➡ Large mass (ton scale)

➡ Low energy threshold

(a few keV)

➡ Background suppression

➡ Deep underground

➡ Passive / active shielding

➡ Low intrinsic radioactivity

➡ Gamma ray background discrimination


Medium in size (in meters)

High cost (USD Millions)

Low threshold (O sub-keV)

Very sophisticated technologies

Limited physics

Deeper is better.

Direct WIMP Detection Detectors


Principle and Detection Technique

,TEXONO, CDEX

Direct Detection


WIMP

Heat

Ionization

Light

Ge

Liquid Xe

NaI, Xe

Ge, Si

CaWO4, BGO

Al2O3, LiF

Elastic nuclear scattering

• ≈ few % detection energy• usually fast• no surface effects ?

≈ 20 % energy

• ≈ 100% detected energy• relatively slow• requires cryogenic detectors

Direct WIMP Detection Techniques


WIMP

Heat

Ionization

Light

Ge

Liquid Xe

NaI, Xe

Ge, Si

CaWO4, BGO

Al2O3, LiF



≈ 20 % energy




WIMP

Heat

Ionization

Light

Ge

Liquid Xe

NaI, Xe

Ge, Si

CaWO4, BGO

Al2O3, LiF



≈ 20 % energy




WIMP

Heat

Ionization

Light

Ge

Liquid Xe

NaI, Xe

Ge, Si

CaWO4, BGO

Al2O3, LiF



≈ 20 % energy




Examples of Direct WIMP Detectors






Rejection of background is the critical issue



Signal in Direct Searches


Kuo Sheng

TEXONO

INODINO

Many experiments are collecting more data and new ones are being built. With theorists

and experimentalists being hard at work, hopefully there will soon be a breakthrough.

The World wide WIMP Search


The World Wide WIMP Search


CDEX-TEXONO (Ge) ,CDMS (Ge, Si), CDMSlite (Ge), LUX (Xe), SIMPLE (C2CIF5),

SuperCDMS (Ge), TEXONO (Ge), XENON 100 (Xe), XENON 10 (Xe)

.....Have upper bounds .....

Most of them found NULL results, and Placed Bounds !!

Direct DM WIMP Searches


• There is MUCH MORE to the Dark Matter problem than I have had time

to discuss in this talk.

• That Zwicky was right!

• Dark Matter does indeed seem to be real, thank you Bullet Cluster.

• The majority of matter, dark or otherwise, is “non-baryonic” exotic

stuff, and we don’t know for sure what it is. It’s likely flying through

this room right this instant in huge amounts.

• WIMPs, not MaCHOs.

• Other detection methods (solid Germanium and Silicon crystals,

Calcium Tungstate, Sodium Iodide)

• There is also MUCH MORE to the technology of liquid xenon based

detectors - gamma background rejection, scale up to huge detectors

with around a tone of liquid xenon.

Summary


Thank you for your kind attention !


Documents

COVID 19 Respect the GoI Order - CUSB