Exploration of Particle Physics and Cosmology with Neutrinos
Unification and Development of the Neutrino Science Frontier

What are the neutrinos?

Neutrino means“Neutral = no electric charge” and “-ino = small (in Italian).”
They are one of the elementary particles.

“Neutral”and“ino”“neutrino”!

Then, what are elementary particles?

Elementary particles are the smallest
water

elements that make up matter! Wellthat doesn’t explain much about
them so here we go!

watermolecules molecule

For example, water is a bunch ofwater molecules, and each watermolecule is made with two hydrogenatoms and one oxygen atom.
oxygenatom

Inside of an atom, electrons areorbiting around a nucleus sitting inhydrogenatom atom

the middle.
Further inside of a nucleus, there areoxygennucleus

protons and neutrons. These two
types of particles are called nucleons

nucleus(A hydrogen nucleus is made up of
one proton only).
Then, what about the inside of

protonneutron

up
quark

down
quark

quark

electron

leptonnucleonnucleons? Nucleons are made withthree quarks.
There are no smaller par ticles
than these quarks and electrons,
the elementary particles. At thismoment, we think we cannot further
break down these particles.

elementary particles

Fermions (matter)

Quark

u

c

t

up quark

charm quark

top quarkdsbdown quark

strange quarke–µ–The elementary particles include; sixtypes of quarks, six types of leptons(including electrons), gauge bosons
which carry forces between particles,
a n d H i g g s b o s o n s w h i c h gi ve abottom quark

mass (weight) to other par ticles.
Furthermore, all these particles haveelectron

τ–

muon

tau

have opposite electric charges. Quarks

Leptonνeνµντelectronneutrino

muon
neutrinotau
neutrino

Higgs
boson

W+

γ

W-

Z0

photonbind to other quarks strongly and they
make up nucleons. On the other hand,
leptons bind weakly and they stayalone. Water, flowers, the universe, andBosonsGauge
boson

partners called anti-particles whichgluon

W and Z bosons

even ourselves, everything around us
is made by these elementary particles.
Neutrinos are a type of lepton.

H0
Higgs boson

Discovery of Neutrinos!

In 1930, a scientist named Dr Pauli found a problem while he was studying neutrons.
Pauli thought the problem could be solved by the existence of very light particles
without electric charges. However, such a small light particle can pass through any object
and Pauli thought it would be impossible to find such a ghost particle. Three years later,
Dr Fermi, who had studied these ghost particles, named these particles neutrinos.
In 1956, two more scientists, Dr Reines and Dr Cowan, finally succeeded the first saw
neutrinos with an experiment that used a nuclear reactor. Dr. Reines won the Nobel Prizein Physics for this achievement.

What are the properties of neutrinos?

These are so many!
There are so many neutrinos around us. Lots of neutrinos
are produced by the Sun during the production of heat, by
the supernova explosion at the end of the life of a star, andby nuclear reactors. About 100 trillion neutrinos are passing
through our bodies every second, but we cannot feel them andthey can't hurt us.

Invisible ghost particle.
Neutrinos are neutral particles without either a positive or
negative electric charge. This means neutrinos do not attract,
repel, or affect any materials. Furthermore, they are extremely
small and they can pass through any atoms. Neutrinos can passthrough our bodies and the Earth. Scientists have a hard timeto see them because these particles are like ghosts - they evenpass through detectors!

They have mass!
For a long time, people believed neutrinos do not have mass.
However, the Super-Kamiokande experiment led by Dr Kajita
and the SNO experiment led by Dr McDonald overturned
this myth. These experiments confirm neutrinos have massby measuring neutrino oscillations, the phenomena throughwhich 1 type of neutrino can change to another type. The
laws of elementary particles, the “Standard Model”, say thatneutrinos are massless, but they are not! This discovery was a
breakthrough in particle physics!

What can we learn?

Neutrinos are the second most abundant particles in the universe only after light. By
studying their properties scientists think it may be possible to understand the mystery of
the beginning of the universe and the origin of matter. Although neutrinos are extremely
important to understand the universe, neutrinos have many mysterious features.

What are the projects of “Unification and development of the Neutrino Science
Frontier” and “Exploration of Particle Physics and Cosmology with Neutrinos”?
Scientists from different fields of science are collaborating to study neutrinos, including
the world’s first study using neutrinos to understand the “difference between matterand antimatter”, and observation of neutrinos from the universe to uncover the mysteryof the origin of the universe, such as “why do we exist?”
We perform a high-precision measurement of neutrino oscillations using a neutrino beam
produced by the world-class accelerator J-PARC at Tokai-village, Ibaraki prefecture and theSuper-Kamiokande detector located at Hida-city, Gifu prefecture, Japan. (T2K experiment)
Neutrino oscillations can be studied by measuring neutrinos from nuclear reactors(Double-Chooz experiment). Furthermore, we aim to establish the technology tomonitor nuclear reactors by applying this technology.
We observe neutrinos from the atmosphere. On top of measurements by theSuper-Kamiokande experiment, we are developing the next generation neutrino
detector “Hyper-Kamiokande”.
We observe neutrinos from the universe. These neutrinos carry information fromthe deep-universe nobody has ever seen (IceCube Neutrino Observatory).
We are developing state-of-the-art particle detectors. They improve the nuclear
reactor safeguard system, nuclear-imaging technology, and new various otherapplications.
Theoretical studies of neutrinos across particle physics, nuclear physics, andcosmology are important to answer fundamental questions such as “what is spacetime?”.

Accelerator Neutrino
T2K Experiment

Neutrino oscillation is a fascinating phenomenon in which a neutrino changes its identity.
In order to study neutrino oscillations, a neutrino beam is shot from the large accelerator
facility J-PARC in Tokai village and the neutrinos are observed at the Super-Kamiokande
detector in Kamioka town, 295 km away. The experiment is named T2K (Tokai-to[2]Kamioka). In the T2K experiment, a new type of oscillation from a muon neutrino to anelectron neutrino was discovered. Recently, we produced a beam of anti-neutrinos, theneutrino's anti-particle, and studied the violation of symmetry between a particle and its
anti-particle, called CP symmetry violation. T2K has the interesting result that CP symmetry
may really be violated in neutrinos. This might be a big hint that neutrinos help explain the
mystery of our universe, where anti-matter is rare compared to matter.

View of the T2K experiment
A neutrino beam is shot from the J-PARC accelerator in Tokai village to the Super-Kamiokande detector in
Kamioka town.

Particle Physics elucidates the mystery of invisible tiny elements
constituting our universe. In Particle Physics research, we havea dream and passion challenging the mystery with large-scale
experiments, such as using a kilometer-scale accelerator or agigantic detector located 1000 m underground. Let’s discover
together how our universe is created.
Dr. Tsuyoshi Nakaya
Professor in Physics, Faculty of Science, Kyoto University

T2K!
Hi, SuperKamiokandechan!

Wow !
J-PARC-chan

Watch out,muon neutrinos!
Wow!

J-PARC-chan:
lives in Tokai-mura, Naka-gun, Ibaraki, Japan.

SuperKamiokandechan

Somethingdifferent...?

It's amiracle!

No!
It’s Neutrino
Oscillation!

Super-Kamiokande-chan:
lives in Kamioka-cho, Hida-city, Gifu, Japan.

……

Reactor Neutrino

Double Chooz Experiment
Nuclear power plants produce electric power from the thermal energy obtained from
Uranium nuclear fission. Did you know that a huge amount of neutrinos are produced at
the same time? Those neutrinos escape to outer space without being used. The Double
Chooz experiment at the Chooz nuclear power plant in France investigated such reactor
neutrinos precisely and measured the θ13 mixing angle, an important parameter for the
study of neutrino oscillation phenomena. It is an international collaboration with sevencountries, and the Japanese group is playing a central role in it. Furthermore, we areconducting R&D application studies for new measures of nuclear non-proliferation byplacing a small neutrino detector outside of the reactor building.

The Double Chooz detector during
its construction, which has a doubleacrylic vessel for liquid scintillators and390 photo-multiplier tubes contained inmagnetic shields.

In elementary particle experiments such as neutrino experiments,
yo u n g g r a du ate s t u d e nt s a n d r e s e a rch e r s wo r k in l a r g einternational collaborations together with others from all over theworld, with an ambition to “see for the first time what mankind has
never seen”. Why don’t you come and join us?

Dr. Masahiro Kuze
Professor at Tokyo Institute of Technology

Near and Far
Double Chooz
Sisters,
What areyou doing?

Hi! SuperKamiokandechan!

We are watching
nuclear power
plant there.

Wow!

anti electron neutrinos

We detectthem fromdifferent
positions.

There are manyanti electron
neutrinos!

400m

Let's study
neutrinos moreclosely,
combining resultsfrom your T2K
experiment.

I detectfar away.

And we investigate
the difference of
numbers of detectedanti electrion neutrinos.

It's neutrino
oscillation!

1km

Right!

I'm going
to help too!

Observe from Near and Far:
By detecting anti electron neutrinos fromthe reactors at two distances, neutrino oscillation
parameters are investigated in detail.

I detect
near by.

Exactly!

Double Chooz Sisters:
Twins living near Chooz nuclear power plant
in France. They measure together the neutrinos
from the reactors.

Double Chooz Sisters

Atmospheric Neutrino

Super-Kamiokande andHyper-Kamiokande Experiments
We observe neutrinos born in the Earth's atmosphere (atmospheric neutrinos) using theSuper-Kamiokande detector to determine the order which type of neutrino is heaviest
and which is lightest (called the "Mass ordering"). The mass ordering can cause a smallenhancement of neutrino oscillations when the atmospheric neutrinos pass throughthe high density core of the Earth. We examined a lot of data in detail and found thatthe hypothesis that the third generation neutrino has a heavier mass than the first andsecond generation neutrinos matches the data better. However, further study is needed
to conclude the order of the masses. The Hyper-Kamiokande detector will provide major
new capabilities to make new discoveries in particle and astroparticle physics. It is apriority project listed in the Roadmap2017 of the Japanese Ministry of Education, Culture,
Sports, Science and Technology, and we are preparing to start the detector construction.

By operating the Super-Kamiokanded e t e c t o r, w e o b s e r v e n a t u r a lneutrinos from the Sun, atmosphere,
and Supernova explosions, andartificial neutrinos from the J-PARC
accelerator to study elementary
particles and celestial bodies. We also
look for not-yet-discovered proton
decay phenomena in the tank water.

Detailed measurements of proper ties of neutrinos andspontaneous proton decays have the potential to make great
progress in understanding the laws of nature. I would like toconstruct the Hyper-Kamiokande detector with sensitivit yexceeding Super-Kamiokande and advance this research.

Dr. Masato Shiozawa
Professor at Institute for Cosmic Ray Research, the University of Tokyo

How to find NeutrinoIt's myspecialtalent!

I prepare ultrapure waterin big tank.

neutrino

Neutrinos collide
electrons andnuclei in watermolecules,
so electron
or muon escapes.
electron or muon

Cherenkov
radiations

I find them byusing light sensors
on the wallsof my tank.
I can find 20-30 neutrinos
in a day by using
50,000 tons of waterand 10,000
light sensors.

Uh-huh....

This istoo big ofa problem tounderstand...

A lot of light sensors:
Light sensors called photomultiplier tubes (PMTs).
There are 11,129 sensors inside the tank.

When electrons
and muons
are traveling in water,
Cherenkov radiations
are generated.

water molecule

Gigantic tank:
It is filled with 50,000 tons of ultra-pure water.
The bigger it is, the more neutrinos
can be detected.

How do you
find neutrinos?
It's difficult tofind thembecause theygo througheverything...

High Energy Cosmic Neutrino
IceCube Experiment

Large amounts of highly energetic matter travels through the cosmos at nearly the
speed of light. This matter is called 'cosmic rays', and mostly consist of protons, the very
basic building blocks of matter in our universe. Some of these cosmic rays have energies
thousands of thousands of billion times higher than visible light. How are all theseproducts of the extreme Universe generated? In fact astronomical objects radiatingcosmic rays are also expected to yield neutrinos. Neutrinos, chargeless elementary
particles only sensitive to the "weak force", are traveling straight over huge distances,
unattenuated. Hunting of these neutrinos can indeed reveal the new image of the highenergy universe we would never see otherwise. We "watch" our cosmos by the world's
largest neutrino telescope, IceCube, built at the South Pole.

IceCube Neutrino Observatory
built at the South Pole. The 5165
photo-detectors are deployedin the deep glacier ice. Signals
from the in-ice detectors aretransmitted via cables to theobservatory, where the primarydata processing to selectneutrino signals takes place.

Your life is one time. Let's challenge whatever stimulates yourenthusiasm. Action first, then you have a plenty of time later toworry if your challenge is successful or not.

Dr. Shigeru Yoshida
Professor at Graduate school of Science, Chiba University

Neutrino Hunter!
Like this,I'm hanging many lightsensor balls called
DOM in the ice...

and neutrinos comingin the ice collide with
nuclei and electrons,

Cherenkov
radiations

and I look for
Cherenkov
radiations frommuons and
electrons frominteractions.

muon neutrino

Super-Kamiokande

But!!!

IceCubewhy don't you
do that at otherplace not theSouth Pole...,it's so cold...

It's so coollike you're
fishing
neutrinos!

Super-K-chan

but
you know
only theSouth Pole
has so muchclear ice.

DOM:
It stands for Digital Optical Module. About 5,000 pcs
of them have been deployed in the deep ice,waiting for a signal from a cosmic neutrino.

It's like doing SuperKamiokande-chan's experiment
but not with a water tank,
but with a large clear ice.

IceCube-san:
is observing neutrinos using Antarctic glacier ice.
These experimentalists are incredible as they goto such remote places to hunt for neutrinos.

DOM

IceCube-sanNovel Neutrino detector:
Nuclear Emulsion

Nuclear emulsion has been contributing to fundamental particle physics for a longtime, especially for charm particles and tau neutrinos so far. To apply a nuclear emulsion
detector for the next step of neutrino physics, neutrino CP violation or physics beyond
the standard model probed by neutrinos, we are developing and improving thetechnology of nuclear emulsion.
In the era of digital photography, the commercial photo film market has shrunk. We
installed a nuclear emulsion production machine in Nagoya University and havebeen producing nuclear emulsion films with the help of retired technicians from a
photographic company. The development and production of optimized nuclear emulsion
for a variety of observations is resulting in fruitful output for not only neutrino physics,
but also observations such as a dark matter search, balloon-borne gamma ray telescope,and cosmic-ray muon radiography.

Production machinefor nuclear emulsion gel
This system makes nuclear emulsion
gel by carefully controlling thetemperature and mixing of a solution ofsilver nitrate and sodium bromide. The
nuclear emulsion gels provided by thismachine hava been used in the neutrino
experiment at J-PARC, gamma-ray
telescopes and muon radiography.

Two dimensional photographic films have largely been replaced bydigital photographic techniques. However nuclear emulsion, as three
dimensional photographic films, still continues to grow. Since aninfrastructure to make nuclear emulsion gel was installed at our laboratory
in this research field, we can try to test easily new methods as soon as we
think up a new idea. This has quickened young scientists drafting andperforming new experimental projects with nuclear emulsion.

Dr. Mitsuhiro Nakamura
Professor at Institute of Materials and System for Sustainability, Nagoya University

Emulsion as popular trend device
J-PARC-chan,what's that?

nuclearemulsion

When charged
particles
pass through,the trajectories
are recorded
as lines.

develop-ment

charged particle(electron etc)

muon

I kinda want tomeasure theneutrinos that
I throw to SuperKamiokande-chanprecisely by thisI want touse this, too!

You have
Photomul,
don't you...?

J-PARC-chan and emulsion:NINJA experiment is planned to precisely measureneutrinos produced by J-PARC-chan.

Recently it looked
through the insideof a pyramid byusing cosmic-ray
muons.

This device needs
no electric powerand has fineresolution tracking,very useful!

Nuclear emulsion:
A kind of particle detector, same principle
as photographic films, has been used for
fundamental particle observations from the dawnof particle physics.

This isnuclearemulsion!

Search for Neutrino Decay:
COBAND ExperimentCosmic background neutrinos are predicted to exist uniformly in space. To performthe COBAND rocket experiment to search for the cosmic neutrino background, we aredeveloping the Superconducting Tunnel Junction (STJ) detector which measures theenergy of far-infrared photons from neutrino decays with an accuracy of 2%. We havedeveloped a cryogenic amplifier which is a key component of the cryogenic far-infrared
photon detector, consisting of the Nb/Al-STJ detector and a diffraction grating, andsucceeded in amplifying the Nb/Al-STJ signal for the visible laser pulse light. We havedeveloped the Hf-STJ detector using Hf as a superconductor with a very narrow energy
gap for the future satellite experiment, and succeeded in observing the Hf-STJ signal forthe visible laser pulse light. We are preparing the whole equipment including the opticalsystem and the 0.4K refrigerator for the rocket experiment.

STJ SOI

4.7μF

T h e N b / A l - S TJ d e t e c t o r i sconnected to the SOI cryogenic
amplifier on the same chip
carrier as the Nb/Al-STJ at 0.4K
refrigerator.

To perform the COBAND experiment which searches for thecosmic background neutrino decay, we have developed theSuperconducting Tunnel Junction (STJ) detector which measuresthe energy of the far-infrared photon from the neutrino decay.
This technology of superconducting particle detectors is expected
to be used for the dark matter search, the coherent neutrino
scattering experiment and so on in the future.
Dr. Shinhong Kim
University of Tsukuba, Faculty of Pure and Applied Science, Professor

For Neutrino Watching
I want to seea heavy neutrino
decaying intoa light neutrino...

heavy
neutrino

light
neutrino

COBAND-san

But this
phenomenon
would happen
so rarely...

Perhaps!
There are a lot ofneutrinos that weremade in a few
seconds after theuniverse was born,and I may be able
to see their decays!

Perhaps!

But the light comingfrom the neutrino
decay is too weak,
it may be difficult
to see...

Cosmic Background Neutrino:
The universe is thought to be filled with Cosmic
Background Neutrinos which became free a few
seconds after the Big-Bang.

photonI may be able tosee it in outerspace noton the earth!

Wow...
you start frommaking chips?
It’s amazing...

That's why

I decided tomake a chip
optimal fora photo-sensor
to see neutrino
decaysCOBAND-san:Try to determine the neutrino masses
by observing neutrino decay.

But there isno detector
that is optimalfor this...

Novel Neutrino detector:

Liquid Ar Time Projection Chamber
The liquid argon 3D imaging detector provides the 3D image of elementary particles
visually with online. It is a kind of the modern updated version of “the bubble chamber”,
Due to its high capability of the detector, it is an ideal and ultimate candidate of the
future neutrino or nucleon decay experiments.
The largest size of the liquid argon 3D imaging detector so far is the ICARUS detector
which has 600 tons, however the enlarged size of the detector is necessary for the
future experiments. For those experiments, R&D of the detector, especially R&D for
the technology with reasonable costs is highly desired. Also the test-beam of thedetector using well defined charged particles such as energy, momentum, angles andidentification is quite important to understand the response of the detector to theelementary particles.
For this purpose, this research program has large amountof R&D for the key device with the reasonable costs forthe future experiments, and the test-beams.

KEK 30L liquid argon 3D imaging detector.

The liquid argon 3D imaging detector is one of ultimate detectors
for the neutrino and nucleon decay physics, therefore there area lot of R&D activities around the world. There are also some ongoing experiments which have order of 100 tons level. In thisresearch program, we have done a lot of R&D of the detector key
devices and the test-beam for the future experiments.
Dr. Takasumi Maruyama
Associate Professor at KEK, Institute of Particle and Nuclear Studies

Even neutrinos are seen?
electronliquid Argon

The ion-electron pairs
are created along
the tracks of charged
particles suchas muons!

muon

positive ion

The electrons are
moved to plus
charged plane.
So, we can recodesignal from electrons
and the track ofcharged particles
finally…

electric signal

Awesome!!

Ahem!

Argon TPC

Argon
neucleus

LHC-chanThis method issimilar to mine!

I want to
make a large
detector like
SK-chanby this.

Neutrinos and TPC:
Neutrinos do not have electric charge, but we cansee the charged particles’ tracks which were
produced by the neutrino-argon interactions.

..but, even theycannot see theneutrinos directly
because of noelectric chargeof neutrino?

Muons or electrons
which have electriccharge areproduced whenneutrinos areinteracted withargon nucleus!!

The Argon TPC:
This detector has the track signals when charged
particles pass the argon volume. TPC isan abbreviation of “Time Projection Chamber”

Argon gas iscooled down andfilled in the tankas the liquid….

Neutrino Phenomenology
A theory called the Standard Model of particle physics explains most of all thephenomena of elementary particles, but neutrino mass is one of the mysteries whichcannot be explained by the Standard Model. One important subject in particle physics
is to search for new physics beyond the Standard Model, and research on neutrinos isbelieved to bring a breakthrough along that direction. Various experimental results
have been announced since the Superkamiokande experiment in 1998, and researchon neutrinos is now entering a new stage. In our group we are doing researches, suchas phenomenology of experiments to determine precisely the parameters of neutrino
mixing, phenomenology of new physics which can be probed by neutrinos, constraints
on new physics which can be obtained through charged leptons at large accelerator
experiments, etc.

e–
e+

γ
γ

Z’
q

q

A process which was proposed to experimentally check a model
which was invented to explain mysterious phenomena.

Research on particle physics, including that on neutrinos, does nothave any direct application to our daily life. Because of suchnature, however, we do not have conflict of interest and we havequite active international collaboration. We are carrying on
research to find out the ultimate law of the universe.

Dr. Osamu Yasuda
Professor at Faculty of Science, Tokyo Metropolitan University

Exactly like...?
Muon neutrino andanti muon neutrino
look exactly likeeach other.

Are they reallydifferent?

muon neutrino

anti muon neutrino

Both of you,why don't you run
from here to
Super-Kamiokande-chan's placein Gifu.

Wow, you have
sharp eyes.
……

This is the firsttime we see thatthey are not
identical.

Anti muon neutrino-chan with a hat moved:
From the T2K experiment we are beginning tosee a tiny difference between the propertiesof anti muon neutrino and muon neutrino.

Gee! anti
particle-chan's
hat is moved
a little.

Can they arrive
here at thesame time?

Electrically neutral neutrino and anti neutrino:
We can tell that they are a particle andanti-particle because of the electric charges ofthe particles produced by the reactions.

Hey!
I got an idea.

Neutrino-Nucleus reactions
Precise description of neutrino-nucleus reaction is crucial to extract neutrino properties
from current and next-generation neutrino oscillation experiments. We are working
to understand how particles such as muon, electron, nucleon and pion are produced
from the neutrino-nucleus reactions in wide neutrino energy region. One of our mainefforts is meson production in the nucleon resonances region. A model of leptonnucleon reactions for both electromagnetic and weak meson production reactionsin the resonance region is developed. The other is neutrino reactions in the deep
inelastic region. Nuclear effects in charged lepton reactions and neutrino reactions areinvestigated.

Workshop on 'Neutrino-Nucleus
I n t e r a c t i o n i n t h e Fe w - G e V
Region' held at Osaka in 2015
(NuInt2015).

Theoretical description of the neutrino-nucleus reactions is achallenging subject. Collaboration among researchers in nuclear
structure, nuclear reaction, hadron physics and particle physics areimportant. We hope that young researchers join the field, enjoy
working with people from various field, and develop new ideas.

Dr. Toru Sato
Guest Professor at RCNP, Osaka University

Nucleus and Neutrino

muon
neutrino

What areyou doing?
SK-chan?

Yaah!
muon
neutrino
Super-Kamiokande

muon

SK-chanIceCube-sannucleus

I am kinda hitting
neutrinos andantineutrinos
on to a nucleus
to see what
happens.

Wouldn’telectrons,muons,
protons,
and neutrons
come out?

muon

like wealways see.
protonelectronneutrino

muon
neutrino

nucleus

For high energy
neutrinos, even
weirder stuff
might come out…
so muchwe don’t know.

neutronelectronmuon

To become a”neutrino master”,
we need to
study nuclei andall phenomena
at everywhere!

proton weird stuff

Through ice
and water!
Gotta
catch'em all!

Understanding neutrino-nucleus reaction:
While unified description the neutrino-nucleus
reactions in the whole energy region not yet available,
we are improving our descriptions step by step.

Yeah,
but sometimes
other weird stuff
comes out withthe protons
and neutrons.

Production of electron and muon:
An electron is produced by electron-neutrino
reaction with nucleus, while a muon is producedby muon-neutrino reaction.

Yaah!

Neutrino physics andthe origin of the Universe
How did the Universe started and how has it evolved into the current form of structures
made of galaxies and clusters of galaxies? The properties of elementary particles arequite important to answer these fundamental questions of our world. Our group has
been studying the properties of neutrinos in the early Universe. Recently, we found thatthe neutrino oscillation phenomena during the Big Bang can explain why there are noanti-particles around us. We are now studying how this hypothesis can be tested. We
have also proposed various new possibilities of particle/cosmology phenomena, such as
explaining the origin of the high-energy neutrinos discovered in the IceCube experimentas the decay products of dark matter particles, the hypothesis of dark matter made of the
Higgs particles, supersymmetry to explain the mysteries of the Universe, and the relation
between the vacuum structure of string theory and the history of the Universe.

The theor y/experiment
joint regular meetings,“New Physics Forum,” havebeen held in Tokyo area.
“New Physics Forum” offers
good opportunities to form
new collaborations among
physicists.

Our theory team works on particle physics and cosmology suchas the origin of baryonic matter in the Universe, nature of dark
matter, and also physics beyond the Standard Model throughthe studies of neutrinos. We build up new hypothesis to attack
unsolved questions in particle physics and cosmology aiming at
finding new facts of our Universe.
Dr. Ryuichiro Kitano
Professor at KEK, Institute of Particle and Nuclear Studies.

Neutrino Magic!
Have agood look!

I see!

anti-neutrinos

Neutrino
oscillation!

The flavor content of neutrinos and that of anti-neutrinos are
modified differently by the CP violation in the neutrino oscillation.

And hit
Higgs bosons!

Higgs boson

The numbers of the heavy neutrinos and the heavy anti-neutrinos
are equalized by hitting the Higgs bosons.

Ta-da!

There aremore antineutrinos?!

More anti-neutrinos than neutrinos?:Starting with the same numbers of neutrinos and anti-neutrinos, some magic under the cloth createdan imbalance between them. This CP violating phenomenon, if it has really happened in the early Universe,
give the reason for the Universe being made of matter rather than anti-matter.

neutrinos

electron neutrino

muon neutrino

tau neutrino

time projection chamberphotomultiplier tube

nuclear emulsion

anti electron neutrino

anti muon neutrino

anti tau neutrino

Published in March 2019

Exploration of Particle Physics and Cosmology with Neutrinos
https://www-he.scphys.kyoto-u.ac.jp/nucosmos/en/index.html
Editor, Designer: Yuki Akimoto (Higgstan / higgstan.com)
Translator: Teppei Katori (Queen Mary University of London)