Presentation topic: Particle Physics Today, Tomorrow and Beyond for undergraduate final year seminar presentation.University of Ruhuna

1. PARTICLE PHYSICS
TODAY,TOMORROW AND
BEYOND
Presented By:
B.A.T.M.Thilakarathne
SC/2016/9691
Supervisor:
Dr.N.M.Wickramage

2. CONTENT
1. Particle Physics
2. Fundamental Particles
3. Higgs Boson
4. Standard Model
5. Beyond the SM
I. Gravity
II. Dark Matter
III. Dark Energy
IV. Matter-Antimatter Asymmetry
V. Neutrino Mass
VI. Supersymmetry-SUSY

3. PARTICLE PHYSICS
1
• Particle physics is the study of the fundamental
constituents of matter and their interactions.

4. FUNDAMENTAL PARTICLES
• In particle physics, a fundamental
particle is a subatomic particle
with no any substructure.
• Fundamental particles include
1. Fermions
2
2. Gauge Bosons + Higgs Boson
Proton

5. Fermions (Matter Particles ):
• Fundamental particles that are the constituents of matter are assumed to be
the six leptons and the six quarks together with their antiparticles.
• These twelve particles are all spin 1/2 particles. 3
Mass
increases

6. Gauge Bosons (Force particles ):
• The modern physics explains the exchange of energy in interactions by the
use of force carriers, called bosons. They are
• All known gauge bosons have a spin of 1.
4
Strength
decreases

7. • A particle containing two or more
elementary particles is called a
composite particle or ‘Hadron’.
• Mesons - Made of one quark and
one antiquark
• Baryons - Made of three quarks
Hadrons:
Hadron
Mesons Baryons
5

8. HIGGS BOSON
• In July 2012 the ATLAS and CMS collaborations announced that they had discovered a
new particle with a mass near 125 GeV in studies of proton–proton collisions at the LHC.
That new particle was “Higgs Boson”.
• The Higgs particle is a massive scalar boson with zero spin, no electric charge, and no
color charge. It is also very unstable.
6
The ATLAS Detector at LHC,CERN The CMS Detector at LHC,CERN

9. • Just after the big bang, the Higgs field was zero, but as the universe cooled and the
temperature fell below a critical value, the field grew spontaneously so that any particle
interacting with it acquired a mass.
• The more a particle interacts with this field, the heavier it is.
• Particles like the photon that do not interact with it are left with no mass at all.
7
What is Higgs Boson exactly?
Tracks of Higgs boson in the CMS detector
• Higgs boson is the carrier particle of the Higgs field.
Tracks of Higgs boson in the ATLAS detector

10. STANDARD MODEL
• The Standard Model provides an organizing framework for the known fundamental
particles.
• It is describes the interaction of quarks and leptons via gauge bosons.
• There are twelve named fermions and five named bosons (which have been experimentally
seen) in the Standard Model
• Detecting the Higgs boson completed the Standard Model of particle physics.
• The Standard Model does not incorporate gravity.
8

11. BEYOND
THE STANDARD MODEL

12. 9
• As time passed , physicists realized that the standard model was incomplete.
• Many problems can not explain using Standard Model.
• For examples
1. Gravity
2. Dark matter
3. Dark energy
4. Matter-Antimatter asymmetry
5. Neutrino Mass
Etc.

13. GRAVITY
10
• Graviton is the particle considered as the force carrier of gravitational force.
• But ,Gravity is so weak in quantum world. Therefore the graviton cannot be
detected in experiments do in large accelerators in the world.
• The graviton has not discovered yet.
• But in ‘Superstring Theory’ and ‘Loop Quantum Gravity’, the Quantum
Gravity has explained.
• The current theory of gravity is Einstein’s general relativity(GR). Up to now,
all attempts to search for a synthesis of QM and GR have failed.

14. 11
DARK MATTER
• Dark Matter does not absorb, reflect or emit light. It can be only observe due to gravitational
effect.
• Many theories conclude that the dark matter would be too light to be produced at the
Particle Accelerators.
• If they were created , they would escape through the detectors unnoticed. However, they
would carry away energy and momentum.
• Their existence can be detected from the amount of energy and momentum “missing” after a
collision.
• In Supersymmetry(SUSY) and Extra dimensions, Dark matter concept arise frequently.

15. 12
DARK ENERGY
• Dark energy responsible for the accelerated expansion of the Universe.
• It is distributed evenly throughout the universe, not only in space but also in time .Its
effect is not diluted as the universe expands.
• Dark energy is thought to be very homogeneous and not very dense, It is not known to
interact through any of the fundamental forces other than gravity.
• Two proposed forms of dark energy are the cosmological constant and scalar fields.
• But there is no evidence of Dark Energy yet.

16. The Distribution of Matter and Energy in the Universe

17. MATTER-ANTIMATTER ASYMMETRY
• Antimatter has the same mass and opposite electric
charge as their matter counterparts.
• After the Big bang, both Matter and Anti-Matter
were created in equal amount.
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• But today everything around us is made from matter.
• Comparatively, antimatter is less in the universe.
• Antimatter is defined as the matter which is composed of antiparticles.

18. 14
• It is a challenge to figure out what happened to the antimatter, or why there is an
asymmetry between matter and antimatter.
• If Matter and antimatter particles come in contact, annihilate one another, leaving behind
pure energy.
• The laws of nature do not apply equally to matter and antimatter.
Matter- Antimatter Annihilation

19. 15
NEUTRINO MASS
• In the Standard Model, Neutrinos are expected to be massless.
• The observed flavor oscillations in solar and atmospheric neutrinos are only possible if
neutrinos are massive.
• Therefore according to neutrino oscillation, neutrinos do have mass.
• So understanding the value of neutrino masses is one of the key questions in fundamental
physics.

20. 16
SUPERSYMMETRY(SUSY)
• Supersymmetry (SUSY) is one of the most
attractive theories extending the Standard Model
of particle physics.
• It introduced a new particle called Super partner
for each particle in the Standard Model.
• These new particles would interact through the same forces as Standard Model particles,
but they would have different masses.

21. 17
• Also the interactions of its three forces could have the exact
same strength at very high energies.(Grand unified theory)
• SUSY particles have a spin that differs by half of a unit of its
Standard Model partner.
• By these properties of SUSY particles
1. Can make a light Higgs boson possible.
2. Link Fermions and Bosons.
• Lightest SUSY particles have characteristics of Dark matter .
• But SUSY particles still not discovered yet. If this theory is correct ,SUSY particles should
appear in collisions at particle accelerators.

22. REFERENCE
1. Home.cern. 2021. Physics | CERN. [online] Available at: https://home.cern/science/physics
2. Martin, B. and Shaw, G., 2010. Particle physics. Chichester: Wiley.
3. Gottfried, K. and Weisskopf, V., 1986. Concepts of particle physics. Oxford: Clarendon Pr. [u.a.].
4. 1998. Elementary-Particle Physics. Washington: National Academies Press.
5. Physics Today, 2012. CERN experiments detect particle consistent with Higgs boson.
6. Sundaresan, M., 2001. Handbook of particle physics. Boca Raton, Fla.: CRC Press.
7. T. Morii, C. Lim and S. Mukherjee, The physics of the standard model and beyond. New Jersey: World
Scientific, 2004.
8. "Fermilab | Science", Fnal.gov, 2021. [Online]. Available: https://www.fnal.gov/pub/science/index.html.

23. Thank you