what are elementary particles, and why should we care? · quarknet masterclass niu, 14 march 2012...

What are elementary particles, What are elementary particles, and why should we care?and why should we care?

Dhiman Chakraborty

([email protected])

QuarkNet Masterclass, NIU, 14 March, 2012

QuarkNet MasterclassNIU, 14 March 2012

Elementary particles & cosmology- Dhiman Chakraborty

2



3

The fundamental questionsThe fundamental questions• What is the world made of?

• What holds it together?

• How did it all start?

• What does the future hold?

• What/who else is out there?

“What is it that breathes fire into the equations and makes a

universe for them to describe? Why does the universe go

to all the bother of existing?”

– Stephen Hawking



4

Unsolved mysteriesUnsolved mysteries

Driven by new puzzles in the understanding of our physical world, particle physicists are finding paths to new wonders and startling discoveries. Experiments may even find hidden extra dimensions, mini black holes, and/or evidence of string theory.



5




6




7




8




9

The smallThe small



10

The largeThe largeGraphics courtesy: NASA


11

Exploring the Universe with Hubble Ultra-Deep Field reveals galaxies forming and evolvingPhoto courtesy: NASA



12

The extremes are connectedThe extremes are connected• We want to explain the structure and phenomena at the largest scales

(cosmology), in terms of the smallest (particle physics).

• Particle physicists, in turn, are getting their cues from cosmological

observations.

• The two are inextricably coupled. Fortunately, they are also easier to

model precisely than anything in between. Systems in biology,

economics, geology etc. are far more complex.

• Particle astrophysics is a rapidly growing field.

• 95% of what constitutes the Universe is yet unknown/ unobserved.

Some of it must be explained by particle physics.

• A revolution of unparalleled proportions is around the corner.


13

CompositionComposition of the Universe of the Universe

Graphics courtesy: NASA


14



15

Ways to study structuresWays to study structures• Cosmology: Look at the object object at all possible wavelengths

• Particle physics: Shoot all possible probes at the object



16

To probe small distances, we need high energies: E = 2/ , where is the wavelength of probe



17

Matter and interactionsMatter and interactions“Matter”: made of FermionFermions.

– Spin-(2n+1)/2 particles that do not share a quantum state.

– Consequently, their production, annihilation, or decay must

be associated with either another fermion or an “anti-

fermion”. This results in the conservation of number of

matter particles.

“Interactions”: mediated by BosonBosons.

– Spin-n particles that gladly share a quantum state.

– Can be radiated, absorbed, or decayed singly. Thus, the

number of bosons is not conserved.

– Bosons can interact among themselves.



18

The four forcesThe four forces (carried by bosons)(carried by bosons)•Affects everything,

•Infinite range,

•No neutralization

•Dominant at planetary-to-cosmic scales

•No quantum description yet.

•Affects only electrically charged bodies,

•Infinite range,

•Bound states are often neutral

•Prominent at atomic-to-stellar scales

•Affects all fermions,

•Very short (sub-nuclear) range,

•Not a binding force,

•Only interaction to cause transmutation of matter.

•Affects only “color”-ed objects (quarks & gluons),

•Very short (nuclear) range,

•Strong neutralization

•Dominant at nuclear scales



19

The matter particlesThe matter particles (fermions)(fermions)

a



20

Beyond SM: Grand UnificationBeyond SM: Grand Unification



21

Unification of forcesUnification of forces

Diagram courtesy: H. Murayama



22

Unification theoriesUnification theories



23

Open questionsOpen questions• What makes fundamental particles massive?

• Why do fermions come in multiple “flavor”s? Could it be

related to their mass?

• What can we learn from the neutrinos?

• Are there undiscovered principles of nature? New

symmetries? New physical laws? “Extra” dimensions? Do

all forces unify at high energies?

• What happened to all the antimatter?

• How can we explain the “Dark Energy”?

• What constitutes the “Dark Matter”?



24

The many connectionsThe many connections



25

A timeline of HEP CollidersA timeline of HEP CollidersThe LHC is almost certain to make revolutionary discoveries within first 2-3 years of full-scale operation.

The ILC/NLC will help us make high- precision measure-ments pin down the details of any new TeV-scale physics.



26

FermilabFermilab



27

Collider DetectorsCollider Detectors

DDØØ CDFCDF



28

A top-antitop eventA top-antitop event



29

A top-antitop event A top-antitop event



30

The Large Hadron Collider (LHC) at CERNThe Large Hadron Collider (LHC) at CERN



31

LHC parametersLHC parameters

Circumference

Collision Energy

Injection energy

Crossing angle

Particles per bunch

Number of bunches

Dipole field

Number of dipole magnets

Number of quadrupole magnets

Number of corrector magnets

Luminosity

26.7 km (16.56 mi)

7+7 TeV

0.45 TeV

300 μrad

1011

2808

8.33 Tesla

1232

about 600

about 7000

1034 cm-2s-1



32

The ATLAS detector at LHCThe ATLAS detector at LHC



33

OutlookOutlook• A large number of particle physics, astrophysics, and

cosmology projects – both theoretical and experimental – are underway. They complement each other toward a common goal – to solve the most fundamental mysteries of nature.

• It is a truly INTERNATIONAL effort.

• We are living through a revolution in our understanding of the Universe on both the smallest and the largest scales.

• The next decade or two will usher us into a new era of observation and comprehension.



34

Feel free to contact the speaker

for more information

[email protected]

THANK YOU!THANK YOU!

what are elementary particles, and why should we care? · quarknet masterclass niu, 14 march 2012...

Documents