Little Particles in a Big Universe

@ f l i p . t a n e d o 26TH REV. FR. CIRIACO PEDROSA, O.P. MEMORIAL LECTURE SERIES
Little Particles in a Big Universe
Flip Tañedo
26 November 2021
The what, why, and how of particle physics

@ f l i p . t a n e d o 26
26TH REV. FR. CIRIACO PEDROSA, O.P. MEMORIAL LECTURE SERIES
What is particle physics?
2
How is it done? Why do we care? How do you get involved?

@ f l i p . t a n e d o 26
What does it mean to do fundamental science?
https://xkcd.com/435/
3
more elementary

@ f l i p . t a n e d o 26
Organizational Principle
https://picturelights.club/galleries/molecular-structure-of-dna-sugar-phosphate-backbone.html; Wikipedia (DNA)
4
more
elementary

@ f l i p . t a n e d o 26
Wikipedia: Periodic Table
5
p+ e-
n
more
elementary
Mendeleev: organizing the elements 
suggests an underlying principle

@ f l i p . t a n e d o 26
6
e-
u
u
u
d
d
d
u d e-
… and more
more
elementary
The Standard Model of Particles

@ f l i p . t a n e d o 26
Periodic table of particle physics
7
/ /
¯ / − /
¯ / /
/ −/
¯ / −
/
matter
particles fundamental forces
Higgs
x3
family
symmetry

@ f l i p . t a n e d o 26
Theoretical framework
Why do we need seemingly esoteric
fi
elds like “quantum
fi
eld theory?”
• Fast is di
ff
erent

• Small is di
ff
erent

• More is di
ff
erent
Referencing Anderson, “More is Di
ff
erent,” Science 177, 4047 (1972)
8
Newtonian

Mechanics
Quantum

Mechanics
Special 
Relativity
Statistical

Mechanics
Quantum

Field

Theory
Field Theory

(Electrodynamics)
Newtonian mechanics is a description  
of nature that breaks down…
Nature behaves di
ff
erently.

@ f l i p . t a n e d o 26
Quantum Field Theory
Originally by Sue Ann Koay (USLHC, 3 Oct 2008)
9
The Standard Model of Particle Physics
Lagrangian
Field: a complex function on space and time that
 
represents the quantum existence of a particle.

@ f l i p . t a n e d o 26
Encoding interactions
10

@ f l i p . t a n e d o 26
What a calculation looks like
An Introduction to Quantum Field Theory, Peskin & Schroeder
11
…
Cross section 
for scattering

@ f l i p . t a n e d o 26
Connecting to experiment
Source: ATLAS Image Gallery from CERN Website
12
https://medium.com/up-scientia/nip-
named-as-associate-member-of-atlas-
collab-83681b3bc3cc

@ f l i p . t a n e d o 26
Particle Physics = High-Energy Physics
High Energy ⟷ Short Distance (“more fundamental”)
13
Image from eyesafe.com
P
l
a
n
c
k
’
s
c
o
n
s
t
a
n
t
S
p
e
e
d
o
f
l
i
g
h
t
wavelength
angular

frequency

@ f l i p . t a n e d o 26
Particle Physics = High-Energy Physics
High Energy ⟷ Short Distance (“more fundamental”)
14
=

@ f l i p . t a n e d o 26
What questions are we trying to answer?
Where did all the anti-matter go? Why are so many fundamental particles
around 100x the proton mass? What is dark matter? Do the forces unify?
“Where Do We Come From? What Are We? Where Are We Going?” Gauguin, via Wikipedia

15

@ f l i p . t a n e d o 26
What questions are we trying to answer?
Where did all the anti-matter go? Why are so many fundamental particles
around 100x the proton mass? What is dark matter? Do the forces unify?
“Where Do We Come From? What Are We? Where Are We Going?” Gauguin, via Wikipedia

Why is there matter,

But no antimatter?
Why is the HIggs boson

Mass so light?
What is the dark matter

That holds our galaxy

together?
Are elementary Particles

Made of smaller things?
How is gravity

Compatible with

Quantum mechanics?
Why are there so

Many particles?
Why did the universe

Become large?
16

@ f l i p . t a n e d o 26
Question: What’s the Difference?
Both are the Millenium Falcon from Star Wars
Images: Millenium Falcon: Wookiepedia, Lego (2017)
17

@ f l i p . t a n e d o 26
Nature vs. Model of Nature
Images: Millenium Falcon, Lego (2017)
18
Model of nature may be enough

to diagnose puzzles in our understanding

… but do not confuse it with nature itself

@ f l i p . t a n e d o 26
Analog from surrealism
“this is not a pipe” (it is a painting of a pipe)
Magritte, "La Trahison des Images" ("The Treachery of Images”), 1929 (LACMA, via Wikipedia)
19

@ f l i p . t a n e d o 26
Analog from surrealism
Cham & Whiteson , We Have No Idea
20
This is not the
 
underlying theory

of nature

… it is just a predictive, mathematical model
Dark matter is not even in our current mathematical or physical models
universe. There is a large amount of stuff out there silently pulling on u
we don’t know what it is. We can’t possibly claim to understand our un
without understanding this huge part of it.
Now, before you start feeling paranoid about weird, dark, mysterio
stuff floating all around you, consider this: what if dark matter is somet
awesome?
Dark matter is made of something that we have no direct experienc
It’s something we haven’t seen before, and it might behave in ways we
haven’t imagined.
Think of the amazing potential that exists here.
What if dark matter is made of some new kind of particle that we a
to produce and harness in high-energy colliders? Or what if in discover

@ f l i p . t a n e d o 26
What do Particle Theorists Do?
Start with a mystery …
21
MYSTERY

@ f l i p . t a n e d o 26
… that does not
fi
t our current theoretical understanding
22
MYSTERY

@ f l i p . t a n e d o 26
Fix the theory to make it work…
23

@ f l i p . t a n e d o 26
Embed into a more complete theory that explains the “hack”
24
MYSTERY
PREDICTION

@ f l i p . t a n e d o 26
How we earn our living
25
HACK
full theory
interpretation
consistency
predictions

@ f l i p . t a n e d o 26
Roadmap for doing particle physics
Be insatiably curious. Develop the tools to satiate that curiosity.
• Undergrad: physics courses, especially quantum mechanics

• Postgrad: quantum
fi
eld theory, general relativity, specialized courses, but
most important: research!

• Find mentors, e.g: gradmap.ph, cienti
fi
colatino.com

• Research experience: needn’t be in theoretical physics at
fi
rst
@gabrielgallardo
26
@Uzziesh
@TramAcuna Miks Solon Marvin Flores

@ f l i p . t a n e d o 26
27
The next most pressing puzzle for me: what is dark matter?
A little about what I work on
Extra slides

@ f l i p . t a n e d o 26
28
Astronomy and Cosmology tell us Dark Matter Exists
Images: Je
ff
Filippini (Berkeley Cosmology 2005), NASA APOD 2006, NASA WMAP
5%
27%
68%
Standard Model is not complete
ROTATION CURVES GRAVITATIONAL LENSING COSMIC MICROWAVE BACKGROUND
This talk: new particle(s)
Conservative assumption 
could be other options
And we know roughly how much there is

A realistic picture of dark matter
Dark Matter Exists (whatever it is)
1. Rotation Curves
Rubin, Ford & Thonnard 1978
What we learn:
mass fraction
distribution
2. Cluster Dynamics
What we learn:
mass fraction
distribution
Zwicky 1937
3. Cluster Gas
What we learn:
mass fraction
distribution
~90% of the luminous
matter in a cluster is
hot gas
4. Strong Gravitational Lensing
What we learn:
mass fraction
distribution
5.Weak Gravitational Lensing
What we learn:
distribution
shape
structure
Dietrich et al. 2016
6. Cosmological Microlensing
What we learn:
mass fraction
smoothness
Lewis & Irwin 1996
Joachim Wambsganss
7. CMB Acoustic Peaks
What we learn:
ratio of DM/
collisional
matter
thermal history
Hinshaw et al. 2013
WMAP 9
SPT
ACT
odd-numbered peaks
boosted relative to even as
baryon fraction increases
8. Matter Power Spectrum
What we learn:
ratio of DM/
collisional
matter
thermal history
Chabanier et al. 2019
9. Large Scale Structure
What we learn:
ratio of DM/
collisional
matter
thermal history
Paul Angel, Tiamat Simulation
Excellent agreement
between simulations
and galaxy distribution
on the largest scales
10. Galaxy/Cluster Collisions
What we learn:
distribution
separation from
collisional
matter
self-interaction
NASA/Clowe et al. 2006
Difficult to explain
without
collisionless matter
11. Big Bang Nucleosynthesis
What we learn:
amount of
baryonic matter
PDG 2018
Remaining mystery:
lithium abundance
(but still need low
baryon fraction)
12. Local Stellar Motions
What we learn:
local dark
matter density
Buser 2000
Estimates:
ρDM ~ 0.3 GeV/cm3
~ 0.008 MSun/pc3
via Katie Mack (ACP Colloquium 2019)

we are here
A cartoon picture of dark matter

Weare swimming in

an ocean of darkmatter
A cartoon picture of dark matter, zoomed out

A representative picture of dark matter physicists
Weare swimming in

Water?

A representative picture of particle physicists
Weare swimming in

Water?
“Do science” options:
Canyou see it?

Canyou touch it?

Canyou hear it?

Canyou smellit?

Canyou taste it?
Be more clever.

@ f l i p . t a n e d o 26
35
Theoretical physics discovers “dark matter”
Urbain Le Verrier and the discovery of Neptune “from math”
Image: Magnus Manske via Wikipedia U. Le Verrier; hubpages.com/
education/The-Drama-of-Neptunes-Discovery

The second “dark matter”
… and the failed discovery of Vulcan
The second “dark matter”

Why do we care about dark matter?
• Cosmic origin story: where did we come from, what are we made of?

• Obvious missing piece in our “periodic table” of elementary particles; we
know that it must exist (or else something more exciting)

• Driver for scienti
fi
c discovery: dark matter may be the key to answering
other open questions in physics (e.g. matter—anti-matter asymmetry, origin of
matter, …)

• Technological byproducts: e.g. DarkSide physicists contributing to low-cost
ventilators, development of the world wide web at CERN

• Intangible: “cosmic origin story” as a uniquely human endeavor
beta.nsf.gov/science-matters/dark-matter-covid-19-and-opportunity-help-people

Little Particles in a Big Universe

Recommended

Recommended

More Related Content

What's hot

What's hot (12)

Similar to Little Particles in a Big Universe

Similar to Little Particles in a Big Universe (18)

More from Flip Tanedo

More from Flip Tanedo (12)

Recently uploaded

Recently uploaded (20)

Little Particles in a Big Universe